Feature Articles—December 2009 Issue
ROV EdVaRD Provides Research, Learning OpportunitiesStudent Group Develops a New Educational Video And Research Device for Scientific Survey
By Stefanie Rettig
Speaker of ROV.AG
Marine Technology Laboratory
Bremerhaven University
of Applied Sciences
Bremerhaven, Germany
Björn Saworski
Electronics Engineer
and
Dr. Oliver Zielinski
Professor, Head
Institute for Marine Resources
Bremerhaven, Germany
A remotely operated vehicle (ROV) has been developed for scientific activities as well as underwater inspection tasks. This educational video and research device (EdVaRD) was designed and realized within a student-managed project, fostering problem-solving and teamwork skills. EdVaRD is intended to operate to a depth of 100 meters. The vehicle is operated with a remote control cable and equipped with a video camera and standard hydrographic sensors. After iterative laboratory and field trials, the ROV is now ready for a variety of scientific survey purposes.
Background
ROVs are a fundamental tool in modern sea exploration and research. As a result, a tremendous variety of vehicles is commercially available, ranging from heavy, work-class ROVs with full ocean depth ratings and a weight of several tons to lightweight micro-ROVs weighing less than three kilograms that are used for inspections of sewers and pipelines.
Additionally, the value of ROVs for educational purposes is widely recognized (e.g., with “ROV in a bag” educational kits and international student ROV competitions). The objective is to connect students and educators with professionals from marine industries while promoting the development of technical, problem-solving, critical thinking and teamwork skills.
Since 2003, the Marine Technology study course (MAR) at the Bremerhaven University of Applied Sciences in Germany has successfully trained engineering students in the development and application of subsea technologies. Dedicated courses in marine science and engineering are coupled with project studies and internships at internationally reputable institutes and companies. Additionally, in 2007 three MAR students founded ROV.AG, a self-organized student working group, to exchange ideas in marine robotics and develop marine sensor platforms. The team’s initial project was designing and constructing EdVaRD. Bremerhaven University and its marine technology laboratory provided ROV.AG with infrastructure, initial funding for equipment and advisory support. However, crucial tasks like design decisions, process documentation, personnel recruitment and fundraising were all the students’ responsibility.
Technical Overview
General Vehicle Design. The ROV is based on a modular design consisting of a mounting frame, a main pressure housing, the sensor housing and five thrusters. The mounting frame is a lightweight structure made of ultrahigh-molecular-weight polyethylene that can easily be disassembled for transportation purposes. EdVaRD’s propulsion motors are directly attached to the mounting frame. The main pressure housing, with a total volume of three liters, can be attached to the frame via two mounting rails without any screws. It includes a power supply, a mainboard and motor controllers. The sensor housing is a Nautilus Marine Service (Bremen, Germany) Vitrovex® glass cylinder with two hemispheres as end caps. The three parts are held together by depression only. EdVaRD is equipped with a combined inclinometer, PNI Corp.’s (Santa Rosa, California) magnetic compass module and a Logitech (Romanel-sur-Morges, Switzerland) USB camera. Further inputs come from a Sea and Sun Technology (Trappenkamp, Germany) CTD 48 (conductivity, temperature, depth sensor) mounted at the front of the ROV. The pilot controls the ROV either with a game pad or a 3Dconnexion (Munich, Germany) 3D space mouse. Since the total weight in air of the 60 by 50 by 40-centimeter system is about 25 kilograms, it can easily be moved by a single person.
Power Management. Power is supplied through a 300-meter Norddeutsche Seekabelwerke GmbH (Nordenham, Germany) aramid-reinforced sea cable. The 120-volt direct current (DC) input voltage is converted in the main pressure housing. Twenty-four volts power the motors; 12 volts are required for the mainboard, the illumination and the CTD sensor; and five volts are needed for the logical circuits and the USB devices. In total, the ROV has a maximum power consumption of 720 watts.
Propulsion. Propulsion is generated by five 50-watt brushless Hanover, Germany-based Kähling Antriebstechnik (KAG) DC outrunner motors. The stators of the motors are grouted with epoxy and the bearings replaced by Teflon fittings to combat corrosion. This assembly makes classic shaft seals unnecessary and reduces maintenance. Off-the-shelf radio-controlled car motor controllers are actuated by the microcontroller via pulse-width modulation.
