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Report on the development and testing of a fully submergible remote operated vehicle for the purposes… Lewis, Byron; McNeill, Adrian Apr 3, 2013

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ii   Report on the Development and Testing of a Fully Submergible Remote Operated Vehicle For the Purposes of Sea Sponge and Coral Analysis   Group 1302 Byron Lewis Adrian McNeill   Project Sponsor Glen Dennison Chris Harvey-Clarke   Phys 459 Engineering Physics University Of British Columbia April 3rd 2013 iii  Executive Summary This report details the results of student work on an underwater remote operated vehicle (ROV) used to view sponge life on the sea floor of the Howe Sound (a depth of ~850ft). The ROV is to be ergonomically viable for operation by a single, or pair or researchers, as well as economical. This project is a continuation of work completed by a previous student team who produced a simple, incomplete, prototype. The ROV is not completed but significant advancements have been made. The project is currently a mechanical shell approximately 1m3 and weights 30kg (this includes electronic components) and several primary electrical systems. The mechanical shell has been extensively upgraded and remade to better fulfill the design requirements. One of the ROV?s defining characteristics is a pressure equalization system that allows deep diving without use of heavy and expensive structural supports. It works by connecting all water tight areas of the ROV to a SCUBA regulator and air tank. This passively maintains the air pressure ambient to the water thus greatly reducing the forces on the unit. Key mechanical features such at the pressure equalization systems, and leak free housings have been tested successfully. The PES is found to consume ~2.6 ft3 over a 15 min dive reaching 51 ft and back to the surface then 133ft and back to the surface. This confirms the model which predicts ~2.5 ft3 consumed. The major electrical systems have been designed, built and tested including the power, motor control and camera systems. The other defining characteristic is the single cable tether system which will carry all signals to and from the unit as well as power. This system has been successfully tested using AC video signal coupled with high voltage DC power. To improve the design t is recommended to clean up the wiring and mounting of the electrical systems as well as construct and test the LED lighting system. The mechanical design can be improved by strengthening some of the connections and supports as well as several wire ports need to added to integrate the required battery housing and electrical systems.  iv  Table of Contents List of Figures ................................................................................................................................ iv List of Tables ................................................................................................................................... v 1.0 Background and Motivation ................................................................................................ 1 3.0 Discussion of Mechanical Systems ...................................................................................... 4 3.1 Theory and Design Considerations .................................................................................. 4 3.2 Initial System.................................................................................................................... 5 3.4 Present Design and Methodology .................................................................................... 7 3.5 Testing ............................................................................................................................ 10 3.6 On-going Work and Recommendations ..........................................................................11 4.0 Discussion of Electrical Systems ....................................................................................... 12 4.1 Theory and Design Considerations ................................................................................ 12 4.2 Final Electrical Design ................................................................................................... 13 4.3 Alternate Designs ........................................................................................................... 16 4.4 Testing ............................................................................................................................ 16 5.0 Conclusion .............................................................................................................................. 19 6.0 Recommendations ................................................................................................................... 21 APPENDICIES ............................................................................................................................. 22 Appendix A: Stability Control in Water .................................................................................... 22 Appendix B: Camera Dome Assembly ..................................................................................... 23 Appendix C: Pressure Equalization System Dive Testing ........................................................ 25 Appendix D: Images of Electrical Devices ............................................................................... 