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General Authors: Robotics A. Meyer E. Aust Limited H.-R. Niemann R. Hammerin K.-E. Neumann D. Gibson ■ J. F. dos Santos

NATIONAL.HYPERBARIC CENTRE GKSS 98/E/14 ISSN 0344-9629 DISCLAIMER

Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. GKSS 98/E/14

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Marinization concept for the TR1CEPT TR600 robot

Authors: A. Meyer E. Aust H.-R. Niemann (GKSS, Institute for Materials Research, Geesthacht, Germany) R. Hammerin K.-E. Neumann (Neos Robotics AB, Taby, Sweden) D. Gibson (The National Hyperbaric Centre, Aberdeen, United Kingdom) J. F. dos Santos (GKSS, Institute for Materials Research, Geesthacht, Germany)

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GKSS 98/E/14

Marinization concept for the TRICERT TR600 robot

A. Meyer, E. Aust, H.-R. Niemann, R. Hammerin, K.-E. Neumann, D. Gibson, J. F. dos Santos

96 pages with 39 figures and 5 tables

Abstract

The need for automated repair systems of marine structures, hulls and nuclear installations had lead to an increasing demand for subsea robots. Considering the application of to perform underwater repairs, a TRICEPTTR600 robot has been identified as the most suitable system to withstand the high reaction characteristic of this process. This study reviews initially the research and development work carried out at GKSS to modify and test a Siemens-MANUTEC robot. After a description of the TRICERT TR600 robot a marinization concept is presented and discussed in detail. Problems of galvanic in seawater are addressed in a separate chapter. The deflection of the robot endeffector in subsea water currents is estimated with a worst-case calculation.

Modifikationskonzept fur einen TRICEPT TR600-Roboter

Zusammenfassung

Der Wunsch, Roboter auch unter Wasser einsetzen zu konnen, wachst mit steigendem Interesse nach automatisierten SchweilSverfahren fur Reparaturen an marinen Bauwerken, Schiffsrumpfen und in Kernenergieanlagen. Fur den Einsatz von ReibschweiBverfahren fur diese Reparaturen wurde der TRICEPT TR600-Roboter ausgewahlt, da dieser auch den charakteristisch hohen ProzeBkraften widerstehen kann. Die notwendigen Modifikationen und Prufungen werden beispielhaft anhand des bei der GKSS modifizierten Siemens-MANUTEC-Roboters vorgestellt. Nach einer Beschreibung des TRICEPT-Roboters werden die notwendigen UmbaumaRnahmen detailliert dargestellt und diskutiert. Auf die Problematik der galvanischen Korrosion in Seewasser wird in einem gesonderten Kapitel naher eingegangen. Zusatzlich wird eine mdgliche Ablenkung des Roboters durch Wasserstromung uberschlagig berechnet.

Manuscript received/ Manuskripteingang in der Redaktion: 8. Juni 1998

PREAMBLE Underwater fatigue cracks in offshore steel structures, and nuclear installations are a well known problem in repair and maintenance for these industries. Repairs are often required in areas which are either hazardous or costly for human intervention. Ships usually require dry docking for underwater repairs, reactors may need to shut down and divers, operating from support ships, are required for offshore platform repairs. This European Commission sponsored project "Affordable Underwater Robotic Welding Repair System" (ROBHAZ) will develop equipment and methods for remotely operated underwater welding using the Friction Stitch Welding technique deployed and operated from Remotely Operated Vehicles (ROV's). Friction stitch welding was developed at The Welding Institute in Cambridge on a project supported by various organisations from the oil, nuclear and construction industries. Two of these sponsors are now partners in a new project to develop the process for underwater repairs. This new BRITE-EURAM III project started in June 1997 and includes participants from five European countries.

The contributors are: The National Hyperbaric Centre in Aberdeen, United Kingdom, which co-ordinates the project and provides testing facilities with its hyperbaric chambers and test tank. Stolt Comex Seaway AS in Haugesund, Norway who provide the expertise and resources for offshore repairs and ROV operation. General Robotics in Milton Keynes, United Kingdom, who will develop the man machine interface. Products Group in Aberdeen, United Kingdom, who are developing the Friction Stitch Welding Head. Neos Robotics in T_by, Sweden who will build the submersible robot for deploying the welding head. Institute De Soldadura e Qualidade in Lisbon, Portugal, who will provide expertise in ship repair and test the system for this application. GKSS-Forschunaszentrum in Geesthacht, Germany, who are providing expertise on the design of electric robots for underwater use, repairs for nuclear applications and will perform the initial weld testing. The project will be completed in the first quarter of 2000.

TABLE OF CONTENTS

1. INTRODUCTION 9 1.1 The Offshore Industry 9 1.2 The ROBHAZ project 14

2. MODIFICATION OF A MANUTEC R15: A REVIEW 18 2.1 Project background 18 2.2 The MANUTEC r15 20 2.3 Modifications 20 2.3.1 Compensation Fluid 21 2.3.2 Optical encoder 21 2.3.3 Brakes 22 2.3.4 Casing 23 2.3.5 Joint sealing 23 2.3.6 Limit switches 24 2.3.7 Electrical connections 24 2.3.8 Control unit 24 2.4 Test Programme 25 2.4.1 Pressure Tests 25 2.4.2 Power consumption 25 2.4.3 Positioning accuracy 25 2.4.4 Sensor feedback 26 2.4.5 Frequency analysis 26 2.4.6 Inspection 26 2.5 Industrial Application and Certification 27 2.5.1 Offshore relevant work 27 2.5.2 Certification 28 2.6 Discussion 28

3. TRICEPT TR600 30 3.1 General Description 30 3.2 Axes Definition 31 3.3 General Features 32 3.3.1 Technical Data of the TRICEPT Robot 32 3.3.2 Work envelope / Pressing capacity 33 3.4 Functional Description 33 3.4.1 General Movement 33 3.4.2 Axes Position Measurement System 34 3.5 Mechanical Description 36 3.5.1 Linear Axes 37 3.5.2 Centre Axis 37 3.5.3 Wrist Assembly 39 3.6 Electrical Connection 41

4. THE MARINE ENVIRONMENT 42 4.1 Galvanic Corrosion 43 4.2 Material Selection 44 5. MARINIZATION CONCEPT 46 5.1 Linear Axes 1,2 and 3 47 5.1.1 Motor Unit 47 5.1.2 Linear Actuators 48 5.1.3 Cardanic Joints 49 5.2 Centre Tube and Axis 4 49 5.2.1 Motor Unit 49 5.2.2 Housing and Centre Tube 50 5.2.3 Cross Roller Bearing 50 5.3 Wrist (Axes 5/6) 51 5.3.1 Claw and Axis 5 51 5.3.2 Axis 6 51 5.4 Structure 51

6. HYDRODYNAMIC FORCES 52 6.1 Idealisation of components 52 6.2 Calculation 53

7. OPERATION OF THE ROBHAZ SYSTEM 56 7.1 Delivery Systems 56 7.1.1 Observation ROV 56 7.1.2 Workclass ROV 57 7.1.3 Tether Management System 59 7.1.4 Operational Limitations 59 7.2 Inspection Methods and Tools 60 7.2.1 Eddy Inspection 61 7.2.2 Magnetic Particle Inspection 61 7.2.3 Ultra Sonic Inspection 62 7.2.4 Radiographic Imaging 62 7.2.5 Video Systems 62 7.2.6 Crack Finding and Refinding 62 7.3 Possible Repair Scenario 63 7.3.1 Launch of the ROV 63 7.3.2 Attachment to the repair site 64 7.3.3 Delivery of the ROBHAZ System 64 7.3.4 Crack Finding 65 7.3.5 Drilling and Welding 65 7.3.6 Checking and Documentation 65 7.3.7 Recovery 66

8. DISCUSSION 67

9. REFERENCES 69

10. APPENDIX A 72 10.1 Harmonic Drive 72 10.1.1 The Components 72 10.1.2 The Principle of Operation 72 10.1.3 Advantages of Harmonic Drive Gears 73 10.2 Calculation of the additional pressure inside the actuators 74

11. APPENDIX B 76 -9-

1. INTRODUCTION

1.1 The Offshore Industry

The development and implementation of new technology has been the driving of the offshore oil and gas industry as it has evolved from its early days in the Gulf of Mexico in the 1940s. This focus on technology was driven by the need to search for oil and gas resources in ever deeper and more hostile environments (Figure 1). The first platforms were installed in less than 10 metres water depth in US waters. Development there continued throughout the 1960s and in the 1970s and 80s attention shifted to the North Sea where many large steel and concrete platforms were designed and put in operation. Other areas of the world also saw the development of new and innovative technologies, in particular the deepwater structures off the coast of Brazil.

Water depths in metres

Figure 1: Offshore production platform milestones, USA/1/ - 10-

Today there are more than 6,500 oil and gas platforms world-wide, located on the continental shelf of some 53 countries. Many different types of platforms and Floating Production Systems (FPS) exist as each one is uniquely designed for the particular reservoir conditions, the location where it will be installed (e.g. water depth, wind, wave and current conditions, and seabed characteristics) and the method of installation. The majority of platforms are steel structures rigidly fixed to the seabed with thick steel pipes 1-2 metres in diameter that penetrate as much as 100 metres into the seabed, Figure 2a. More than 30 piles may be required in some cases. Some platforms are gravity based structures sitting on the seabed and stabilised by their own (Figure 2b); others are floating installations, tethered to the seabed by anchor chains or in the case of tension leg platforms, by "rigid" steel tubes (Figure 3). Fixed steel platforms and concrete platforms range in water depth from only a few metres to more than 300 metres and floating installations to more than 1000 metres.

Owing to the 400 offshore oil and gas installations in Europe, more than half of Europe's hydrocarbon requirements today come from resources within its own borders.

Approximately 25%-30% of the fixed steel platforms in the North Sea are classified as large (over 4,000 tonnes weight and installed in more than 75 metres water depth), reflecting the severe environmental conditions, water depth and the size of the producing fields. They represent the greatest of large jacket Figure 2: Bottom supported structures anywhere in the world (in the Gulf of Mexico platforms /I/ less than 5% of the 4,000 platforms are large steel jackets).

To resist winds of more than 180 km/h and storm ocean waves of as much as 30 metres in height the large offshore platforms installed in the North Sea require massive amounts of steel construction. The lattice frame or jacket which is pinned to the seafloor and supports the deck with all the production and drilling equipment and living quarters to house the offshore workers can vary in weight from a couple of thousand tonnes in the southern North Sea to over 30,000 tonnes in the northern North Sea.

A typical steel platform consists of two elements (Figure 4); the "topside" containing the processing, drilling and accommodation facilities and the "substructure" or "jacket" comprising a lattice-work of steel tubes, which at their largest may reach 3 metres in diameter with a wall thickness of up to 75 millimetres.

Installations of this type typically only have a useful life of about 20 years. At the end of that time it must be decommissioned, unless it is re-used or redeveloped. Up to the end of 1995, 6 small, shallow-water steel platforms and some 25 sub-sea installations have been decommissioned in the North Sea. All have been totally removed to shore for recycling and disposal or re-used. A further 10 small steel platforms were removed during 1996/97 /2/. -11-

Currently, much of the focus of new technology is on FPS using increased application of subsea production systems, tanker unmanned satellite platforms, floating production systems, and tension leg platforms (TLPs). Some of these new facilities have been installed in water depth * ► m £ of 1,709 metres (Marlim field, Campos Basin, Brazil), with developments in water depth exceeding 2,000 metres in the planning stage.

The exploration and production of oil and gas in deep waters and from marginal fields is becoming increasingly important to Europe to ensure a continuous - yet * and independent energy supply. The advent of advanced technologies such as multiphase transport and deep water production techniques has made the FPS using semi- exploitation of such fields possible. However, the use of submersible such technologies would imply in an extension of the operational life of existing structures and pipelines beyond their design life, as well as a requirement for repair capabilities using unmanned techniques. The availability of unmanned repair capabilities would be instrumental in protecting the environment from the consequences of catastrophic failures in oil and gas producing installations in adverse and hostile fields.

Such requirement creates the need for reliable and cost- effective repair techniques which ideally should be performed without direct human intervention (diverless). As a matter of fact, unmanned repair techniques are Tension presently being developed even for standard repair and maintenance work since in this way the risks to human life are substantially reduced. The availability of unmanned repair capabilities would therefore be instrumental in prolonging the expected life of structures and pipelines, safeguarding the health of those involved. Moreover, due to its intrinsic characteristics (i.e. unmanned and fully automated) such technology would help protecting the environment from the consequences of catastrophic failures in oil and gas producing installations in adverse and hostile fields.

It seems clear that pipeline and platform repair concepts for water depths greater than 300m - 400m must focus on robotics and remote sensing if repair intervention is going to catch up with the capabilities that already exist in the drilling, production and transportation phases of the offshore industry.

l '

Figure 3: Floating platforms /!/ - 12-

Elf Enterprise PIPER ‘B’ PLATFORM | | Wellhcads/Drilling Services |; | Production m Compression M Utilities Accommodation

DECK: SIZE: aa.Sm x 38.0m (203* x 124') dimensions between main grid lines WEIGHT: 24800T target dry weight 20500T target operating weight

JACKET: BASE DIMENSIONS: 72.0m x 60.0m (236" x 1977 TOP DIMENSIONS: 72.0m x 24.0m (23 S' x 791) WEIGHT AT LAUNCH: 2214ST target launch weight

ANODES: SOOT target weight BUOYANCYTANKS: 1900T target weight (excess 15%)

PILES: 20 off 2.43m dia. (9S' dia) vertical skirt piles (5 off each comer teg) WEIGHT: 7000T target weight DESIGN PENETRATION: 6S.0M (2137

CONDUCTORS: 0 off 26* dia, lie back from template 18 oft 26" dia, platform Installed

RISERS: 301 dia Oil Export, 16" dia Gas Export 16" dia Gas Import, 16" dia Wotor Injection

CAISSONS: No 1 34* dia containing Oil and Gas Lines No 2 28* dia containing Power Cables No 3 34* dia containing Umbltlcals No 4 34" dia containing Oil and Gas Lines

Water Depth: 145m (475*) Struct Natuidl Period: 3.70 ticca Design Wave Height: 27.5m (907 100 year Design Wove Period: 15.1 to 18.5 secs Design Wind Speed: 43.4m/scc (97mph) 100 year

Figure 4: A Steel-jacket platform, Elf Enterprise /3/ The two different diverless underwater repair methods for pipelines generally employed for deep water repairs are the installation of mechanical connectors and hyperbaric welding. Various repair systems based on mechanical connectors have been designed, such as the Hydratight MOREGRIP system. Mechanical connectors are believed to offer slightly better pre-conditions for automation than hyperbaric welding and, as a matter of fact, some of the available systems have already undergone offshore trials /4/. However, they also present some disadvantages such as the requirement for accurate metrology of the contact surfaces, the likely need for dummy nodes and the lack of mechanical strength. Moreover, the efforts for pre- and post- repair activities offers no additional time benefit.

Underwater repairs on fatigue cracks in offshore tubular steel platforms in the North Sea are carried out either by dry hyperbaric welding, wet welding or by installation of clamps. Up to 250 cracks on a single platform had been found in the various dimensions /5/, whereas 450 cracks up to 2900 mm length were found on a single platform after the fabrication /6/. Some of these failures have to be repaired and the others have to be monitored. In situ repair techniques are well established, but all of them rely on divers for their implementation. -13-

Hyperbaric welding is performed inside a large, purpose built, underwater dry habitat, with a typical volume of 25 cubic meters, sealed onto the damaged area and installed by divers (Figure 5). enter the habitat and work in a dry environment. Wet welding, which means welding with the electric arc directly in contact with seawater, is currently limited to the welding of minor structures because insufficient weld quality. The reason for this is the presence of hydrogen and in the weld due to dissociation of H20 in the electric arc, and quenching by the surrounding seawater. Friction clamps or grouted clamps add weight and hydrodynamic drag to underwater structures and their performance during service life is difficult to monitor. Furthermore, they restrict access for later inspection work.

