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Autonomous Underwater VehicleDevelopment for RoboSub 2018

McGill Robotics - ClarkeLouis-Jacques Bourdages, Bei Chen Liu, Jeremy Mallette

Abstract—For McGill Robotics’ fifth year participat-ing in the Robosub competition, we are happy to bringour first C-Class AUV to San Diego. It boasts a numberof upgrades over its predecessors, while retaining theiradvantages and qualities. It was designed with theconstraints inherent to the Robosub competition, andthus makes the most of some circumstances, such as theshort mission time. It also builds significantly on pastyears’ breakthroughs and research on the software side,while integrating milestones attained this year.

It also makes use of our brand new custom parts, suchas new pressure vessels, as well as new sensor suites,including a DVL.

I. COMPETITION STRATEGY

The new McGill Robotics Autonomous Un-derwater Vehicle has been in development sinceFall 2017; it is an autonomous platform dedicatedto the completion of specific tasks defined bythe Robosub competition. As such, the natureof the competition and the aforementioned tasksinfluence Clarke’s design at every level.

From a high-level perspective, Clarke takesadvantage of the constrained environment of run-time of the competition relative to other explo-ration and utility marine robots. Due to the shortmission times, a power supply was chosen tooptimize size and weight, but not necessarilyruntime. A single 16,000 mAh Lithium Polymerbattery was chosen for the power density andreliability. In comparison to previous models ofour AUV, which employed two separate batteries,this has allowed Clarke to store its power supplyin its main hull; however, this also necessitated amore sophisticated power distribution board. Onelarge constraint of the environment is the depthof competition. The pressure vessels, though able

to withstand far more pressure at greater depths,the design criteria was to withstand pressure at10 meters. In a similar fashion, to the powersupply, the low depth requirement allows Clarketo use more accessible materials and reduced wallthickness on all of the pressure vessels. Generally,the competition’s tasks require a great deal ofmaneuverability, but the shallow depths and stillwaters do not demand as much raw torque. For thisreason, Clarke is outfitted with BlueRobotics T200thrusters –which provide well-balanced controland thrust– mounted in an array that provides theAUV with six degrees of freedom.

Clarke is designed to favour certain aspects ofthe competition that previous models have hadrelative success with; namely, performing acousticnavigation and performing visual recognition ofthe inter-task markers to traverse between them.Building on this previous success, these systemshave been maintained, but made more robust inorder to keep the forward momentum of the de-sign. For instance, though using machine learn-ing principles for complex objects like the dice,classical computer vision (static filtering) is stillapplied to detect the inter-task markers. Theserobust and improved systems are mainly related tonavigation, which have been further improved bythe team’s acquisition and integration of a DVL,a sensor that provides accurate measurement ofvelocity underwater.

Though aiming at maintaining previous successin the realm of navigation, tasks such as "Buya chip", "Play Roulette", and "Cash In" haveinduced a complete reimagination of how theAUV performs object manipulation. Where previ-ous models had more traditional arm and gripperassemblies, Clarke is equiped with an underwater

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vaccuum and release unit. This mechanism takesfull advantage of the exemplary maneuverabilityof the AUV itself, and increases the efficacy ofthe object collection by having an ’area of effect’.Where previous object manipulation strategieshave required extremely precise control of a sub-system, sometimes with its own several degreesof freedom, the new device relies on the controlof the AUV itself. Only one axis of complexitywas added to the system, to rotate the device,and there is no longer the need to control agripper. The reason why this simplified systemcan continue to be competitive is because it hasan inherent ’area of effect’. Robosub tasks havetypically made it easier to dispense objects withcontainers that are much larger than the objectintended for them. Past models of the AUV havefound the most difficulty obtaining task items tobegin with. This difficulty is because servoing andmaintaining position, while controlling a separatesub-system to retrieve a small object is not trivial.The ’area of effect’ essentially moves favour backtowards obtaining the task items to begin with,at the cost of a less reliable release, by operatingwithin a radius rather than at a point. This systemmarks the most radical deviation from previousdesigns.

