Pitch Motion Control of a Soft Bionic Robot Fish Based on Centroid Adjustment

This paper discussed the pitch motion control problem of a 3D soft bionic robot fish with Body/Caudal Fin propulsion mode. The fish has a polyurethane resin made body and is powered by two pieces of Macro Fiber Composites (MFC) smart materials inside it. The straight and turning motion of the fish is realized by applying symmetric and asymmetric driving signals to the MFC materials. To regulate the depth of the fish, a new centroid adjustment mechanism is designed and installed inside the fish. By changing the centroid of the fish while it is swimming, the fish could realize the floating upward and diving motion. A simple feedback PID controller is also designed to stabilize the pitch angle of the fish during its floating upward and diving motion. Experiments are carried out to test and certify the successful design of the fish.