Figure 5: Special designed welding habitat at the Magnus platform at 180 msw /7/ From a technical point of view, dry hyperbaric welding is generally perceived as the most desirable repair method, but it is also by far the most costly one because of the excessive time required from a construction and with divers. The maximum water depth to which it can be used is also limited by the need for divers. The maximum depth in which divers can operate is much less than the maximum feasible depth for welding /4/. Manual pipeline welding has met the British Standard 4515 and API 1004 at 450 m simulated water depth. Mechanised orbital welding systems are presently successfully operated down to 500 m depth using gas tungsten (GTAW) and gas arc welding (GMAW) processes. The high technological level and reliability achieved in underwater welding have already encouraged the development of a system using an orbital welding set-up assisted by a manipulator which can form the basis for a future diverless repair spread. More relevant to repair in deep waters are the satisfactory results obtained with a robotic station down to 1100 msw using the GMAW process /8/.However, all these systems require the use of a welding habitat to establish a dry area around the repair location. -14-

At any rate, regard ­ less of the repair method selected, diverless interven ­ tion will have to rely on the use of Re ­ mote Operated Ve ­ hicles (ROV). There are many different types of ROV's on the market, depend ­ ing on which job they are designed for. They vary from small inspection ROV's equipped with several cam­ eras up to huge Workclass ROV's (WOROV) with big manipulators and a W lift capacity up to S| several tonnes. All ROV's are self pro ­ Figure 6: SOLO-ROV equipped for pipeline inspection pelled vehicles usu­ ally powered by a hydraulic driven propulsion system. They are linked to the surface with an umbilical for video, data and electric supply. For special jobs "tools" could be attached to the bigger ROV's and WOROV's. These tools are special designed for each kind of intervention like pipeline-inspection, wellhead intervention or pile cutting for decommissioning of platforms. All platforms in the North Sea have to be inspected once every four years. During this period every structural part has to be inspected at least once, depending on the sensibility to fatigue of the component. Appropriate inspection methods are visual inspection, Non Destructive Testing (NDT), wall thickness measurement and X-ray. The inspection is done either by divers or by ROV's equipped with the necessary tools and controlled from the sur­ face.

1.2 The ROBHAZ project

The need to reduce costs and to maximise safety of the divers is leading to the phasing out, as far as possible, of manned diving operations in the North Sea. Remotely operated systems have been developed for detection and excavation of fatigue cracks on offshore steel structures. Welding systems for underwater repair of such defects are, however, dependent on the use of divers in a dry hyperbaric "habitat" to manually weld complex geometry's on large tubular intersections, called "nodes".

Research and development done on underwater dry welding processes has shown that stable welding conditions can be achieved at depths well beyond the limits of operational manned diving (i.e. deeper than about 450 m, /9/). At the present time, however, there is no fully mechanised or robotic, diverless underwater welding system available to the industry for use at any depth /4/.

The "state of the art" hydraulic manipulators, currently in use on ROV's offshore, are not capable of moving with the degree of precision required for welding operations. Amongst -15-

the current systems on the market, only electric robots can achieve the necessary precision of ±0.2 mm/10, 42/. Teleoperated electric robot arm repair welding systems developed so far for the nuclear industry have been expensive "one off" units which are capable of producing only single pass fillet welds on thin material, and have not yet been adapted for underwater use. Steels used on offshore platforms and ship hulls are relatively thick (typical 25 mm).

The project "Affordable Underwater Robotic Welding Repair System" - ROBHAZ -, carried out in the framework of the BRITE-EURAM programme, intends to develop welding repair techniques and affordable robotic equipment which can be readily available to underwater inspection and maintenance contractors, operating in offshore, maritime and nuclear industries /U/. The technology developed will replace the use of men in hazardous underwater environments. In order to achieve this, recent advances in lower cost industrial robotics, sensors, control systems and computers will be exploited.

Figure 7: The ROBHAZ system on a node of an offshore platform /12/

A submersible welding robot arm with a controller, will be developed to deploy and move the welding system. The prototype robotic welding system will be delivered to and clamped on underwater node sections on offshore platforms by a Super Work Class ROV, of the type presently used by underwater contractors (Figure 7). Such a system can also be used without the assistance of a Remotely Operated Vehicle in a nuclear power plant.

This equipment will also be suitable for in-water inspection and repairs to large ships in the maritime transportation industry (Figure 8). Costly unscheduled dry-docking can therefore be avoided by performing inspection and repair in-water, while large vessels such as oil tankers “16“

and container carriers are transferring cargo in ports. In the future it will be possible to perform the majority of hull survey, inspection and maintenance cleaning and repair tasks using robots. The ROBHAZ project will make an important contribution towards this objective.

The technology to be developed will also have applications for repair welding or cutting in other hazardous environments such as the nuclear and chemical industries. The results of this project will be exploited to provide Figure 8: The ROBHAZ system on a ship hull /12/ an affordable system which can weld cracks and perform other intervention tasks in nuclear fuel storage facilities and further areas of nuclear power plants.

The welding process used will be friction hydropillar welding (FHPP), which has recently been developed for welding thick steels either under normal dry conditions or directly in water (Figure 9) /13/. This technique involves drilling a hole (typically 10 mm diameter) in the crack and filling it by rotating a consumable steel bar in the hole producing a friction weld. This operation is completed in a few seconds. Cracks are repaired by producing a series of such welds overlapping each other (Figure 10). During this project a hydraulically powered friction hydropillar welding head will be developed for deployment on the submersible electric robot arm. An axial pressing force of approximately 1,500 kg will be necessary to fill a hole of 10 mm in diameter. In addition to this a high torque has to be applied depending on the- shape of the hole and the bolt. The deployment system should take all these loads but also has to provide the necessary precision and flexibility. The NEOS TRICEPT (a) Consumable industrial robot fulfils the basic mechanical requirements (b) Plasticised zone (i.e. carrying load) for such a repair operation. Therefor it (c) Pillar of extruded material has been selected for the marinisation concept.

Figure 9: The Principle of Friction y^g NIEOS TRICEPT industrial robot, designed for heavy Hydropillar Processing/13/ duty processing and high speed machining, will be modified to deploy the welding head, take all the process loads during drilling and welding as well as the milling or grinding of the surface after each weld. The robot will also be used to do the pre- and post- inspection with NDT techniques. 17

Friction Jink Friction link — interlocking • • . ■ - • ■ dovetail arrangement

Figure 10: Typical Joint Configuration for FHPP/13/ -18 ”

2. MODIFICATION OF A MANUTEC R15: A REVIEW

2.1 Project background

The research and development programme on underwater techniques of the GKSS research centre began in 1986. An increasing need of automatic subsea intervention - especially the repair of jackets - was expected due to the growing number of old offshore installations.

Further applications were envisaged in connection with the increasing exploitation of oil and gas fields in very deep water, where, due to high pressure, manned intervention is often not possible. One to facilitate operations in such an environment would be a subsea production unit which was built, inspected and maintained by an intelligent underwater handling system. Based on this range of possible applications, GKSS initiated a comprehensive research and development programme in underwater techniques. Part of this programme was a prototype of a handling system called OSIRIS (Offshore Integrated Robot Inspection System). Its main components are a ROV for the transport to the location and the docking to the structure and a modified industrial robot for Non-Destructive Testing (NOT), repair tasks and related work /14/.

Figure 11: Siemens MANUTEC r15 robot - 19-

This robot had to satisfy the following specifications /14/:

- high kinematic flexibility with at least 6 degrees of freedom - ability to withstand the loads of tools and reacting forces of running processes such as high pressure water jet cutting - high positioning accuracy for the NDT - closed pressure-tight or pressure-compensated case to avoid seawater leakage into the inside of the unit - modern robot control unit with interfaces for sensor signals and off-line programming

Amongst the systems on the market, GKSS chose the SIEMENS robot MANUTEC r15 as the robot seemed to be easily modifiable to satisfy these criteria. -20-

2.2 The MANUTEC r15

Table 1: Technical data of the industrial version of the MANUTEC r15 robot Industrial version with six electrically actuated axes Kinematics Axis range of rotation maximum rotary (jointed arm; 6 axes) speed 1 ±165 degree 200 degree/sec 2 ±110 degree 100 degree/sec 3 +135 degree 200 degree/sec 4 ±190 degree 365 degree/sec 5 ±120 degree 400 degree/sec 6 ±265 degree 280 degree/sec Positioning accuracy ±0.1 mm Speed PTP: max. 5.9 m/s LIN: 1.5 m/s Acceleration PTP: centrifugal max. 18 m/s2, tangential max. 9.3 m/s2 LIN: max. path acceleration 6 m/s2 Load capacity nominal oad capacity: 15 kg nominal moment at axis No. 6: 22 Nm moment of inertia at axis No. 6: 0.34 kgm2 Working volume spherical radius 1.30 m Drive permanent excited brushless three-phase servo motors Position control incremental optical position encoder Material of housing aluminium Power supply 380 V, three-phase current ±10%, 50/60 Hz, about 1.2 kVA Weight 320 kg Operating condition : 0 - 45 °C humidity: 20 - 90 % relative

2.3 Modifications

In order to limit development costs, R&D work was initially focused on the adaptation of the robot forearm (axes 4, 5 and 6). to seawater conditions /15/. The idea was to adapt the robot subsystem to withstand an outer pressure of 110 bar by filling the forearm with a pressure compensation fluid /16/. A membrane would lead the outer pressure into the fluid to generate pressure equilibrium between seawater and fluid (Figure 13). Due to high pressure and the total flooding with compensation fluid in the inside, a number of modifications turned out to be necessary. Figure 13: Pressure Compensator - 21 -

2.3.1 Compensation Fluid

This fluid had to meet a number of quite diverse requirements /17/. Low viscosity is necessary for acceptable performance of the electric motors, good lubrication is required for the gears, and the optical encoder needs adequate optical qualities of the fluid. In addition, it should provide electrical insulation and be chemically inert, (see also "Electrical connections" page 24). During tests, the synthetic fluid FOMBLIN was found to be most adequate for these purposes, although the mineral oil OPTIMOL performed acceptably as well /15/. Due to economical reasons, FOMBLIN was used only for the tests with the robot-forearm. Later on the cheaper OPTIMOL was used to fill the whole modified robot /18 /.

2.3.2 Optical encoder

The position, acceleration and speed of each axis of the robot is measured by photoelectrical scanning of a very precise partition with an incremental optical sensor (Figure 14).

A small lamp with a condenser lens produces a bundle of parallel light beams. This light bundle passes through the scanning reticle before reaching the photovoltaic cells (Figure 15). Placed in the gap between the scanning reticle and the photovoltaic cells is a rotating graduated disk which is fixed to the axis of the motor. The size of the fissures in the scanning reticle is the same as in the graduated disk. Each encoder contains four photovoltaic cells. Rotation of the graduated disk causes light pulses to the photovoltaic cells. Analysing of the pulses on the four photovoltaic cells yields a very accurate measurement of position, acceleration, speed and the direction of rotation of each robot axis. The graduated disk also has a reference mark to define the zero position.

On account of the different optical properties (reflection, Figure 14: Optical encoder with diffraction) of oil in comparison to air the encoder had to graduated disk be modified.

Another problem was caused by small gas bubbles which appeared in the fluid when decompressing the system. When these gas bubbles came into the trajectory of the light rays, the light was partially reflected at the bubble surface and the sensors failed. To avoid inaccurate sensor data, two alternative approaches were investigated /17, 19/. The first one used an additional lens to compensate the different indices of refraction. The second approach required encapsulation of the lens system. The lamp was substituted by an infrared lamp which was encapsulated in air together with the condenser lens into a pressure-tight housing. In addition to this, the gaps between the rotating graduated disk and the photovoltaic cells and between the rotating graduated disk and the scanning reticle were reduced to 0.5 mm to minimise gas bubble penetration. Both alternatives performed well in several tests, but only the version with the encapsulated lens system was used for the modification of the entire robot system. The system with the additional lens was too easily confused by the small gas bubbles. -22-

Condenser lens it source Scanning reticle

Graduated disk Photovoltaic cells

Figure 15: Function of HEIDENHAIN encoder /20/

2.3.3 Brakes

The function of the brakes is to hold the robot in position when the system is switched off. During operation, an electrical counterfield is generated which compensates the magnetic field of the permanent magnet and releases the brake. If movements cannot be prevented during the switch-off period, the robot has to be calibrated before any further work. To achieve the necessary performance of the magnetic brakes in oil the gap between the permanent magnet and the brake lining was minimised and Figure 16: Optimised brake for axis 4 the radius of the friction surface was enlarged. Additionally stronger magnets were used /21/and the brake lining were ground very accurately. -23-

2.3.4 Casing In view of the compensation fluid inside the case, additional sealing was necessary. When ­ ever possible, packing cord sealing in milled grooves was used, and otherwise paste ­ sealing was chosen. During the tests, this kind of sealing did not prove to be sufficient and alter ­ native means of sealing need to be investigated. All cavities inside the cases had been connected to each other to ensure the complete filling of the robot. Cavities not filled by compensation fluid would lead to a extreme increase of tension in the housing which might col­ Figure 17: Part of the robot casing with paste-sealing lapse when pressurised /17/.

During initial tests with the ro­ bot forearm in seawater, rapid corrosion of the aluminium case occurred after only a few hours of use. This problem was overcome first by coating the case, and later by using a more suitable aluminium alloy for the prototype.

Figure 18: Corrosion attack during initial tests with the robot forearm

2.3.5 Joint sealing

The revolute joints of each axis had to be improved by a special sealing. Due to limitation of space, it was not possible to add such a sealing without changing the construction of the case. After preliminary examination, auxiliary flanges were mounted in-between each revolute joint. In these flanges a sealing system consisting of a combination of a Teflon ring and an o-ring was included /17/. This sealing showed good running qualities and tightness without impairing any of the robot's functions. -24-

2.3.6 Limit switches

These inductive switches are posi ­ tioned inside the robot case and re ­ strict the rotation angle of each axis. They contain an inductive coil and some electrical components cast in a plastic compound. During preliminary tests in gas atmosphere under pres ­ sure up to 110 bar, several switches malfunctioned. The reasons for these defects were enclosed gas bubbles in the plastic casting, which collapsed under increasing pressure, destroying inner components /14/. It was found that this was no systematic failure, and switches without defects were se ­ lected by performing a selection test at Figure 19: BERO limit switch 160 bar on a large number of switches.

2.3.7 Electrical connections

All cables to the underwater control unit and to the robot have been exchanged for water-tight cables with wet connectors. The cables inside the robot have not been changed. After several years, the isolation of some of these cables have become brittle, others have become soft. In tests, the isolation of the cables became brittle because of out- of the sof­ tener. Softener was therefore added to the compensation fluid in an adequate concentration. Because of the great number of different types of isolations it was not possible to find a Figure 20: Electrical connector for underwater use mixture to guarantee long-life conditions during prototype examination /14/. To avoid such problems in the future, all cables with contact to the compensation fluid should be of the same material to allow a better balancing of the fluid.

2.3.8 Control unit

The maximum distance between the robot and the control unit is limited to 30 m. For the planned combination of a ROV and an additional arm wearing the robot (OSIRIS System /14/), a new control system for 8 axes and up to 20 ms increased cycle time was developed. The new control unit was divided into a topside commanding PC and the control equipment close to the robot itself. This system was designed to fit into a pressure tight housing near the robot (Figure 21) /22, 23/. This configuration allows to increase the distance between operator and robot from 30 m up to 2500 m /24/. -25-

2.4 Test Programme

2.4.1 Pressure Tests

After a series of atmospheric tests, wet trials in a water depth of 6 m were per ­ formed with the entire system /18/. During these tests some pre ­ programmed tasks were executed. The same programme was repeated in a pressure vessel in simulated water depth of up to 1000 m.

2.4.2 Power consumption

In order to get information about the hy ­ drodynamic forces on the robot, the electrical power for each motor was monitored. The electric motors for the horizontal axis showed a reduced power consumption owing to the buoyancy of the robot. However, the electric motors for the vertical axis had an increased power consumption because of the increased drag under water. In the course of operation from still to streaming water conditions there was an increase of power consumption of up to 20 % at 1 m/s water current /25, 18/.

