Empirical modeling of rotating thruster for underwater robotic platform

A rotating thruster model is needed for the design and control of an underwater robotic platform. Thruster rotation is used to generate an additional degree of freedom for reducing the number of thrusters. The rotation of a thruster during thrusting generates an additional reaction force and torque. A rotating thruster model is required to analyze the dynamic model of a robotic platform by considering rigid body dynamics and hydrodynamics simultaneously. We considered the empirical dynamic modeling of a rotating thruster using frequency and impulse response analysis. A rotating thruster model is derived as a transfer function of longitudinal and tangential thrust forces and rotational torque during the rotation. Simulation is performed using the proposed transfer functions, and the validity of the model is verified by comparison with simulations and the results of experiments. The proposed empirical model can be applied to control an underwater robotic platform with rotating thrusters.