29  List of Figures Figure 1: Sponge Life          1 Figure 2: Pressure, Volume at Increasing Depths       4 Figure 3: ROV Initial Prototype Images        7 Figure 4: Present Prototype Images         9 Figure 5: Block Diagram of Pressure Equalization System      10 Figure 6: PES Connections          10 Figure 7: Signal Frequency Domain for the Main Tether      12 Figure 8: Biasing Tee          13 Figure 9: Biasing Tees          14 v  Figure 10: Power Supply Diagram         15 Figure 11: General Block Diagram of ROV Electronics       15  Figure 12: Power System Test Diagram        17 Figure 13: Motor Control Test Diagram        17 Figure 14: Camera Test Diagram         18 Figure 15: Integration Test Diagram         19 List of Tables Table 1: Major Objectives          2  Table 2: On Going Mechanical Work         111  1.0 Background and Motivation Project sponsors: Glen Dennison and Chris Harvey-Clarke The coral beds and sponge life in the Howe Sound area are a fascinating part of BC?s natural habitats. The myriad of life in this sparsely explored sea bed is a strong attraction for marine life researchers.  This environment can prove dangerous for divers. Diving past just 40m can expose divers to the dangers of decompression sickness, nitrogen narcosis and oxygen toxicity. Divers are also limited in dive time by their personal oxygen supplies. To combat this, researchers utilise remotely operated vehicles (ROVs) to brave the environments for them. These vehicles can be engineered to handle significantly greater pressures and harsher environments. This allows for deeper and longer dives that grant access to marine environments that a diver might never be able to reach without unnecessary risk human life. ROV?s may be equipped with a variety of tools to aid underwater exploration ranging from simple video recording and sonar surface mapping to more complex controllable limbs for sample collection. Typical ROV?s can cost thousands of dollars, with prices increasing drastically as deeper depths are required. This puts the technology out of the hands of many researchers who simply don?t have the capital to invent in these units. Furthermore, commercial units which are able to reach depths required in the Howe Sound can weigh hundreds of pounds making them ergonomically unviable for smaller research operations. Project sponsors Glen Dennison and Chris Harvey-Clarke have requested an ROV capable of collecting video samples of Bioherms such as the Cloud Sponge and Glass Sponge found along the Howe Sounds underwater mountain rangers at depths reaching 260m and the marine life that collects near them. The final unit is to be light weight for easy transport and economically viability.  Figure 1: Sponge Life 2  2.0 Project Objectives  The purpose of this project is to construct a working prototype of an economically viable underwater remote controlled vehicle (ROV). This vehicle will be easily released by hand from a boat/dock and dive to the sea floor to film/capture pictures of sponge life in the Howe Sound. The ROV will be controlled from the surface using a radio frequency handset on the surface.   This full scope of this project is beyond one term of work. As such, the focus has been to work to accomplishable goals while keeping future goals in mind. Our primary object is to produce a working prototype of a remote controllable submersible. As the previous group built a rough mechanical shell, this team is focusing on improving the current design and constructing the major electrical components required. Project Objectives and Future objectives are listed in the table below. Table 1: Major Objectives Objective  Weight Current State Setbacks encountered Motor Control The ROV position and yaw can be controlled using two horizontally oriented propellers. ROV depth can be controlled by the use of a single vertical propeller.  These propellers receive signals from the ocean surface. The ROV can attain and maintain depths of up to 30m. The ROV can hold horizontal position to within 2m at these depths. 10         Significant reworking was required before the motors can be remounted. This limited testing to what could be accomplished on the lab bench.  Physical Limitations The ROV is able to dive to a depths of <30m without developing leaks or structural failure. The ROV can be recovered in the event of a mechanical or electrical failure. The mechanical shell can be easily moved by 2 people. The mass of the ROV (with peripherals) should be less than 45kg and no dimension should 10 The bulk of the physical structure has been completed as outline in the Mechanical System discussion of this report. However no handles for transport have been installed yet. Successful testing of the Pressure Equalisation System (PES) has been completed confirming the systems operation. Any leaks discovered have been fixed. The structure, despite requiring minor additions and modifications, is ready for safe integration with the electrical system and further testing. Significantly more changes needed to be made to the system as well as delays on part orders and testing dates delayed deadlines preventing integration with electrical system. 3  be greater than 2m.  The shell should robust enough to survive handling and/or bumping into debris during operation. Power Systems The ROV is powered from a surface power supply with an onboard battery providing boost power as necessary for thrust. One power source is sent from the surface, and then split as required to power onboard electronics and propellers. The power supplied to the ROV will be 380V at 1Amp.   The maximum power usage of the motors is 13.8V at 60Amps. 9 The power switching system has been ex situ tested using a 100ft coaxial cable and filtered through biasing tees. The power supply was able to power two motors as well as power the camera. The battery was not required for this test.  The power system is designed and constructed. Some minor cleanup of cables and connectors is still required.      