Figure 21: MANUTEC r15 UW with underwater control unit as used during pressure tests 2.4.3 Positioning accuracy

The first trials to monitor the positioning and repetition accuracy were done with the robot forearm (three axes only). To measure the accuracy, a lightning torch was mounted on the end effector of the robot forearm. The task was to position this torch in front of a separate scanning reticle, which was observed by a video camera. The video-records allowed to measure the achieved accuracy. The positioning accuracy of the complete robot prototype under water was monitored by moving a sensor cube along two reference rulers /21/. The cube was fixed to the hand of the robot and equipped with eddy current sensors to measure the deflection between the cube and the ruler caused by hydrodynamic forces. For the trials the rulers were either located at the foot of the robot or at the equator of the workspace and positioned where the robot showed its maximum silhouette against the water current. The distances between the sensor cube and the ruler were measured for the two ruler positions and in water current up to 1.1 m/s. A maximum deviation of 0.5 mm was found in both position and path. This deviation is mainly the result of gearing backlash and elastic deformation of the arm induced by the drag of the robot. The orientation failed less than 0.1 degree in all directions. - 26-

2.4.4 Sensor feedback

For remotely controlled systems sensor feedback is essential. Initial trials to enhance the positioning accuracy by sensor feedback gave good results /21/. But with regard to the data processing and the working speed an improvement of the system is necessary.

2.4.5 Frequency analysis

The natural frequencies of the MANUTEC r15 UW robot have been determined for three different poses in air as well as under water. The natural frequencies were found to be between 10.9 and 13.4 Hz in air depending on the robot's position and 5-9 % less under water /21/. These frequencies are far away from the frequencies of excitation from turbulence and eddy formation. Tests indicated that a impairment should not be expected.

2.4.6 Inspection

Different types of inspection methods have been tested in an experimental programme using a pipe node mock-up /14/. Ultrasonic testing as well as visual inspection by CCD- camera have been performed on a circumferential welding seam. The robot was also able to change tools during the tests by using a modified tool changing device, which was developed for underwater use /26/.

Figure 22: MANUTEC r15 UW, inspection of a weld on a pipe-node-mock- up in the GKSS C2-pool -27 -

2.5 Industrial Application and Certification

2.5.1 Offshore relevant work

The results of the robot development programme showed the potential of automation for . For demonstration purposes, several tasks on a mock-up of a deepwater template have been performed. A quarter section of a PETROBRAS deepwater template "OCTOS" was built to test the connection, disconnection and exchange of electrical connectors in a completely remote manner at 100 bar in a pressure chamber. The work has been conducted automatically in an extended experimental programme/1 4/. -28 -

2.5.2 Certification

The modification of the MANUTEC robot has been performed in close co-operation with THE GERMANISCHER LLOYD (GL) to ensure that the various certification-criteria were met /27, 28, 29, 30/.

The following tests were performed:

- function of improved brakes in oil - function of the robot after collisions - function under arctic and tropic of the surrounding water - extended operation time in dry and wet environment - repeatability of position, path and orientation - electrical insulation and high-voltage safety - function of the robot during changes of the supply voltage to consider the GL-rules for operation with power supply from a vessel.

A GL-certificate containing the results of these tests was issued which certifies, that the robot prototype has been successfully modified to work under subsea conditions down to 1100 msw. A robot based on these design criteria and modifications will be suitable for deep water application /31/.

2.6 Discussion

As mentioned above the modified MANUTEC robot fulfilled all certification criteria and passed several test programmes without any major problems. However, an intensive review of the 11 year development process indicated some points which should be changed in further developments. Although the modification of the optical encoder was very time consuming and expensive, the encoders are still susceptible to malfunction due to debris or gas bubbles in the oil. In addition to this, requirements on the compensation fluid are rather stringent. Nowadays, most robots use inductive resolver, which are less sensible to the environment. Resolver have the additional benefit of allowing for an absolute measurement system which might be main-power independent. In case of a collision shut-down of the control unit these robots do not have to be re-calibrated because the information about the robot's position will be monitored even during the main power shut off. Today a more suitable compensation fluid might be on the market with diminished impact to the internals. In the meantime the used OPTIMOL changed the isolation of the electrical cables to an uncertain amount. Some cables become brittle while others become soft. If it turned out not to be possible to find a fluid with no interference to all the different electric components, all cables would have to be changed to the same type of isolation material. The paste sealing show several leakage's which might be the result of the small over ­ pressure for several years and the oil tunnelling the sealing. The contact between the sealing and the aluminium housings is rather poor at some places, which might be the effect of aluminium oxide. The whole sealing concept should be reviewed and where possible the paste sealing should be changed to O-rings. Due to the paste sealing mentioned above and the restrictive requirements for purification of the oil, the maintenance of the robot is very complex. It will be very difficult to guarantee these requirements during a repair offshore on a vessel deck. For the industrial use offshore the robot would have to be modified to allow easy maintenance. In addition to this the coating should be changed for a more resistant type to withstand scratches and collisions. -29-

The protection of the applied coating is poor and the unprotected aluminium housing would corrode after seawater contact. Even the improved brakes are sometimes too weak, for instance if the robot moves a heavy tool. Under water the additional buoyancy of the robot decreases the applied load on the brakes to an adequate amount. If the MANUTEC should be implemented on a tool for a ROV, the underwater control pods should be reviewed in order to accommodate the control unit in more suitable and smaller electronic pods. This would decrease the size and weight of the tool and allow the use in more restricted areas. Even after 11 years of extensive development in underwater technology this MANUTEC r15 robot is still a unique system for remote underwater intervention. - 30 -

3. TRICEPT TR600

3.1 General Description

The Tricept TR600 robot (Figure 24) is an industrial robot with six degrees of freedom built on a frame structure to ensure maximum rigidity. The design characteristics make it suitable both for precision handling and heavy duty processing. Its capacity and high accuracy make it suitable for applications such as: high speed machining of wood and plastic, aluminium and steel, deburring drilling and polishing, riveting and precision / heavy assembly.

This robot can be characterised by the following performance data:

- Maximum pressing force: 15 000 N;

- Extremely rigid construction for reducing bending deflection and oscillations;

- Path following and accuracy figures comparable to the ones of many NC machines;

- Extremely compact wrist design (see 3.5.3 Wrist Assembly, page 39);

Provisions for fitting optional devices:

- The robot centre tube has internal channels for cabling or pneumatic lines.

- The wiring includes an independent service line connected to the distribution signal assembly, equipped with a connector on the upper part of the robot centre tube.

Figure 24: TRICEPT TR600 robot - Optional accessories include a kit for mounting additional tools and equipment on the lower part of the robot centre tube. -31 -

The robot is operated by a Comau C3G control system (Figure 25) which is able to execute various processes that can be programmed by the user. The processes may be either for logic functions or controlling of point-to-point or continues movement with linear and circular interpolation.

Figure 25: Comau C3G 901 Controller 3.2 Axes Definition

Figure 26 presents an schematic view of the axes configuration of the TRICEPTTR600. - Axis 1: Linear axis, moves the robot platform when working in parallel with axes 2 and 3.

- Axis 2: Linear axis, AX. 1 AX. 3 moves the robot AX. 2 platform when working in parallel with axes 1 and 3.

- Axis 3: Linear axis, moves the robot platform when working in parallel with axes 1 AX. 4 and 2 i % Z7X+ 4?FT^ - Axis 4: Rotation of the robot wrist around the robot centre axis. Tp

- Axis 5: Rotation of the wrist on an axis at jsb right angles to the AX 6 robot centre axis. Axis 6: Rotation of Figure 26: Definition the tool mounting flange around its axis. -32-

3.3 General Features

3.3.1 Technical Data of the TRICEPT Robot

Table 2 presents the performance features of the TRICEPT TR600 robot.

Table 2: Technical data of the industrial TRICEPT TR600 robot Number of axes 6 Stroke (speed) Axes 1, 2 and 3: 600 mm (0.33 m/s) Axis 4: ±300° (270°/s) Axis 5: ±115° (267°/s) Axis 6: ± 3600° (270°/s) Speed in trajectory control 0.9 m/s Speed point-to-point, max. 1.5 m/s Cycle times PTP 1000 mm: 0.8 s Neos Cycle (1): PTP, rounded corners (fly): 2.9 s PTP, sharp corners: 4.2 s linear, rounded corners (fly): 4.7 s linear, sharp corners: 6.1 s Repeatability ±0.02 mm Positioning accuracy ±0.20 mm Path following accuracy at 0.2 m/s ±0.10 mm Incremental motion 0.01 mm Static bending deflection X and Y directions: 0.0003 mm/N Z direction: 0.0001 mm/N Max. load on wrist (2) 60 kg Max. total load 100 kg Max. pressing force (3) 15000 N Max. lifting capacity 100 kg Max, static torque Axis 4, 5 and 6:137 Nm Positioning measurement system (feedback) Absolute with resolver Type of motors AC synchronous brushless Ambient temp, range 0-45 °C Robot Weight 520 kg Software limits Standard and programmable on all axes Assembly position Vertical, other positions on request Stand Optional 1) Neos cycle: 200mm vertical up, 1000mm horizontal, 200mm down and return the same way. 2) See Figure 27; Maximum Load on Wrist 3) See Figure 27; Maximum Pressing Force -33-

3.3.2 Work envelope / Pressing capacity

Figure 27 shows the work envelope and the pressing capacity of the TRICEPTTR600 robot.

Work Envelope / Pressing Capacity

3SOO N 3500 N 3500 N

3500 N 3500 N 3500 N 3500 N 800 • 3500 N 3500 N 3500 N 3500 N

1200 • 15000 N 15000 N

1200 800 -100 1200 (mm) 1600 1200 800 800 1200 (mm) -Y + -X-

Load on Wrist

1600 1700 800 400 400 800 1700 (mm) 200 400 600 800 (mm) Y. X

Figure 27: Work envelope, pressing capacity and load on wrist

3.4 Functional Description

3.4.1 General Movement

The movement of all axes is controlled by sinusoidal AC brushless motors. These reduce the need for maintenance and have the advantage of lower inertia and greater heat dissipation. There are two types of motors, one type for the three linear axes, 1, 2 and 3, and another type for the three rotary axes, 4, 5 and 6. The motors for axes 1, 2 and 3 are built with internal resolver and brakes. The frameless motors for axes 4, 5 and 6 are directly integrated into the wrist design and the centre-tube together with a separate brake and resolver.

For the three linear axes, ball screw actuators are used. The three rotational axes are moved by "Flarmonic drive" reducers (see 10.1 Flarmonic Drive, page 72). -34-

The robot structure has been designed to integrate, as far as possible, the diverse functions of the various parts of the machine.

For the linear axes internal mechanical limit stops ensure personal safety as well as machine protection. For all axes software limit stops are programmable.

3.4.2 Axes Position Measurement System

Axes position measurement is absolute with one resolver built into the motor and one RPT (Resolver Position Tracker) absolute transduction module housed in the robot distribution signals assembly.

The fact that there is only one resolver, with no joint and built into the motor, means that fewer cables are used between the control system and the robot, which considerably increases system reliability.

Position Definition

SERVO AMPUF1ER ROBOT MOTION CONTROL ANALOG CURRENT TORQUE . REFERENCE POSITION TRAJECTORY AND VELOCITY MOTOR GENERATOR CONTROLLER

RESOLVER

RESOLVER ® PATENTED POSITION TRACKER'

Figure 28: Servo control system (Patented by CO MALI)

The absolute transduction function is performed by the RPT module, mounted on the robot. This module supplies the transducers with energy and reads the robot axes position even when there is no mains voltage or no connection between the control system and the robot, and consequently replaces the signal provided by the control system.

The count of revolutions of every robot axis resolver is stored in non-volatile memory (with a back-up battery), hence the absolute position of the different machine axes is always available.

The RPT module also contains information about and characteristics of the robot on which it is installed, such as: number of axes, electrical and mechanical characteristics, as well as robot code number. This allows the control system to check for system congruity. -35-

Figure 28 shows the control system-to-robot interconnection block diagram for axis position definition.

The motor is a sinusoidal current generator driven by a torque reference on two vectors. Depending on the axis position values provided by the resolver, the control system will close both position and speed loops and will supply the drive with the torque analogue reference.

Back-Up Battery

The back-up battery allows the RPT module to work even when there is no external power supply and to retain the data for up to 600 hours. It has a recharge circuit that is enabled when the control system is switched on.

The battery retains the resolver revolution count for each axis as well as some data about the robot on which it is installed. -36-

3.5 Mechanical Description

Figure 29 presents an schematic view of the TRICEPT robot.

1. Axis 4 motor assembly 6. Centre shaft 2. Spiral cable 7. Wrist assembly 3. Axes 1,2,3 motor 8. Gyro assembly 4. Main structure (YOKE) 9. Actuator assembly 5. Cardanic joint 10. Linear bearings

Figure 29: Robot mechanical parts -37 -

3.5.1 Linear Axes

Design of the Linear Axes

The linear axes, or actuators, (axes 1, 2 and 3) connect the main structure, the cast iron "yoke", with the "platform" (see 3.5.2 Centre Axis, page 37) via cardanic joints at the lower end of the actuators (Figure 30). The "yoke" supports three forks connecting the actuators to the "yoke". Several pairs of pre-loaded angular contact bearings are used for these joints. Owing to this the bearing clearance is neglected to achieve the necessary precision of the robot. Any uncorrectness in these points would cause a five times bigger unprecision at the end effector.

Each linear axis consists of a motor rotating a ball screw, which in turn is drives the pushrod that moves the platform through the cardanic joint. The motor includes an electromagnetic brake and an inductive resolver. The actuator housing is made of aluminium and the pushrod is made of steel.

1 Motor unit 2 Pushrod 3 Cardanic Joint Figure 30: Linear Actuator

Axes 1, 2 and 3 motion transmission

The linear axes, or actuators, (axes 1, 2 and 3) move the platform, and thus the wrist, in a pendulum-like motion, with centre in the gyro assembly.

The motion is transmitted from the motor via the ball screw and pushrod to the cardanic joint and the "platform" Figure 30.

3.5.2 Centre Axis

Design of the Centre Axis

The centre axis (Figure 31) consists of the platform (1), the centre tube (2), the centre shaft (3), the spiral cable (4), the gyro assembly, the axis 4 motor assembly (5) and octagonal housing (6). -38 -

The centre axis transmits the rotational forces of the wrist to the main structure via the gyro assembly. It also transmits the rotation of axis 4 through the centre shaft to the wrist assembly.

The platform is made of cast-iron and contains the cross roller bearing that supports the wrist assembly.

The centre tube is made of extruded aluminium, and is the main torque transmitter from the wrist assembly to the main structure. The torque is transmitted to the gyro via the linear bearings. Inside the centre tube, channels provide space for the necessary installations to supply electricity and other media to the tool.

The gyro assembly is made of cast iron and provides a path for the torque from the centre axis to the main structure. The centre shaft is at one end flanged to the robot wrist and at the other end mounted to the output flange of the axis 4 reducer.

The axis 4 motor assembly is similar to the axis 5 and 6 motor assemblies. The motor is mounted with the reducer flange of the "Harmonic Drive" gear box to the centre shaft, and the motor housing to the top lid of the axis 4 octagonal housing. The motor assembly includes an electromagnetic brake and an inductive resolver. Figure 31: Centre Axis (axis 4)

Axis 4 motion transmission

The axis 4 rotates the wrist around the centre tube. Its movement is transmitted from the motor via the "Harmonic drive reducer" to the centre shaft. The centre shaft conducts through the centre tube to the wrist assembly. -39-

3.5.3 Wrist Assembly

Figure 32 shows the wrist of the TRICEPT TR600 robot.

Figure 32: TRICEPT TR600 wrist -40-

Wrist Design

The wrist assembly (Figure 33) consists of the oscillating axis 6 housing (1), of the "claw" (2) (the axis 5 housing) and of the supporting plate (3).

The axis 6 housing is made of cast iron and contains the motor unit of axis 6 (4), and the "Harmonic Drive" (5) and brake of axis 5. The axis 5 motor (6) is mounted in the claw. The axis 5 motor shaft, thus, passes directly through the axis 6 housing from the axis 5 motor to the "Harmonic Drive". The claw is made of cast iron and contains, in addition to the axis 5 motor, the axis 5 resolver. The motor unit of axis 6 is very similar to the motor unit of axis 4 and consists of an electric motor, an inductive resolver, an electromagnetic brake and the "Harmonic Drive" gear as the output flange. Figure 33: Wrist assembly The output flange of axis 5 reducer is connected to the fixed supporting plate (3) and rotates the axis 6 housing around axis 5.

