ISARC2006

Development of Unmanned Caisson Installation System (UCIS)

Takumi MANABE Tatsuya HIRAYAMA Civil Engineering Divisions Group Civil Engineering Divisions Group PENTA-OCEAN CONSTRUCTION CO.,Ltd. PENTA-OCEAN CONSTRUCTION CO.,Ltd. 2-2-8, Koraku, Bunkyo-ku, Tokyo 2-2-8, Koraku, Bunkyo-ku, Tokyo 112-8576, JAPAN 112-8576, JAPAN

Abstract: Unmanned Caisson Installation System (UCIS) is an unmanned and remote-control though wireless LAN for performing a series of operation involved in caisson installation, which has been performed on caissons by manpower. The system enables one operator in a remote control room to perform diverse works involved in caisson installation, such as pouring water into the caisson and manipulating winches, and thus sharply reduces the required manpower. The system also ensures the safety of caisson installation works since there will be no persons on the caissons. It also improves the efficiency and precision of the works since the IT-based system centralizedly controls the movement of caissons and pouring and discharge of water. This paper describes the performances of the system and an example of actual application of the system.

Keywords: UCS(Unmanned Construction System), Caisson Installation, Wireless LAN

1. Introduction items other than camera images, as as camera images, Breakwater construction in harbors involves installing based on the goals and rules determined in advance. The caissons, which has been performed by floating a large latter, or the module for supplementing human operation, caisson, manipulating several haul winches by is a fail-safe multiple safety circuit system for predicting approximately 10 workers boarded on the caisson to move and avoiding danger to enable works to be performed in the caisson to a predetermined location, and injecting water constantly changing oversea environment. using several pumps by monitoring the water levels in the Waves are always high, and periods of chambers. Since the surface of a caisson is congested with tranquil sea conditions appropriate for wires for moving the caisson, water and drainage pumps, installation are short. and other devices, the space over the caisson is not only Efficiency is improved by difficult to work but is also dangerous since wires may monitoring and performing strike the workers on the caisson when they break due to installation centralizedly from a remote place. extensive tension caused by waves, etc. Moreover, Efficiency caisson caissons must be maintained leveled throughout the installation work installation work, and the conventional method requires The job safety is workers to operate water and drainage pumps by The water levels in improved by remote the chambers of a monitoring and monitoring the water level in the chambers and is caisson and the operation and inaccurate and inefficient. inclination of the Strict leaving the surface of Thus, a new one-man-operated remote-control system caisson are monitored control of Improving from a remote place water pouring job safety the caisson for installing caisson was developed by extracting factors in real time to start and draining unmanned during involved in the work. The background of the UCIS and stop water installation. pumps and drainage development is shown in Figure 1. pumps. Today, unmanned construction systems for land works The differences in water level Caissons may roll and pitch have already been deployed. Most of these systems are between two adjacent chambers of a large by long-period waves and may be crowded by wires and water and drainage pumps, based on remote control by monitoring images from caisson, which has many chambers, are maintained to not exceed 1 m. and wires may break and strike workers. cameras. However, information from camera images is insufficient for remote installation of caissons since the Figure 1 Background of UCIS development marine environment, in which caissons are to be installed, is never constant. Just providing environmental data, such 2. Overview of the system as winds and waves, to the operator is likely to not solve (1) Overview the problem. Creating a virtual reality space around the The UCIS is a remote control system to improve the operator of being on the caisson is not practical. Thus, two efficiency and safety of works by centralizedly modules were added to the UCIS: a module for assisting monitoring and controlling caisson movement, winches, appropriate human operation and a module for and water and drainage pumps via wireless LAN. A supplementing human operation. In the former, the system schematic provides the operator, who remotely controls winches and diagram is shown in Figure 2, and a flow of caisson pumps, with guiding information of remote monitoring installation is shown in Figure 3.

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(2) Characteristics The system has the following characteristics: 1) It remotely and centralizedly monitors caissons (position, direction, and inclination) and the water levels in the chambers and operates haul winches and water and drainage pumps. 2) It is installed with a fail safe system that enables safe and certain installation of caissons. 3) It can monitor and operate from a distance of up to 500 m. 4) The system enables one operator to monitor and install caissons.

3. System configuration The UCIS consists of four key , which are shown in Figure 4. 1) Remote system for monitoring the movement of caissons, the water levels in the chambers and the operation states of winches and water and drainage pumps, 2) Remote system for operating winches and water and drainage pumps, 3) Multiple safety system consisting of multi-channel systems for transmitting emergency stop and for operating winches, and Figure 2 Conceptual diagram of the system 4) Devices for predicting and avoiding danger, such as Stopping winches at over loads torque limiters of winches and alarm equipment Stopping winches warning abnormal system operation. when over feeding occurs Stopping winches START ASTART Multiple safety circuit systems when overwinding occurs Outfitting a caisson Switching between modes of remote and -side control of winches Floating the caisson A Discharging water from the caisson Multiple emergency stop circuits Towing the caisson Measuring the water levels in the chambers Preventing wires from receiving excess loads Positioning the caisson Systems for predicting Measuring the draft of the caisson Warning abnormalities and avoiding danger Attaching fixing wires Measuring the inclination Calculating the stability of the caisson NO Pouring water into of the caisson the caisson (first time) B Starting and stopping the drainage pumps Discharging water Tensioning the wires Systems for YES to the target level Starting and stopping remote control the water pumps Guiding the caisson to END Running and reversing the winches the location C Key technologies B START Pouring water into Displaying images of joints the caisson(second time) B Displaying an image of Pouring water into the caisson Seating the caisson the entire caisson to the bottom of the sea Monitoring the loads acting on Measuring the water levels water and drainage pumps Checking the location in the chambers Monitoring the operation states where the caisson is to be installed of water and drainage pumps Measuring the draft of the caisson Monitoring the attachment and Pouring water into the caisson detachment of winches from crutches Measuring the inclination (third time) NO Systems for Monitoring the loads acting of the caisson remote monitoring on winches Releasing the caisson Monitoring the states of Pouring water to winch operation YES the target level END END Displaying images of the winches Monitoring the location and C START direction of the caisson ： Works performed using the system Monitoring the inclination of the caisson ： Works outside the scope of the system Operating winches Monitoring the draft of the caisson Surveying the location Monitoring water level of the caisson in the chambers of a caisson NO Target location of Figure4 Key technologies of the Unmanned Caisson Figure 3 Flow of caisson installation YES caisson installation Installation System END

