Seawolf II Rendering

Seawolf II is a complete redesign with cost effectiveness, simplicity of operation, and reliability in mind. Borrowing many of the innovative features of the previous Seawolf I, the new vehicle is lighter, simpler to operate, and has a number of new features aimed at improving reliability.

Mechanical

The vehicle's triangular chassis is cut from high-density polyethylene, chosen for its cost, ease of machining, and rigidity. Surrounding the chassis are custom-fitted fiberglass flow-hulls, designed to present a uniform drag surface to the water. Expanding closed-cell foam and lead fishing weights were attached to the hulls to tune trim and buoyancy.

Seawolf II Frame

Three Seabotix thrusters are mounted to the chassis. The two front thrusters are able to rotate 180 degrees, while the aft thruster is vertically mounted but cannot rotate. This configuration greatly simplifies the control scheme over that of Seawolf I, which had 3 rotating thrusters mounted at 120 degree intervals around the vehicle.

Electronics

The power system uses a lithium polymer battery to provide voltages of 5 and 12 to the electronic components. Two additional lithium polymer batteries are used to power the thrusters. Special care must be given when using lithium polymer batteries not to over drain them since this can easily damage the battery and can cause it to ignite. Each battery has a separate voltage monitoring circuit that lights an LED to indicate low voltage.

A custom data acquisition board controls thrusters, servos, and the dropper. This board communicates to the main computer, a Lippert-AT CoolRunner4 PCI-104, via a serial interface.

Software

Seawolf II's software is written in C#. The subsystems communicate to each other by using an event handling mechanism, making it possible for something that may be asynchronously receiving data to alert the main control loop when new data arrives. For instance, while searching for the pipe, the main control loop can busy itself with maintaining depth, heading and orientation until the camera gets a good shot of the object it is searching for.

Seawolf II

Years Used
2006, 2007, 2008

Computer
PC/104

Material
Fiberglass shell
Plastic frame

Hull
Acrylic Tube

Weight
44 lb

Journal Papers

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