Computation and Communication. Sensor signals can be provided either via RS-232, USB or Ethernet and are converted to TCP/IP on the mainboard, a VIA Epia N700 embedded board with a C7 1.5 gigahertz processor. The board runs Ubuntu Linux V8.04, which is responsible for all communication tasks as well as the video compression. In order to increase performance, especially for video processing, the board will soon be replaced by an Intel-Atom microprocessor board. This will enable the application of machine-vision algorithms, for example, optical marine bubble detection and the quantification of seeps and leakages. Communication with the ROV pilot’s computer is based on a 100-megabit Ethernet connection. All signals can be continuously observed and recorded using a homemade software suite.
Sensors and Options. For navigation, the ROV includes a tilt sensor, a magnetic compass and the depth information as derived from the CTD. Together with a Tritech (Aberdeen, Scotland) Micron sonar that will soon be attached, these signals will provide full orientation in 3D. Furthermore, the ROV pilot can use the webcam for orientation and documentation. A manipulator arm for grabbing and a water sampler are currently under construction. Additional options can be easily attached, as Ethernet and USB ports are extendable by hubs.
Validation and Scientific Studies
EdVaRD was officially presented at the IEEE OCEANS Conference in Bremen, which took place from May 11 to 14, offering a good opportunity for a first exchange with experienced engineers in the field of marine science. The first training dive in the OCEANS showcase aquarium was successful, with only small buoyancy and trim problems that were adjusted before the official presentation on the final day of the conference (a video is available at www.youtube.com/watch?v=IaaA0MVFObA).
In the following months, the team made minor changes and improvements in software and hardware and completed two successful tests in a local freshwater lake.
Although systems were working properly and the ROV showed surprising agility, a dive in a sheltered tank or lake cannot provide conclusive evidence on the behavior and endurance of the system under open-sea conditions or in the presence of strong currents in estuaries. Thus, the next tasks for the group are further tests and step-by-step improvements within the River Weser estuary and the German Bight section of the North Sea.
Conclusions and Future Steps
The ROV.AG students were able to develop a fully functional ROV within a year and a half. Students improved teamwork skills, learned about acquiring funding and made continuous progress in the engineering and construction of the ROV.
A major challenge for ROV.AG is a constantly changing membership. Because the MAR course term is three years long, experienced students leave the working group and new members join continuously.
Preserving and transferring knowledge is thus becoming a crucial element of the group’s success. The importance of work documentation and the promotion of early-stage students is recognized.
Aside from further improvements to EdVaRD, ROV.AG plans to start a second ROV project with a hydrodynamically optimized disc shape. In order to enhance maneuverability, the new ROV will use six thrusters, with two thrusters providing lateral thrust. In contrast to EdVaRD, the new ROV will use in-runner motors with lower rotational speed and larger propellers.
These improvements will lead to less power consumption, allowing battery packs to be used for power supply. This is an important first step toward another of ROV.AG’s goals, to build a fully autonomous underwater vehicle.
Acknowledgments
ROV.AG thanks main sponsor Beluga Shipping GmbH (Bremen, Germany). ROV construction was supported by Nautilus Marine Service, Meerestechnisches Büro Turla (Kiel, Germany), Sea and Sun Technology, KAG, Norddeutsche Seekabelwerke and Christian Proeber Unterwassertechnik (Bremen, Germany).
The authors thankfully acknowledge support from Stephen Wood of the Florida Institute of Technology, Christoph Waldmann at MARUM, and Julia A. Busch and Jan Schulz of the Institute for Marine Resources.
References
For a full list of references, please contact Oliver Zielinski at oliver.zielinski@imare.de.
Stefanie Rettig is speaker of ROV.AG and a third-year marine technologies student with an area of specialization in wind energy and offshore technology. Her interests include the construction and operation of oceanographic sensor platforms.
Björn Saworski is a founding member of ROV.AG and works as an electronics engineer, focusing on image processing at the Institute for Marine Resources. He received his B.Sc. in marine technologies from the Bremerhaven University of Applied Sciences.
Dr. Oliver Zielinski is a professor of measurement and control systems, head of the marine technology laboratory at Bremerhaven University of Applied Sciences and head of the Institute for Marine Resources. His research interests include autonomous sensor systems and environmental optical sensor technologies for coastal impact assessment.
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