Camera Systems The camera will be mounted at the head of the ROV. It will look out though a clear lens. The video signal will be sent back to the surface to be viewed on a monitor by the operator. The camera title angle can be controlled by the operator. The camera can be held within ?5? of angle requested.  6 Camera signal system completed. Power and signal apparatus constructed. Some clean-up of cables and connectors required. Lots of connectors make complicated systems hard to test. Signal is noisy when using biasing tees. The camera can be powered by a number of different supplies all of which require a different cable setup. Light Emitting Diode (LED) Spotlight The LED lighting strip will illuminate the area in front of the ROV. These LEDs can illuminate an area of 1m? (from a distance of 2m) at an ocean depth of 30m. 4 Not completed. The circuit for the controller has been designed but not tested.  Lack of documentation by controller manufacturer increased the learning curve of the controller significantly. Telemetry Depth and direction measurements are taken 2 Not attempted. Infrastructure constructed to allow for the signal to be carried via an RF  4  by instruments onboard the ROV and sent to the operator. Depth measurements accurate to ?1m and compass readings accurate to ?10?. signal.  3.0 Discussion of Mechanical Systems 3.1 Theory and Design Considerations  In order to understand the challenge of ROV construction it is important to have a basic understand of pressure and volume behaviors in salt water. Figure 2: Pressure, Volume at Increasing Depths shows the linear pressure increase with depth and an exponential decrease in volume as depth increases. That means at just 10m the pressure has increased by 3 atmospheres and the volume of an air capsule is 1/4th of its surface volume. Extending this to the required 260m places a pressure of ~26 atmospheres and a volume reduction to 1/26th original size. The second important quality of the ROV that needs to be understood is its ballast. This is the general term used to describe how the unit will settle in the water. Will it sink or float? Will it roll or tip? These are important factors in controlling the ROV and should be carefully accounted for in design. Comments on creating a stable system may be found in Appendix A. The overall design will be positively buoyant as a failsafe to allow easy recovery in case of power failure.  Figure 2: Pressure, Volume at Increasing Depths 0204060801001201401601802000 5 10 15 20 25Pressure (Absolute in kPa), Volume (Units)Depth in MPressure, Volume vs Depth in salt waterPressureVolume5   Typically the compression effects of the water pressure would be counteracted by implementation of expensive and bulky reinforcement, their goal being to maintain a constant internal pressure equal to surface pressure. This projects goal is to design a robust systems cable of handling the full depth of the Howe Sound/ Lions Bay area while being light enough to be transported by an individual or pair of researchers. This ROV will implement a Pressure Equalization System (PES) in order to maintain structural integrity. This will allow the ROV to be light weight and made mainly of retail hardware parts such as ABS plumbing piping. The PES is created using a SCUBA air regulator and tank to equalize the internal pressure of the unit with the external water pressure. The result is a robust system which only needs to be water tight and does not need to withstand the immense forces involved. This means that as long as the ROV is attached to an air tank that is able to provide adequate volume and pressure, then the same light weight design may be used for shallow or very deep dives. A drawback of this system is that any electronics used must be able to operate under high pressures. 3.2 Initial System The team will be working with Glen Dennison on a prototype created by Phys 459 group 1157 as shown in Figure 3. They have provided a basic vehicle hull: o Including central air chamber connected to air tank and regulator, basic structural support features, water tight electrical component housing unit and horizontal motor mounts o Excluding a mount for the video dome, a mount for the vertical thruster, air system interfaces, storage basket, and electrical system interfaces. Significant additions will be made to this model as well as many of its design problems will be addressed.  Air Tank Support Structure Horizontal Thruster Central Air Tube/ Water Trap Battery Incomplete Storage Basket Side View 6    Air Tank and Regulator Horizontal Thruster Central Air Tube/ Water Trap Incomplete Storage Basket Electronics Storage Air Tank Horizontal Thruster Uninstalled Vertical Motor Support Structure Electronics Storage Central Air Tube/ Water Trap Rear View Top View 7   Figure 3: ROV Initial Prototype Images 3.4 Present Design and Methodology A layout of the present design is illustrated in Figure 4.  Air Tank Horizontal Thruster Uninstalled Vertical Motor Support Structure Electronics Storage Central Air Tube Vertical Thruster Horizontal Thruster Support Structure Respirator/ Water Trap Front View Side View 8    Electrical Housing Horizontal Thruster Support Structure Camera Dome Air Tank Mount Tether mount Electrical Housing Horizontal Thruster Camera Dome Central Air Tube Tether mount Vertical Thruster Respirator/ Water Trap Front View Top View 9   Figure 4: Present Prototype Images  The primary thoughts in the structural layout of the ROV are ballast, power/air connections and motor control.  