Human Powered Submarine

UNIVERSITY OF WASHINGTON Human Powered Submarine

2015-2016 Design Report

Table of Contents List of Figures ...... 4 List of Tables ...... 5 Preface ...... 6 Executive Summary ...... 7 Hull ...... 8 Overview ...... 8 Hull Form Performance ...... 8 Safety Systems ...... 10 Pneumatics ...... 10 Pop Up Buoy ...... 11 Hatch Latch ...... 11 Life Support ...... 12 Ballast ...... 14 Propulsion ...... 15 Gearbox ...... 15 Overview ...... 15 Goal ...... 15 Concept Generation ...... 15 Testing ...... 16 Concept Selection ...... 17 Conclusion ...... 20 Propeller ...... 21 Overview ...... 21 Goal ...... 21 Concept Generation ...... 21 Concept Selection ...... 21 Design ...... 22 Manufacturing...... 24 Timeline ...... 25 Conclusion ...... 25 Hub ...... 25 Overview ...... 25 Goal ...... 25 Concept Generation ...... 26 Concept Selection ...... 26 2

Design ...... 26 Manufacturing...... 33 Conclusion ...... 33 Controls ...... 34 Overview and Purpose ...... 34 Control Planes ...... 34 Overview ...... 34 Goal ...... 34 Concept Generation ...... 34 Concept Selection ...... 35 Manufacturing...... 37 Conclusion ...... 38 Mechanical Controls ...... 38 Overview ...... 38 Goals ...... 38 Concept generation ...... 38 Concept Selection ...... 38 Manufacturing...... 39 Conclusion ...... 41 Electrical Controls ...... 41 Overview ...... 41 Goal ...... 42 Concept Generation ...... 42 Concept Selection ...... 42 Manufacturing...... 44 Conclusion ...... 45 Electrical Systems ...... 46 Core ...... 46 Joystick ...... 46 Design Specification ...... 46 Design Procedure ...... 46 System Architecture ...... 47 Testing ...... 47 Stepper Controllers...... 47 Problems with Servo Control ...... 47 Research Last Year ...... 48 3

Motor Specifications ...... 49 Further Defining the Problem ...... 49 The New Board ...... 51 Closed Loop Control ...... 54 The Prototype ...... 55 Programming ...... 55 Appendix A: Testing ...... 57 Appendix B: The Team ...... 58 Captain - Bentley Altizer ...... 58 Mechanical Controls – Tyler Nichol ...... 58 Dive Manager – Robert Karren ...... 58 Marketing Director – Colin Katagiri ...... 58 Electrical – Jack Gentsch ...... 59 Computer Science – Joseph Jimenez ...... 59 Gearbox – Andrew Fitzgerald ...... 59 Propeller and Hub – Gavin Denzer ...... 59 Pilot – Carol Nishikawa ...... 59 Pilot – Dominic Forbush ...... 60 Adviser – Andy Stewart ...... 60 Team members ...... 60 Appendix C: Hull ...... 58 Hatch Latch ...... 58 Appendix D: Gearbox ...... 60 Appendix E: Hub ...... 66 Appendix F: Code ...... 70 Appendix G: Future 2-Person Submarine ...... 80 References ...... 81

List of Figures Figure 1.1: Female Mold Drawing ...... 9 Figure 1.2: Fiber Laying ...... 9 Figure 1.3: Mold Destruction ...... 10 Figure 2.1: Static diagram of Crank arm and Belt Pulley ...... 16 Figure 2.2: Belt test fixture mounted on Instron 5585H universal testing machine ...... 17 Figure 2.3: Final gearbox design with side plate and miter box made transparent for visualization .. 18 Figure 2.4: Space between transverse shaft and final shaft ...... 19 Figure 2.5: Belt contact wheel at the front pulley...... 20 Figure 2.6: Structural Analysis of Propeller Blade in Operation ...... 23 Figure 2.7: Three Part Carbon Fiber Propeller Compression Mold ...... 24 Figure 2.8: Propeller Blade with Flash and with Flash Removed Post Production ...... 24 Figure 2.9: Different Angles of the Hub Showing Both Static and Dynamic Seals ...... 26 Figure 2.10: Controllable Pitch Propeller Hub Assembly Cross Section ...... 28 Figure 2.11: Electronics Cylinder ...... 29 Figure 2.12: Assembly of the Electronics Cylinder, Hub, and Collar...... 30 Figure 2.13: Efficiency vs. Advance Coefficient ...... 31 Figure 2.14: Optimum Angle Spectrum ...... 32 Figure 2.15: Thrust Spectrum ...... 32 Figure 2.16: Hub Being Machined Using Rotating Jig ...... 33 Figure 3.1:Proposed Control Plane Geometries...... 34 Figure 3.2: Pathlines Shown Over Preliminary Design ...... 36 Figure 3.3: Flow Modeled Over the Submarine and Control Planes ...... 36 Figure 3.4: Selected Control Plane Geometry ...... 37 Figure 3.5: Photo of Fin Mold Half ...... 37 Figure 3.6: Mechanical Joystick ...... 39 Figure 3.7:Mechanical Control System ...... 40 Figure 3.8: Close up of Pulley Groove Design ...... 40 Figure 3.9: Mechanical Cable Tensioner ...... 41 Figure 3.10: CAD Model of Stepper Motor Housing ...... 43 Figure 3.11: CAD Model of Core Electronics Enclosure ...... 43 Figure 3.12: Electric Joy Stick Design ...... 44 Figure 4.1: Old Stepper Driver Electrical Schematic ...... 48 Figure 4.2: Old Stepper Driver Board Layout ...... 49 Figure 4.3: Sparkfun Pro Micro Schematic ...... 49 Figure 4.4: Pololu AMIS-30543 Stepper Motor Carrier Driver ...... 50 Figure 4.5: Ground Plane Heat Sink for AMIS-30543 ...... 50 Figure 4.6: New Stepper Controller Board ...... 51 Figure 4.7: NI Multisim Model of Power Regulation ...... 52 Figure 4.8: 12V Supply ...... 52 Figure 4.9: -12V Supply ...... 53 Figure 4.10: 12V Supply 80% Duty Cycle ...... 53 Figure 4.11: 12V Supply 20% Duty Cycle ...... 53 Figure 4.12: 12V-7V Supply 12V 80% of the time ...... 54 Figure 4.13: 7V Supply ...... 54 Figure 4.14: SLA Pin When Coils are at Zero Current Crossing ...... 55 Figure C.1: Static Diagram of Latch Forces ...... 58 Figure C.2: Tensile Test Results ...... 59 5

Figure D.1: Instron Universal Testing Machine ...... 60 Figure D.2: Static Diagram of Transverse Shaft ...... 60 Figure D.3: Load in vs. Extension 5mm Belt Single Tooth...... 63 Figure D.4: Load vs. Extension 5mm Belt Two Teeth ...... 64 Figure D.5: Load vs. Extension 5mm Belt Three Teeth ...... 64 Figure D.6: Load vs. Extension 5mm Belt Six Teeth ...... 65 Figure E.1: Aluminum Propeller Blade Adapter ...... 66 Figure E.2: Bevel Gear Assembly ...... 66 Figure E.3: Stepper Motor Adapter ...... 67 Figure E.4: Hub Attached to Electronics Cylinder ...... 67 Figure E.5: Retaining Collar Connecting the Hub to the Electronics Cylinder ...... 68 Figure E.6: Coupling Drive Shaft Adapter ...... 69 Figure G.1: 2-Person Hull First Half Construction ...... 80 Figure G.2: 2-Person Hull Construction ...... 80

List of Tables Table 1: General Specifications ...... 8 Table 2: Hull and Propeller Data ...... 22 Table 3: Power Supply Results and Reasoning ...... 52 Table 4: Max Load and Extension at Max Load Per Trial for HTD 5mm Belt Test of Single Teeth ... 63 Table 5: Max Load and Extension at Max Load Per Trial for HTD 5mm Belt Test of Two Teeth ...... 64 Table 6: Max Load and Extension at Max Load Per Trial for HTD 5mm Belt Test of Three Teeth .... 65 Table 7: Max Load and Extension at Max Load Per Trial for HTD 5mm Belt Test of Six Teeth ...... 65

Preface The University of Washington Human Powered Submarine (UWHPS) was founded in 1989 for the first International Submarine Races held off the coast of Florida. Over the years the team has developed 9 submarines in both single person and two person categories. The current team is comprised of 44 members from the Colleges of Engineering, Business, Oceanography, and local community members with the vision of developing world class project engineers through hands on learning. The mission of the current team is to produce the fastest submarine possible capable of navigating the European International Submarine Races (eISR) course. UWHPS had, until recently, been in a long pattern of consistent decline in interest, performance, and support. In 2013 we lost our workspace and all but four members. Against the odds, our small, dedicated group of students chose to pursue eISR 2014. With less than eight- thousand dollars, we were able to attend, compete in, and place sixth of twelve at eISR. With nothing to lose and hopes of inspiring a new wave of interest at the University of Washington we chose to manufacture a new submarine hull more aggressive than any done before. The next year, as participation and interest grew, we decided to adopt a more aggressive production strategy by building a new hull from scratch. We named it “What Sub Dawg?” (WSD) and while requiring a pilot under five-foot, six-inches with shoulders squished to fourteen inches, it is capable of outputting 750 watts in the hopes of breaking the world speed record. We also took on other challenging projects, such as fly-by-wire controls and a controllable pitch propeller hub. By ISR14, WSD was in full working order. Although we were not able to fully test our controllable pitch propeller or fly-by-wire control systems for that race, we are still committed to making those projects viable. WSD was able to reach 6.01 knots with our male pilot and 5.44 knots with our female pilot at ISR14. Both were school records, and our female pilot was 0.06 knots from beating the world record. With all of this behind us, our leadership team recognized that in order to progress, we needed to address the non-engineering challenges of running a team as much as the engineering challenges or building an optimized submarine. This means performing an in depth assessment of leadership, corporate support, university support, and recruitment of not just capable engineers, but committed, dedicated teammates. This new, broader focus directly affected our decision when adopting a new faculty advisor who is aligned with our vision through the Applied Physics Lab (APL). In addition to preparation for eISR we have begun the design and manufacture of a new two-person hull through the Northwest School of Wooden Boat Building. The goal of this submarine is not only to break the two-person sub world speed record, but also to combine local history, heritage, and master craftsmanship with cutting-edge technology. We hope to involve as many people in the development of this submarine as wish to participate. Already, the project has drawn community members ages 12-46 to participate in some fashion.

Executive Summary This report outlines the design of our submarine, “What Sub Dawg?”, and its preparation for eISR 2016. The hull of WSD was built on a two-year design cycle and is being raced for the second time after debuting at ISR13 during the summer of 2015. The hull geometry is unchanged, but all of the internal systems have been redesigned as well as the control planes and propeller. At ISR14, WSD achieved 6.01 knots with our male pilot and 5.44 knots with our female pilot. Our speed goals for eISR are to surpass 7 knots with our male pilot and 6 knots with our female pilot. The largest factors inhibiting our ISR14 performance were pilot restriction and bubble entrapment in the propeller. Resolving these issues was the focus of our largest design changes by implementing a belt-drive gearbox system and a smaller propeller. Other upgrades include the implementation of an electronic control system, a controllable pitch propeller, and lower drag control planes as well as improved pilot air supply delivery, hatch release, and pop-up buoy.

Hull Overview The current hull, “What Sub Dawg?”, is in its second year of use. The original design began in 2014 during preparation for eISR 2014. The hull must completely surround the pilot while providing maximum hydrodynamic benefit and acting as a platform for mounting the life support, propulsion, and control systems. Previous UWHPS hulls have included excessive internal room for convenience and pilot comfort. We diagnosed this as one of the main factors limiting speed so, when designing and manufacturing WSD, we sacrificed space for speed. Table 1: General Specifications Dimension Specification Hull Only With Appendages Length 2.44 meters 2.67 meters Beam 0.51 meters 0.99 meters Draft 0.64 meters 0.99 meters Egress 0.91 meters 0.91 meters Volume .401 푚3 .402 푚3 Wetted Surface Area 3.46 푚2 4.02 푚2 Center of Gravity NA 3cm Below Centerline Center of Buoyancy NA 2cm Above Centerline Drag at 7.5 knots NA 190 N

Hull Form Performance

The hull was designed primarily in the 2013-2014 academic year. The methodology used was to determine the minimum feasible dimensions based on a certain size pilot. The primary dimensions of concern were the knee room needed to run the gearbox and the shoulder width. Several concept designs were generated based off of the minimum dimensions and the design optimized for speed among them was pursued. We created an equation by applying the basic equation of motion to compare the concept designs. The equation evaluated velocity as a function of mass, cross sectional area, and coefficient of drag. The coefficient of drag was determined by using CFD through ANSYS. The final design we selected had a substantial reduction in mass and a slight increase in drag coefficient compared to previous hulls. We reached out to Janicki Industries, who had assisted us in hull manufacturing in previous years, to produce the hull. With large envelope 5-axis milling capabilities, Janicki was able to mill a female mold for the submarine with great precision and detail. The mold design chosen would extend one inch past centerline to allow a wax strip to be laid along the top edge for the top half of the submarine The intention was for this to make a uniform lip which would mesh with the other half in a lap joint. Also included was an offset lip in the front of the submarine as a mounting point for the 9

window and a 45-degree flange around the entire mold to give a precise cutting edge and a solid foundation for laying down the reinforcement fibers.

