ARCS By Bruce Butler, P.Eng.
CANADA’S FIRST AUV
In 1982, the Canadian Hydrographic Service (CHS) identified the need to perform cost-effective hydrographic surveys in Canada’s Arctic waters. In 1983, CHS awarded International Submarine Engineering Ltd. (ISE)—based in Port Moody, BC—a contract to design and build an underwater vehicle that would meet those survey needs.
Named the Autonomous Remote Controlled Submersible, ARCS was originally considered an “autonomous ROV” (hence its name) but was soon referred to as an AUV. ARCS was not the world’s first AUV; that honour falls on the University of Washington Applied Physics Laboratory and their SPURV vehicle back in 1957. ARCS was, however, Canada’s first AUV.
VEHICLE DESIGN ARCS is torpedo-shaped, rated for 300m depth, with a length of 5.2 metres, a diameter of 82 cm, and weighed 1360 kg. A second, option battery hull section increased the length to 6.4 metres and weight to 1820 kg. It was propelled by a single stern propeller powered by a pair of independent, direct-drive brushless DC motors. Vehicle maneuvering was via a pair of horizontal fore planes and four stern planes (“+” configuration). ARCS could run at 5 knots for 7 hours on a single, 10 kWh bank of rechargeable NiCd batteries. When outfitted with the optional second battery hull section, endurance was roughly doubled.
CONTROL SYSTEM In the early 1980s, research into vehicle control systems was in its infancy and embedded computer hardware was large, costly, and had little processing power or memory. ARCS needed a control system that would meet the demands of under-ice missions, and ISE engineers came up with a novel solution. Drawing on the experience of one staff member who was a former submarine captain, ISE modelled the control system on the command hierarchy of a manned submarine. The control software would reside on a bank of three Intel 8086-based, single-board Multibus-II computers running the RMX real-time operating system. The Engineering computer (“Eng”) handled the vehicle’s engineering functions such as thruster motor, dive planes, and most sensors. Eng also accepted data from the obstacle avoidance sonar and determined the appropriate avoidance maneuver. The Navigation computer (“Nav”) interfaced with the navigation sensors to determine the vehicle’s attitude and position. It also determined the heading and depth setpoints needed to steer towards the current mission waypoint (and
Courtesy of Bruce Butler / International Submarine Engineering Ltd.
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