Given the prototype provided the first concern was placing the single vertical motor. The provided style motor of is not an ideal vertical control system however in economic interests it is being utilised. To provide greatest stability it is ideal to place the motor closest to the center of the ROV however this is difficult due to geometric considerations of the electrical housing box. To counter this, the central air tube and electrical housing box are shifted forward while the water trap is shifted backward and the vertical motor is placed between them as shown.  The PES system connects the water trap, electrical housing and central air tube with motor housings to the dive regulator and air tank as per the block diagram in Figure 5. Connections between systems are made using water tight tube connectors and flexible tubing as shown in Figure 6. The electronics housing is a stock 12?x12?x6? plastic water tight box while the water trap and central air tubes are welded ABS pipe. The motor housings have been fitted such that they screw into the central air tube to make a water tight seal. The camera dome is one of the few relatively complex custom components on the ROV. Its lens is removable to allow access to the camera and wiring inside the central body tube, and it held watertight by pitching a rubber seal between the lens and the end of the ABS pipe piece. A step by step assembly can be found in Appendix B for greater detail.  Electrical Housing Horizontal Thruster Central Air Tube Tether mount Vertical Thruster Respirator/ Water Trap PES Connection Rear View 10   Figure 5: Block Diagram of Pressure Equalization System  Figure 6: PES Connections 3.5 Testing Before integrating the electrical and mechanical systems it is vital that the mechanical system is proven to work properly and robust. Any failures or major leaks would destroy valuable electronics and should be prevented. The testing done to date and been completed in two parts, leak testing and PES testing.  Leak Testing:  The individual water trap, electrical housing, central air tube, and camera dome have all been leaked tested. The criterion for this test is a pass fail system. Each system is submerged for ~10 minutes and no visible signs of leaks have been detected were found in the electronic housing and water trap. A small leak was found in a faulty weld in the central air tube and in the seal of the camera dome. The weld joint has been filled, showing no further leak, and reconstruction of the camera dome shows no further leaks as well. This testing highlights that weld joints in the ABS could be potential failure points if not filled properly and the camera dome assembly should 11  be done carefully to prevent exposing the camera electronics to sea water through leaks.  PES Testing:  The PES tests served two purposes, first is to determine if the system functioned properly, second to determine air consumption rates compared to the theoretical model. The test was carried out in the Howe Sound, just outside of Lyons Bay. It consisted of two dives during which the pressure inside and outside the vessel were monitored. The details of each dive are outlined along with the calculations for air consumption in Appendix C. Both show successful operation of the PES system through a pressure reading inside the vessel matching those outside the vessel, thus showing that ambient pressure is maintained in the ROV. This finding is furthermore supported by large plumes of bubbles released during assent of the ROV. The air consumption is determined to be ~2.6ft3 over both dives, this supports the theoretically calculated ~2.5ft3 with the difference of  0.1ft3 air loss which is hypothesized to be natural leaking of the system over the ~15 minutes of dive time. Extrapolating these results it can be calculated that the ROV will consume ~11.3ft3 leaving ~3.7ft3 safety margin for leaks with the current 15ft3 dive tank. Given a constant leak rate this margin could sustain dives of ~1 hour. Further test dives will contain significantly more sources of air consumption as the ROV may be constantly changing depths to examine sponges and thus expelling more air. Recommend further air consumption testing be done to determine appropriate safe maximum dive time. 3.6 Required Work  With a working PES it is appropriate to shift the focus on the mechanical work towards integration with the electrical system. The ground work for most of this is in place however there are modifications that are needed to be made before it is possible.  Table 2: On Going Mechanical Work Item Description Lighting Mount A PVC cross bar similar to the tether mount needs to be inserted above the camera dome to house the LED lighting grid. This system should be removable to allow interchanging light systems. Battery Housing A similar, but smaller, electronics housing box needs to be purchased and fitted with two water tight cable slots for boost power to the system. This may be mounted either in the center of the cage below the air tank or below the water trap. Testing will determine which location is better for mass balancing. Vertical Motor Support Supports need to be constructed for the vertical motor mount to reduce forces on its connection joint during operation. As seen on the other motors, this location is vulnerable to breakages. 12  Electrical Wire Ports A port to accept the larger wire carrying signal from motors and camera between the central air tube and electrical housing needs to be added to the electrical housing. 4.0 Discussion of Electrical Systems 4.1 Theory and Design Considerations The electronic components of this project are built around using a single cable tether to send power and signal between the surface and the ROV. The signal will have several different electrical signals at various frequencies passing up and down the cable. Power is sent as DC voltage from the surface to the ROV. Electrical signals for the camera and motor control are passed through the cable as radio frequency (RF) signals. The electrical signals can then coexist on the cable but require signal processing on both ends of the system. The signals must be modulated from their native format to an RF frequency and then demodulated back at the receiving end.  