Figure 1.1: Female Mold Drawing For the layup we chose to use 4 layers of fabric. One glass layer on the inside and outside and two layers of the carbon fiber sandwiched in between. This is shown in Figure 1.2.

Figure 1.2: Fiber Laying 10

While the mold was originally meant to be two halves, significant issues came up during the production process. When making the first half (the bottom half), the sealant applied to the outside of the foam mold was chosen incorrectly and bonded with the infusion resin instead. Unfortunately, this meant we had to destroy the mold in order to remove the half that had been bonded incorrectly. In order to compensate, we used the first half as a male mold instead of building a new mold due to time limitation. Using the first half as a male mold meant that significant body work and faring on the top half was required to properly connect and align the two halves.

Figure 1.3: Mold Destruction

Safety Systems Pneumatics The safety systems are run pneumatically off of a 6 cubic foot air supply dedicated to releasing the hatch and pop-up buoy. Within the general layout of the system the only change made was to reduce the pneumatic tubing diameter in order to use less of our air supply per deployment.

The internal diameter of last year’s tubing was 0.18”, so we chose ⅛” tubing with an internal diameter of 0.0625”. To compare the deployment volumes of the old and new systems, we used the following assumptions and equations:

● There are 20 feet of tubing in both systems. ● The pneumatic cylinders have 0.5” stroke length, and bore lengths of 7/16” and 9/16”. ● We have an air tank that holds 6 cubic feet of air and delivers a pressure of 100 psi with the use of a pressure regulator. ● The volume of air used at standard pressure (14.7 psi) can be calculated using the equation:

푃푖푉푖 = 푃푓푉푓 11

With the use of our old tubing at system pressures of 100 psi, each deployment used approximately 41.5 in3. Using the new tubing, each deployment uses approximately 6.37 in3.

The use of the narrower tubing results in around an 83% decrease in air consumption per deployment.

Pop Up Buoy The pop up buoy is a buoy used for identifying where the submarine is in the case of an emergency. It is attached to a pneumatic dead man’s switch the pilot is actively holding. If the pilot lets go of the switch, the pneumatic system is connected to actuators that release the hatch hold and the buoy pin. The buoy is a 3D printed structure filled with buoyancy foam. It has a hole in the base where the release pin ordinarily rests, counteracting the buoyancy force and keeping the buoy down. When the actuator pulls the pin, the buoy rapidly rises to the surface. The buoy itself is connected to a bright neon orange string attached to a reel on the buoy housing that keeps the buoy attached to the submarine hull. This string can also be used to pull the entire submarine in the event of an emergency.

Figure 1.4 Pop-up Buoy

The basic design of the buoy is a holdout from last year, but while effective, there were some weaknesses we fixed. First was the size. The submarine is very compact and the old buoy was fairly large and protruded down into the buoyancy area and also impeded the hub. This year we halved the height of the buoy and moved the reel, originally on the housing, to behind the housing, which in turn freed up space near the propulsion system. We also adjusted some of the reel support so it was less elongated, thicker, and generally less susceptible to breaking while still maintaining efficient volume and spacing requirements.

Hatch Latch The latch securing the pilot hatch is the one of the most critical safety systems on board the submarine. The latch must hold the hatch in place securely, but more importantly have a 100% reliability for releasing when a pilot or rescue diver needs to open the hatch. 12

The chosen design relies on the pneumatics for the pilot to release the hatch and has a direct mechanically linked handle for rescue divers to use. We also wanted the pilot to have a failsafe in case of an emergency situation where the pneumatics had failed, and rescue divers were not nearby to remove the hatch. For this we chose to have a designed point of failure which the pilot could bump the hatch off with their own strength. Our pilots chose to have a break point of 100 pounds of force needed to break the hatch free. To accommodate this, we chose 4-40 nylon nuts to secure the latch and performed tensile tests to determine how many of the nuts were needed to reach the 100-pound limit. Details of this test can be found in Appendix C Figure 1.5 shows a schematic of the latch design with arrows representing the forces at play in an emergency situation when the pilot would try to break free.

Figure 1.5: Hatch Latch Static Diagram Recovery Tow Point The Recovery Tow Point is located inside of the hull, directly forward of the pilot’s hatch.

Life Support Primary Air Supply The primary source of air for the pilot is the onboard air in the submarine. The onboard air is contained in a 5L tank with a working pressure of 232 bar. This tank is sized and placed in the submarine such that it does not impede the pilot’s motion as they are pedaling. To calculate the available volume of gas for the pilot, the following calculation is used:

푉푎푣푎푖푙푎푏푙푒 = 푉푐푦푙푖푛푑푒푟 × (푃푓푢푙푙 − 푃푟푒푠푒푟푣푒)

푉푎푣푎푖푙푎푏푙푒 = 5 L × (232 bar − 50 bar reserve) = 910 L gas available

A typical run in the submarine takes about 7 minutes: 5 minutes to prep and ballast after the pilot has entered the submarine, and 2 minutes of exercise. According to the International Marine Contractors Association, a diver working hard in an emergency uses 40 L/minute of gas [1]. In the interest of safety, our estimations will double that value to 80 L/minute for the exercise portion of the run. When the pilot is not exercising, their air consumption is approximately 25 L/minute. The following calculations show how much air a typical run will use of the onboard air, as well as how many runs could be completed on one fill:

푉푟푒푞푢푖푟푒푑 = (5 minutes × 25 L/min) + (2 minutes × 80 L/min) = 285 L gas required

Gas available 910 L Total runs = = = 3 possible runs Gas used in one run 285 L

This shows that a full primary tank can support 3 full runs, in addition to a 50 bar reserve.

Secondary Air Supply

In addition to the main onboard air in the submarine, the pilot carries a 3L tank, attached to their body with a harness. The regulator for this tank is secured with a necklace for easy access by the pilot in case of emergency. In an emergency situation, we expect the pilot to use 40 L/min of air. To calculate the available gas in the secondary supply, the same calculation as above is used, as well as a calculation for the amount of time this gives the pilot:

푉푎푣푎푖푙푎푏푙푒 = 3 L × (232 bar − 50 bar reserve) = 546 L gas available

푉 546 L Time = 푎푣푎푖푙푎푏푙푒 = ≈ 13 minutes Gas consumption rate 40 L/min

These calculations show that in an emergency, the 3L secondary air supply gives the pilot approximately 13 minutes to get to safety, in addition to a 50 bar reserve. Mask and Regulator To allow for efficient use of space inside the submarine, the pilot wears a low-profile Aqualung Sphera mask so they can position their head further forward in the sub. To allow for the strenuous breathing required by the race, the pilot will use a Scubapro S600 second-stage regulator. This regulator was chosen for its reliability as well as ease of breathing under high load.

Figure 1.6: Aqualung Sphera mask Ballast Ballasting is one of the most key elements to completing a successful run. Having a neutrally buoyant submarine makes it so that the pilot will not have to fight the pitch, which in turn causes more drag or in extreme cases a breach or bottoming out. A properly ballasted submarine will not pitch upward or downward, maintains its depth in the water column, and has a slight roll. Under normal operation, this roll will be cancelled out by the propeller torques and cause the submarine to travel at a zero yaw angle. The ideal ballasting technique requires first a positively buoyant submarine. As much as possible floatation should be placed above centerline to increase roll stability. Small lead weights with Velcro can then be easily manipulated to different positions on the submarine to achieve neutral buoyancy. Between each run, and for each pilot, ballasting must be repeated to achieve perfect buoyancy. Under perfect circumstances the submarine will rise and drop with the pilot’s breath. We have used this system for the past several years with no problems. The simplicity and low profile of the lead weights allows them to be easily shifted around to adjust for variable situations.

Propulsion Gearbox Overview The designed system as a whole, for the purposes of this paper will be referred to as the “gearbox” for historical and contextual reasons. What Sub Dawg was purposefully designed to reduce its internal volume in an effort to reduce the mass needed to be accelerated by the limited power of a human pilot. A consequence of the small hull of WSD was twofold: first, the pilots, especially the male pilot, had problems with interference between their feet and the hull; second, the pilots were unable to extend their bodies into a more prone and ergonomic position.

Goal The task of redesigning the gearbox came with the constraint of needing to relocate the axis of the spindle aft-ward by about 5 inches (12.7 cm). This relocation would allow for better pilot ergonomics but would also aggravate the issue of heel and toe interference with the hull. To mitigate this interference problem, the pilot’s feet were to be moved inward (together) as much as possible. Moving the pilot’s feet inward provides more space for the pilot’s feet because the centerline is the tallest portion of the hull. Historically the gearbox was a simple bevel gear system with a typical gear ratio of 3:1. This system was simply too wide to meet the constraints placed upon the new system. An alternative to the bevel gear system was proposed. A belt, initially driven by the pedals, transfers motion to a small 90-degree miter box further aft in the hull. The belt also provides the gear ratio, instead of the bevel gear.

Concept Generation Discussion about the new gearbox design first centered on whether to select a chain drive or a belt drive. Both chains and belts are among the most efficient forms of power delivery known. Bicycle chains are quite slim, with an external width of about 7mm. The slender nature of the chain would be desirable for the purpose of reducing the width of the gearbox. The largest detractor from the chain was concerns with the metal chain and chain wheels being submerged in water repeatedly over the course of the few months leading up to the European International Submarine Races competition. The efficiency of chains versus belts was considered next. A report, by a company called Friction Facts, which compares the efficiencies of bicycle chains and belts was found. This report suggested that if preload on the belt can be reduced and rider (pilot) output is greater than 208 W the frictional losses of the chain will be greater than that of the belt [2]. This hinted that it may be possible to reduce the relative inefficiencies of a belt especially if the chain ends up with corroded bushings. Initially the belts of interest were direct replacements for chains on bicycles such as the Gates Carbon Drive. After exploring the idea of using a Gates Carbon Drive belt, it was found that they are not made in short enough lengths for application in WSD. The next best alternative, a High Torque Drive (HTD) timing belt, was selected. HTD belts are readily available from various suppliers and in a large variety of lengths.

Testing In order for the belt drive gearbox to be viable the belt must be capable of withstanding the load applied by the pilots. The tension in the belt is calculated by treating the system as a statics problem, see the free body diagram in Figure 1. This would be a more extreme loading condition than will be seen by the gearbox. Assuming that the pilot can put out 890 N (200 lbf) of force onto the pedal attached to a 160mm crank arm and the belt pulley has a radius of 87.5mm, then the tension in the belt can be calculated, as shown in Appendix B, to be 1630 N (365 lbf).

Figure 2.1: Static diagram of Crank arm and Belt Pulley The conventional wisdom for synchronous belts is that a minimum of six teeth should be engaged on a pulley to keep the force acting on individual teeth at acceptable levels. If too few teeth are engaged, the belt will have an increased tendency to skip on the pulley, both increasing wear and reducing efficiency [3]. Being a human powered system, efficiency is of paramount importance to the submarine as a whole. The rear (small) belt pulley of the designed gearbox has 22 teeth with a minimum of 8 teeth engaged. In order to test if the specified belt was capable of withstanding a load of 1630 N the belt was tested on the mechanical engineering department’s universal testing machine, an Instron model 5585H, similar to the machine shown in Figure A1. The belt required a special fixture to be manufactured to be able to attach to the tension jaws of the Instron machine. A fixture was designed to be compatible with different belt tooth patterns. The belt test fixture mounted in the Instron 5585 machine is shown in Figure 2. Belt test coupons were tested in tension to determine their failure load. The tests began by setting up the belt coupons with six teeth in the lower fixture and one tooth in the upper fixture. The test progressed to two, three, and six teeth in the upper fixture. When three teeth were engaged in the upper fixture the lowest max load on the coupons were larger than 1550 N, a mere 80 N less than the necessary load capacity. Three trials were run with six teeth engaged in both fixtures, with an average max load of 3125 N. One trial was run with seven teeth engaged in both fixtures with a promising max load of 4186 N (941 lbf). With a minimum of eight teeth engaged on either pulley the belt should be sufficiently strong for WSD.