The forces from the external load are transmitted to the structure via the cross roller output bearing inside the "Harmonic Drive" of axis 5 and the roller bearing connecting the axis 6 housing to the claw.

The wiring from the centre shaft passes through the top of the claw. The axis 5 motor and resolver cables are lead to their respective units, and the rest of the cables are lead into the oscillating axis 6 housing.

Axis 5 motion transmission

Axis 5 rotates the wrist along an axis at right angles to axis 4. The movement from the motor is transmitted to the "Harmonic Drive" output flange. The output flange is connected to the fixed supporting plate, thus moving the axis 6 housing.

Axis 6 motion transmission

Axis 6 is the rotation axis of the robot output flange (Figure 33, No. 8 - tool mounting). The motion of the motor is transmitted via “Harmonic Drive" reducer directly to the output flange. The flange is fixed on top of the dynamic spline of the gearbox. -41 -

3.6 Electrical Connection

The robot wiring is designed to limit the number of sectioning to a minimum and to improve reliability. From the distribution panel four bundles of cables lead to the robot. One bundle leads to each of the linear axes, 1, 2, and 3 and one leads to the three rotational axes, 4, 5, 6.

The cables for each of the three linear axes may be passed trough the column via the holes in the main structure and connected directly to the motor of each axis. The cable for the three rotational axes is connected to the octagonal housing of axis 4, where the spiral cable transmits the signal internally to each of the three axes.

The distribution signal assembly interfaces between the robot (motors and resolver), the control system and the electrical power supply. It houses the back-up battery, the RPT module and the interconnections between input and output connectors. - 42 -

4. THE MARINE ENVIRONMENT

Parts of this section have been taken from 1321.

There are many different environmental conditions to be found in different offshore areas world-wide. The North Sea is known to have the most challenging conditions altogether, which becomes apparent in the design and type of installations in contrast to moderate areas. Depending on the type of installation the structures are exposed to several subenvironments like the marine atmosphere, the splash zone, the subsea and the subsoil zone. Exposure could be continuously or intermittent to one or also simultaneously to all of these zones.

The following extremes have been monitored in the northern North Sea off the Norwegian coast I5J:

Wind speed 40 m/s Wave height 17 m Water current 1.75 m/s at 10 m water depth 1.11 m/s at 800 m water depth Monthly mean sea temperature 6 ... 12 °C at 0-20 m water depth -1 °C more than 1,000 m water depth Monthly mean air temperature 3 ... 13 °C Extreme temperatures -10 ... 23 °C

In addition to these environmental conditions submerged installations have to withstand the hydrostatic pressure, equivalent to the water depth. The maximum depends on the design depth of the structure.

For ROV's and tools like the ROBHAZ tool, temperature variations might be of significant value. The deepwater temperature can be as low as -1 °C, whereas the tool could be heated up in the sun on the vessel deck to temperatures higher than 30 °C. This high temperature could cause condensation inside the robot or the electronic-pod of the ROV. The different coefficients of thermal expansion of the various materials should not cause any problems in face of such temperature differences. However, critical assemblies should be checked for this problem, to ensure a correct fitting for all environmental conditions.

The chemical activity of seawater causes marine corrosion. This includes the deterioration, of structures and vessels immersed in seawater, the corrosion of machinery and piping systems that use seawater for cooling and other industrial purposes, and corrosion in marine atmospheres. Although saline water is generally considered to be a corrosive environment, it is often missed how corrosive saltwater is in comparison to other environments, such as fresh (salt-free) water. Figure 34 shows the Concentration of NaCI, wt% corrosion rate of iron in aqueous sodium chloride Figure 34: Effect of NaCI (NaCI) of various . The concentration on the corrosion rate maximum corrosion rate occurs near 3 % NaCI, the of iron in aerated room-temperature approximate salt concentration of seawater/34/. The solutions mean surface salinity in the North Sea varies between 3.0 and 3.5 %. Whereas the salinity changes during the year and with the water depth /35/. - 43 -

4.1 Galvanic Corrosion

Whenever two dissimilar are placed in electrical contact and immersed in seawater, galvanic corrosion will take place, with the less resistant material corroding faster and the more resistant slower than either one would alone. The galvanic series allows one to predict which of the two metals will suffer accelerated corrosion (i.e., which will be the anode). It also allows one to say in a very qualitative way how severe the corrosion damage is likely to be. In the galvanic series presented in Fehler! Verweisquelle konnte nicht gefunden werden., metals and alloys are listed in order of decreasing inherent corrosion resistance. One indicator of this resistance is their electrochemical potential in seawater, measured as the potential difference between the alloy in question and a saturated calomel reference (SCE).

Table 3: Galvanic series of metals and alloys in seawater (abstract from /32/) Alloy Potential Range on Saturated Calomel Scale [V] Graphite +0.3 .. . +0.2 Platinum +0.35 . .. +0.2 Tantalum about +0.2 Titanium and titanium alloys +0.06. .. -0.05 300 Series stainless steels (passive) -0.00 .. .-0.15 Monel 400 -0.04.. .-0.14 Silver -0.09 .. .-0.14 99.99% about -0.14 Inconel 600 (passive) -0.13 .. .-0.17 Molybdenum about -0.17 Common lead -0.19.. . -0.25 Tungsten about -0.24 430 and 431 (passive) -0.20 .. . -0.28 80-20 Copper-nickel -0.21 .. . -0.27 90-10 Copper-nickel -0.21 .. . -0.28 410 Stainless Steel (passive) -0.24.. . -0.35 Red -0.20 .. . -0.40 Aluminium -0.30 .. . -0.40 Inconel 600 (active) -0.30 .. . -0.42 Austenitic nickel cast irons -0.35 .. . -0.47 300 Series stainless steels (active) -0.35 .. . -0.57 410, 430 and 431 stainless steel (active) -0.45 .. . -0.57 High strength steels -0.60 .. . -0.63 Low alloy steels -0.57 .. . -0.63 Plain carbon steels -0.60 .. . -0.70 Cast iron -0.60 .. . -0.72 Aluminium alloys -0.70 .. . -0.90 -0.98 .. .-1.03 99.99% Aluminium -1.25 .. .-1.50 Magnesium -1.60 .. . -1.63

The lower the metal or alloy is placed on the list, or the more negative (active) its potential, the more likely it is to suffer accelerated corrosion. Conversely, the higher the metal is on the list, the more positive (noble) is its potential, and the less likely it is to corrode. For each metal, a range of potentials is given rather than a single value. Some materials, especially - 44 -

stainless steels, have two positions on the series, one corresponding to the passive or noncorroding state and the other to the active or corroding state. If any two materials from this series are coupled and immersed in seawater, the one that is lower on the list will become active or anodic and will suffer accelerated attack. The one that is higher on the list will become cathodic and will corrode slower, if at all.

It should be mentioned, that graphite has a very noble potential and is often used in the form of carbon black as a filler or UV stabiliser in plastics. If such a plastic is brought into contact with an active metal such as an aluminium alloy, it may cause serious corrosion damage to the aluminium.

The rate of attack on the anodic member of the couple depends primarily on two factors 1321:

1. The potential difference: The farther apart the two materials are on the list (or the greater the potential difference between them), the more severe will be the accelerated attack on the anodic member of the couple. Conversely, materials close together on the series can often be coupled without adverse effects. 2. The cathode-to-anode area ratio: The larger the ratio of the exposed surface area of the cathodic member is to that of the anodic member, the more rapid will be the rate of attack on the anodic member.

There are several possible approaches to avoid or minimise galvanic corrosion problems:

- If possible, all parts of a given structure should be made out of the same material.

- When the same material cannot be used for all parts of the structure, dissimilar metal parts should be electrically isolated with plastic gaskets and washers.

- Large cathode-to-anode area ratios should be avoided. This can be done by making small or crucial parts of the structure (nuts, bolts, washers, cotter pins, etc.) out of the more noble material. When using coatings, always paint the cathodic or noble member, to decrease its exposed surface area. Painting only the anode is dangerous because a scratch in the coating will produce a large cathode-to-anode area ratio, leading to a high rate of attack on the bare metal exposed at the scratch.

- Installation of a sacrificial anode of a third metal that is more active on the series than either member of the original couple.

4.2 Material Selection

It is neither economically nor technically reasonable to make all parts of the TRICEPT robot, which might get in contact of seawater, out of the same material. To prevent corrosion a sufficient coating and sacrificial anodes should be considered. Galvanic corrosion problems might occur at points like drill holes for the bearings, where coating might not be possible. Direct contact of steel and aluminium should be avoided wherever possible, or these joints have to be very carefully protected for seawater contact. Not only metal alloy combinations are critical for corrosion, but also PVC plastics cause accelerated corrosion on austenitic steel. Similar problems arise when Titanium is brought together with Teflon.

Table 4 shows the several materials which might get in contact with seawater on the TRICEPT robot. It can be considered that not all parts are isolated against each other and galvanic corrosion will not be inhibited at the standard version of the TRICEPT robot. - 45 “

Table 4: List of materials used on the TRICEPT robot Object Material Dustcaps for bearings nitrile-rubber O-rings nitrile-rubber

Helicoil threads 1.4571

Housing, centre tube 4212, (aluminium) Parts of the lin. actuators 6060, Al 233, AlCuMgPB, (aluminium)

Structural parts SS 0125, SS 0727, (cast iron)

Caps, spacer blocks, SS 2172, SS 2391 Motor housing, flanges, plates, bearing necks SS 1650, 16 MnCr 5, SAE 5115, 5117, (alloy steels) Motor housing, end effector SS 2541 Centre shaft, caps SS 1312, SAE 1017, (carbon steel) Puck, bearing cap SS 1672, SAE 1045, (carbon steel) Disk on housing axis 4 SS 1142, SAE 1008, (carbon steel) Parts of the lin. actuators St 37, SAE 1013, (carbon steel)

Screws and bolts carbon steels - 46 ~

5. MARINIZATION CONCEPT

After the review of the marinization and the test programme of the MANUTEC r15 robot (item 2, Modification of a MANUTEC r15: a Review, page 18) and the description of the TRICEPT (item 3, TRICEPT TR600, page 30), it is now possible to develop a concept for the modification of the TRICEPT robot. Although the design of this robot is not quite comparable to the design of the MANUTEC, it will be possible to use many ideas and technical approaches from this original work.

Parts of the TRICEPT housing will be filled with a compensation fluid to avoid strengthening the housing and to protect critical parts like electric motors from seawater contact. It is not possible to use electric motors in contact with seawater because it may build electric contact between parts of the motor. In addition to this, seawater is a very corrosive fluid and most parts of the motors would rapidly corrode.

It would also be possible to fill the housing with gas instead of a fluid, with even less impact on the internal parts. To level the pressure difference between the outside and the inside of the housing, an active control mechanism would have to be used, which would increase the possibility of system break-down. Owing to the compressibility of gas, a big amount of gas would have to be stored near of the robot or would have to be led down to it. In case of any leakage the gas would instantly blow out and water would flow in. If this incident occurs with a fluid-filled housing only a certain amount of fluid will pour out until the pressure is balanced. After this, water can only get into the housing, if fluid escapes at the same time. Hence fluid instead of gas as the compensation medium gives additional safety in the case of a leakage.

An "1-bar" pressure tight housing might be a suitable solution for some small parts, but as soon as moving parts have to be sealed-off is would cause major problems to get a suitable sealing. Usually the increased friction at the sealing surface leads to a early break-down of the sealing /36/.

Due to the "open design" of the TRICEPT it would be difficult to fill the complete robot with a compensation fluid. On the other hand, it is not necessary to compensate and protect every part of the robot. For all the parts, for which seawater contact is not critical, or for which seawater resistant options are available, no compensation is required. Only for parts like electric components and Harmonic Drive gears, the housings should be sealed off and filled with a compensation fluid.

Before presenting the necessary modifications of all parts in detail the main parts and most important modifications are briefly described below:

- All bearings for the gyro and the support of the linear actuators have to be changed to seawater resistant types, and in some cases the bearings will be lubricated with seawater only. - The linear actuators should be totally sealed off and filled with the compensation fluid. Special attention has to be paid on the "pumping-effect" of the pushrod in the actuators. - The electric motors for the linear actuators could be exchanged with the KOLLMORGEN submersible servo systems. - The sealing of the housing of the axis 4 motor unit on top of the centre tube should be improved and the housing has to be filled with compensation fluid. The octagonal housing around the motor unit should be flooded by seawater. - The wrist should be completely filled with compensation fluid. This includes the cross- roller support bearing in the platform and both housings for axis 5 and 6. - 47 -

- All housings which will be filled with compensation fluid should be connected to a central pressure compensator. This component provides a certain amount of compensation fluid for minor leakage's and thermal expansion. - The control unit as well as the RPT module should be treated in the same manner as the MANUTEC control unit. Since the modification of these two electronic parts is not part of the scope of this study, it will not be further considered.

5.1 Linear Axes 1,2 and 3

The technical drawings which I will refer to with the drawing number in brackets are presented in appendix B. Reference to special parts in the drawings is made by the part- numbers used in the drawings (i.e. No.12).

5.1.1 Motor Unit

(Drawing 1) The electrical motors for axes 1,2 and 3 are part of an enclosed unit for each axis. The units consist of the electric motor with two additional modules for the resolver and the brake. These modules are flanged on the shaft on top of the motor, with an electrical junction box on the side of the resolver module. The complete motor-unit (No. 11) is flanged on top of the corresponding linear actuator (No. 3) with a coupling (No. 6) in-between. The experience gained with the marinisation of the MANUTEC robot, several discussions with the company Ziehl-Abegg /37/ and related literature /36/, indicate that the brushless servo motors could be used in oil without any major modifications. Problems might occur due to the additional frictional heat of the rotor. In combination with the inductive heat produced by the coils, the temperature might get high enough to damage the oil /37/. As long as the robot is used under water, the heat-dissipation is assured by the surrounding water. To avoid any critical temperature level during the use in air, the heat dissipation should be checked during preliminary tests with an oil filled motor unit in air as well as under water. Only a minor pressure dependence of the power consumption has been monitored /36/, and up to a pressure of 150 bar common motor components should not have to be modified /37/. For the use of electric motors in oil, the inductive resolver should be used instead of optical encoder. The resolver has been successfully tested in oil with no dependence on pressure or the type of oil /36/. Mineral oil seems to have less impact to the isolating coating of the coils than synthetic oil /37/. For the motor units of the linear axes the housing had to be sealed with some additional O- rings between the brake and resolver modules and a strengthened cap on top of the housing. The electrical connections have to be changed to water tight electrical connectors on top of the cap, or on the side of the resolver module. In case the linear actuators are opened to seawater, the shaft of the motor unit has to be sealed. If the linear actuators should also be filled with oil, the motor unit should be opened to the actuator to build just one cavity. The connection to the pressure compensator could be included to the junction box of the motor unit or on the linear actuator. KOLLMORGEN, the manufacturer of the electric motors, offers a series of submersible servo systems. This includes electric motors with resolver which are pressure compensated up to a depth of 6,100 metres. Brakes are not enclosed in such systems and could not be offered as assessories. There are still ongoing discussions with KOLLMORGEN about this problem. - 48 -

5.1.2 Linear Actuators

(Drawing 1) The linear actuators (No. 3) consist of a ball screw with a pre-loaded recirculation nut driving a pushrod. Pre-loading of the nut is necessary to minimise any slackness, which will be several times as much at the end effector. The pushrod is connected via the cardanic joint (No. 1) to the platform. Ball screw and pushrod are both surrounded by an aluminium tube which also supports four angular contact bearings. It does not seem to be possible to open up the actuator's housing and let contact with seawater. At first sight, it appears to be the most appropriate concept, accepting the ne ­ cessity to modify the ball screws and nuts. This concept includes other additional benefits, e.g. no sealing would have to be included in the housing, and the "pumping-effect" of the pushrod causes no problems at all. The changes to get seawater resistant and water lubri ­ cated ball screws and nuts would be very expensive in manufacturing with no guarantee that the appropriate lifetimes can be achieved /38/. Two materials which have the appro ­ priate seawater resistance are Titanium (Ti 6AI 4V) and austenitic steel (1.4404), but Titanium can not be hardened to the necessary level for ball screws. In addition to the in ­ appropriate mechanical properties, both materials have a large difference in the galvanic series in comparison to the aluminium housing. Even if the housing is well coated, a small scratch in the coating would lead to a very large cathode-surface of the ball screw and a very small anode-surface of the scratch. This means, that the active anode would suffer accelerated corrosion and would be badly damaged after a short time. To avoid such serious corrosion problems the housing of the actuators should not be opened but sealed and filled with compensation fluid, avoiding any modifications of the ball screws. To build tight actuators, sealing should be added between the aluminium tube and the flanged parts to both ends. Flat sealing should be suitable for these parts. The pushrod is sealed with an adequate lip-seal. The cavity of the actuator has to be linked to the cavity of the motor unit. Any sealing of the roller-nut has to be removed to guarantee a sufficient lubrication of the balls and the recirculation system. Rotating of the ball screw forces the roller-nut to move the pushrod in and out. This changes the volume of the actuator housing significantly. This difference in volume should have to be supplied by the pressure compensator not only in volume, but also in the adequate time (fast response). The displaced amount of oil is equal to the volume of the pushrod (D= 48 mm) over the full length of the stroke (l= 600 mm). This gives a volume of 1 litre of oil to be pumped in or out of the compensator unit for a full stroke of one linear actuator. The oil pressed through the tube to the compensation unit induces an additional pressure in the linear actuator due to the resistance in the tube. The resistance depends on the velocity and the viscosity of the oil. To get a first value for this additional pressure, calculations will be done with the data of an oil suitable for the Harmonic Drive gears, which could be lubricated with the same oil. An additional pressure inside the linear actuators of 1.22 bar could be withstand by the sealing but might deform the aluminium housing. It has to be considered, that the sealing has to withstand the pressure in both directions, regarding a positive- or negative movement of the pushrod.