On the other hand, there has been a muchslower design transition throughout the courseof years: migrating from classical to machinelearning computer vision. Over the past two years,our robots have attempted to use machine learn-ing to solve the various computer vision-basedtasks at Robosub. Until now, the only task tohave been executed using machine learning arethe buoy-based tasks and with limited success.The repeated difficulty created a strong debateamongst team members regarding its efficacy;however, this year it gained more support. Withthe increasingly rising interest in AI, both in andout of the academic community, the team hasgrowing knowledge and access to resources for AIdevelopment. Leveraging the past experiences ofteam members and accessibility of high-poweredGPU’s (applied in the learning phases of AI),and due to the complex visual nature of thisyear’s tasks, Clarke is prepared to attempt mostof the complex tasks using machine learning –

this includes "Play Craps" and "Play Roulette".However, with consideration to the team’s pastexperiences and the dynamic visual nature of theTRANSDEC pool, last year’s classical implemen-tations have been retrofitted as fallbacks for someof the tasks.

II. DESIGN CREATIVITY

Using a team structure similar to past years’,the AUV team was once again divided in threeDivisions: Mechanical, Electrical and Software.Those divisions then each had a few differentsections which focused their efforts on a certainpart of the overall system. Division leaders en-sured the various Sections’ efforts were kept ontrack while the Systems Team, which includes theProject Manager and Division Leads, oversee theintegration of all subsystems into a functional andoptimal whole.

Our new C-class AUV, Clarke, is a few yearsin the making and finally ready to be used ata competition. It’s primary purpose as a newclass was to integrate new systems into our AUVplatform, namely the new main hull, the DopplerVelocity Log, the stereoscopic cameras, as well assupport upgraded and improved versions of othercomponents, particularly the new hydrophone andpressurized manifold pressure vessels. The mem-bers of the team coordinate using the private socialmedia platform Workplace. This allows us to keepdedicated lines of contact between every memberof the team and to schedule events.

The new main hull strives to accomplish aseries of objectives. It must first ensure that asimilar level of ergonomic design is maintainedin terms of access to electronics, whether that befor switching out components, completing repairs,routing wiring or others. As such, an open generalstructure for the mounting of the electronic com-ponents was desired. From our experience withthe B-class main hull, we also knew we wantedto improve the accessibility of the volume withinthe center ring itself, which was made hard toaccess when electronic components were installed.Finally, we also decided to install the batterywithin the main hull itself, which has the advan-tages of removing the need for a bulky, heavy andhighly buoyant pressure vessel, of requiring one

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Figure 1: Battery being inserted into the main hullfrom the back of the center ring.

less external underwater connector and of makingthe operation of swapping a battery even easierand quicker. See Figure 1 for a picture of thisoperation.

The new mounting system for our electronicswas also designed to be as flexible and future-proof as possible. We also had issues with theracks of the B-class main hull sagging underthe load of the PCBs, which made installing theacrylic caps more difficult and put the electronicsunder more stress and vibrations. To correct this,the racks were attached on two points along theirlength, on the front and back of the center ring,and the racks are directly fastened to a threadon the support plate itself, rather than an L-bracket. This increases the rigidity of the wholeassembly tremendously and virtually eliminatessagging. This setup also has the additional util-ity of providing an easy mounting point for thebatteries.

Creative design was also involved in the cre-ation of the new frame. Our main objectivesfor this assembly were to preserve the good er-gonomic characteristics of the past frame, easeassembly, and be flexible enough to be used forboth current and future components. The firsttwo objectives were accomplished by switchingfrom a L-bracket-based assembly method to aT-joint-based one. This reduces significantly theamount of parts involved in the assembly process,increases the rigidity of the structure, and makesassembly easier.

III. EXPERIMENTAL RESULTS

McGill Robotics is lucky enough to have accessto the pool of our sports center. We book two ofits lanes every weekend and use this time to testour systems and make attempts at the various chal-lenges. Building the obstacles themselves is oneof the tasks our members have to complete. Ourstandard operating procedure is to start by testingthe newest capabilities that have been added to theAUV recently by members, follow up with testingmore thoroughly tasks that would benefit fromtweaking parameters using experimental results,and finally increase the amount of training dataand footage we have at our disposition with theremainder of the pool time.

