A study on fuzzy based controllers design for depth control of a 3-joint Carangiform fish robot

Fish robot can move independently in the water, so controlling of it in six degree of freedoms (6 DOFs) is a difficult problem. To simplify, we can assume the motions of fish robot include two main motions: the movement of fish robot on the horizontal plane and movement of fish robot to the desired depth. This paper proposes a simple method to control a 3-joint Carangiform fish robot swim to the desired depth by using pectoral fins´ motions. The role of pectoral fins is similar to the rudder in Z direction that can change the pitch angle of the fish robot. By controlling the rotation angle of the pectoral fins which is called pitch angle, we can control the up and the down motions for fish robot. Fuzzy and Self-tuning PID controllers (Fuzzy-PID) are developed to control the fish robot´s pectoral fins in order to make it swim to the desired depth.