Figure 2.2: Belt test fixture mounted on Instron 5585H universal testing machine

The belts failed in two ways under this purely tensile load. The first failure was in the teeth of the belt coupons were sheared off of the face of the belt in nearly every trial, regardless of the number teeth engaged in the fixtures. The other failure occurred when the fixtures bolts were purposefully left an eighth turn loose from finger tight. In this condition the belt and teeth were drawn between the two jaws of the fixture, appearing to flatten the teeth. An example of the results of a loose fixture trial is seen in Figure C1, trial 5.

Concept Selection The final design of the gearbox consists of two subunits. The first is the forward housing that contains the spindle and initial belt pulley. The forward housing is shown on the left in Figure 3. The second subunit is the miter box, shown on the right. The miter box contains the rear belt pulley which is linked via shaft to a 90-degree miter gear. The miter gear then turns the final driveshaft. 18

Figure 2.3: Final gearbox design with side plate and miter box made transparent for visualization The initial design had the rear pulley on the outside of the miter box. This forced the front pulley to be too far to the side making the design only marginally slimmer than the old gearbox. It was noticed that if the miter gears had a large enough pitch diameter, then there would be enough space between the final drive shaft and the transverse shaft to incorporate the rear pulley into the miter box. This alteration allowed the belt to be placed directly onto the centerline of WSD. Having the belt on the centerline allowed for the design to be narrowed significantly. The width of the designed gearbox is 1.54 in (3.91 cm) wide while the old gearbox was 4 in (10.16 cm) wide. After the concept of the final design was conceived, the components of the gearbox needed to be specified. A factor of safety of 1.5 was used for all critical calculated dimensions. The peak power output of the pilot was estimated to be 1200 W. A final output shaft speed was specified by the Hub and Propeller lead, Gavin Denzer, to be targeted at 400 RPM. Specification started with the transverse shaft, the weakest link of the gearbox other than the belt. The minimum transverse shaft diameter was calculated, as shown in Appendix B, to be 0.625 in (1.59 cm). With the addition of a keyway the diameter was increased to 0.75 in (1.91 cm). The final shaft does not have any bending stresses, but is instead under a 190N axial compression force. The stresses in the final drive shaft are lower than in the transverse shaft. The final drive shaft was specified to be equal diameter to the transverse shaft, at 0.75 in (1.91 cm). Miter gears with a large pitch diameter was then selected to allow space between the final drive shaft and the transverse shaft for the rear pulley as shown in Figure 4. 19

Figure 2.4: Space between transverse shaft and final shaft Using a HTD 5mm synchronous timing belt a maximum rear pulley size was found to have 22 teeth and a diameter of 35 mm (1.378 in). This rear pulley size allowed for the sizing of the front pulley. The male pilot, Dominic Forbush, reported that he expects to be able to achieve a cadence of 80 RPM. By dividing the final output RPM by the pilot’s output a gear ratio of 5 to 1 was found. This gear ratio allowed the front pulley to be sized to 110 teeth and a diameter 175mm (6.890 in). In an effort to reduce to the pre-tension in the belt, which is a source of frictional losses, a method of keeping the belt engaged with the pulleys was devised. This system consists of small wheels as shown in Figure 5. The belt must pass between the wheels and the pulley, therefore is not allowed to ratchet (skip teeth), because there is not enough space for the teeth to pass through without being engaged in the pulley. Anticipating a need to tension the belt with approximately 110 N (25 lbf), a tensioner for the slack side of the belt was designed. The tensioner mounts on the bottom of the miter box, using the same screw holes as are used to secure the bearing holders. It consists of a bracket that attaches the tensioner to the miter box, and acts as the fulcrum for an arm with an axle and needle bearing on the end. The arm can be made to apply force in two ways, using either a spring which pushes off of the bottom of the miter box or a series of indexing holes that lock the arm into position with a clevis pin. Because of the extremely limited space around the drivetrain, the tensioner was made to have a width of only one inch, such that it could move freely inside of the holes of the chassis.

Figure 2.5: Belt contact wheel at the front pulley

The materials of all components, except for the miter gears, were selected because they are corrosion resistant such as 6061 aluminum. Limited options exist for corrosion resistant metal miter and bevel gears. The forward pulley will be produced from ultra-high molecular weight polyethylene (UHMWPE). UHMWPE has very high abrasion resistance, a low coefficient of friction, and is less dense than aluminum. The gearbox requires the addition of sources of frictional losses such as extra bearings. These losses will be outweighed by the better pilot ergonomics of the new gearbox. The forward pulley housing was made to be enclosed in order to reduce the risk of anything, such as a shoelace, from being caught between the belt and pulley.

Conclusion The previous gearbox, a simple bevel gear system, was too wide to be placed far enough aft in WSD for efficient pilot ergonomics. A belt was selected due to their slim nature and corrosion resistance. In order to ensure that the belt could withstand the loads it would be subjected to, the belt was tested on a universal testing machine. A belt with a width of 15mm was tested and determined to be sufficiently strong. The gearbox was then designed around the belt. The gearbox allows for better ergonomics and reduced width, decreasing interference between the hull and the pilot’s feet. These ergonomic changes will allow for greater pilot power output. The new gearbox is a more complicated system than the old gearbox. The increase of complexity comes at a price of increased frictional losses; however, these losses will be offset by the increased power output of the pilots. This increase in power will translate into greater submarine performance. The new gearbox is 1.54in (1.91 cm) wide, only 39% the width of the old gearbox. With the assumption that the chassis onto which the miter box is mounted is in the same location as the old system, the new system places the pilot’s feet 4.6 inches (11.7 cm) rearward.

Propeller Overview A propeller in this case is a rotating element on a craft that creates thrust from the motion of its operating fluid around its dynamic surfaces.

Goal The goal of the propeller on this submarine is to operate with the highest possible efficiency, have a small diameter for both beneficial interactions with the hull and to avoid running into the bubbles exhaled by the pilot, have low drag, have low tip losses, have low cost, and have high manufacturability. An additional goal of our team is to have separate propellers optimized and manufactured for each of our two pilots – one male and one female.

Concept Generation In this stage of design, we considered many variations on the standard propeller drive. Some of these included counter rotating propellers, contra rotating propellers, a fixed pitch propeller, a controllable pitch propeller, a ducted propeller, and even the number of blades the propeller should have. In concept generation, the team must also consider the materials the propeller can be made out of as well as the methods in which it can be manufactured. Some material options include steel, aluminum, titanium, plastics, wood, and composites. Some manufacturing techniques include milling, casting, composite layup, 3D printing, and compression molding.

Concept Selection In this stage of design, the characteristics of each of the options created during the Concept Generation phase were considered. Ultimately we decided to use a two bladed, controllable pitch propeller without a duct made from compression molded carbon fiber. While a propeller duct can add efficiency in certain situations, simulations showed that the decrease in diameter and increase in RPM necessary to utilize one would result in a net decrease in efficiency. We chose two blades because each additional blade creates parasitic losses on the system in the form of various types of drag as well as additional fluid disturbances that decrease the efficiency of all the blades. While additional blades can increase efficiency by decreasing the thrust that each blade would have to generate, this benefit is lost at the higher aspect ratios and tip speed ratios that our propellers operate in. The decision to make the propeller out of compression molded carbon fiber was made because compression molded carbon fiber has both good strength and stiffness characteristics while remaining easy to manufacture and light. Machining a metal propeller blade generally takes hours for each blade on an advanced mill. However, a compression mold takes about the same amount of time to manufacture as a single propeller blade but on a three-axis mill with a simpler, more rigid setup. Once the mold is made, each blade can be produced with a few minutes of preparation followed by a few hours sitting in a hot press – a per-unit cost much lower than that of machining. After the new blade is removed from the mold, the finish work that needs to be done on it is substantially less than the milled propeller blades. 22

The decision to utilize a controllable pitch propeller balances an increase in the submarine complexity, increased rear weight that makes ballasting more difficult, increased hub size that also increases drag while also decreasing propeller efficiency, and creating the need to add another system, with operating in a more efficient range, both hydrodynamically and for pilot performance, over the race course. In the case that the controllable pitch function fails, the submarine is still viable with a fixed pitch propeller, and it allows us to be able to design a propeller with higher efficiency over a smaller range without jeopardizing as much of the performance of the drive train at the off- design conditions. The biggest factor in our decision to use a controllable pitch propeller was ultimately the human factor. Testing showed that our pilot is capable of producing the power necessary to hit the velocity we are designing for but only for a short period of time. While the controllable pitch device does not affect our maximum on-design efficiency, it increases the off-design efficiency of the propeller, characterizing the majority of the time spent on the course. This added efficiency over the course of the race allows our pilot to achieve the velocity profile necessary for reaching the design speed. Since the creation of a controllable pitch propeller is so complex the description of the controllable pitch hub is split off into its own section.

Design

We designed the propeller taking into account the concept we selected for propulsion as well as other considerations. The actual data relating to the propeller design is shown below in Table 2.

Table 2: Hull and Propeller Data

CONSTRAINTS

Speed Thrust Power Rotor Diameter Hub Diameter RPM (Knot) Required (N) Limit (kW) (m) (m) 0 0 0.8 0.625 0.127 400 1 4.123 0.8 0.625 0.127 400 2 15.51 0.8 0.625 0.127 400 3 33.04 0.8 0.625 0.127 400 4 56.83 0.8 0.625 0.127 400 5 87.11 0.8 0.625 0.127 400 5.5 106.3 0.8 0.625 0.127 400 6 124.5 0.8 0.625 0.127 400 6.5 145.1 0.8 0.625 0.127 400 7 168.0 0.8 0.625 0.127 400 7.5 190.0 0.8 0.625 0.127 400 8 216.9 0.8 0.625 0.127 400 9 272.2 0.8 0.625 0.127 400

For the male pilot’s propeller, the thrust requirement of 190 Newtons for our submarine to reach 7.5 knots was found using CFD. The RPM of the propeller was decided to be 400 by the combination of the highest gear ratio that fits in our space and the RPM that the pilot produces at his peak power output. The diameter of the propeller was decided as the largest diameter that the submarine can support that is still small enough to pass under the pilot’s exhaust bubbles and avoid ventilation. Choosing the largest diameter keeps the efficiency that comes with larger diameters, while not losing efficiency from exhaust bubbles and ventilation. The hub diameter was a fixed 5 inches to allow enough room for the controllable pitch system. The chord profile was found parametrically by creating reference points along the length of the propeller blade and iterating with incremental adjustments across all of these points to create propeller profiles then analyzing these profiles to find the most efficient iteration. The thickness profile was also created parametrically but the focus of the process was in creating a propeller thick enough to survive the forces it would experience structural analysis shown below in Figure 2.6.

Figure 2.6: Structural Analysis of Propeller Blade in Operation The female pilot’s propeller was made the exact same way as the male pilot’s propeller with a thrust requirement of 125 Newtons at a velocity of 6 knots and all other inputs identical (see Table 2.1). The propeller itself was designed and analyzed using an open source MATLAB program called OpenProp. This program takes in details like thrust, velocity, diameter, number of blades, and RPM to design and analyze a propeller using lifting line theory. While this program is not as advanced as others on the market, it is the best available to us students, and as long as reasonable constraints are kept in mind during the design process then the results will be reasonable as well. Lifting line theory analyzes the airfoil characteristics and environment for each differential blade element to describe how the propeller should perform. While this can be slightly less accurate than more robust techniques we can generate and analyze a propeller blade in about 15 seconds.

Manufacturing The aluminum compression mold needed to produce the complex geometry of the propeller blades as well as the base used to connect to the controllable pitch propeller hub requires three pieces – one for each of the two sides of the propeller blade and the third for its base. The two parts of the mold that make the propeller blade each require hours on a 3 axis mill while the portion that forms the base can be made with a 2 axis mill over a much shorter timeframe (see Figure 2.7).

Figure 2.7: Three Part Carbon Fiber Propeller Compression Mold The forming of the propeller blade itself is done by forming a mass of compression molding carbon fiber into the rough size and shape of the propeller then placing it in the mold and pressing it together with heat for six hours. After curing, a wedge is used to pry apart the two blade sections of the mold and a hydraulic press is used to force the propeller out of the base-forming portion of the mold with a large pin. Once the blades are out they require only a light sanding and bright orange painted tips for safety shown in Figure 2.8.

Figure 2.8: Propeller Blade with Flash and with Flash Removed Post Production Timeline The propeller design and analysis came to completion in late January with the molds going into the manufacturing phase in April. The male and female propeller molds then move from manufacturing to use in May. Blades are semi-continuously produced until the time of the competition. This ensures that we have a large selection to choose from so that we can select the best, most balanced blades.

Conclusion The propellers have come together well with high efficiency, usability, and manufacturability. As we continue testing, this project’s success will be dictated by the propeller’s performance and survival. This testing involves the use of the submarine. We quantitatively analyze the submarine’s performance and qualitatively consult with the pilots’ experiences as well as external observers to understand the performance of the system.