The new battery Clarke uses provides a longermission time which is greatly appreciated duringour pool tests, reducing how often taking Clarkeout of the water to complete a battery swapis necessary. The new center ring configurationalso did make this operation quicker in and ofitself. Those changes to the main hull can thus beconsidered to have fulfilled their objectives verysatisfactorily.

Where specific tests are concerned, as men-tioned before, all of them were conducted in theuniversity’s campus swimming pool. This is aspecific environment which differs from the com-petition environment in some ways. They differfirstly in their obvious physical characteristics; theTRANSDEC pool is much deeper and larger thanthe McGill Pool. This changes the functioning ofthe DVL which uses bottom-tracking, and willlikely require adjustments in some of its parame-ters. The shape of the pool also affect the acousticprofile of the testing environment. TRANSDEC isdesigned to replicate an open ocean environmentwith minimal resonance, while the pool used bythe team can create reflections of the sound waves,which can affect the output of our hydrophones.Finally, the McGill pool has very clear, transpar-ent and homogeneous waters. TRANSDEC hasslightly more cloudy waters, which adds noise tothe images obtained by cameras. This factor mustbe accounted for in computer vision algorithms.

By being aware of those factors while designingand tweaking our algorithms, we can be better

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prepared to adapt them to the conditions in theTRANSDEC pool.

IV. ACKNOWLEDGEMENTS

Once again this year, it was only possible forMcGill Robotics to bring an AUV to Robosubthanks to the numerous people who support usin all our efforts. This includes, of course, allthe members of McGill Robotics, as well as oursupervisor, Professor Nahon Meyer. We are alsoimmensely thankful to the machining specialistswho have guided and helped us in the productionand design of our parts, namely Don Pavlasek,Sam Minter, Andy Hofmann, Miesam Aghajani,Mathieu Beauschene and Lydia Dyda. Thank youto Jason Boivin and the Lifeguards at the McGillAthletics Center for access to a pool for testing.None of this would be possible without our spon-sors either, especially our gold sponsors: TexasInstruments, SBG Systems and Protocase. Andof course, huge thanks to the AUVSI team formaking Robosub possible! We’re very excited tosee you again at TRANSDEC this year.

Table I: Technical Specifications of Clarke

Component Vendor Model/Type Specs CostFrame Protocase Designed in-house, lasercut with Protocase 340 USDWaterproof Housings Designed and machined in-house, anodized with UltraspecWaterproof Connectors Subconn and Teledyne MacArtney’s Ethernet and ImpulseThrusters BlueRobotics T-200 1467 CADESCs HobbyKing Afro A3 108 CADHigh Level Control Arduino Arduino UnoBattery HobbyKing MultiStar Lipo Pack XT90 16000mAh 4S 10C 60 CADConverter Mini-Box DCDC-NUC 6-48V input for NUC, 12V or 19V outputCPU Intel NUC6CAYB Intel Celeron processor 175 CADProgramming Language 1 C++Programming Language 2 PythonInertial Measurement Unit X-IO Technologies X-IMUDoppler Velocity Log Teledyne Workhorse Navigator Bottom-track velocity 5000 CADSonar Tritech Micron Uses RS232Cameras Sony Chameleon (Sony ICX445) 1296 x 964, 18 FPS, 1.3 MPHydrophones Teledyne Reson TC4013Algorithms: vision DarknetAlgorithms: acoustics In-HouseAlgorithms: localization and mapping UKFAlgorithms: autonomy SmachOpen Source Software Sonar and DVL drivers ROS toolsTeam Size 30 membersHW/SW expertise ratio 50-60%Testing time: in-water 12 hours

V. APPENDIX A

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VI. APPENDIX B

A. FALL 2017

1) Robotics Challenge, Oct: The OpenRobotics Challenge took place in the roboticsworkshop where all the attendees got a chance tohave a hands-on experience of the Mars Roverarm and drive systems. The students then had theopportunity to attend a presentation coordinatedby one of the professors from the Rutherfordphysics department followed by a demonstrationset up by the team. McGill Robotics was offered aGold sponsorship by the hosts of Open Robotics.What a great way to celebrate Thanksgiving!