The resistance of the oil could be minimised by the following parameters:

- Use of a special oil for the linear actuators with a more suitable viscosity. The oil only has to meet the requirements for the lubrication of the ball screws and the angular contact bearings. - A separate pressure compensator for the three linear actuators. This unit could be placed near to the actuators to reduce the tube length. - The maximum speed of the linear axes could be reduced, to decrease the compensation flow rate of the oil. -49-

A possible reduction of the oil volume which has to be moved in and out by 70% could be achieved by a modification of the pushrods. It should to be prevented that the part of the pushrod which moves out of the actuator had to be filled with oil. This could be achieved by a sealing "plug" inside the pushrod fixed to the end of the ball screw. This sealing will be loaded from both sides, depending on the movement of the actuator, forming a lower or a higher pressure inside the housing of the actuator. The lower end of the pushrod at the cardanic joint has to be opened up to the environment, to let the seawater come in. The holes should be as big as possible, to avoid any additional pressure on the sealing when the pushrod moves in. Another problem may arise from pressure peaks which will build up when the movement starts or stops. This is induced by the inertia of the fluids (oil inside the housing and water around and in the pushrod).

Before any final modification, a prototype should be tested, to verify the calculated loads and estimated . Any recommendation for the finial modification has to be validated based on this test.

5.1.3 Cardanic Joints

(Drawing 2) The cardanic joints constitute a flexible connection between the linear actuators and the platform. They are made out of phosphatized steel with precision needle roller bearings. The bearings are sealed off and filled with grease for lifetime lubrication. The phosphatization should be changed to chroming in order to get a better corrosion protection. Chroming is one of the standard surface treatments offered by the supplier of this component. To protect the bearings and to avoid gap corrosion in-between the moving parts of the joint, one option would be to cover the joints with grease filled bellows. These bellows are offered from the supplier in different sizes, but the material is not seawater resistant. Suitable bellows can be made of a seawater resistant hose clamped over the joint. During preliminary tests the amount of grease and the movements under pressure have to be determined.

5.2 Centre Tube and Axis 4

5.2.1 Motor Unit

(Drawing 3) The housing for the motor unit (No. 36) for axis 4 is made of aluminium covering the electric motor (No. 13,14 and 15), the electromagnetic brake (No. 19) and the inductive resolver (No. 22 and 23). The lower end is covered by the "Harmonic Drive" gearbox (No. 2). The upper end is flanged to the cover of the octagonal housing. This housing surrounds the whole motor unit, the spiral cable and the upper part of the centre shaft. Only the internal of the motor unit will be filled with compensation fluid, the rest will be flooded by seawater. The housing of the motor unit has to be built of seawater resistant material to withstand the seawater corrosion. The upper cover, which includes the cover of the octagonal housing, has to be strengthened to withstand the pressure of the compensation fluid in the motor unit and made out of seawater resistant material. In this flange a wet electrical connector and a connector for the compensation fluid have to be installed. Internal disks and O-rings have to be removed or opened to allow free flooding of the compensation fluid in the whole unit. A standard motor unit should be modified as a prototype with additional sealing at the "Harmonic Drive" and at the upper end for first trials. During these trials the performance in the compensation fluid of the electric motor, the resolver and the brake will be tested. -50-

To use electric motors in mineral oil will cause no problems /36/. Problems may occur from heat accumulation in the electric motors which could lead to the burn of oil additives /37/. In use under water, the cold seawater will cool the housing of the motors, thus avoiding any heat accumulation problems. The principle of the inductive resolver is the same as an electric generator and should work as well in oil without any negative impact (Drawing 4). Preliminary tests should be done to avoid any unexpected influence from the fluid or due to pressure. The modification of the brake has to be supplemented by an intensive test programme to evaluate the modifications. The design of these brakes is very similar to the ones used in the MANUTEC r15 robot. Owing to this, the modifications can directly be based on the experiences from the previous modification (Drawing 5) /21, 31/. The Harmonic Drive gears are usually filled with a certain amount of oil, depending on the orientation of the flexspline. A lip-sealing is used to seal the flexspline against the circular spline, where the design pressure of this sealing is 0.5 bar (Drawing 6). Owing to this, the pressure of the compensation fluid must not exceed this limit. It is not possible to change the material and to manufacture the Harmonic Drive. The current standard material used for the flexspline and the circular spline is not corrosion resistant. Both parts will be in direct contact to seawater and have to be coated very accurately to prevent corrosion.

5.2.2 Housing and Centre Tube

The octagonal housing and the centre tube, both made of aluminium, have to be well coated to prevent seawater corrosion. (Drawing 7) To allow easy water flow in and out of the housings, the octagonal housing, the centre shaft (No. 1) and the centre tube have to be opened with additional holes at the lower and upper ends of the tubes. The spiral cable has to be changed to a water tight cable with wet connectors at the ends. The linear bearing at the outside of the centre tube is a pre-loaded linear ball bearing sliding in a steel profile (Drawing 8, No. 6 and 7). It is not possible to get a seawater resistant ball bearing slider due to the properties of available seawater resistant materials. A PTFE-coated V-shaped profile would be an alternative. The profile could be manufactured from any kind of material /38/.

An additional hose will lead compensation fluid from the motor unit through the centre shaft to the cross roller bearing and to the wrist.

5.2.3 Cross Roller Bearing

(Drawing 9) This bearing (No. 2 and 3) transmits the loads from the wrist into the platform. It is sealed-off against the centre tube with an O-ring (No. 1) at the flange of the centre shaft (No. 13). This sealing is not suitable to withstand the pressure of the compensation fluid and has to be changed. The O-ring sealing against the "claw" (No. 14) of the wrist has also to be changed for a better sealing. The disk (No. 4) inserted in the bearing provides the possibility to mount the bearing in the very exact position in reference to the output-flange of axis 6. This disk will also provide the space for a wet electrical connector to the spiral cable and for a connector to the hose for the compensation fluid. It should include some holes to enable the compensation fluid to lubricate the cross roller bearing. -51 -

5.3 Wrist (Axes 5/6)

5.3.1 Claw and Axis 5

(Drawing 9) The wrist will be filled with compensation fluid through the connector mounted in the disk (No. 4) of the cross roller bearing (No. 2 and 3). The performance of the electric motor, the resolver and the brake should already been examined during preliminary tests for the modification of the axis 4 motor unit. Sealing has to be provided between the "Harmonic Drive"(No. 15) and the fixed support plate (No. 16) and to the housing of axis 6 (No. 17), as well as at the flange (No. 18) on the motor side of the claw. For these sealing O-rings could be a possible solution, because no moving sealing is required. Another option needs to be found for the sealing between the claw and the axis 6 housing. This joint has to be sealed- off, because the electric cables are led through this connection.

5.3.2 Axis 6

(Drawing 10) The motor unit (No. 14) of axis 6 is nearly the same as for the axis 4. Owing to this the same improvements for the sealing has to be done. This means an additional O-ring at the Harmonic Drive, to seal against the cast iron housing, and the improved sealing of the Harmonic Drive output-flange. No other modifications are required for this axis.

The configuration of the wrist are shown in the drawing 11. Furthermore the connection of the housing of axis 6 with the Harmonic Drive of the axis 5 is demonstrated. The arrangement of the brake for axis 6 can be seen in the same drawing.

5.4 Structure

(Drawing 12) The forks (No. 1), which transmits the loads from the linear actuators (Swedish description in the drawings: Stalldon) into the structure (Swedish description in the drawings: OK-Gyro), should run in pre-loaded angular contact ceramic ball bearings. Owing to this, the bearings not only need no protection against the seawater, but could also be lubricated with seawater. To improve the performance of these bearings they could be lubricated with grease, since the grease will be washed out after a while under water. This means that the bearings are sufficiently lubricated for the work in air and still better lubricated under water. It is very important to prevent corrosion with an adequate coating of all cast iron parts, even inside the drill holes for the bearings (Drawing 13). The bearings of the gyro will be changed in the same manner like the forks (Drawing 14, No. 6). The drill holes for the bearings will be covered with dust caps to hold as much grease as possible in the bearings. After every use underwater the caps have to be removed to clean the bearings with fresh water and grease them again. Without this maintenance the lubrication might not be sufficient for further use in air or under water. In addition to this, the remaining seawater would cause corrosion inside the drill holes if the coating has any failure. -52-

6. HYDRODYNAMIC FORCES

The TRICEPT robot has to withstand several environmental impacts during intervention subsea. Loads caused by surface waves are exponential convergent with the water depth /39/. The sea conditions and waves at a jacket are strongly influenced by the structure itself. The exact value of the current around parts of the structure needs extensive numerical calculation. Within the scope of the present work, only the influence of subsea currents will be examined. Subsea currents cause a hydrodynamic drag on the submerged object. A deviation of 0.5 mm was measured during sensor feedback trials with the MANUTEC r15 UW robot in a water current of 1.1 m/s /21/. This deviation was mainly caused by gear-backlash and deflection of the robot-arm. Although the TRICEPT robot is much stiffer in design, a substantial deflection my be caused by the hydrodynamic drag. In order to get a preliminary idea of the possible effect of hydrodynamic forces the maximum drag will be calculated. As long as the TRICEPT is deployed by an ROV, the limits of the ROV will determine the maximum current. The physical limitation for a standard Workclass-ROV (WOROV) are weather conditions up to sea state 6 and sea current of max. 2-3 knots (approximately 1-1.5 m/s) /33/. Therefor, the maximum sea current, in which the TRICEPT robot has to work, is 3 knots. The calculation will be done for a static robot, because any additional forces due to an increased relative velocity between the robot and the water will only result in an increased deflection of the robot during the movement. This deflection will instantly disappear when the robot stops its movement. For the tasks the robot has to perform in this project, only "static" accuracy is required due to the working procedure for the Friction Stitch Welding. The hydrodynamic drag is caused by boundary-layer separation of the water current around the object /40/. The drag is influenced by the velocity of the current, the Reynolds number and by the shape and the front area of the object. Owing to the interference of adjacent objects, a reduction of the drag could be possible, but the absolute value is complex to be calculated exactly /40/. In a first approach it will not be necessary to include the influence of interfering objects. To estimate the drag of the whole robot, the drag of single parts could be calculated and summarised /41/. The maximum drag of the TRICEPT will turn out, when all three linear actuators are fully extended and the current flows from aside of the robot. Structural parts of the robot will be idealised by simple geometric objects like cylinders and boxes. For the calculation of the drag, each part is taken with the value and with the centre of impact to give the possibility to relate the whole load on the wrist. Especially the load on the wrist is important to know, because this allows to calculate the deviation of the end effector.

6.1 Idealisation of components

The entire robot could be idealised by five simple objects:

- The structure (yoke) together with the gyro will be represented by a flat box with sharp edges encircling the yoke and the gyro. The gaps in-between both parts have only little impact on the drag of this object, because they are in the area of the separated boundary- layer /40/. - The centre tube including the platform will be calculated as a cylinder with the diameter of the centre tube. This forms one piece together with the wrist (idealised as a cylinder) and the housing of the axis 4 motor (idealised as a box) - The linear actuators will be idealised with a long box for the actuator itself and another bigger box for the motor housing. Any shoulders along the actuator and changes in measures will not be taken into account. -53-

6.2 Calculation

Initially the calculation will be carried out for the housing of axis 4 in detail while the data for the whole robot will be presented in a "short-form".

The drag (D) of a submerged body depends on the dimension of the object, the velocity (v) of the fluid and the nondimensional fluid-dynamic drag coefficient (CD). This coefficient describes the shape of the body and the type of the flow. The direction of the drag is in the same direction like the direction of the current. The value of the drag depends on the angle of attack, since the highest value occurs in transverse current conditions. Hence all calculations will be done for the transverse current conditions.

^object ‘ Piseawater Yrea ^object

With the dimensions of the actuator housing and the value of the sea current, the Reynolds number can be calculated.

Vsea = 3 kn

= 1.5 m/s Vseawa,er=^m2/S

Pseawater^^SOkg/m3

a«d,4.«w.r=210mm 280mm

Vrea ^axisA.motor V seawater Re = 3.15-10=

In the range of Reynolds numbers between 2*10s and 5*10s (critical range) the boundary layer of cylinders and spheres changes from a laminar to a turbulent flow, resulting in a reduction of the drag (and the nondimensional fluid-dynamic drag coefficient). Currents below (subcritical) or above (supercritical) this range show nearly constant drag coefficients /41/. The correct value of the drag coefficient in the critical range can not be determined /AO/. For these calculation drag coefficients for the subcritical range will be used. This will give a higher value for the drag, but represents a worst-case determination. Bodies with sharp edges do not show changes of the boundary layer, since the sharp edges lead to a definite point of separation for the boundary layer. The nondimensional fluid- dynamic drag coefficient of such objects is approximately constant. The drag coefficients for various shapes of bodies are given in the literature /40/.

^'D.axisA.motor 1-56

^axisA.motor = 106AT - 54-

Owing to the position of the axis 4 housing, a moment is applied at the point where the centre tube has the contact to the gyro. In the case of fully extended linear actuators the distance between this point and the centre of impact on the housing is xazMmotor=260 mm. Together with all other forces building a moment in this point a balance could be made in order to get the force at the end effector of axis 6. The same calculation had been made for all parts mentioned above. The results are shown in the following table.

Table 5: Calculation of the hydrodynamic drag for the single objects of the TRICEPT Object Dimensi on [mm] Area cD Drag a I [m2] [N] Structure 250 660 0.165 1.05 200 Centre Tube 133 1550 0.206 1.17 280 Wrist 250 250 0.063 0.63 46 Axis 4 motor 210 280 0.059 1.56 106 Lin. Actuator 1 90 1690 0.152 2.05 361 Lin. Actuator 2 90 1690 0.152 2.05 361 Lin. Actuator 3 90 1690 0.152 2.05 361 Motor 1 130 400 0.052 1.56 94 Motor 2 130 400 0.052 1.56 94 Motor 3 130 400 0.052 1.56 94

This gives a total drag of

D. total 1,991 N

Each of the five objects (structure, centre tube and three linear actuators) had been balanced at their respective points where they are attached to the structure. The structure itself has no impact on the deflection of the wrist, because the structure will have no deflection due to its drag. The balances leads to four loads (3 lin. actuator and the centre tube) applied to the end effector of the wrist.