Hub Overview As discussed above this submarine utilizes a controllable pitch propeller hub. A standard propeller hub is the junction between the propeller blades that connects them to the drive train. A controllable pitch propeller hub is a platform that fulfills the same purposes of the standard propeller hub but is also capable of either mechanically or electrically changing the angle of attack of the propeller blades to change how they interact with the operating fluid. Goal The goal of the design of the hub was to create a controllable pitch propeller hub that has components that fit into the hub size; is balanced, light, and capable of surviving operating loads; can adjust over the propeller’s angular operating range; has sufficient battery life; utilizes effective programming; executes accurate data acquisition and utilization; and provides an adequate increase in efficiency over the course of the race. 26

Concept Generation For this system we considered many different strategies for designing and manufacturing the controllable pitch propeller hub. After considering designs made in the past, methods of adjusting propeller angles, location of hardware, types of hardware, recording and utilization of data, method of adjustments, materials used in the hub, and overall layout we came up with a few options.

The first two major design options are a mechanically and electrically operated controllable pitch hub. The second consideration is whether the pilot would have direct control of the pitch or if the hub would control pitch independently. The third consideration is the method used to adjust the propeller blade angles. Examples methods include linear linkage from thread rod or worm gear or adjustment through bevel gears. Finally, various locations for elements of the designs were considered. A consideration for the entire submarine is that the aft section, which contains most of the mechanical systems, ends up being very heavy. As a result, we considered alternative materials including steel, aluminum, titanium, plastics, and composites. Concept Selection The final selected design is a controllable pitch propeller hub that adjusts the angle of the blades using bevel gears, with the bevel gears controlled by a stepper motor mounted, along with the rest of the hub electronics, in the rotating reference frame of the hub fore of the propeller, and the entire hub running autonomously off of on-board batteries and sensors. Additionally, we decided to make nearly every major component out of plastic. The plastics we chose are Acetyl plastic and HDPE for their machinability, availability, mechanical characteristics, and weight. The benefits of an electronic controllable pitch propeller hub are that an electronic system over a mechanical system creates less loss on the drive train, both the propeller and the driver operate more efficiently and in a more comfortable range over the race course, the submarine would remain viable in the event of a controllable pitch function failure with the fixed pitch propeller, and it allows a propeller design with a higher efficiency over a smaller range without jeopardizing as much of the performance of the drive train at the off-design conditions. The downsides of the controllable pitch propeller hub include an increase in submarine complexity, an increase in rear weight making ballasting more difficult, an increase in hub size which increases drag and decreases propeller efficiency, and necessitating the addition of another electronic system. However, the choice of using plastic over an alternative material, such as aluminum, lets us have a lighter device overall while also dissolving the need for alignment bushings and spacers on the internal components. Design The components were designed with concept selection, manufacturing techniques, and material properties of our chosen materials in mind. The controllable pitch propeller hub is split into two main components; the hub and the electronics cylinder.

Figure 2.9: Different Angles of the Hub Showing Both Static and Dynamic Seals The two propeller blades are mounted in the hub seen above in Figure 2.9. The propeller blades are mounted in an aluminum adapter as shown in Figure E1 that fits into the plastic and glass ball bearings in the hub. This adapter also contains the shaft that connects to the bevel gears through which the trim of the propeller blade is changed. This adapter is necessary because of the constraints on the size, accuracy, and material characteristics of the carbon fiber propeller blades. The adapter was made out of aluminum as opposed to plastic because the torque and bending moment that the 0.25-inch shaft experiences would cause excessive deformation in plastic. Aluminum also facilitates use of a simple set-screw instead of a more cumbersome machine key. The bevel gear assembly is shown in Figure E2. The pinion side of the bevel gear set is attached to a different aluminum adapter shown in Figure E3 that is rotated by the stepper motor fore of this assembly. This second adapter is necessary for the same reasons as the first, as well as providing a slightly larger surface that can be finished smoothly and used as the sealing surface for the single dynamic rotary shaft seal shown in Figure 2.9. The entire hub assembly has one static seal and one dynamic seal. The dynamic seal, as mentioned before, is at the interface of the bevel gear pinion shaft and the hub and is executed using two 0.125-inch female gland O-ring seals. The static seal is at the interface between the hub and the electronics cylinder shown in Figure 2.9. This seal is executed using two 0.125-inch male gland O-ring seals. Great effort has been taken to design this system to have as few seals as possible. Finally, the hub component is made out of HDPE because it is particularly light, low friction, and machineable; its light weight allowing the component to be large enough to counteract its limited strength. The cross section of the system assembly is shown below in Figure 2.10 with hub in blue, plastic bearings in red, 3D printed parts in green, aluminum adapters in medium grey, stepper motor in black, and bevel gears in light and dark grey.

Figure 2.10: Controllable Pitch Propeller Hub Assembly Cross Section

Figure 2.11: Electronics Cylinder

The electronics cylinder shown above in Figure 2.11 connected to the hub is the water-tight vessel that contains all of the electronics needed for the hub to operate by having a cylindrical internal cavity with a diameter of 2.5 inches and a length of 8.5 inches. This component is lathed and milled out of a single piece of acetyl plastic, allowing us to make a cylindrical cavity that has only one end that must be sealed. The electronics cylinder mates to the hub on its aft end with the internal cylinder, acting as the female bore to the male gland seal on the hub. With this design, in order to increase stability and decrease hub size, the electronics must be placed forward at the hub. However, in order to do so, the electronics cylinder must also act as a sealed vessel and act as a portion of the submarines drive shaft. The electronics cylinder must be capable of taking the entire torque and thrust that the pilot supplies. To make this possible, the axial mating surface on the aft end of the electronics cylinder has a 3-D profile that fits into a mating profile milled into the hub much like a mortise and tenon. To fasten these two parts together and allow the wall thickness of the electronics cylinder to remain relatively thin, a threaded collar is made as shown in Figure E5. The assembly of the hub, electronics cylinder, and collar are shown below in Figure 2.12. 6-32 machine screws pass through the clearance holes in the hub and screw into the retaining collar that locks onto a lip on the electronics cylinder. This collar only supports small incidental loads that would most likely be seen during transportation or assembly. The collar is also used because plastic cannot hold threads under load, so the stiff screws -- if placed directly in the plastic electronics cylinder – would end up taking much of the torque from the drive train, forcing the screw holes out of round. Another added benefit of the retaining collar is that at high amounts of torque, it prevents the tenons on the electronics cylinder from displacing outward, effectively increasing the operational torque of the system.

Figure 2.12: Assembly of the Electronics Cylinder, Hub, and Collar

The drive shaft of the submarine is designed to be as thin as possible to reduce weight and is made of aluminum for ease of use and manufacturing. As a result, the point where the plastic electronics cylinder attaches to the drive shaft must be thicker on the plastic side than the aluminum side. To facilitate this change in drive shaft size we must also create a coupling shaft adapter shown below in Figure E6. This coupling is an aluminum cylinder with bored holes on each end, with one having the diameter of the aluminum drive shaft at 0.75 inches and the other having the diameter of the plastic portion of the drive shaft at 1.25 inches. Since the torque is transferred using machine keys from one shaft through the coupling and into the other, there is a milled slot in each shaft to act as a key way and the coupling needs a similar slot on each end. On the smaller 0.75 inch end a simple broach could be used but because the larger 1.25-inch end necks down to the smaller diameter, a milled through-slot is used instead to hold a captured machine key. A collar must also be used here in conjunction with a set screw to hold the collar and machine key in place. A design consideration for the collar and adapter is that the adapter can be made especially thin on the larger 31

end because the larger diameter will be subjected to less loads at a given torque, and the collar can support some of the hoop stress created by the machine key on the coupling allowing us to make that portion of the coupling even thinner. The electronic cylinder holds a stepper motor, an adapter for the stepper motor shaft, the same printed circuit board used to control all the stepper motors in the submarine, three optical sensors that see out of the plastic windows in the walls of the electronics cylinder, and two lithium polymer batteries capable of powering the hub for 90 minutes of continuous use. All of these components are mounted on a simple 3D printed bracket that attaches to four mounting screws in the hub. Not a load bearing part, the bracket is coupled to the hub using helicoil reinforced threads, which will aid durability during repeated assemblies. The final stage in the design process is to map out the controllable pitch programing. To do this, we analyze the propeller blades at off-design conditions and map out their efficiencies and characteristics at these conditions. Examples of these charts are shown below in Figures 2.13, 2.14, and 2.15. This data helps us determine what angle to set the propeller blades at based on the data recorded by the onboard sensors. The fine-tuning of this program is done iteratively based on pilot feedback.

Figure 2.13: Efficiency vs. Advance Coefficient 32

Figure 2.14: Optimum Angle Spectrum

Figure 2.15: Thrust Spectrum

Manufacturing Many of the components of the hub system are easily machined in one or two set-ups in a mill or lathe. The only two more complex components of this assembly are the hub and electronics cylinder. Each of these parts required four set-ups, jigs to safely machine, and some CAM. Though these two parts had the greatest amount of stock to remove, their plastic composition expedited the process greatly.

Figure 2.16: Hub Being Machined Using Rotating Jig

Conclusion For this system to prove successful it must easily survive the loads applied to it as well as effectively control the pitch of the propeller blades. Additionally, it must remain easy to operate for the pilot and in an efficient operating range over the course of the race.

Controls Overview and Purpose The task of the Controls team is to design, fabricate, test, and maintain the systems that give the submarine its maneuvering capabilities. The components of primary focus include the control plane and fairing geometries, the mechanism to actuate the control planes, and the helm control box which enables the pilot to steer the submarine. Control Planes Overview Control planes are necessary for both straight-course stability and maneuvering of the submarine. Selecting the optimal geometry and configuration of control planes will maximize the submarine’s performance. Computational Fluid Dynamics simulations are used as a guide in the selection process. Goal The design of the control planes and fairings should minimize the parasitic drag they introduce while maximizing the stability and maneuverability they provide for the submarine. This will enable the submarine to travel as fast as possible through the straight sections of the races, while remaining nimble enough to navigate the slalom course with ease. Pilot reports following ISR 2015 indicate that the control planes employed at that competition were more than adequate for maintaining stability and maneuverability, therefore one goal for the 2016 competition is to reduce the control plane area, thereby reducing overall drag, while maintaining adequate control performance. Concept Generation In the beginning of the design process, several control plane geometries were proposed for analysis. These geometries were presented as sketches and reviewed by Controls Team engineers, where they were categorized into groups consisting of multiple variations on 3 basic designs. Also, a design was proposed which included a fixed leading edge and ailerons similar to those found on aircraft wings. The theory behind this design was that in using an asymmetric (when actuated) airfoil profile, the separation of flow from the back of the control plane could be decreased for a given angle of attack, without sacrificing lift. This would ideally allow for reduced drag in all turning maneuvers, without a reduction in overall turning ability. However, due to shortage of time, resources, and the additional complexity of this design, we were unable to develop this control plane design for testing on the submarine this year.

Figure 3.1:Proposed Control Plane Geometries 35

Additionally, the introduction of either a small, fixed-pitch canard or a set of fixed control planes at the midpoint of the hull was discussed. These were considered as potential modifications with the goal of allowing for smaller control planes at the tail, without sacrificing the turning capabilities of the submarine. Time and resource constraints inhibited this idea from being pursued, though it is likely this will be a project for future submarine designs. Finally, we discussed using an X-pattern for the tail fins, which was inspired by a research paper detailing the control surfaces used on the USS Albacore naval attack submarine that suggested that an X-pattern provides superior maneuverability over the traditional cross-shaped orientation. The issue with implementing this design was that it would require the use of an electronic control system to actuate each control plane independently, and at the time this was not a component we felt we could safely depend on having completed for competition. The alternative, a cross-shaped orientation, allowed us to build a back-up mechanical control system while developing our electronic system, so this was the design selected. Concept Selection Next, five control plane geometries were chosen for Computational Fluid Dynamics (CFD) analysis to estimate their drag contribution to the submarine with varying flow velocity. When modeling the fluid flow problem, we created a cylinder which represented the fluid domain itself, then modeled the submarine geometry as an empty volume within this cylinder (Finite Volume analysis), creating a 3D mesh of small cells which comprised the entire volume of the fluid domain around the submarine hull. Then, various parameters of the fluid, including those describing the boundary layer at the surface of the submarine, were specified to the greatest accuracy available in order to mimic the conditions expected on the submarine at the competition. Considerable research was carried out to evaluate which Reynolds-Averaged Navier-Stokes (RANS) turbulent flow model would be ideal for modeling the flow around the body of the hull and the control planes. Numerous models including K-omega, K-epsilon, pure Shear Stress Transport, and a K-omega–SST hybrid were considered, and ultimately the K-omega-SST combination was used for the final modeling. It was later discovered that we were unable to specify all the necessary parameters for the solver and turbulence model without experimentally obtained data that we did not have. So, these values were estimated and used consistently for testing of each control plane design. We believe that the results of the CFD analysis still yielded comparatively accurate data, which we used to decide on the most efficient geometry. Additionally, various meshing techniques were explored in order to attempt to capture the control plane and submarine geometry with as much detail as possible. For relatively simple geometries, such as the submarine hull, or one control plane in isolation, we used a mesh with many extremely thin layers inflated orthogonally outward from the surface of the object, allowing for us to resolve the boundary layer flow at the surface of the object in considerable detail (see Figure 3.2 below). Color is used to indicate dynamic pressure on the body. 36

Figure 3.2: Pathlines Shown Over Preliminary Design However, we wanted to capture the interplay of fluid flow patterns from the submarine hull and the control planes together, by running CFD simulations with the entire submarine geometry at once. This proved to be especially challenging with regards to meshing, though, and we were unable to capture the entire submarine with the same level of detail that we had attained for the simpler shapes. Furthermore, the student version of ANSYS imposed minor limitations on our testing capabilities, particularly in that it has a limit on the number of cells that can be created in a mesh for CFD problems, which limited the level of detail we could achieve in modeling the geometry of the hull and control surfaces together due to the increased complexity. However, we were eventually able to run successful simulations, using a coarser mesh, for the entire submarine (see Figure 3.3 below). Color is used on the body of the submarine to indicate pressure, and on the surrounding plane to indicate fluid flow speed.