2) John Abbott Outreach Event, Oct 20th:McGill Robotics was kindly invited to host apresentation at the John Abbott College and talkabout our robots with future engineering students.Aside from sharing our knowledge and passionfor robotics, we were also able to discuss withthe attendees about university robotics challengesto come. Many of them were very intrigued byRoboHacks and showed a strong interest in par-ticipating to our hackathon which took place inMarch 2018.

3) McGill Open House with McGill Robotics,Oct 29th: Members of McGill Robotics spent theday meeting students, family and friends fromaround visiting McGill’s Open House. Despite therainy weather, we were pleased to meet manyexcited faces, and to present the Mars Rover armsystem in action. Tabling alongside other DesignTeams fostered a sense of unity, and demonstratedthe many opportunities brought upon by studentinitiatives.

4) National Society of Black Engineers – AWalk for Education, Nov 3rd: At the end of lastyear, McGill Robotics participated in A Walk forEducation hosted by the National Society of BlackEngineers. Adrien Sauvestre, Jeslan Rajendram,Clara Chu, and Olu Olabimtan represented theteam in the Lionel Groulx community, wherethe event took place. This impactful expositionencourages children of minority background toexplore and develop interest in STEM topics(Science, Technology, Engineering and Mathemat-ics), with the Mars Rover and Arm duo creatingexcitement in the crowd. Many came up to uswith technical questions after interacting with the

robots, and are fascinated by its possibilities asmuch as we are!

5) McWiCS x RoboHacks Present: MLH LocalHack Day! Dec 2: Calling all you hackers outthere! Join McWiCS and RoboHacks in kickingoff the hackathon season with this MLH LocalHack Day!! You don’t want to miss out on thissingle largest day of student hacking ever! Fellowhackers from all around the world will be simulta-neously hosting their own MLH Local Hack Dayat their school, and you can participate in this 12-hour global event right here at McGill!

B. WINTER 2018

1) Engineering Involvement Day with McGillRobotics, Jan 23rd: Although it was a busyweek day in the McConnell Engineering Buildingas students traveled between classes, the McGillRobotics table was visited by many at the En-gineering Involvement Day. Inquiries varied andranged from the desire to be recruited to the even-tual possibility of being an active participant ininternational robotic competitions. Furthermore, acouple of upper-year mechanical engineering stu-dents showed interest in the specific mechanismsand functions of our Mars Rover Arm, which wasdisplayed at the event. Others were curious aboutthe Marketing Division of our Business Team, theprevious events we’ve participated in, as well asthose they could expect us to be joining. Overall,we were pleased to hear about students’ eagernessto join the team.

2) Les Filles et Les Sciences with McGillRobotics, Mar 17th: Les Filles et Les Sciencesis an initiative that aims at promoting STEMamongst high school girls, and the professionsthat emerge from this field. McGill Robotics wasgrateful for the opportunity to have worked withthese bright young minds in the last few years, andis happy to announce that we will be once againparticipating in Les filles et les sciences Montreal-Sherbrooke STEM immersion event at Polytech-nique Montreal, held next month on March 17!This year, we wish to organize a workshop ac-companied by a demonstration and a presentation,all given in French, to give participants a true feelof what robotics is about.

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3) McGill Robotics Robohacks, Mar 30-31st:RoboHacks is a robotics exhibition and hackathonhosted at McGill University, Montreal. Join 250awesome CEGEP, Undergraduate and Graduatestudents in powering through 24 hours of thrillingrobotics exhibition, caffeine fuelled invention, andengaged learning. We’re there to provide the per-fect environment to spark learning, innovation anda whole load of fun.

4) My Day @McGill with McGill Robotics,April 5-6th: Over 150 elementary school studentswill be joining our campus to tour, and participatein workshops and activities for academic engage-ment. MR tabled our robots in the EUS Commonsto show off what we’d been up to lately!