1 actuatorl 64.84 AT

1 actuatorl 64.84#

1 actuator3 64.84#

L centertube 134.75#

1 endeffector 329.27#

The static bending deflection of the robot is given in the technical data sheet for several directions of the load applied to the end effector. With the calculated force on the end effector the static deflection can be determined.

Staticbending deflection : 0.0003 mm/N

Deflection : 0.0988mm - 55 -

The static deflection caused by the hydrodynamic drag of the robot is in the same range as the positioning accuracy. This would reduce the feasible accuracy to 0.2 mm, but would be still appropriate for the required tasks (i.e. Friction Stitch Welding, drilling or milling and Non ­ destructive Testing).

Any additional part and tool on the robot might increase the deflection. The Friction Stitch Welding head will be comparable to the existing welding machine HMS 3000 from Pressure Products Group. This tool will be mounted at the end effector and will increase the static deflection. The HMS 3000 welding machine is a cylinder-shaped design with the following dimensions.

aHMS = 200mm lHMS ~ 560mm

CD =1.17

Fhms ~ 152W

Together with the deflection due to the drag of the robot itself a total static deflection could be determined. Total static deflection: 0.1443mm

Depending on the required precision of the respective tasks, the additional static deflection, caused by the tools on the end effector, could reach a substantial value. The actual value of the robot's drag could be measured in a test tank which would include the effects of interfering objects. The result of this test is only the total drag and moments referred to the mounting flange on the structure, where the robot will be held during this test. The static deflection could be directly measured by a dial gauge at the end effector in a jet-pool. This test will give no information about the value of the drag, but the correct value of the static deflection of the robot in water currents. - 56 -

7. OPERATION OF THE ROBHAZ SYSTEM

Parts of this section are based on the ROBHAZ project-report "Design Criteria's for Friction Stitch Welding" /33/.

7.1 Delivery Systems

The term “Remote Operated delivery system ” denotes the system to deliver tools and end effectors to the work site under water.

Such systems are normally divided in two different categories:

1. Remote Operated Tools, ROT 2. Remote Operated Vehicles, ROV

ROT’s are normally weight suspended systems for vertical operations of large modules only and will not be further defined.

The various ROV's could be classified roughly in two categories:

7.1.1 Observation ROV

Observation ROV's (OBSROV’s) are small "eyeballs ” containing:

- 1 to 3 Video cameras - Electric propulsion systems - Cathodic Potential probe for check of sacrificial anodes - Small manipulators - Lift capacity up to 50 - 100 N - Limited electric and electronic interfaces, no hydraulic interfaces - Vehicle weight of 100 to 1,000 kg (Figure 35)

A OBSROV system may consist of following modules:

1. Surface control module with power supply and remote Figure 35: The Offshore Hyball, Hydrovision Ltd. /43/ controls normally fitted in a 10 to 20 feet operation container

2. Launch and recovery system (LARS) including:" - Winch up to 1000 m lifting - A-Frame mounted on a skid designed for launching capabilities of 1,000 to 1,500 kg - Hydraulic power pack for winch and A-Frame -57 -

3. Tether Management System including: - Winch up to 250 m neutral buoyant tether cable - Locking devices on top to lock to LARS and on bottom to lock to ROV 4. ROV including: - Electric propulsion systems with 4 to 7 thrusters - Viewing system with video cameras and still cameras - Small Manipulators - Automatic functions (Automatic depth, automatic heading, automatic altitude, automatic pitch/roll) - Electric distribution system for sensors - Electronic multiplexer for distribution of control signals - and other acoustic systems including: deg. scanning sonar's and position detectors (Hydro acoustic position reference) - Cable termination for: Electric Power up to 1000 V, 10 KVA Coax cables Twisted pairs and twisted quads Fibre Optics

7.1.2 Workclass ROV

Workclass ROV's (WOROV's) are heavy duty work task oriented vehicles including:

-Up to 2 master/slave manipulators - 3 to 5 video cameras - 100 Hp hydraulic power unit or more - Hydraulic propulsion systems - Maximum weight load of 1000 to 1500 N in free-fly operation - Up to 5 tons through-frame lift capacity - Accommodation for a vast number of hydraulic, electric and electronic interfaces - Vehicle weight of 2,000 to 5,000 kg Figure 36: Scorpio WOROV with a tool for pipe cutting

Typical main sizes for WOROV's are:

- Front and rear areas 1,7 Wx 2 H metres - Side areas 3,5 L x 2 H metres - Top and bottom areas 1,7 W x 3,5 L metres

These specifications are common figures only and may vary greatly between the various manufacturers. -58 -

The WOROV system may consist of following modules:

1. Surface control module with power supply and remote controls normally fitted in a 20 feet operation container 2. Launch and recovery system (LARS) including: - Winch up to 3000 m lifting umbilical cable - A-Frame mounted on a skid designed for launching capabilities of 10 -15 tonnes — Hydraulic power pack for winch and A-Frame 3. Tether Management System (TMS) including: - Winch up to 250 m neutral buoyant tether cable - Locking devices on top to lock to the LARS and on bottom to lock to ROV 4. ROV including: - Propulsion systems with 4 to 7 thrusters or more - Viewing system with video cameras and still cameras - Manipulators, normally two 7 functions Master/slave arms - Hydraulic power unit with up to 100 Hp or more - Automatic functions (automatic depth, automatic heading, automatic altitude, automatic pitch/roll, automatic parking) - Hydraulic distribution system with servo and on/off valve controls - Electric distribution system for accommodation of tools and sensors - Electronic multiplexer for distribution of control signals and sensors - Sonar and other acoustic systems including: 360 deg. scanning sonar Side scan sonar Altitude echo sounder Bottom profiler echo sounder Sub bottom profilers echo sounder Range detectors Position detectors, hydro acoustic position reference Depth detectors Ultrasonic sensors for wall thickness measurements - Cable termination for: Electric Power up to 3000 V, 150 KVA Coax cables Twisted pairs and twisted quads Fibre Optics

The manipulators mentioned above may be divided in the following categories:

- 3 to 9 function rate controlled manipulator for constant speed with on-off functions - 5 to 7 function rate controlled grabbers for attachment to a structure - 7 to 9 function master/slave controlled manipulators - 7 to 9 function Computer Assisted Telemanipulators (CAT, Robotics arms with teach/learn functions) - Force-feedback manipulators (rarely used)

The use of the manipulators spans from the need of keeping the ROV in a steady position relative to a structure, to any worktask requiring the fine manoeuvrability like scanning sensors. Repeatability and accuracy of CAT's has proven to be in the centimetre/millimetre range depending upon the steadiness of the ROV system /33/.

The tools operated by the manipulators may be compared to the use of tools and sensors for surface handicraft and are normally unlimited. -59-

The hydraulic system on a WOROV system may accommodate any hydraulic tool and hydraulic operation as will be required for the performance of a worktask.

The electronic systems may accommodate a vast number of electronic interfaces. The range of interface possibilities are dependant upon the selected system, but will normally be adequate for most tasks needed to be performed. One should, however, be aware of the fact that older systems may have limited possibilities for computer controls as they may be equipped with on/off or digital to analogue conversion of signals in the multiplexer unit which would for some interface requirements be inadequate. Such problems may not be evident for newer PC-network operated systems.

The electric systems are normally provided as a high voltage transmission through the umbilical to the ROV unit. The voltage is between 1000 to 3000 Volts. Both higher and lower voltage systems are available. The high voltage are normally used directly in the motor for the Hydraulic Power Unit (HPU). The high voltage power will pass through the umbilical winch sliprings and the lifting umbilical, through the TMS slipring and the tether cable to the ROV unit. In parallel there will be provided instrumentation power to the vehicle. This power will be transformed in the ROV for distribution to the various instrumentation, tools and lighting systems.

7.1.3 Tether Management System

The Tether Management System (TMS) provides a soft neutral buoyant umbilical with a length of up to 250 metres. The TMS is fitted to the end of a armoured umbilical and can be described as an underwater winch for the soft umbilical. The advantages of this is that the TMS/ROV could lowered to the working depth or seabed by the umbilical winch. Without a TMS the ROV has to use it's propulsion system to get down to the worksite. The TMS provides a base from which the ROV can move laterally up to -the length of the soft umbilical.

Figure 37: Seaworker WOROV with a TMS system and garage

7.1.4 Operational Limitations

The operation of the ROVs have many physical limitations and constrains:

- Weather conditions (max. sea state 6) - Weight and size of tools (through frame max. 40 to 50 kN lift force) - Weight and size of variable loads (max. 1000 to 1500 N weight load) -60-

- Horizontal outreach from vessel position (max. 200 to 300 meters with IMS) - Sea current (max. 2 to 3 knots depending upon direction) - Depth (300 to 3000 meters, deeper systems exists) - Manipulator capacities (max. 2000 N lift force)

These constraints are individually limiting the operational capabilities of ROV's but some may be adjusted by the design of the ROV's and their handling systems.

The access to nodes are limited and the nature of the ROV is that it is desirable to have available payload, power and telemetry sufficient to provide:

- High ROV propulsion (thrusters) - High quality viewing and tracking - High quality sonar systems - Accurate depth measurements - Accurate headings (North, south, east, west) - Sufficient floatation elements - High quality and accurate manipulators - Variety of tools

These parameters and more will all together eventually add mass and size to the ROV which would limit its accessibility to narrow areas.

The Free-Fly capabilities are also normally sufficient to provide full outreach of the Tether length which is up to 250 metres from the surface vessel position.

The front area of the ROV may, limit the access to narrow nodes or other narrow areas. All tools for ROV's are therefore required to be as "deliverable" and self operational as possible to extend the reach beyond the reach of the ROV front and that the tools are as small as possible to fit into areas not accessible by the ROV.

7.2 Inspection Methods and Tools

Cracks in offshore steel structures are normally invisible by visual methods and are normally only found by special non-destructive testing methods as follows:

1. Magnetic Particle Inspection (MPI and Eddy Current): The magnetic sensors are normally dependant upon clean surfaces and for MPI, the steel must be cleaned to bare shiny metal before the inspection starts. 2. Ultrasonic Inspection (Spot and area measurements): The ultrasonic sensors are also dependant upon clean surfaces but are slow to use and are less exact to findings and position of the findings. They are therefore used to a limited scale only. 3. X-ray techniques (Radioactive source and film): The X-ray techniques are used to special applications only and would be of more interest to determination of corrosion than to finding cracks.

The inspection method normally applied is preleeded by cleaning the area for inspection using brushes, high power water jet systems, water jet system with grit and other contact or proximity methods. Once the area is cleaned to the standard required for the selected inspection method, the inspection tool is positioned and scanned over the area. Findings are recorded in digital or analogue form (Eddy current and ultrasonic), recorded on video (MPI), provided as film (X- - 61 -

ray) and/or noted on paper. The position of the finding will be recorded on paper and provided as verbal input on videotapes. It is of high importance that the position of a finding is accurate and traceable for future monitoring of the finding. Therefore the finding on tubulars are indicated as clock positions where 12 o'clock is up or north or any other predetermined orientation. All other clock positions are referenced to these positions. It is obvious that this position description is reasonably poor for a correct tracing of the position.

The different inspection methods are described as follows:

7.2.1 Eddy Current Inspection

The description of the Eddy Current system refers to the Millstrong Electronic Ltd's Lizard system. Other competitive systems exists, but the main philosophy and operation characteristics are similar.

Probes for spot or area measurements and other methods exists. They are often purpose built for special tasks.

The Eddy Current system consists of the following main items:

- Surface computer system including display and data storage - Transmission link (twisted pair) - Subsea control box - Scanning Probe

The scanning probe needs a smooth and accurate movement in a predetermined trajectory by a manipulator arm or other moving method. Only one system to perform such movements by remote operated methods has yet been provided by the industry and the method has therefore only partly been proven.

7.2.2 Magnetic Particle Inspection

The Magnetic Particle Inspection (MPI) system uses the special light effect caused by iron content fluorescent ink illuminated by ultra violet light and viewed by video cameras.

The cracks are made visible from following method:

1. The steel around a crack is magnetised by a magnet and the area is flushed by iron content fluorescent ink 2. The magnetism will cause the iron in the ink and the ink itself to be dense over the crack opening 3. The area is illuminated by ultra violet light 4. The dense ink will glow over the cracks in the steel surface and will be visible in a video camera as glowing light traces

The MPI system consists of following main items:

- Surface controller - Power through umbilical and tether cable - Main transformer unit - Magnetic yoke - 62 -

- Florescent ink container and pump - Ultra violet light source - Ultra violet sensitive video camera

The MPI system is by nature visual inspection method and apart from the video tapes, no other recordings of findings are normally possible.

7.2.3 Ultra Sonic Inspection

Ultrasonic sensors are using the effect of reflection of sound in the steel. The reflection, return time of the sound is measured to determine the distance the sound travelled before returned to the ultrasonic sensor. This effect may be used to determine the steel wall thickness and theoretically also may be used to indicate a 3D representation of the sound reflection trajectories.

This method is not recognised as an underwater operational system for crack finding and would need further development to be operational for such purposes.

7.2.4 Radiographic Imaging

The Radiographic (X-ray) technique is well recognised and a well proven technique to look for internal cracks in steel. It is mostly used to verify that new welds in a construction are sound and without inclusions or other welding defects. Micro fatigue cracks are normally invisible by the X-ray as no material loss is caused by the crack at this stage. The opening within the crack is too small for any indications on the X-ray film.

The X-ray technique is best on single plates without water or other liquids between the radioactive source and the film. On an offshore structure consisting of tubulars, single plates inspection is not possible and a shot through the full tubular may not be sufficiently detailed.

7.2.5 Video Systems

As micro fatigue cracks are invisible on the surface of the steel, standard video techniques may not be used for revealing or finding defects in a steel structure.

7.2.6 Crack Finding and Refinding

The inspection methods are selected to increase the speed of scanning and to enhance the expected finding results.

- Eddy current method is by far the best method with respect to the inspection speed. The method is also less dependant upon clean surfaces. Residual marine growth and paint may be tolerated. However, it requires an accurate manipulation for moving the probe over a selected trajectory and the probe is susceptible to wear. The result is digital and computerised - MPI requires bare metal at the inspected area. The overall inspection speed is therefore much slower than Eddy current, but only MPI will give an image of the defect. The result is visual and stored by a standard video recorder. - Ultrasonic is used for spot measurements only and is therefore slow and time consuming. Ultrasonic scanners have been made, but they are normally dedicated for a - 63 -

special tasks only. Such scanners may be used, but the results are normally not recognised as proper crack finding tools. - X-ray methods will normally look for larger cracks and corrosion. It has not yet been tested to find micro cracks in steel by X-ray methods /33/.

As indicated above, there are virtually only two methods for crack detection underwater by remote techniques, the Eddy Current and the MPI inspection methods. All other methods have not proven successfully or have no records for underwater applications. For the ROBHAZ tool the MPI method and the Eddy Current method may be required to re-find a crack that has previously been revealed by other inspection methods.

7.3 Possible Repair Scenario

Prior to the decision of performing a repair operation on an offshore structure, it is assumed that the crack to be repaired has been detected and thoroughly examined for depth, length and position on the structure. The result of such examination must have been presented as record of measurements from one of the inspection methods described in the sections above, or presented as a hardcopy report including sketches, pictures and drawings.

It is not envisaged that the ROBHAZ system shall be capable or made economical interesting for the inspection tasks to reveal new and former unknown fatigue cracks on offshore platform structures unless the cracks are obvious or visible by video directly. The re-finding operation described above is to position the welding head on a crack of known approximate position and to accurately determine the position of the drilling and welding tool for the welding operations. The required accuracy to position the repair tool should be better than 0.5 - 1 mm in any direction.

In addition to the drilling and welding tool, the ROV would need to carry a cleaning device for the inspection requirements. The cleaning device could be wire brushes, high pressure water jet with or without grit, or a combination of these tools. The video cameras should be a combination of 2 - 3 colour cameras mounted on pan and tilt units. At least one of the cameras should include zoom function.