This system could be expanded to include a large number of signals for further development, with additional frequencies for each new signal. The mixed signal will be split at the surface and at the ROV using biasing tees.  Figure 7: Signal Frequency Domain for the Main Tether Biasing Tees The biasing tees are integral to the power and signal processing system this ROV uses. They act as filters to separate the DC and AC components of a mixed signal. Biasing tees are splitters with an inductor and a capacitor acting as filters. Figure 8 shows a graphical representation of this concept. The inductor acts as a low pass filter and only allows the DC signal to pass through. The capacitor acts to block the DC component and allow the high frequency signal through. The capacitor and inductor are chosen to match the impedance of the tether (75?) to avoid voltage splitting. Biasing tees are extremely useful for this application but have some restrictions. The inductor must have a high current limit to be able to transmit the DC power. The capacitor must have a very high (in this case 500V) voltage breakdown limit to allow for large DC offset on the AC signal. The frequency of the AC signals needs to be higher than the cut off frequency of the circuit to avoid clipping the signal. Neither the Inputs: Propeller control, camera control Output: Video data 13  capacitor nor inductor are perfect filters and will clip signals if the frequency is in the wrong range. The cut off frequency for the tether is 10MHz so RF frequencies (~60MHz) will be able to pass through without attenuation.  Cut off Frequency Equation:             Figure 8: Biasing Tee Circuit Diagram LEDs  LEDs operate best under constant current conditions instead of the standard constant voltage. There are several reasons for this; under constant current LEDs are more efficient, have more consistent brightness outputs, and, as there is less fluctuation in current, there is a lower likelihood of violating the maximum current rating (and therefore breaking the LEDs).  As the rest of the system operates under constant voltage - variable load, a specific converter is required provide signal and power to the LEDs.   4.2 Final Electrical Design The design and testing methodology for this project was based on completing individual systems then integrating them with the previously constructed systems. The first system completed was the power supply system, then the motor control system and finally the camera system. The LED grid was designed by not constructed. The three completed systems underwent ex-situ experimentation. One of the main obstacles that occurred during test was building/finding connectors between the interfaces. Biasing Tees The biasing tees use store bought electrical components housed in a steel casing. The inductance and capacitance were chosen to match the characteristic impedance of the tether with a 70MHz signal.  BNC connectors were chosen to allow for easy connection to a variety of cable types (the lab has BCN female to wire connectors which allows for temporary connections during testing). 14   Figure 9: Biasing Tees Power Systems   The power systems for the ROV is comprised of an external power supply (located on the surface) to provide the motor and sensor power with a 12V lead acid battery stored on the ROV to provide any boost power the motors require. The main design considerations for the system are reducing power loss and minimizing the complexity of the system. Optimally the all the electrical systems will be run off one power line, as this would minimize the number of electrical components required on the ROV. Most of the power losses are a result of the voltage converters and the resistance of the tether. The system was designed to reduce these losses while maintaining overall simplicity. The ROV is powered by a North American standard electrical socket (120V AC). During testing the power is drawn from the wall sockets but during diving the power is taken from the boat battery.  A graphical diagram of the system is shown below. The AC signal is passed through a rectifier and step up converted (1) to 380V DC on the surface. A high voltage signal is used to reduce the power loss through the tether.  Inside the ROV the signal is split through the biasing tee then passed to a linear voltage switcher (2). The switcher turns the signal into a ~14V signal that can power both the motors and the camera. AC signal     DC signal Mixed Signal 15   Figure 10: Power Supply Diagram  Video System The camera used to capture video is a Wren MiniGlobe auto iris camera. This camera was chosen because another project was currently using a similar model and the camera could operate on the power system chosen. A video signal is transmitted from the camera mounted on the front of the ROV in NTSC format to a RF modulator. This RF modulator converts the signal into a 65MHz signal (Channel 3 in North America). This signal is inserted into the coaxial tether via the AC terminal of the biasing tee. On the surface the signal in then filtered using the other biasing tee then demodulated (back to NTSC) using a VCR then transmitted to a simple monitor where the video is displayed.   Figure 11: General Block Diagram of ROV Electronics  16  LEDs The LED grid is controlled and powered by an Agrello A6211 buck converter is used to take the 14V line and provide constant current power for lighting display. The circuit for this controller is designed, but not built or tested.   