This paper deals with maneuver issues of a multilink biomimetic robotic fish, particularly focusing on turning control in free swimming. The characteristic parameters determining turning performance involve magnitude, position, and time of the deflections applied to the links, which are discussed via a series of simulation calculations and actual experiments.

This paper presents a three-dimensional, dynamic model of robotic fish which synthesizes both the carangiform and anguilliform swimming modes. The designed robotic fish is composed of three parts: stiff anterior body with a pair of pectoral fins for up-and-down motion, flexible rear body, and an oscillating lunate caudal fin. We use unsteady flow theory to analyze the motion of the anterior part and the links, and adopt experimental result from oscillating foil for the caudal fin. So the dynamic equation of each part can be obtained, and by summing up these equations, the dynamic equation for total swimming robot can be derived. The desired propulsive characteristics including forward velocity, sway velocity, pitch velocity, three velocity of Eulerian angles of the stiff anterior body, motion trajectory as well as propulsive efficiency can then be obtained by solving ordinary differential equation. The circular motion, based on asymmetrical kinematics of flexible rear body, can be achieved by adding different deflections to the oscillatory links. Comparisons between simulation results and real experiments are then conducted and discussed. A good agreement on dynamic characteristics demonstrates the validity of the proposed model

This paper deals with maneuver issues, in particular turning control of a free-swimming, multi-link biomimetic robotic fish propelled by a flexible rear body and oscillatory tail fin. Taking into account of both hydrodynamic model and engineering use, we develop a practical method to execute a circular maneuver. The turning control, based on asymmetrical kinematics and dynamics, can be achieved by adding different deflections to the oscillatory links. The characteristic parameters affecting turning performance include magnitude, position, and time of the deflections applied to the links, which are discussed with a series of simulation calculations. The experiments of circular motion with a four-link, infrared sensor-equipped robotic fish acquire a satisfactory maneuverability. Moreover, the feasibility of adding deflection angles to maneuver the robotic fish in the path planning is explored both analytically and experimentally