Swimming study on an ostraciiform fish robot

Fish-like robot is considered to be one of the candidates in the future underwater vehicle design for marine exploration and surveillance. In the BCF propulsion type, the ostraciiform swimming mode permits the robot to have a simple mechanical design and control strategy for swimming. Propulsion is achieved by flapping the caudal fin and the turning motion can be controlled by adjusting the mean angle, which is the averaged caudal fin angle measured from the fish robot longitudinal axis over a flapping period. In this paper, an ostraciiform fish robot was constructed to study its swimming behavior and efficiency. The orientation of the fish robot was recorded by an inertial measurement unit (IMU) during swimming. The drag coefficient was determined via the deceleration measurement method. The effects of flapping frequency on cruising and maneuvering ability were studied through the terminal velocity and turning angular rate measurements. Caudal fins with different size and shape were attached to the robot to explore the effects of caudal fin geometry on these measurements. The experimental results were used to extract some model parameters and to compare with mathematical analysis.