Figure 3.3: Flow Modeled Over the Submarine and Control Planes After the completion of the CFD analysis, one design consistently showed approximately 5% decreased drag over the others at each of the flow speeds tested. This design, along with a few 37

other preliminary geometries, was then 3D printed for assembly with the rest of the control system, before entering the final manufacture stage.

Figure 3.4: Selected Control Plane Geometry Manufacturing The preliminary test fins are rapid prototyped from PLA plastic using 3D printing technology. These fins are used for submarine test sessions conducted prior to manufacture of the competition fins. The final production fins are cast Urethane using a machined aluminum mold supplied by Breedt Production Tooling and Design Ltd. Modifications to the mold design which was provided for the 2015 fin design were requested due to common occurrence of bubbles in the fins cast with last year’s mold, which had the inlet and air vents positioned at the fin root. Although that design seems optimal since the only finishing required occurs at the root and therefore has less impact on the fin performance compared to finishing and sanding the leading or trailing edges, the bubble formation which resulted from this design negated that benefit. This year’s mold keeps the inlet at the fin root, but the air vents were moved to the leading edge of the fin. It is expected that the smoother transition from the control plane surface to the air vent opening will enable more air to escape.

Figure 3.5: Photo of Fin Mold Half 38

Conclusion The numerous challenges encountered in the analysis and fabrication of the control planes proved to be an excellent learning opportunity for our team members, and ultimately yielded an optimized control plane geometry. Our students will take the experience gained from the CFD analysis, prototyping, and manufacturing forward with the team into next year, where we will continue to explore new concepts such as the use of the aileron-style design which was discussed early this year.

Mechanical Controls

Overview The Mechanical Control system is the basic method of directing the control planes. The system relies on a series of keyed rods, gears, and pulleys mounted onto the backside of the chassis with brackets. Tension cables attached to the pulleys run along the side of the inside of the hull to a cable tensioner. After passing through the cable tensioner, the cables connect to the helm control box, which allows the pilot to turn the fins one way or another.

Goals The goal for this system is to establish a baseline control over the trajectory of the submarine. The system is designed to be both lightweight and durable without losing precision. The system consists of a joystick, cable tensioner, and a series of pulley-gear-rod systems connected directly to the fins. Targeted areas of improvement over the 2015 system are greater deflection angles from the control planes and smoother operation of the joystick.

Concept generation The main focus of this year’s design is to decrease the size and the weight of the system while improving the turning capabilities. The system is based off previous year’s model, opting for a cable-based system due to simplicity and reliability. Interference with the propulsion system in last year’s design was resolved with the addition of a u-shaped bar attached to the pulley system to transfer motion across the central drive shaft. However, while effective, this mechanism resulted in an inhibited degree of maneuverability. Therefore, much consideration went into designing a more effective method of transferring rotational motion across the chassis. Another major consideration was the design of the pulleys. Previous pulley systems involved securing the tension cables down with a nut connected to an attachment of the pulley. With the current model, we wanted to design a simpler, more secure method of attachment. A system to increase the tension in the cables was also needed since they would no longer be tensioned at the pulley itself.

Concept Selection The controls chassis used in the 2015 competition proved effective as a platform on which to mount the control mechanism. However, this addition contributed significant weight to the rear of the submarine. A new chassis was designed for this year’s competition which borrowed heavily from the existing chassis, but was constructed from 1”x2” aluminum rectangular tube with 1/8” wall thickness, as opposed to 2”x2” and 1/4” wall thickness. 39

The joystick design is an evolution from last year’s design, which was constructed from PLA 3D printed components. This year’s joystick uses a PLA printed housing and two nested aluminum spindles. Goals for the joystick are greater effective range of motion and smoother operation. Additionally, pilot suggestions after the 2015 competition indicated that better joystick feedback would help them better control the submarine. Therefore, the new joystick design includes spring feedback such that a restoring force directing the joystick back to center position is applied. When designing the pulley system, we decided to use a series of small rods connected with gears. The addition of gears allowed for transfer of motion between fins across the chassis without restricting the degree of motion of the fins. The rods and gears are held in brackets screwed onto a base which can be bolted into the chassis. Rods traversing across the chassis connect one bracket to another, which will allow both fins to turn as a single pulley is moved. When designing the pulley, we considered several ideas of how to secure the tension cables. The final idea involves a groove built into the pulley similar to brake cables on a bike. While in tension, the cables will lock against the groove in the pulley. In order to remove the cables, the tension must be reduced. When designing the tensioner, the initial design involved crimping the cables to turn bucklers which could tighten the cables. However, after some difficulties with assembling, the tensioning system was redesigned to two blocks with several cable barrels. With the cable running through the block, the barrels could be turned to increase/decrease the tension as needed. Cables running from the joystick will connect to cables coming from the pulley after passing through the boxes. Manufacturing Since the overall goal for the submarine redesign was to reduce weight, any parts which could afford to not be machined out of metal were manufactured using alternative materials such as PLA, Delrin, and Carbon fiber. Any parts made of metal are constructed with Aluminum due to its relatively light weight. The mechanical joystick is assembled from a printed PLA housing, machined aluminum spindles, machined stainless steel spring-arms, and various purchased bearings, springs, and hardened shafts. Due to complex design, however, the machined components, particularly the outer spindle, required a significant machining effort. The outer spindle, for example, required two sets in a lathe and five sets in a mill. Future design iterations should focus on simplifying the design to reduce the manufacturing demand.

Figure 3.6: Mechanical Joystick For the construction of the pulley system, all metal was machined with 6061-T6 aluminum stock. The fin connection rods and the motion transfer rods were both lathed and milled on 2-axis machines. ⅛” key ways were milled onto rods to allow for connection with the gears and pulleys. The brackets are sections of a 1.5” x 3” rectangular aluminum tube with portions milled away. In order to 40

accurately replicate the brackets during machining, a tool block was first constructed to support the part while milled. The base blocks were machined using delrin. The rods designed to transfer motion between brackets are made of carbon fiber with holes drilled in the sides to connect via screws to aluminum rods in the brackets. All gears, bushings and screws are sourced parts.

Figure 3.7:Mechanical Control System The pulleys and spacers are 3D printed parts using PLA filament. All cables are sourced bike tension cables. The cable tensioners are machined out of delrin using a mill. The added cable barrels are recycled from used bikes.

Figure 3.8: Close up of Pulley Groove Design

Figure 3.9: Mechanical Cable Tensioner

Conclusion The mechanical control system was fully assembled and tested in water for the first time on May 15, 2016. Though functional, there are several matters needing attention prior to competition. Considerable play was observed in the gear mechanism, particularly at the point where the carbon fiber torque-transmission rods couple to the gear shafts. Due to complications during assembly of the cable mechanism, there is greater resistance in the cable shrouds than expected. Furthermore, it was found that the spring-return feature of the joystick did more to inhibit normal operation without accomplishing the goal of joystick feedback. Simple fixes are available to all these issues. Gear mechanism play will be addressed with more secure coupling between the transmission rods and the gear shafts. Cable resistance will be solved by replacing the existing, somewhat frayed cables with new ones. Finally, joystick operation will be improved by removing the spring-feedback mechanism. Overall, the mechanical control system built for the 2016 competition accomplishes its goal. Future design iterations will focus on improving the robustness of the mechanism in the interest of minimizing the kind of complications encountered on this build. Electrical Controls Overview There are many advantages to an electronic control system. While the strictly mechanical system is restricted in the sense that it only controls pitch and yaw, the electronic system additionally allows roll-control since all four fins are able to deflect independently. Electronic controls also allow for some degree of auto-pilot to be incorporated into the control strategy. Sensors connected to the CORE computer would monitor submarine trim and actuate the fins to correct for perturbations in pitch and roll, facilitating the pilot’s task of maintaining course. The focus of this year is on robust design and implementation of the electronic control system as a means for reliable course correction and modification. This section describes the design and implementation of the mechanical components intended to support the electronic system such as dry-housing enclosures.

Goal The goal of this project is to develop components which enable full electronic control of the submarine. The system is to be easily interchangeable with the mechanical control system described in a previous section. The electrical components required for this system are a joystick, battery, CORE computer, and motors to drive fin deflection.

Concept Generation The electronics enclosures have gone through several design iterations since we first began implementing electronic control. Fly-by-wire was first successfully utilized in eISR 2014. This design used servo motors enclosed in welded acrylic housings with a cast-latex boot which transmitted motion to the fins via rigid linkages. The joystick housing also contained the embedded computer system, which was connected to the servo motor housings via wires routed through vinyl tubing. Despite this system being used successfully at competition, it suffered from minor yet persistent leakage issues. Additionally, the servo motors were found to be underpowered at 179 oz.in. As a result, long term reliability was poor and the servos would burn-out only after a few runs. Because of this, the housing design and motor selection was revisited for the 2015 competition. The new design for last year’s competition replaced the servo motors with stepper motors. The latex boot was removed in favor of a dynamic O-ring shaft seal. Due to space constraints on the motor housing size, the motor housings were mounted to the front of a chassis fixed to the hull. A belt and pulley system was implemented to position the control planes sufficiently aft for stability by transmitting the motor rotation to an axis aft of the chassis where the fins were connected. Unfortunately, it was not used in competition due to complications with the motor driver circuitry and damage done to the housing enclosures. Upgrades and improvements to the 2015 motor enclosure and chassis design were desired for the 2016 competition. The chassis itself proved to be much larger and heavier than necessary. Mounting the stepper motor housings to the front of the chassis also meant the pedals needed to be located farther forward in the submarine, which led to ergonomic issues for the pilot. Therefore, the goal for this year’s control system was to mount the stepper motor dry housings on the rear face of the chassis and connect the output shaft directly to the fin rod. This also required a redesign of the stepper motor housings into a smaller package.

Concept Selection Stepper Motor Dry-Housing The most significant changes from the 2015 design are the move from a rectangular to a cylindrical geometry for the housing shape and the use of barrel-type O-ring seals in place of face- type seals. The cylindrical housing greatly facilitates manufacturing; whereas the box-shaped housing required several pieces to be machined and cemented together (presenting many opportunities for micro-cracking and leaking), the cylindrical housing was cut as a single piece from polycarbonate tube. Furthermore, the face-type O-ring seal depended on the clamping force from bolts around the housing to maintain the seal. Barrel seals, on the other hand, create a seal between the inner surface of the housing cylinder and the outer diameter of the cap (or plug), so no clamping force is necessary. This provides a much more reliable seal. Other features of the stepper motor housing are carried over from the 2015 design. The output shaft is sealed with a double O-ring, though the male-gland was replaced with a female-gland 43

following the recommendation in the Parker O-ring guide that dynamic rotary seals not be placed on the rotating shaft. [4] The final stepper motor dry-housing design is shown in Figure 3.10. Four motors are to be mounted on the same chassis utilized by the mechanical control mechanism.

