Fin Actuated Autonomous Underwater Vehicle

(National Science Foundation CAREER Award CMS-0238461 and UW Royalty Research Fund; collaboration with D. Dabiri)

side view of robo fishThe multivehicle underwater testbed in the Nonlinear Dynamics and Control Lab consists of three fin-actuated untethered autonomous vehicles. The current vehicles are the second generation built in our lab. Each vehicle contains a microprocessor to collect sensor data, to handle communication with other vehicles, and to determine control commands to the servos. Each robot is equipped with a custom RF transceiver for communication. In small spaces such as the tank in our lab, or caves and littoral zones, noise in acoustic communication becomes prohibitive. In the case of our tank, RF communication has been demonstrated to be effective. Onboard programming can be used to allow the RF system to emulate the acoustic system.

The robots are each powered by four servos. Two are located in the rear of the robot and power the two links of the tail assembly. The other two servos control the motion of the forward fins; their motion is fully independent of one another. To be able to orient itself, the robot has a depth gauge (a pressure sensor) and a 3-D magnetic compass. The fish is tuned to be neutrally buoyant; that is, when placed at some depth, it will neither float nor sink. Due to pressure changes and compression/decompression resulting in volume changes of the vehicle, the buoyancy is not constant. For purposes of development and testing, an instrumented tank has been built in the lab. The tank is an above-ground swimming pool 8ft deep, 8ft wide and 20ft long. Underwater cameras connected to an external computer provide the ability to track the vehicles in the water in real time. This data is processed for 3D position information and transmitted via RF broadcast to all vehicles in the tank. The broadcast information contains vehicle identification codes and can also include information for simulated vehicles to provide a group effectively much larger than the existing three vehicles.

Videos of the first two prototypes in action are below. Movies are in wmv or avi format. If the video will not stream correctly, please right click and save the video to your computer.

Coordinated Tracking (mp4)

Robofish 1.0 & 2.0 (wmv)

Robofish 2.0 (avi)

Robofish 1.0 (avi/mpg)