A study on controllers design based on centroid displacements for depth motion of a 3-joint carangiform fish robot

Abstract

Fish robot can move independently in the water environment, so controlling it in six degrees of freedom (6 DOFs) is a difficult problem. To simplify the problem, we can assume the motions of fish robot include two main motions: the movement of fish robot on the horizontal plane and the movement of fish robot on the vertical direction to the desired depth. This paper proposes a simple method to control a 3-joint Carangiform fish robot swim to the desired depth which is based on the centroid displacements method. The mass, which is controlled by the RC motor, is used to change the center of gravity position of the fish robot that can change the pitch angle of the robot. By controlling the rotation angles of the RC motor which is called alpha angle (α), we can control the up and the down motions of the fish robot. Fuzzy and Self-Tuning PID controllers (Fuzzy-PID) are developed to control the α angle in order to make fish robot swim to the desired depth. © Springer-Verlag Berlin Heidelberg 2014.