Figure 3.10: CAD Model of Stepper Motor Housing Core Electronics Enclosure The main logic circuitry and power source driving the fin-control motors reside in the core electronics enclosure. The design of this housing borrows extensively from the design of the stepper motor housings. A clear polycarbonate cylinder is used as the main housing, with aluminum end- caps on each side utilizing a male barrel-type O-ring seal. Peripheral components of the electronic control system, i.e. stepper motors and joystick, are connected to the battery and logic circuit within the core enclosure via 4-wire cable. Waterproof cable penetration into the dry-housing is achieved using cable glands on each housing end-cap. The forward end-cap cable gland accommodates one cable-line (connected to the joystick) and the aft end-cap accommodates four cables (each connected to one stepper motor). The core electronics enclosure design is shown in Figure 3.11.

Figure 3.11: CAD Model of Core Electronics Enclosure Electronic Joystick Housing One of the trickiest components of the electronic control system is the joystick. Achieving water-tightness around a two-axis pivoting stick presents a formidable challenge. The chosen solution employs a flexible membrane sealed around the pivoting stick and secured at the periphery of the joystick housing. A 1/16” neoprene rubber sheet is selected as the sealing membrane (the red component shown in the figure below). The intent is that the membrane will be flexible enough to 44

allow full range of the motion of the joystick while being supported on the underside such that water pressure will not cause the membrane to interfere with the moving internal parts. The electronic joystick selected by the electronics team is the Aurora 9 Gimbal, as shown in Figure 3.12. The housing designed to hold this component is shown in Figure 3.12.

Figure 3.12: Electric Joy Stick Design

Manufacturing Each of the four stepper motor dry housings has seven components that were made in- house. In an effort to save weight and time, as many parts were 3D printed as possible. Specifically, the front and rear brackets as well as the stepper motor coupling plate were printed using PLA filament. The cylindrical housing made from polycarbonate tubing was cut using a horizontal band- saw and was then sanded down to the necessary length. The difficulty associated with this procedure was securing the tubing in such a way that it could be cut effectively without crushing or cracking the delicate polycarbonate. The horizontal band-saw offered the control and stability that was necessary. The output shafts were produced from 6061-T6 aluminum bar stock on 2-axis lathes and mills. After being turned on a lathe to the correct diameter of 0.500 inches, each shaft had a keyway milled into them to ensure connection to the fin rods. 8-32 tap holes were drilled into each of the shafts which allows them to connect to the stepper motor. The motor mounting plates was turned on a 2-axis lathe from 6061-T6511 aluminum 3-inch bar stock. Each had grooves lathed to accommodate (type of O-rings) O-rings and were fit tested with the polycarbonate tube before manufacturing proceeded. Then each plate had a ½ pipe tap hole, each approximately 0.82 inches deep, milled into the side of the plate. Tapping these holes proved to be difficult because the only ½ pipe taps on hand were tapered which did not allow enough room for the cable glands to be installed. The eventual solution was to create a custom, non-tapered tap by essentially cutting off the tapered portion of a ½ pipe tap and to achieve the desired thread diameter. The rest of the features on the plates were finished on 2-axis mills with little to no complications. All of the features on the pressure cylinder caps were completed on 2-axis lathes from the same 6061-T6511 aluminum 3-inch bar stock used for motor mounting plates. These each had preliminary tests done on them to ensure fit and water tightness with the polycarbonate tubing. 45

The electronic joystick housing main component is manufactured from delrin plastic. The Arduino compartment is sealed with a machined aluminum cap and O-ring. The joystick compartment is sealed with an aluminum cap assembly consisting of neoprene sandwiched between two aluminum rings. The electronics are secured in the main housing component using 3D-printed bracket.

Conclusion The manufacture of these parts proved to be challenging due to the high tolerances characteristic of a waterproof enclosure. Many times throughout the manufacture process, it proved necessary to test the fit of interacting parts to see if they would perform as designed. For most of the features of the stepper motor enclosure, no foreseeable redesign could make the manufacturing process easier. However, there are some exceptions to this. For future iterations of the motor mounting plate, there is a way to do all of the features in one sitting on a 3-axis mill. This would drastically cut down the time and effort put into the manufacture of this part. The depth of the main pocket on the motor mounting plate could be much shorter and still fulfill its design intent, which can also cut down manufacturing time.

Electrical Systems Core The core provides the central power output and data management for the electronic control system. One 11.1 V, 8000 mAh, LiPo battery is regulated to provide approximately 12 V output, in order to supply current to the stepper motor drivers. In order to precisely control the stepper motor actuation, a Raspberry Pi 1 is utilized as the submarine’s central CPU. The Raspberry Pi communicates on a 3.3 V I2C network, and is programmed to behave as the master of the network. Slave Arduino Uno devices reside in the joystick and stepper controller housings, and are managed by the primary algorithm residing in the Raspberry Pi core. An I2C network was chosen for the system in last year’s design, with primary motivation being the ability to readily add devices to the network, and the three wires necessary to link devices (serial data, serial clock, and ground). Pull-up resistors for the I2C line are housed in the core, and bidirectional logic-level shifting is utilized to link the 3.3 V logical Raspberry Pi and inertial measurement unit (IMU) to the 5 V logical Arduino Uno devices. A single chip was designed to reside in the core, which includes 5 V and 3.3 V regulators, reverse polarity protection, and voltage regulation to minimize voltage droop. The chip also integrates logic level shifting, pull-up resistors, and ports for the I2C network. Previous iterations of the electronic controls design suffered from the excessive current draw to the motors leading to voltage drop sufficient to disable the core Raspberry Pi, thus isolation and regulation were critical additions to this year’s design. Joystick Design Specification The Joystick is comprised of two potentiometers (one for each axis) and several switches used for various functions including turning the submarine on, correcting for roll, slowing the sub, and aligning the fins along its central axis. In previous years, the x/y axes were sensed by powering one end of each potentiometer, grounding the other, and reading the center armature voltage via the Arduino AnalogRead function. This year’s design utilizes a differential position sensor where two resistors of equal value are tied to each end of the potentiometer. The ends of these resistors must be powered and the central arm grounded where voltage is now given in two readings each on each end of the potentiometer. Additionally, power going to the device is filtered to handle power failure for at least 50ms duration. The device is able to detect flood conditions using a water sensor. Design Procedure The joystick can be seen as two separate parts, making up the user input module. One part is the digital switches. These switches, though unlikely, have the potential to come in contact with the pilot’s fingers. To eliminate the possibility of harmful current flowing through the diver, the switches supply a maximum current of less than 1 mA while connected. The low current signals are then amplified on an internal circuit before being read by the Arduino. The second part of the joystick is the analog direction control. Again the diver has the potential to short the circuit while using the physical input and thus the circuit must not supply more than 1 mA. Another concern was fluctuating input voltage. To overcome this, a differential voltage divider was used. Fluctuating power input also yields the possibility of crashing the Arduino. A capacitor was placed close to the supply power to reduce this risk. The system is able to detect water breaching the box and shut itself down accordingly. This was implemented by reading a bare wire which runs around the seals of the box. If 47

the wire gets wet the system reads a different voltage and shuts off the Arduino before the water can damage it.

System Architecture Inputs ● 5 V ● Ground ● Button 1-8 ● Analog X ● Analog Y ● Water Sensor ● I2C Data ● I2C Clock Outputs ● I2C Data

Testing The conceptual circuit was tested in Modelsim to ensure functionality of digital amplifiers and voltage dividers. Once resistor values were finalized, the system was built on a breadboard and tested for functionality with the physical joystick and buttons. Potential short circuit currents were monitored. Once the hardware for measuring physical inputs was finalized, the Arduino was tested for proper signal processing and I2C functionality. Finally, stability was then inspected. Stepper Controllers The design goal of the stepper motor drivers was to produce a driver board compact enough to fit into the housings in the aft of the submarine that could both drive the boards and provide closed loop control. Previous attempts to design a stepper motor controller were unsuccessful, with much of the recent work impossible to assemble perfectly. Our original design involved integrating an AMI-30543 controller and ATmega32u4 on a single chip, but issues with the USB connector and time constraints forced us to scrap the idealistic design, in favor of that presented in this report. Thus, we resorted to purchasing a simple L298N dual H-bridge motor controller for each stepper motor. The usage of the H-bridge is fairly straightforward – four data lines are inserted into the chip, and a 12 V and ground input are supplied to the chip from the core. By selecting different data lines simultaneously, the direction of current through the stepper motor’s driving inductors can be precisely controlled. A local Arduino Uno is used to enable the 5 V data pins, and is connected to the I2C network to receive commands from the Raspberry Pi. Thus with four L298N’s and Arduino microcontrollers, the stepper motors can be actuated electronically. Problems with Servo Control In the past, the UW Human Powered Submarine Team has faced several issues with fin actuation. Traditional PWM controlled servos have been used to regulate fin position, but due to the following issues, they do not provide a complete solution: 48

1. Hobby grade servos do not provide enough torque for fin actuation. In order to use servos for fin actuation, industrial grade servos must be used, which are significantly more expensive. 2. Hobby grade servos have been found to have unreliable specs. Constant operation below rated torque has been found to cause damage to servo’s internal electronics. 3. PWM over required distances cause distortion. This distortion contributes to observed servo jitter. Inaccurate position readings have been observed with both 5V and 5.8V PWM signal 4. Lack of true position feedback has caused issues with debugging and autocorrect systems Research Last Year Last year, research into stepper motor actuation began. Advantages include: 1. Holding torque of stepper motors allow fins to draw far less power than traditional servos over the course of the race 2. Due to the nature of stepper motors, the fin position can be set at a high degree of accuracy 3. Holding torque allows fins to maintain position even in the event of power failure. 4. Stepper motors can provide a much higher torque per dollar (after cost of control solution has been considered) than traditional servos. As a result, last year the first prototypes were built (as seen in Figure 1 and Figure 2) but demonstrated the following problems: 1. Missed steps became issues due to lack of a closed loop system. 2. Thermal issues often caused damage to assembled board 3. Lack of proper power regulation caused enough distortion to adversely affect other electronics. 4. PCB size could have been reduced for space 5. Lack of quick, polarized disconnects proved to be troublesome. Accidental battery reversal caused damage to several components and prototyping disconnects proved tiresome for submarine assembly.

Figure 4.1: Old Stepper Driver Electrical Schematic 49

Figure 4.2: Old Stepper Driver Board Layout Motor Specifications We had the following stepper motors from last year. They are geared bipolar stepper motors with a 12V 1.7A input. [6] Further Defining the Problem Due to the need for novice programmers to be able to use this board, an Arduino compatible microcontroller was chosen. One of the disadvantages of last year’s board was that an external programmer is required due to the ATMEGA328P’s lack of an on board USB controller. To combat this difficulty, the ATMEGA32u4 was chosen. The ATMEGA32u4 has an on board USB 2.0 interface allowing it to be programmed by the Arduino IDE without the need of an intermediate chip for ICSP programming. Likewise, the chip is fully compatible with the Arduino language as several Open Hardware Arduino prototyping boards have been designed around the ATMEGA32u4. One of which, the Sparkfun Pro Micro [7], was heavily relied upon for this project. The design is shown below.

Figure 4.3: Sparkfun Pro Micro Schematic

After researching several stepper controller drivers on the market, the AMIS-30543 was chosen as it is one of the few rated above 1A and offers a large range of features. The board can supply up to 3A per channel with integrated SPI programmable current limiting. The board also features an integrated micro step controller, a speed/load angle output used for stall detection, thermal monitors, an on board charge pump, and several other features useful for dealing with various error scenarios. Additionally, the Open Hardware Pololu AMIS-30543 Stepper Motor Carrier Driver [8] was likewise heavily relied upon and offered several insights on dealing with reverse protection in the circuit.

Figure 0.4: Pololu AMIS-30543 Stepper Motor Carrier Driver

Due to increased size constraints, the new board takes advantage of surface mount chips in order to reduce footprint and weight. Considerations were made for assembly difficulties, so it was decided not to use components smaller than the SMD 0805 package. Additionally, the new board is mounted to the rear of the motor and uses both the PCB and motor housing as a heat sink for the AMIS-30543. Further research into the effects of heat dissipation in the AMIS-30543 revealed that a current lower than 1.5 Amps will not need a heat sink as the heat will be dissipated across the PCB assembly. It was also stated that the IC circuit was designed with heat dissipation in mind. The documentation mentions a ground plane print for heat dissipation (Figure 5). It should be mentioned that using the following configuration will mean the boards must be reworked with a hot air gun to ensure proper contact with the ground plane after soldering. Testing on this configuration will continue after the first print, which will be manufactured so that both the PCB heat sink and a contact to the motor via thermal paste can be made and tested independently.

Figure 4.5: Ground Plane Heat Sink for AMIS-30543 51

The New Board The following electrical schematic was made taking into account the above considerations.