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Water and ta da drainage pumps l a Operator o at tr d Monitored n n o io C at O data er Judging pe p ata Winches ra O ol d a tio ntr at n Co n d atio per Remote monitoring O Location and and control panel direction data GPS Wireless LAN Wireless Wa ter l network control panel evel Water level Remote control room In an cl d d I i raf sensors m na t da a ti ta Figure 5 Model of the system g on e da da ta Expertise is required to install caissons since water ta Inclinometers should be poured and winches should be operated timely to the rolling and pitching of the caissons, which are caused by waves. The operation also depends on waves, the Monitoring cameras capacity of used, and the shape of the caisson. Caisson Thus, the system installs caissons not automatically but by an operator from a remote place. A model of the system is shown in Figure 5. An operator makes judgments and operates machines based on information from instruments installed on the caisson. Instruments on the caisson include an RTK-GPS receiver for determining the location and direction of the caisson, inclinometer for measuring the inclination of the caisson, water level gauges for monitoring the water levels in the chambers, a draft gauge for monitoring the draft, hauling winches, water and drainage pumps, monitoring cameras, and a wireless control panel. In the remote control room, a remote monitoring and control panel is installed to monitor and control the instruments on the caisson. Throughout the entire process of caisson installation, Figure 6 Remote monitoring and control panel sensor data, images and control signals are communicated between the wireless control panel and the remote monitoring and control panel through wireless LAN. The operator watches the monitor on which the information is displayed to correctly understand the movement of the caisson and the water levels of the chambers and can alone operate two or more winches and several tens of water and drainage pumps efficiently from a remote place. A remote monitoring control panel is shown in Figure 6, and a wireless control panel is shown in Figure 7.

4. Fail safe technologies The introduction of the UCIS will improve the safety of caisson installation works since there will be no workers on the caissons, but unmanned operation may also face other kinds of risk. Figure 7 Wireless control panel Risk factors include: 1) Maintaining the stability of caissons, To avoid these problems, the aforementioned multiple 2) Bad wireless LAN , safety systems and systems for predicting and avoiding 3) Sudden over feeding and over winding of broken wires, danger are implemented. These mechanisms are and indispensable since unexpected effects by external factors 4) Duplication of remote operation and machine operation. on caissons and malfunctioning of systems may lead to

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serious accidents in unmanned installation of offshore caissons. Water level measurements in each chamber and inclinometer data may be insufficient for remotely controlling draining water from caissons in which the center of gravity of the caisson shifts from the center of buoyancy when the same amount of water is poured into and discharged from all chambers, such as those for the upper slopes of banks. Thus, the UCIS calculates the appropriate water levels in the cambers in advance, sets the simulation results as the ultimate and intermediate target water levels, and displays the then target water levels on the monitor to control pouring and discharge of water while maintaining the stability of the caisson. Winches are to be remotely controlled by continuously transmitting winch operation signals when the control lever Figure 8 Installing caissons is inclined, and no self-maintaining circuit is used. This is to prevent unintentional movement of the winch when the wireless LAN fails to transmit signals. Multiple emergency stop circuits are ensured, and the system can be shut down during emergencies even when one wireless LAN circuit links down. To prevent damages by breakage of winch wires, the system is equipped with a mechanism for detecting over winding and over feeding of the wires and stopping the winches. However, the wires are very little likely to break since each winch is equipped with a torque limiter, which automatically release the wire when a load exceeding and arbitrarily set load acts on the wire. Like all other remote control systems, the switch for changing the control modes from remote to machine-side and vice versa is on the machine to prevent duplicate operation. The system also enables the loads acting on Figure 9 Remote monitoring and controlling installation winches and water and drainage pumps to be monitored work from a remote place and warns when the machines receive excess loads. 6. Conclusion Efficient and cost-reducing construction technologies 5. Example of system application are increasingly demanded accompanying changes in the The UCIS was used to install two caissons (weight: 8,900 environment surrounding the construction industry. Safe tons, 30 m (D) × 26 m (W) × 22 m (H)) of a breakwater for construction systems are needed to cope with reductions in controlling damages to onboard cargos by swells experts and aging workers. The author expects this (long-period waves), which are characteristic to the Pacific unmanned installation system be an aid to solve these coast. The construction of the on which the problems. caissons were to be built started in 2000, and this caisson Finally, the author would like to sincerely thank all installation project was for the installation of the first people involved in the development and implementation of caissons of the breakwater. the system. The first caisson was installed on December 6, and the second caisson was installed on December 16. The caissons were floated and towed to the specified sites approximately 2 km off the shore. An operator in a remote control room about 300 m from the sites operated and monitored the work centralizedly. On both days, the meteorological pressure pattern was that of the winter type, and adverse effects by high waves were concerned for. The use of the UCIS enabled safe and smooth installation to be performed. Views of the caisson installation are shown in Figures 8 and 9.

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