Motor Controller The motors will be controlled using an RF handset (similar to a model airplane) and receiver. The receiver has four channels (which correspond to the four axis of the handset (up-down, left-right for the left and right knobs)). Three of the channels are used to control motor signals and one is left open to control the camera tilt angle. There are two motor controllers as part of this ROV. One is for controlling the vertical motor and one is a two channel controller for the horizontal motors. Both controllers use pulse width modulated (PWM) signals as triggers to determine the duty cycle to output to the motors. The two channel controller takes two input signals, one to determine thrust and one to determine steering. The mechanisms behind this controller are very complicated and beyond the scope of this project but quite simple in application (push button, receive thrust).  4.3 Alternate Designs Cable Design and Signal Processing  Wireless capabilities are beyond both the technical expertise and financial restrictions of this project. The equipment required to wirelessly communicate to the ROV are way beyond the budget of this project.  Additionally in the event of a malfunction it would not be feasible to recover the ROV.  Using a multicore cable to transmit the signal would drastically change the electrical requirements for the ROV. There are two major reasons for not using multicore or multiple cables. The first is weight. Possible (financially reasonable) multicore cables are several times heavier than the single coaxial cable chosen. This would increase the power required to lift the ROV by almost an order of magnitude (as well as increase an already large moment on the ROV). The second reason this option was disregarded is concerning the transmission of clean data signals. While multicore cable would allow for different signals to be passed to the surface on similar bandwidths the data signals will still need to be modulated to AC signal to decrease signal noise. As much of the processing would still be required, there is little gain in switch to a multicore tether. Power Switchers A linear switching supply is used on the ROV instead of a linear regulator to reduce power loss. The switcher has the added benefit of being smaller and lighter than an equivalent linear switcher. However the switching supply produces some signal noise that can interfere with the camera signal. Most of this noise is lower frequency than the camera signal and is filtered out during demodulation.  4.4 Testing Power Systems 17   The power system was tested by examining the voltage out of each component. A power resistor was used as load. This setup was the foundation for the rest of the testing. The labels on the following diagram mirror the jack label on the physical component. This test was a proof of concept test.  Figure 12: Power System Test Diagram The output voltage of the power switcher was determined to be 13.8?.5V.    Motor Control System The motor system was first tested using a variable power supply connect directly to a motor. The motor requires a minimum of 8?.5 volts and could draw up to 8?1 amps. The next test conducted was controlling the motors using the two channel controller. A RF handset and receiver was used to produce the PWM inputs for the controller. The power supply described in the previous test was used to provide power to the motors. Two motors were wired up to test the abilities of the controller. The following diagram shows the wiring diagram of the test. This test was a conducted to determine the capabilities of the motor controller.   Figure 13: Motor Control Test Diagram The four channels of the receiver correspond to the four axis of the RF handset. Channel 1 and 2 corresponded to up-down and left-right for the left knob respectively. Channel 3 and 4 were controlled by the right knob. The 18  controller provided movement similar to tank treads; a hard right signal produces a forward signal for the left motor and a reverse signal for the right motor. The controller preformed as expected. Camera System The camera system was tested in a variety of configurations. First the camera was powered using a wall adaptor and the signal was connected directly to the monitor. Then the system was tested by modulating the video signal to RF (Channel3) then demodulating the signal using the VCR. This stage required much fiddling with the VRC and modulator to find the correct configuration and channels to use. Finally (as describe below) the power and modulated signal were mixed via the biasing tees. Several tests were conducted using different power supplies and tether lengths. This test was for proof of concept and quality assurance.  Figure 14: Camera Test Diagram It was discovered that different power supplies did not appreciably affect the quality of the picture. Similarly there was no noticeable difference between a 2ft and a 100ft cable separating the biasing tees, even though the 100ft cable was of considerably lower quality. This was a pleasant surprise. However it is expected that this is because the cable is too small to start seeing degradation due to cable resistance. It remains to be seen if the 1000ft cable will have a noticeable impact. The most significant lever for video quality was determined to be the quality of the connections between the components. Switching the BNC to wire connectors to spliced and soldered connections removed most (but not all) of the signal noise. Some of the noise is hypothesised to be produced by the power switcher.   Integration The final electrical test conducted used the two channel motor controller and the camera running off the same power supply. This test was conducted with both the 2ft and 100ft tether. This test was to investigate the quality of the video signal when the system is loaded. 