Figure 4.6: New Stepper Controller Board Power regulation and reverse protection (top) supplies a reverse protected input voltage to the AMIS driver (left) and then further filters and regulates the input voltage down to 5V for the microcontroller (right). Both the microcontroller and stepper controller portions are virtual copies of the Sparkfun Pro Micro and Pololu Carrier Board with the necessary connection made between the two to enable both an SPI and a TTL interface. Power regulation allows for input from the USB line to bypass the 5V linear regulator. Since this bypass comes after D2, the filter diode capacitor pair for the logic side of the board, presence of a USB connection allows the board to be powered up, but does not allow power flow to the attached motor. As a common precaution, a 500mA thermal fuse is also attached to the USB connection to avoid overloading a computer’s USB 5V rail. Power regulation was modeled using NI Multisim. Due to modeling difficulties with microcontrollers and motors, resistor loads were used and represent the absolute maximum power draw for each component (See Figure 7). A resistor (R2) was added to more realistically simulate the battery’s internal resistance. Data was determined using battery’s maximum instantaneous amperage output and rated voltage. R_LOGIC_LOAD represents the maximum load capable of being drawn by the logic side of the board. Both the microcontroller and AMIS-30543 draw 100mA giving a 200mA draw rounded up to 250mA for good measure. R_MOTOR_LOAD represents the maximum load capable of being drawn by the motor. Since the AMIS driver is capable of micro stepping and has internal current limiting, the current draw was determined by taking the maximum draw of the motor once both coils were activated giving a total of 3.4 Amps. It should be noted this kind of draw is when the AMIS driver is in its square step mode. The square step mode is limited to only providing half steps and will activate both coils at full current. The team intends to use true micro steps in which the coil current models a sine and cosine function with position. Since the maximum of this function is given at the angles pi/4, 3pi/4, 5pi/4, etc. The maximum current intended for use is 1.7 cos (pi/4) + 1.7 sin (pi/4) or about 2.4 Amps. 52

Figure 4.7: NI Multisim Model of Power Regulation The following data was gathered by testing under various conditions on the battery input line: Table 3: Power Supply Results and Reasoning Supply Results Reasoning

12V Supply Stable Logic, Stable Motor Operating Conditions -12V Supply Off Reverse Protection Test 12V 80% Duty Cycle Stable Logic, Unstable Motor Periodic Shorting Out 12V 20% Duty Cycle Stable Logic, Unstable Motor Heavily Shorting Out 12V-7V 12V 80% Duty Stable Logic, Passable Motor Battery Overdraw Cycle 7V Supply Stable Logic, Passable Motor Battery Nearly Depleted

Figure 4.8: 12V Supply 53

Figure 4.9: -12V Supply

Figure 0.10: 12V Supply 80% Duty Cycle

Figure 4.11: 12V Supply 20% Duty Cycle 54

Figure 4.12: 12V-7V Supply 12V 80% of the time

Figure 4.13: 7V Supply Closed Loop Control A large portion of this project has been ensuring the board is viable for closed loop control. As the project was explored further, it became apparent that Back-EMF may have been a viable option for position feedback. This possibility was researched and determined not to be viable. Back EMF is measured at the zero current crossing or when each coil has the same amount of current flowing through it. This means that if using back-EMF an initial half-step is required to ensure that back-EMF will be measured by the stepper driver. The board can then be placed in full step mode and each successive step will be at the zero current crossing or the user can continue using a half step mode. A prototype board was built and this theory tested. It was found from the Figure 14 and 15 that the back EMF is too small to be detected within reasonable error on the ATMEGA32u4. Static on the line has a measured peak of +/- 600mV while the produced Back-EMF has an approximate amplitude of +/- 500mV. 55

Figure 4.14: SLA Pin When Coils are at Non-Zero and Zero Current Crossing Respectively Because of this, an optical device will be integrated into the circuit for rotary encoder feedback. The Pololu QTR-1A [9] was chosen for its size and power requirements. The Prototype A prototype board was built. The board functioned as expected and was used in the Back-EMF tests. On the prototype, an ATMEGA328P was substituted for the ATMEGA32u4 because it came in a through-hole packaging and is nearly identical to the ATMEGA32u4.

Programming The controls consist of two main types of devices that need to be programmed, Arduinos and the raspberry Pi. The system works on an i2c network with the Pi as the master and the Arduinos as slaves. There is also an IMU as a slave. The general idea is the Pi reads values from a joystick connected to an Arduino, and then sends those values to Arduinos connected to the stepper motors in order to turn the fins to steer the submarine. The Arduinos are programmed in the Arduino IDE, which accepts special Arduino type code as well as C/C++. The Pi on the other hand was programmed using python. Python is easier for new members to learn so they can program, but in the future it would be wiser to use C/C++ on the pi as well due to its performance benefits and ability to better interact with the Arduino code base. core.py 56

This program is the main worker, it actually sends and receives data from the Arduinos and the IMU on the network. imu.py This is a class that controls the IMU data and abstracts it into convenient functions to be able to call to get the pitch and roll of the submarine. iSquaredC.py This program abstracts the python smbus library into easy to call read and write functions. joeFilter.py This is a class used to smooth out data being read into the Pi. It creates a null zone that ignores small values that are in high probability irrelevant, and keeps a running average of previous values to use as a guide when reading the next value. HumpSub_JoyStickControllerV3.ino This program controls the joystick, and waits for read requests from the Pi. Stepperdriver.ino This controls the stepper motors, get sent values and sets fin positions.

Appendix A: Testing Two in-water tests of the submarine were conducted. The first test occurred on March 5th, 2016. At that time, most systems had been upgraded to the 2016 design, however not all systems were in an operational state. The planned control cable tensioning strategy proved infeasible, therefore even though the joystick and the fin control mechanism were installed, the linkage between them was not functional and the fins had to be secured in their neutral position. Additionally, the updated propeller and hub design had not yet been manufactured and the 2015 model was used. This first test revealed major improvements to pilot ergonomics as a result of the design decision to move the pedal area farther back and reduce the separation distance between the pedals. This allowed the pilots to transfer more power to the cranks without the concern of hitting the interior of the hull or other components in the submarine. The second test occurred on May 15th, 2016. The submarine at this point was fully fitted with 2016 components and additional performance improvements were observed over the previous year’s configuration. Unfortunately, although the mechanical control system was fully connected, the pilots had difficulty operating the joystick due to high resistance in the mechanism. This constitutes a major issue which will require remedial action prior to the 2016 competition. Positive results of this test came from the new propeller design. Pilots reported experiencing less resistance in the pedals compared to the March test when the 2015 propeller was used. Additionally, the submarine was observed to get up to speed with far less roll perturbation than previously experienced. This will allow for better course control as the pitch and yaw planes remain largely parallel to their nominal orientations. Final testing is scheduled for the weekend of May 28-29. On the 28th, the mechanical control system will be tested again to ensure the issues encountered at the previous test have been remedied. On the 29th, the electrical control system will be tested for the first time.

Appendix B: The Team Captain - Bentley Altizer Mechanical Engineer. Senior. Bentley is going into his fourth year on the Human Powered Submarine Team, and his second as Team Captain. He is always pushing to bring team performance to the next level, and will enjoy his first year of not running any specific design projects concurrent with his leadership role. Mechanical Controls – Tyler Nichol Mechanical Engineer. Ph.D. Student. Tyler’s research interests include mooring dynamics and numerical modeling. His interest in underwater vehicles stems from a deep passion for underwater exploration and discovery. As an active Divemaster, he strives to maintain a squad of top-notch divers. His main focus, however, is on the design and manufacturing of the mechanical components that comprise the submarine control and maneuvering systems. He is eager to build on the success of the previous year and help turn What Sub Dawg? into a force to be reckoned with. Dive Manager – Robert Karren Intended Mechanical Engineer. Music Minor. Sophomore. Robert is a sophomore at the UW, and joined UWHPS last April as a scientific diver, just in time to travel to ISR 13 with them. He’s excited to continue working with the team as dive team lead, and will be traveling with the team to eISR 2016. Marketing Director – Colin Katagiri Oceanography BS. Marine Biology Minor. UW Alumnus. Colin is a UW alumnus from the School of Oceanography. His love for the sea and ocean technology aligns perfectly with the vision of this team as both a diver and machinist. He has been a scientific diver for the past two years and is thrilled to join them in preparation for eISR 2016.

Electrical – Jack Gentsch Electrical Engineer. Junior. Jack is a junior undergraduate in the UW Electrical Engineering program. His love for robotics and automation combined with his quirky personality initially drew him to work on the submarine. As a newly certified diver, he is excited for the coming year and ready to rock eISR 2016.

Computer Science – Joseph Jimenez Computer Science and Engineering – Junior Joe is a sophomore in the Computer Engineering program at the University of Washington. He found out about the team from his roommate freshman year, and has been a part of it ever since. The various aspects of programming a submarine makes this a very fascinating activity for him

Gearbox – Andrew Fitzgerald Mechanical Engineer. Senior. Andrew is a senior in the University of Washington Mechanical Engineering program. Andrew has many years in the manufacturing and construction industries. His interest in the water has lead him to sail for the University of Washington, dive for fun and get involved with the human powered submarine team. Propeller and Hub – Gavin Denzer Mechanical Engineering. Mathematics minor. Senior. Gavin’s past experiences and future goals line up perfectly with the challenges presented in the Human Powered Submarine competitions. He is the propeller hub team lead as well as a machinist for the team. He looks forward to learning everything he can from the challenges presented in designing and manufacturing components of the submarine this year as a returning member.

Pilot – Carol Nishikawa Psychology. Music; Education, Learning, and Society Minor. Senior. Carol is a Psychology major at the UW and will be a senior for the upcoming school year. She is minoring in both Music and Education, Learning, and Society. She has fallen in love with diving thanks to the HPS team, and looks forward to competing in Europe this summer!

Pilot – Dominic Forbush Mechanical Engineering. Ph.D. Student. Dominic is a graduate student from the University of Washington. His research focuses on performance characterization and control of marine hydrokinetic turbines. He is proud to be the male pilot for the team, and is excited to push the sub and himself to their limits in eISR 2016.

Adviser – Andy Stewart Faculty Advisor - Andy Stewart, Ph.D. Principal Engineer. Affiliate Assistant Professor.

Andy's broad range of interests, beyond just marine engineering, have helped guide the team on a streamlined path to success. His research interests of next-generation ocean science technology and the creation of new tools to both advance scientific exploration has been an invaluable inspiration to the team.

Team members Anthony Douse Andrew Farrell Andy Stewart Sharon Luo Marilyn Jasmer Vincent Loputra Ashley Han Jordan Wagner Tremaine Ng Elliot Gunnarsson Riley Harris Zach Inoue Ryan Pennell Joe Zacharin Ahrif McKee Gabrielle Pang Sean Lam Varun Viswanath Ashley Huynh Sean Sung Yong Lee Jesse Castleberry Timmy Lee Ryland Bryant Riley Lyle Giorgio Rojas Josh Dailey Evan Kirkpatrick Kyleah Hess Harlin Wood Aman Arya Brendan Greetham James Kurniawan Connor Hughes

Appendix C: Hull Hatch Latch

Figure C.1: Static Diagram of Latch Forces

In order to achieve the desired load per nut we tensile tested 4-40 nylon nuts. Some nuts had threads selectively stripped using a drill bit to artificially weaken the nut and make it more susceptible to stripping. Figure C.2 below shows the results from 3 59

such test. You can see that Nut 1, which was stripped using a number 31 drill bit had approximately half the tensile strength of the unmolested nut. This information, paired with in water trails gave us enough information and experience to secure the hatch in a way which it could be forced off in an emergency situation.

Figure C.2: Tensile Test Results 60

Appendix D: Gearbox

[5] Figure D.1: Instron Universal Testing Machine Sample Calculations:

Sum of the moment about the gearbox spindle, where F2 is the tension in the belt.

퐹1 ∗ 퐿1 + 퐹2 ∗ 퐿2 = 0

퐹1 ∗ 퐿1 퐹2 = 퐿2

Figure D.2: Static Diagram of Transverse Shaft

Sum of the moments at C is used to calculate the reaction force Ra.

∑ 푀 = 0 푅푎 ∗ (퐿1 + 퐿2) − 퐹 ∗ 퐿2 = 0

퐹 ∗ 퐿2 푅푎 = (퐿1 + 퐿2)

Sum of the forces in the Y direction is used to find reaction force Rc.

∑ 퐹푦 = 0 푅푎 − 퐹 + 푅푐 = 0

퐿2 푅푐 = 퐹 ∗ (1 − ⁄ ) (퐿1 + 퐿2)

The maximum shear is equal to Ra.

푉 = 푅푎

The maximum moment is equal to the shear force multiplied by the distance from the support.

