Simulation Study on the Body Side-Sway Characteristic for Rigid Robot Fish

This paper reveals a new phenomenon of the body side-sway for rigid robot fish and proposes three effective restraining methods. The body side-sway problem is produced by the lateral component of hydrodynamic force and inertial force, while influenced by mass distribution of fish body and oscillating rules of caudal fin. Considering the body side-sway, a virtual prototype for two-joint robot fish, which is the simplified form of multi-joint robot fish, is established in MSC-ADAMS^reg to conduct the simulation. Simulation results indicate that the body side-sway can reduce the amplitude of tail peduncle and change the attack angle of caudal fin, and then affect the thrust and the propulsive efficiency. To inhibit the harmful body side-sway which also contributes to the energy loss, we last summarize three restraining methods: attaching dorsal fin and pelvic fin, using the vibration absorber and building two parallel tail mechanisms.