19   Figure 15: Integration Test Diagram The video signal was not appreciably affected by static load compared to a zero load case (previous test). Again there was no noticeable difference between the two cables. However the signal was briefly interrupted during periods of dynamic loading. For example if the motors are off and then quickly driven the video signal briefly (<1s) becomes choppy then smoothes out. The larger the change the more the signal distorts. This was expected and is of little concern as most video shot will be done during periods of static load 5.0 Conclusion  Although an initial prototype is provided significant work to the mechanical systems have been required. Many problems such as ballast, vertical motor placement, storage, and connections between systems had not been addressed. The present prototype?s mechanical systems can be broken down into several major sections, the respirator and water trap, the electrical housing box, the central air tube and motors, and external structural features. The respirator and water trap have been mounted to the rear of the ROV and one pressure equalization system (PES) air line have been attached to the respirator to feed the electrical housing box, a further line is required to feed the yet to be installed battery housing. Testing showed that the respirators mounting may need rotating to reduce leaks during pressurizing. All required air lines have been integrated into the electrical housing box for the PES however some water tight wire ports are still required for power delivery. The central air tube now comprises the three motor mounts and camera housings. It has been outfitted with the required PES air line, as well as water tight wire port leading to the electrical housing. It still requires the addiction of a convenient water drainage system.  Testing on the mechanical systems has been very successful. All preventable leaks have been sealed, while methods of reducing leaking in the respirator have been determined. The PES test dives showed the system worked as expected.  The data collected in the 51 ft and 130 ft dives from pressure gages show that the pressure inside and outside the vessel appear to be held equal implying successful maintenance of ambient pressure by the PES. These two dives were predicted to consume ~ 2.5 ft3 of air. They were determined to consume ~2.6 ft3 of air. This result 20  confirms the model which doesn?t account for the leaking of the respirator that possibly accounts for the 0.1 ft3 increase in the measured volume verse the theoretic volume. This model is extrapolated to predict ~11.32 ft3 of air consumption in a full 850 ft3 dive. The electrical systems of the project are broken down into four major components (power, camera, motor control and LED control), the three most important systems (all but LED control) have been constructed, tested and integrated into one system.  A power system was constructed to use a standard 120VAC to power the on board electronics at reasonable voltage and current levels. To do this the signal is converted to a high voltage (380V) DC signal for the tether then (at the ROV) switched to a 13.8V DC signal to power the motors and camera. This system was tested ex-situ on the lab bench. The camera system was intended to pass video signal from the ROV to the surface at an AC frequency of 65MHz. This system was constructed using a MiniGlobe camera a RF modulator, a VCR to act as a demodulator and a monitor. This system was tested using a variety of power supplies and tether lengths. The system was constructed successfully, the major sources of noise were determined to be poor connections and the power switcher.  The motor control system is designed to allow for control of vertical motion as well as planar motion and rotation about the vertical axis. To do this a two channel motor controller determines the drive of two horizontal motors to provide forward (or reverse) thrust and rotation while a third, vertical motor is controlled using another controller. The three motors are identical and each run at a minimum of 8?.5V and have a maximum current draw of 8?1amps. The two horizontal motors have been mounted to the ROV shell while the vertical motor has not. The controllers have been ex-situ tested using the power system described previously. These three electrical systems have been integrated together to prove that they can work concurrently. Tests have shown a single power supply can be used to drive the motors while camera sends and displays video signal on a monitor. The power and video signal were carried by the same cable. Biasing tees were used to split the signal into power (DC) and data (AC) to be manipulated separately on the surface and at the ROV. It was determined that bursts of power temporarily disrupt the video signal, but static motor drives did not. These tests were conducted using an 100ft tether.  The LED system was not completed. The circuitry has been designed but not built or tested. This system was put aside to focus on testing and troubleshooting of the other electrical systems. The majority of individual objectives were completed thought the integration of mechanical and electrical systems has yet to be completed.  Although the full ROV has not been completed, this term has brought significant progress to both the Mechanical and Electrical systems. We are confident in passing this project on to our sponsors as a successfully completed term. With a small amount of testing and adaptation the systems will be ready for integration. From that stage the basics of the ROV are completed and the vehicle will only require calibrations and personal additions. 