퐹퐿1퐿2 푀푚푎푥 = 푅푎 ∗ 퐿1 = 퐿1 + 퐿2

Bending Stress: 푀푦 휋푟4 휎푏 = ⁄퐼 푦 = 푟 퐼 = ⁄4 4퐹퐿 퐿 휎 = 1 2 휋(퐿1 + 퐿2)

Shear stress: 푉푄 2푟3 휋푟4 휏푠 = ⁄퐼푡 푉 = 푅푎 푄 = ⁄3 푡 = 2푟 퐼 = ⁄4

16퐹퐿1퐿2 휏푠 = 2 2 3휋 푟 (퐿1 + 퐿2)

Shear Stress from torque: 푇휌 휋푟4 푃 휏푡 = ⁄퐽 휌 = 푟 퐽 = ⁄2 푇 = ⁄휔 2푃 휏 = 푡 휔휋푟3

Combined loading Shear dominant: 62

There are only shear stresses in this situation therefore the sum of the shear and torque shear are equal to the primary stresses.

휏 = 휏푠 + 휏푡 = 휎1, −휎2 These primary stresses are input into octahedral shear stress yield criterion. Generalized plane stress applies. 1 휎 2 2 2 푦푖푒푙푑 √(휎1 − 휎2) + (휎2 − 휎3) + (휎3 − 휎1) = √2 퐹. 푆.

Inputting τt and τs and solving for r gives the minimum shaft radius for the conditions.

Combined Loading Bending Dominant:

휎푏 = 휎푥 휏푡 = 휏푥푦 These stresses are input into octahedral shear stress yield criterion. Generalized plane stress applies.

1 2 2 휎 2 2 2 2 푦푖푒푙푑 √(휎푥 − 휎푦) + (휎푦 − 휎푧) + (휎푧 − 휎푥) + 6(휏푥푦 + 휏푧푦 + 휏푧푥) = √2 퐹. 푆.

Inputting τt and τs and solving for r gives the minimum shaft radius for the conditions.

HTD 5mm belt tensile test results:

Figure D.3: Load in vs. Extension 5mm Belt Single Tooth.

Table 4: Max Load and Extension at Max Load Per Trial for HTD 5mm Belt Test of Single Teeth

Figure D.4: Load vs. Extension 5mm Belt Two Teeth

Table 5: Max Load and Extension at Max Load Per Trial for HTD 5mm Belt Test of Two Teeth

Figure D.5: Load vs. Extension 5mm Belt Three Teeth 65

Table 6: Max Load and Extension at Max Load Per Trial for HTD 5mm Belt Test of Three Teeth

Figure D.6: Load vs. Extension 5mm Belt Six Teeth

Table 7: Max Load and Extension at Max Load Per Trial for HTD 5mm Belt Test of Six Teeth

Appendix E: Hub

Figure E.1: Aluminum Propeller Blade Adapter

Figure E.2: Bevel Gear Assembly 67

Figure E.3: Stepper Motor Adapter

Figure E.4: Hub Attached to Electronics Cylinder 68

Figure E.5: Retaining Collar Connecting the Hub to the Electronics Cylinder 69

Figure E.6: Coupling Drive Shaft Adapter

Appendix F: Code Core.py from iSquaredC import * import imu import joeFilter

#Addresses of arduinos to connect with joystick = 0x05 topFin = 0x06 rightFin = 0x07 botFin = 0x08 leftFin = 0x09 xIMU = imu.IMU() xIMU.init() xFilter = joeFilter.JoeFilter(0, 3) yFilter = joeFilter.JoeFilter(0, 3)

#Reads the x and y values from joystick def readCoordinates(address): numbers = [] for i in range(0, 2): num = readInt(address) numbers.append(num) return numbers

#Sends fin values to all fins def sendFinVals(x, y): top = x; bot = -1 * x; right = y; left = -1 * y; writeInt(topFin, top) writeInt(botFin, bot) writeInt(rightFin, right) writeInt(leftFin, left)

#Main loop to get and send fin values while True: numbers = readCoordinates(joystick)

xIMU.updateAngles() xX = xIMU.getRoll() xY = xIMU.getPitch() if not numbers: continue x = xFilter.joeFilter(numbers[0]) y = yFilter.joeFilter(numbers[1]) 71

try: writeInt(topFin, int(x)) except IOError: print "problem" print "Arduino - x: %d, y: %d, roll: %d, pitch: %d" %(x, y, xX, xY) imu.py import smbus import math import joeFilter class IMU: xAng = 0 yAng = 0 accelAddress = 0x1e addressX0 = 0x28 addressX1 = 0x29 addressY0 = 0x2a addressY1 = 0x2b addressZ0 = 0x2c addressZ1 = 0x2d ctrlReg1 = 0x20 ctrlReg2 = 0x21 xxFilter = joeFilter.JoeFilter(0, 12) xyFilter = joeFilter.JoeFilter(0, 12) xzFilter = joeFilter.JoeFilter(0, 12) bus = smbus.SMBus(1)

def init(self): self.bus.write_byte_data(self.accelAddress, self.ctrlReg1, 0b01100111) self.bus.write_byte_data(self.accelAddress, self.ctrlReg2, 0b00100000)

def readAccel(self, axis): add0 = 0x0 add1 = 0x0 72

if axis == "x": add0 = self.addressX0 add1 = self.addressX1 elif axis == "y": add0 = self.addressY0 add1 = self.addressY1 else: add0 = self.addressZ0 add1 = self.addressZ1 accL = self.bus.read_byte_data(self.accelAddress, add0) accH = self.bus.read_byte_data(self.accelAddress, add1) acc = (accL | accH << 8)

if acc >= 32768: acc = acc - 65536

if axis == "x": acc = self.xxFilter.joeFilter(acc) elif axis == "y": acc = self.xyFilter.joeFilter(acc) else: acc = self.xzFilter.joeFilter(acc)

return acc def updateAngles(self): rad2degree = 57.29578 accX = self.readAccel("x") accY = self.readAccel("y") accZ = self.readAccel("z") newX = (math.atan2(accY, accZ) + math.pi) * rad2degree newY = (math.atan2(accZ, accX) + math.pi) * rad2degree self.yAng = newY - 270 73

self.xAng = newX - 180

def getPitch(self): return self.yAng

def getRoll(self): return self.xAng

iSquareC.py

joeFilter.py import Queue class JoeFilter:

smoothingFactor = .6

def __init__(self, startVal, const): self.data = Queue.Queue() self.nullZoneConstant = const for i in range(0, 10): self.data.put(startVal)

def joeFilter(self, val): prediction = 0 for i in range(0, 10): nextVal = self.data.get() prediction += nextVal 74

self.data.put(nextVal) prediction /= float(self.data.qsize()) prediction = int(prediction) final = self.lowPassFilter(val, prediction) final = self.nullZoneFilter(final) self.data.get() self.data.put(final) return final

def lowPassFilter(self, val, old): return (self.smoothingFactor * val) + (1 - self.smoothingFactor) * old

#Creates a null zone, filtering out small #values from wiggle def nullZoneFilter(self, coor): if coor < self.nullZoneConstant and coor > -1 * self.nullZoneConstant: return 0 else: return coor

_HumpSub_JoyStickControllerV3.ino #include #include int xDir[100]; int yDir[100]; long count; long last; int xDirFin; int yDirFin; int xDirFinal; 75

int yDirFinal; int i; int index; int maxim;

// double collectData(int x, int y) {

// Mark: - Init

double dir; int a; // Analog input 1 int b; // Analog input 2 double POT; // total potential resistance double safR; // Safety resistor 1, change based on what maximum current will hurt people double AK; double AR; double BK; double BR; double QB; double resistorTwo;

// Mark: - Define Non-null Values

POT = 5; safR = 1.9;

// Mark: - Read Analog Inputs

a = analogRead(x); // Analog input 0 pin <- 0 b = analogRead(y); // Analog input 1 pin <- 1

// Mark: - Process Data // Calculate number between -50 and 50 that conveys the direction 76

AK = a * POT; AR = a * safR; BK = b * POT; BR = b * safR; QB = AK - AR - BK - BR; resistorTwo = (sqrt(QB*QB - 4 * AR * (BK - AK)) + QB) / (2 * (a - b)); dir = ((resistorTwo / POT) * 256) - 128; return dir; }

QueueList byteQue;

// void sendData(int testInt) { //Serial.println(intQue.count()); if (byteQue.isEmpty()) { int front = testInt >> 8; int back = testInt; byteQue.push(front); byteQue.push(back); } if (byteQue.count() > 0) { Wire.write(byteQue.pop()); } }

// This method calls sendData twice to send // both x coordinate and y coordinate at the same time void sendCoordinates() { if (byteQue.isEmpty()) { 77

int front = xDirFinal >> 8; int back = xDirFinal; byteQue.push(front); byteQue.push(back); int front2 = yDirFinal >> 8; int back2 = yDirFinal; byteQue.push(front2); byteQue.push(back2); } if (byteQue.count() > 0) { Wire.write(byteQue.pop()); } } void sendButtonStates() { int statesSum = 0; // set Digital read pins here int a = 2; int b = 3; int c = 6; int d = 7; int e = 8; int f = 9; int h = 10; int i = 11; int states[8] = {a, b, c, d, e, f, h, i}; for( int j = 0; j < 8; i++) { if(digitalRead(states[j])) { statesSum += pow(2, j); } } sendData(statesSum); }

void setup() { // put your setup code here, to run once:\ maxim = 0; for(i = 0; i < 10; i++) { xDir[i] = 0; yDir[i] = 0; } index = 0; Serial.begin(9600); Wire.begin(0x05); // 0x05 - Slave Address Wire.onRequest(sendCoordinates); //Wire.onRequest(sendButtonStates); } void loop() { count++;

//if(count - last == 1000) { // This structure was written to // create a psuedodelay because the // delay function is no bueno in i2c xDirFin = 0; yDirFin = 0;

for(int i = 1; i < 100; i++) { xDir[i] = xDir[i - 1]; xDirFin += xDir[i]; yDir[i] = yDir[i - 1]; yDirFin += yDir[i]; }

xDir[0] = collectData(0, 1); // Analog inputs 0 and 1 should be for the x direction xDirFin += xDir[0]; // adds each value to a sum yDir[0] = collectData(2, 3); // Analog inputs 2 and 3 should be for the y direction 79

yDirFin += xDir[0];

// Calculate running Average xDirFinal = xDirFin / 100; yDirFinal = yDirFin / 100;

//last = count;

// MARK: - Report / send data //if(count - last == 500) { Serial.print("x: "); Serial.print(xDirFinal); Serial.print(", y: "); Serial.println(yDirFinal); //last = count; //}

// for(int i = 0; i < xDir[0] + 50; i++) { // Serial.print("*"); // } // Serial.println();

//} }

// THINGS TO DO // OTHER BUTTONS to set up - Autocorrect()

//OTHER STUFF - Data filtering // - straightening the fins // - collect data and interpret // - runtime -.- 80

Appendix G: Future 2-Person Submarine The team has been working on the design a 2-person submarine, with aspirations to break 8 knots. Design on the hull form was completed during Fall 2015 and construction began January of 2016 at the Northwest School of Wooden Boat Building.

Figure G.1: 2-Person Hull First Half Construction

Figure G.2: 2-Person Hull Construction

References [1] P. Williams, The diving supervisor's manual. London: International Marine Contractors Association, 2000. [2] “Gate carbon drive systems vs traditional chain drive efficiency test, “Friction Facts LLC., Boulder, CO, USA, 2012 [Online]. Available: https://www.friction- facts.com/media/wysiwyg/Gates_Carbon_Belt_Drive_rev.pdf [3] E. Oberg, F. D. Jones, H. L Horton, and H. H. Ryffel, Machinery’s Handbook 29th Edition. New York, NY: Industrial Press, 2012. Controls [4]"Parker O-Ring Handbook", Parker, 2016. [Online]. Available: https://www.parker.com/literature/ORD%205700%20Parker_O-Ring_Handbook.pdf. [Accessed: 19- May- 2016]. [5] Instron. "Testing Systems," www.instron.us. [Online]. Available: http://www.instron.us/en- us/products/testing-systems [Accessed: Dec. 15, 2015]. [6]"12V, 1.7A, 416 oz-in Geared Bipolar Stepper Motor", Robotshop.com, 2016. [Online]. Available: http://www.robotshop.com/en/12v-17a-416oz-geared-bipolar-stepper-motor.html. [Accessed: 18- May- 2016]. [7]"Pro Micro - 5V/16MHz - DEV-12640 - SparkFun Electronics", Sparkfun.com, 2016. [Online]. Available: https://www.sparkfun.com/products/12640. [Accessed: 18- May- 2016]. [8] "Pololu - AMIS-30543 Stepper Motor Driver Carrier", Pololu.com, 2016. [Online]. Available: https://www.pololu.com/product/2970. [Accessed: 19- May- 2016]. [9] "Pololu - QTR-1A Reflectance Sensor", Pololu.com, 2016. [Online]. Available: https://www.pololu.com/product/958. [Accessed: 19- May- 2016].