7.3.1 Launch of the ROV

The residual movements of the ROV can not be sufficiently avoided by any of the common claws or suction pads. To prevent a transmission of these movements to the ROBHAZ tool skid the ROV will be removed from the tool during the repair procedure. It will stay in a back ­ up position approximately 1 metre away /33/. The drilling and welding tool must therefore be designed for a stand-off operation during the drilling and welding process. Interfaces between the ROV and the tool must be provided as an umbilical containing necessary power and signal lines to support all functions of the tool during the welding process. No mechanical interfaces of permanent nature can be provided. The ROV must therefore be prepared to accommodate the tool during the launch and retrieval of the system through the splashzone. This can be achieved by the provision of a cradle or ROV Skid based support structure for use during launch and recovery.

The normal procedure for the launch and recovery is as follows:

1. Check of all functions of the tools and the ROV system 2. Lift of the TMS and the ROV with tools to a locked position in the A-frame 3. The A-frame is tilted outwards over the sea and the TMS lock is deactivated. -64-

4. The winch lowers the IMS, the BOV and all tools through the splash zone to the operational depth for the mission 5. The TMS unlocks the BOV to allow for free swim of the BOV to the work position 6. ROV Operation on the work area 7. Return of the ROV to the TMS and locking of the ROV to the TMS system 8. Ascend of the TMS/ROV toward the surface 9. Ascend of the TMS/ROV through the splash zone to a locked position in the A-frame 10. Landing of the TMS/ROV on the ship deck.

Throughout all the 10 phases described above, the ROV pilot has full control of all functions of the ROV system and may monitor hydraulic pressure and instrumentation behaviour. Tools and additional equipment attached to the ROV may be monitored and secured by the manipulators or special designed systems.

There are normally no limitations to the quantity or complexity of the additional equipment during launch and retrieval, but following constraints are still to be observed:

- Total Air weight of the additional equipment can not exceed the maximum "Throughframe" lifting capacity of the ROV system. (May be from 500 - 5000 kg) - Total Water weight of the additional equipment can not exceed 100 - 250 kg if the ROV is supposed to "free-fly ” the equipment to a work site. Air weight of the equipment including buoyancy is limited to the limitations set above. - Physical size of the additional equipment must be kept within the maximum allowed sizes for the Launching and Recovery System (LARS). - Hydraulic, Electric and Electronic interface requirements must be within the specifications of the ROV.

7.3.2 Attachment to the repair site

The ROV tasks have to be well defined such that the pilots are able to free swim directly to predetermined worksite. After the worksite has been reached, the ROV will use its manipulators and grabbers to attach to the area as found required. This attachment requirement is dependant upon the expected stability for the ROV during the task operation but will normally be of temporary nature only. Dependant upon the ROV configuration, it may be equipped with suction pads in addition to grabber arms. For the drilling and stitch welding operation, it would be required to release the drilling and welding tool from the ROV frame and let the tool be self-contained with drilling unit, welding unit, crack detection unit, underwater robot, and any other additional feature to perform the drilling and welding action.

All interfaces required between the ROV and the tool must be connected through the tool umbilical routed from the tool to the ROV. This connection must be a soft one and no mechanical interfaces shall be included.

7.3.3 Delivery of the ROBHAZ System

When the ROV has been placed on the repair site, the ROV manipulators will be used to retrieve the ROBHAZ tool from its storage position on the ROV and place it in a proximate position near to the actual crack to be repaired. As indicated above, this position must be predetermined prior to the implementation of this procedure and provided as a report including MPI readings, Eddy Current readings or other data to assist during the tool placement. - 65 -

The tool shall than operate its own fixture to the steel structure. Such fixtures are suction pads, electromagnets, hydraulic clamps or any other selected attachment provision.

7.3.4 Crack Finding

After the ROBHAZ tool has been attached to the structure, the drilling and welding head must be positioned relative to the crack with a variation of ± 0.5 mm over the full length of the crack. Assuming the crack is of non-visible nature and must be detected by instrumentation, the two only possible tools for such measurements are the Magnetic Particle Inspection (MPI) system and the Eddy Current system, as indicated above. Using the MPI tool will reveal the crack, but will give a 2D image of the crack only. The images may not easily be interfaced with an automatic "teach-learn" process unless the operator assists by placing the drilling unit in each of the ends of the crack and interpolating the intermediate trajectory. The Eddy Current tool may both locate the crack, interface the findings back to the drilling head automatically and control the progress of the drilling and welding operation. This action will require that the drilling unit is sufficient intelligent to accept such automatic functions. MPI system may be used to verify the completed welding action.

7.3.5 Drilling and Welding

As described above, the drilling head should be automatically positioned in accordance to the inspection report rather than through a visual-manual position. As all visual feedback should be regarded as 2D video presentation, manual positioning of tools within the accuracy required for the drilling and stitch welding should be avoided and regarded as impossible operations. From the discussions above, the only possible automatic function is to use an Eddy Current probe /33/.

The welding head positioning will be similar to the drilling position operation and should therefore also be automatically performed from the Eddy Current system.

Once the true trajectory of the crack has been measured and logged, the drilling and welding heads should be automatically controlled. The system should be programmed to automatically drill and weld continuously. Operator interference should be limited to the adjustment of the speed and supervision of the process only.

7.3.6 Checking and Documentation For final documentation of the repaired area, MPI and X-ray methods should be considered. The MPI method would indicate if the complete crack length has been removed. If this is not achieved, new drilling and welding actions should be performed before the release of the tool attachment to the structure. As a final documentation of the repair, X-ray systems may be used.

A final repair report including information like -video. X-ray films, MPI Video, issued in hard copy and electronic format and other relevant information shall be available prior to demobilisation from the repair site. -66-

7.3.7 Recovery

The ROV will dock on the ROBHAZ tool again and the fixtures to the structure will be released. The ROV is to return to the TMS and park in a locked position. The TMS will be winched to the surface and the A-Frame will bring the TMS and the ROV including the ROBHAZ tool back onto the vessel deck. -67-

8. DISCUSSION

In the present work, the marinization of a MANUTEC r15 robot, previously carried out at GKSS, has been initially reviewed (see chapter 2, Modification of a MANUTEC R15: a Review) to serve as basis for the marinization concept for the TRICEPT TR600 robot. This review summarises the main aspects of the development work and the related test programme and certification. A discussion of this development work is presented in chapter 2.6.

The TRICEPT robot is an industrial robot built on a frame structure to ensure maximum rigidity. Its design makes it suitable for various applications such as high speed machining and precision/heavy assembly. Due to the tripod framework the working envelope is more restrict than the envelope provided by jointed arm robots like the MANUTEC. On the other hand, the TRICEPT robot offers an operational performance which is far better than that found for jointed arm robots of similar dimensions (i.e. maximum pressing force of 15,000 N, etc.). Particularly, these performance data qualify the TRICEPT robot for the handling of a friction welding head, whereas a suitable working envelope has to be provided by the performance and design of the entire tool.

The TRICEPT is commonly used in the car and aluminium manufacturing industry. To the best of the author's knowledge no attempts have been yet made to extend the scope of application for underwater work or for any other kind of environment rather than air/. Hence the marinization concept for this tripod type robot can not rely on specific experience from previous developments or existing literature. As mentioned above, the design of the TRICEPT robot is not comparable to that of the MANUTEC in all components. The structure of the TRICEPT is a open framework design with multi-axial movements between the single components, whereas the MANUTEC has enclosed joints with well defined relative movements. Hence, the experience with the marinization of the MANUTEC r15 can only be applied to components as the electric motors, resolver and brakes. Therefore, the proposed marinization concept for the TRICEPT robot involves some new ideas regarding the modification of components like the linear actuator which are unique for tripod type robots.

The modification of the motor units for the axes 1,2 and 3 as well as for the axes 4,5 and 6 will not in a first approach, present technical problems. The modifications proposed for these units are firmly based on the experience from the marinization of the MANUTEC and reported by Jackel /36/. The use of ceramic bearings should avoid any technical problems related to corrosion of the bearings or insufficient lubrication in seawater operation. The modification of the linear actuator might cause some kind of technical problems due to the extreme movements inside the actuator housing. As mentioned in item 5.1.2 the pumping effect of the pushrod could be minimised with a "plug" at the end of the ball screw, but the feasibility of this suggestion is not proved until now. In addition, the linear actuator will pose some restrictions for the selection of the compensation fluid. The ball screws need an adequate lubrication, whereas the viscosity should be rather low to minimise internal resistance and pressure peaks when moving the pushrod. The fluid filled linear actuator might lead to a reduction of the maximum acceleration and speed of the robot, if the internal resistance and pressure peaks are too high. I must be poited out that for the proposed application of the system the speed of the robot's end effector is not of fundamental importance.

The performance of the proposed V-shaped linear bearings for the centre tube have to show their aptitude in appropriate component tests. The achievable accuracy might not be sufficient for this kind of application. The modifications suggested for the linear actuator should be tested on a single actuator to prove their feasibility. - 68 -

If the ceramic bearings prove to be inadequate or too expensive to be economical acceptable for this application, the bearings presently used might have to be encapsulated. This might lead to a change of the structure and of the gyro assembly. These changes may cause technical problems which might not be overcome in a acceptable manner.

The deflection caused by the hydrodynamic drag of the TRICEPT itself may be too high in some cases and restrict the system to calmer environmental conditions and slower movements at subsea application. For a given current of 1.5 m/s a static bending deflection of 0.14 mm has been determined for the TRICEPT together with the welding head. It has to be considered that this deflection will increase with the extension of the distance to the base of the system. Such a deflection will also have a negative influence on the accuracy of NDT inspection eventually leading to reduced operational capabilities of the system. The required accuracy for the friction hydropillar welding has not yet been defined. Nevertheless, an inaccurate positioning of the consumable stud in the dill hole might lead to welding defects, in particularly lack of bonding.The influence of inaccurate positioning on the friction hydropillar welding process needs further examination within the development of weldability lobes.

It can be concluded that the TRICEPT robot is presently one of the most adequate tools (available in the market) for the planned application. The present work has shown that from a technical point of view all environmental-sensitive components could be marinized without significantly affecting the operational performance of the robot.

ACKNOWLEDGEMENT

This work has been carried out within the framework of the project ,,Affordable Underwater Robotic Welding Repair System (ROBHAZ)" (contract no. BRPR-CT97-0422), supported by the BRITE EURAM III programme of the European Commission. The financial support of the European Commission is gratefully acknowledged. -69-

9. REFERENCES

/1/ Shell International Petroleum Company Ltd.: The offshore challenge. Shell Briefing Service, London, 1993

/2/ Offshore Decommissioning Communications Project, Several Publications in the World-Wide-Web, http://www.oilrigdisposal-options.com/back/text1 .htm - /text 8.htm, State of October 12,1997, London

/3/ Hull, T.: Platforms and Pipelines. Proceedings of the conference „An Overview of the North Sea Oil Industry", University of Aberdeen, Aberdeen, 1996

/4/ Gibson, D.: Achieving diverless repair of pipelines and other subsea equipment in hyperbaric environments. DEEPTEC'94, (Conf.) HR Conferences, Aberdeen, 1994

/5/ Moldskred, S.: Private Communication. Stott Comex Seaway A/S, Haugesund, Norway, 1997

/6/ Thurlbeck, S.D. ; Stacey, A. ; Sharp, J.V. ; Nichols, N.W.: Welding Fabrication Defects in two Offshore Steel Jacket Structures. Proceedings of the 15th International Conference on Offshore Mechanics and Arctic Engineering, Volume III - Materials Engineering, pp. 233-246, 1996

PI COMEX (Compagnie Maritime d'Expertises) S.A., Annual Report 1990, Marseilles, France, 1991

/8/ Aust, E. ; Dos Santos, J.F. ; Bohm, K.-H. ; Hensel, H.-D.: Mechanized hyperbaric welding by robots. GKSS 88/E/54, GKSS-Forschungszentrum Geesthacht GmbH, 1988

/9/ Brooke, S. T.: Identifying the Needs and Limits for Deepwater Diver Intervention. DEEPTEC '94, (Conf.) HR Conferences, Aberdeen, 1994

/10/ The National Hyperbaric Centre: A technical and economic review of deepwater intervention techniques. Document RE.HC.409.001, NHC for OSO, 1994

/II/ Project Programme of the BRITE EURAM III project "ROBHAZ" (Affordable Underwater Robotic Welding Repair System), Project No. BE96-3692, The National Hyperbaric Centre, Aberdeen, 1996

/12/ The National Hyperbaric Centre, Publications for the ROBHAZ project, Aberdeen, 1997

/13/ The Welding Intitute: TWI Connect. TWI, Abington, Cambridge, Issue No. 89, 1997

/14/ Aust, E. ; Niemann H.-R. ; Bbke, M. ; Gustmann, M. ; Wesche, A.: Six-years development in subsea robotics. (GKSS 95/E/2); Proceedings of Underwater Intervention 1995, Man & Machine Underwater, Jan 16-18, 1995, Houston, Texas, USA

/15/ Aust, E. ; Niemann H.-R.; Biemann, P.: Bericht uberdie Qualifizierung des Robote- Teilsystems r!5-UW fur den Einsatz bis zu 1100m Seewasser. GKSS 89/I/7 -70-

/16/ Pritschow, G. ; Horn, A.: Dynamik derzeitiger Sensorregelkreise fur Industrieroboter. Robotersysteme 7,178-184,1991

/17/ Aust, E.; Niemann H.-R.; Schultheiss, G.F.; Markfort, D.; Brutsch, E.; Schmidt, H.: Anpassung eines Roboterteilsystems fur den Seewassereinsatz und Erprobung bis 1100m Wassertiefe. Robotersysteme 5, 233-237,1989

/18/ Gustmann, M. ; Niemann H.-R. ; Aust, E. ; SchultheiG, G.F.: Modifizierter Industrieroboter geht in die Unterwasser-Erprobung. (GKSS 91/E/36); Robotersysteme 7, 37-40, 1991

/19/ Aust, E. ; Domann, H.: Modifikation eines inkrementalen Drehgebers fur den Unterwassereinsatz von Robotern bis zu Wassertiefen von 1200m. Robotersysteme 4, 205-208, 1988

/20/ Heidenhain, Product Catalogue "Incremental Encoder", Traunreuth, Germany, 1997

/21/ Gustmann, M.: Untersuchungen zum dynamischen Verhalten eines Unterwasser- Roboters unter StromungseinfiuR. (GKSS 95/E/61)

1221 Wesche, A. ; Aust, E. ; Niemann H.-R.; Robotersteuerung fur den Unterwassereinsatz verfugbar. (GKSS 96/E/26); wt Werkstattstechnik - Produktion und Management, Band-Nr. 86 (1996), pp 169-170

/23/ Boke, M. ; Miss, R.W. ; Deeg, H.-J.: Offline-Programmierung und grafische Simulation als Planungsinstrument fur den Robotereinsatz unter Wasser. (GKSS 93/E/89); VDI Berichte, Nr. 1094, pp 209-218,1993

/24/ Niemann H.-R. ; Aust, E. ; Gustmann, M. ; Hahn, G.: A six DOF robot allows diverless intervention, (GKSS 92/E/44); Proceedings of „4th EC Symposium Oil and Gas Technology in a wider Europe", Nov. 3-5, 1992, Berlin

/2b/ Gustmann, M. ; Aust, E.: Einsatz eines modifizierten Industrieroboters im Unterwasserbereich. (GKSS 93/E/88); VDI Berichte, Nr. 1094, pp 199-208, 1993

/26/ Aust, E. ; Niemann H.-R. ; Seeliger, D.: Tiefsee-Roboter. Spektrum der Wissenschaft, Marz 1995, pp 107-111

/27/ Germanischer Lloyd: Rules for Classification and Construction, Offshore Technology, Part 1 Underwater Technology. Germanischer Lloyd, Hamburg, 1991

/28 / Germanischer Lloyd: Vorschriften fur Klassifikation und Bau von stahlemen Seeschiffen, Kapitel 3 - Maschinenanlagen, Kapitel 4 - elektrische Anlagen. Germanischer Lloyd, Hamburg

/29/ Germanischer Lloyd: Richtlinien fur die Durchfuhrung von Baumusterprufungen. Germanischer Lloyd, Hamburg

/30/ VDI: Richtlinie 2853, Sicherheitstechnische Anforderungen an Bau, Ausrustung und Betrieb von Industrierobotern.