21  6.0 Recommendations  1. Compile a list of all connectors required between electrical components as well as approximate length. a. Cut and connect (crimp, solder, or splice) these connections.  This will improve signal quality for the system and make testing setup much faster and easier to follow. 2. Move the ROV side Biasing Tee onto a printed circuit board with the LED controller. The current biasing tees are malleable and bulky. a. Build two extra biasing tees.  3. Design a mounting board for all the ROV electrical components. This will prevent the components from moving around inside the box during the dive and clean up the design. a. Mount the components 4. Redesign the camera to servo mount to make plugging and unplugging the signal cable easier. 5. Find a multichannel (preferably 3 or 4) RF modulator and demodulator to remove the need for extra components. This will also allow for easy expansion of the system when new components are introduced. 6. Test the Agrello A6211 buck converter and tune the circuit to work with LED grid.  a. Design the circuit in a PCB cutter program (include the biasing tee). b. Cut the PCB on the lab printer or send it to a company for printing. 7. Further testing of safe dive time before failure of PES. 8. Carrying Handles. a. Allow for easier deployment and collection of unit 9. Rebuild respirator and rotate its mounting to reduce passive leaking. 10. Add tether mount support to reduce chance of breakage during ROV recovery 11. Create designated central air tube drain to ease draining of water from motor leaks 12. Repair horizontal motor connectors at threaded interface. a. Improper assembly leak to weak points that are cracking 13. Strengthen water trap mount   22  APPENDICIES Appendix A: Stability Control in Water                             FBD of original prototype                                 FBD of new layout  Electronics Housing Central Air Tube Vertical Motor Water Trap Electronics Housing Central Air Tube/ Water Trap Vertical Motor Center of buoyancy in line with and above the approximate center of mass creating a stable system.  Vertical motor provides torque around stable center creating instability when attempting to dive or ascend. Electronic housing and central air tube shifted forward while water trap is moved to rear of ROV. This maintains the approximate location of the center of buoyancy while allowing the vertical motor to be moved closer to the center of mass and buoyancy, thus reducing the torque it applies. 23  Appendix B: Camera Dome Assembly  1 2 3 4 24     5 6 7 1) Ensure mount is clean of any debris 2) Place plastic guard around rim of mount 3) Insert thick rubber ring into guard, careful to lay it evenly 4) Insert lens into thin rubber ring 5) Insert lens and thin ring into guard. This may require some force, make sure before moving on that the rubber rings lay even. 6) Attach and line up face mount and support semi-rings. 7) Finger tighten each bolt then starting with the outermost screw on each semi-ring (the two closest to gap between semi-rings) tighten the bolts until the guard is firmly caught between the face plate and supports. 25  Appendix C: Pressure Equalization System Dive Testing Test Procedure: The ROV is brought to a suitably deep test sight then place in the water to test ballast. It is found to be stable but positively buoyant. Weights are added until the ROV begins to sink slowly. The ROV required a total of 29 lb?s of added weight before it sunk. The required length of rope is approximated then tied off to the boat and the ROV is lowered deeper into the water. After a minimum of 5 minutes the ROV is pulled to the surface and data from the pressure monitors is taken.          ROV Floating Stably                              29lb?s of Weight Added                                          ROV Sinking                 26  Dive 1 Depth Planned: 33ft, Depth Reached: 51 Depth Monitor: Outside housing, Depth Gage: Inside housing   27  Dive 2 Depth Planned: 100ft, Depth Reached: 133ft Depth Monitor: Inside housing, Depth Gage: Inside and Outside housing   28   Results:  It can be seen that the graphs showing pressure inside the housing and outside the housing follow similar behaviors. This plus the confirmation of the maximum depth by pressure gages gives confidence that the internal pressure is being held ambient with the surroundings.   Air Consumption: The tanks air consumption is determined through Boulyes law:           First the equivalent volume of 2900 psi air must be determined for the tanks maximum 15 ft3 atmospheric air.                                                  Next, holding the tanks physical volume constant as the PSI drops from 2900 to 2400, the remaining internal volume can be expressed as a volume at atmospheric pressure.                                                              Apply                                                                                                                           Therefore the air consumed is 2.6ft3 Theoretical Volume Consumption: Using:            , It can be determined that:                        Initial volume of ROV ~0.45 ft3 Dive 1:                                          Dive 2:                                          Total:                       850 ft Dive:                                              29  Appendix D: Images of Electrical Devices                                                                              Camera       Two Channel Motor Controller  RF Modulator       One Channel Motor Controller                                                                                         Monitor             Biasing Tees 30   Rough Layout of Electrical Box  


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