/31/ Germanischer Lloyd: Prufbescheinigung, Nr. 80 480 HH, Unterwasser-Roboter „r15 UW". Germanischer Lloyd, Hamburg, 1991 -71 -

/32/ Dexter, S.C.: Handbook of Oceanographic Engineering Materials. John Wiley & Sons, New York, 1979

/33/ Moldskred, S.: Design Criteria's for Friction Stitch Welding. ROBHAZ project-report, Document RE-615705-001, Stolt Com ex Seaway A/S, Haugesund, Norway, 1997

/34/ Heidersbach, R.H. ; Dexter, S. C.: Marine Corrosion, ASM international metals handbook, Int. Handbook Committee, Volume 13, USA, 1987

/35/ Dietrich, G. ; Kalle, K. ; Krauss, W. ; Siedler, G.: Allgemeine Meereskunde - Eine Einfuhrung in die Ozeanographie. Gebrtider Borntraeger, Berlin, Stuttgart, 1975

/36/ Jackel, G.: Untersuchungen zur Entwicklung elektrischer Unterwasser- Handhabungsgerate. Fortschritt-Berichte VDI, Reihe 1: Konstruktionstechnik / Maschinenelemente, Nr. 168, VDI-Verlag GmbH, Dusseldorf, 1989

/37/ Lagies, Mr.: Private Communication. Ziehl-Abegg, Kunzelsau, Germany, 1997

/38/ Schuler, B.: Private Communication. SKF-Linearsysteme GmbH, Germany, 1997

/39/ Clauss, G. ; Lehmann, E. ; Ostergaard, C.: Meerestechnische Konstruktionen. Springer-Verlag, Berlin, Heidelberg, 1988

/40/ Hoerner, S.F.: Fluid-Dynamic Drag. Published by the author. Midland Park, New Jersey, USA, 1965

/41/ Blendermann, W.: Umgebungsbedingungen und Lastannahmen in der Meerestechnik. Handouts of the lecture course. Institute for Naval Architecture, University of Hamburg, 1995

/42/ Terribile, A. ; Prendin, W. ; et al.: An innovative electromechanical underwater telemanipulator present status and future development. Oceans 94, Conference Proceedings, Volume II, Brest, 1994

743/ Hydrovision Ltd., Offshore Hyball Product Catalogue, Aberdeen, Scotland, 1994

/44/ Harmonic Drive Antriebstechnik GmbH, Product Catalogue, Limburg/Lahn, Germany, 1995

/ -72-

10. APPENDIX A

10.1 Harmonic Drive

10.1.1 The Components

The Harmonic Drive set consists of three parts (Figure 38): - The wave generator: which is a thin raced ball bearing fitted onto an elliptical plug serving as a high efficiency torque converter. - The flexspline: a flexible steel cylinder with external teeth and a flanged mounting ring. - The circular spline: a solid steel ring with Wave Generator Flexspline Circular Spline internal teeth.

Figure 38: Components of a Harmonic Drive Gear/44/

10.1.2 The Principle of Operation

1. The flexspline is slightly smaller in diameter than the circular spline resulting in having two fewer teeth on its outer circumference. It is held in an elliptical shape by the wave generator and its teeth engaged with the teeth on the circular spline across the major axis of the ellipse. 2. As soon as the wave generator starts to rotate clockwise, the zone of tooth engagement travels with the major elliptical axis. 3. When the wave generator has turned through 180 degrees clockwise the flexspline has regressed by one tooth relative to the circular spline (Figure 39). 4. Each turn of the wave generator moves the flexspline two teeth anti-clockwise on the circular spline. -73-

10.1.3 Advantages of Harmonic Drive Gears

The construction of the gear has several advantages:

- Excellent positioning accuracy and repeatability Harmonic Drive gears are available with positioning accuracy of better than one minute of arc and repeatability within a few seconds of arc. - High torque capacity Since power is transmitted through multiple tooth engagement, Harmonic Drive gearing offers high output torque capacity equal to drives twice its size and three times its weight. - Zero backlash Harmonic Drive may operate with essential zero backlash between mating teeth because of natural gear pre-load. - High single-stage reduction ratio With only three elements the single-stage reduction ratios range from 50:1 to 320:1. - High torsional stiffness Harmonic Drive gears exhibit very high torsional stiffness over the whole speed range. The nearly linear stiffness characteristics guarantee optimum operating behaviour. - 74 -

10.2 Calculation of the additional pressure inside the actuators

The volume (V) of the linear actuators depend on the outgrowth of the pushrod. The length (/) and the diameter (£>) of the pushrod gives the amount of oil which has to be moved in and out of the linear actuators.

D = 48 mm l = 600mm

V = --7t-Dz-l 4 V = 0.00109m3

This volume will be pressed through the pipe to the pressure compensation unit. The velocity inside the pipe depends on the diameter of the pipe and the speed of the linear actuator pushing the oil. For a first assessment, a tube diameter of dwbe = 20 mm and the maximum speed of the actuators will be used.

dlube = 20mm

Vactuator, max 0.33 tnfs

V-v _ a r Yactuaiortmax oil,tube 4' hn% , 2 lube

^oil,tube = 1.75m/j

The oil pressed through the tube to the compensation unit will induce an additional pressure in the linear actuator due to the resistance in the tube. The resistance depends on the velocity and the viscosity of the oil as well as of the surface roughness. To get a first estimate for this additional pressure, the calculation will be done with the data of an oil suitable for the Harmonic Drive gears. The compensation fluid will be an oil of the same type like the oil which is used for the lubrication of the gears. The oil for the Harmonic Drive gears has to satisfy the class 32 specification. For the following calculation, a BP mineral oil was chosen.

p = B00kg/m3

77 = 0.168Pas (at 10°C)

To calculate the additional pressure a friction-energy (wr) has to be estimated depending on the length (a2) and the number of installations (a,) of the tube. A length of 5 meter and a number of 10 installations (knees) has been chosen. The Reynolds number (Re) describes the type of the internal flow, whether turbulent or laminar. -75 -

&Pac'"a,or=P-Wr M

/ 2 "\ Voil.tube m / W,v=E £•0/ 2 ) L /s 0i =10 [-] 02=250 [-] 64 ;= Re

^oil.tube ^tube P Re = V Re = 167

Due to the high viscosity of the oil, the flow is still laminar, although it has a rather high velocity.

APac,ua,or=1-22bar

As the final result we get an additional pressure of 1.22 bar inside the linear actuators. -76-

11. APPENDIX B

Technical Drawings and Data Sheets

Some drawing titles are the original Swedish titles from NEOS Robotics.

Drawing Drawing Title Page Number 1 SMST Stalldon 77 2 Cardanic Joint 78 3 SMST Axel 4, motor 79 4 Litton Resolver data sheets 80-83 5 Broms 84 6 Harmonic Drive data sheets 85-86 7 SMST Roraxel 87 8 SMST Centrumror 88 9 SMST Handled Kmpl. 89 10 SMST Axel 5, motor 90 11 SMST Axel 5, Lagring 91 12 SMST Axel 1, 2 och 3 92 13 SMST OK 93 14 SMST Gyro 94 -77-

Drawing 1: SMSTStalldon

t! i 1

k i i B L i I 1L

5 2 - li

>

v-NKHH-

© (

>

*

L J Drawing 3x120° M 20x1,5

2:

Cardanic

0 Joint

5x5

fief -78- 2x180°

0 5 0 - 0 . 5 -79-

Drawing 3: SMST Axel 4, motor -80 -

Drawing 4: Litton Resolver, Page 1

- Genauigkeit ± 6’, auf Anfrage ± 4’ - Montage direkt auf Welle - keine Kupplung erforderlich - keine Biirsten Oder Koniaklc - keine Lager - Hohlwellen 0 max. 12mm bzw. 17mm - Made in Germany

- accuracy ±6', on request ± 4’ - mounting directly on motor shaft -no coupling needed - no brushes or contacts - no bearings -hollowshaft 0 max. 12mmor 17mm - made in Germany

Biirstenlose Resolverernioglichen eine gcnaue Kommulation, absolute Lagercrfassung und Drclrzahlcrfassung von biirsicnlosen Elektromotorcn ohne mcchanischc odcr tcmperalurbcdingte Einschriinkungen, wie sic von anderen Scnsorcn bckannt sind. Biirstenlose Resolver sind Itir den induslricllen Einsalz unler ratthcn Umwcllbedingungcn gecignct. Sic sind wcitgehcnd unempfindlieh gegen Vibration, Scliock und erhiiluc Tempcratiirbeanspruchtuig.

Brushless resolvers provide accurate commutation, absolute position and feedback velocity of brushless electrical motors, without the mechanical or enviromenlal restrictions imposed by other feedback devices. They are well suited for applications in the industrial sector, because resistant to shock and vibration levels encountered in the factory environment.

• Biirstenlose Moloren • Brushless motors • Roboter • Robots • Produktionsaulomatisierung • Factory automation equipment • Werkzeugmaschinen • CNC machine tools • Verpackungsmaschinen • Packaging equipment • Medizinische Cerate • Medical instrumentation • Fordcranlagen • Material handling equipment • Elektro-Schrauber • Electro hand tools • Posilionierung und Drehzahlmessun • Feed back and/or speed control

Litton Servotechnik - 81 -

Drawing 4: Litton Resolver, Page 2

Eingangsspannung Input voltage 7V ff Eingangsstrom Input current 58 mA max. Frequenz Frequency 5 kHz Primiir Primary Rotor Anzahl Polpaare Speed 1 Transform. Verhaltnis Tranformation ratio 0,5 Impedanzen (nom.) Impedances (nom.) Zpu Z,» 75 + J 98 z,s zps 70 + J 85 Z.o zs„ 180 + J 230 z« z„ 170 + J 200 Gleichstromwiderstand (nom.) D.C. Resistance (nom.) Stator Input 40 n Rotor Ouptut 102 n Genauigkeit Accuracy ± 6’, on reqn Phasenverschiebung Phase Shift 10° ±3°

.Eingangsspannung Input Voltage 7V (r Eingangsstrom Input Current 40 mA max. Frequenz Frequency 5 kHz Primiir Primary Rotor Anzahl Polpaare Speed 1 Transform. Verhaltnis Tranformation ratio 0,5 on request Impedanzen (nom.) Impedances (nom.) Zpo Zpo 132 + ) 120 z„ Zp, 120 +J 107 z„ Z„, 215 + J 385 z„ z„ 193+ J 340 Gleichstromwiderstand (nom.) D.C. Resistance (nom.) Stator Input 90 Q Rotor Output 62 £2 Genauigkeit Accuracy ± 6', on reque Phasenverschiebung Phase Shift 11°+ 3°

Arbeitstemperalurbercich Operating temperature -50°C.... +150°C Gewiclu Weight 255 g KurzschluBfesligkeit Hi-Pol 500V bei 50Hz

Litton Servotechnik -82 -

Drawing 4: Litton Resolver, Page 3

300 era Teflon isolierle Lilzen AWG28 300 era Teflon insuloied lends AWG28]

yy/A

Belesliqunqsklanaer 3x ora Uafonq Servoclonp 3 places equal spaced

Honloge-Bohrunq: M3x6 lief Nounling-Hole: H3x6 deep

= 12mm, HolofMonsch Motor/longe

|/| 0,075 1 Ah 300 aa Teflon isolierle lilzen AVG2I I/I0.07SIAH 300 era Teflon isolierle UIzen AWG24 300 aa Teflon insuloied leads AVG2I 300 era Teflon insulated leads AM32<

I/I Q.1 IaH 27.3^ Vi 0.1 IA r —------\HolorHonsch y\ \Holofflansch \\ Holorllange \\ Holorllange Honloaebohruno: H3x7\ \

max rotor = 17mm, d™«r = d -0.7mm

Positive Drehrichtung ist rcchLs auf die Spulenseite (X ->) gesehen. Positive direction of rotation is cw as viewed from bobbin end (X ->).

Litton Servo technik - 83 -

Drawing 4: Litton Resolver, Page 4

Technische Anderungcn sind ohne Ankiindigung moglich. Dieses Datenblutt ersetzt alle vorangegangenen Datenbliitter. Technical changes are subject to change without notice. This data sheet supersedes ail prior data sheets.

Wtlnschen Sie weitere Informationen. wenden Sie sich bille an: For further information please contact:

Litton Litton

Litton Precision Products Servotechnik Precision International Inc. Products Oberfohringer Strafie 8 D-81679 MOnchen Telefon (089) 92204*0 Telex 524596

Telefax (089) 985184 97/03 - 84 -

Drawing 5: Broms

Nr Ant Sndring Datum Inf. Godk.

Mod.nr Amne Oet.nr Ant. Benamning Material Dimension Anm. Konstr. Ritad, Kop. Kontr. Stand. Godk. Skala, Ers&tter Ersatt av SH 1:1 Filnai yiE4150:8 at93-02-04

Ritn.nr NEOS BROMS NE4-15030 -85-

Drawing 6: Harmonic Drive Unit HFUC-20-2UH v

bis

HFUC-65-2UH

0 O h7

0RH7

m

@T h7 -86 -

Drawing 6: Harmonic Drive, Technical Data in mm

HFUC-2UH BaugroBe

W Js9

M6x9 M10 x 15 M10 x 15 M14x21 M16x24 M16X24

(O-Ring) (O-Ring) 79,5x2 124,5x2 204,5x2

Torsionssteifigkeit

! 14 I » | 58 HFUC-2UH BaugroBe 17 LJE 32 40 45 50 65

Ti in Nm | 1,96 | 3,9 I 7 14 j 29 j 54 76 108 168 235 Tg in Nm I 6,9 L 11.8 ! 25 48 | 108 i 196 275 382 598 843 Ki in Nm/rad 0,337x1 05 | 0,81x104 ! 1,3x104 j 2,5x104 5,4x104 | 1,0x105 1,5x105 2,0x105 3,1x105 | 4,4x105 i=50 Kg in Nm/rad 0,472x104 ! 1,08x104 ! 1,8x104 I 3,4x104 7,8x104 j 1,4x105 2,0x105 2,7x105 4,4x105 j 6,1x105 __ K3 in Nm/rad - ! | 2,3x104 j 4,4x104 9,8x104 ! 1,8x105 2,6x105 3,4x105 5,4x105 1^8x105 !Ki in Nm/rad I 0,472x104 1,01x104 | 1,6x104 3,1x104 j 6,7x104 ! 1,3x105 | 1,8x105 2,5x105 | 4,0x105 1 5,4x105 i>50 ;K2 in Nm/rad | 0,610x104 1,35x104 I 2,5x104 5,0x104 1,1x105 i 2,0x105 ! 2,9x105 4,0x105 j 6,1x105 8,8x105 ! 9,8x105 ___ |K3 in Nm/rad ! 0,710x104 1,55x104 i 2,9x104 5,7x104 ' 1,2x10= | 2,3x105 i 3,3x105 4,4x105 | 7,1x10= - 87 -

Drawing 7: SMST Roraxel

i "

L J - 88 -

Drawing 8: SMST Centrumror 7 V Drawing tEL —« I — l« I

9:

SMST

Handled

Kmpl.

^W | | HataM ^ M r f“-n -EEkJ flMM NEOS SMST HANDLED KMPL "V* Draw ing 10: SMST Axel 5, m otor -91-

Drawing 11: SMST Axel 5, Lagring r1 1 ing Draw EEC 1 CIO |w. |e.«. ~1

TTORAGNINfiSHOHEHT 9 8 fta

12:

T S M S

< xel A

1,

2

och

SHST STALLDOH

3

JAimc Otfjtf |Anl. | BcnSaning | Material 0»ernt«en Aft*. ■~"sMr"sHr |ML U..II .. '“TlEZIIOI Pn-m-u NEOS SMST AXEL 1. 2 OCH L i V -93-

Drawing 13: SMST OK

> rwing Draw

14:

T S M S

Gyro

s