Trajectory Planning and Current Control Optimization of Three Degree-of-Freedom Spherical Actuator

The study in this paper covers torque modeling, trajectory planning and optimization control of current input of spherical actuators, in which the latter two are the major contributions. Trajectory planning is an effective way to improve the smoothness and stability of rotor motions. A novel three-dimensional (3D) orientation representation method based on manifold of S-2 is proposed to facilitate the trajectory planning of rotor. Current redundancy of spherical actuator is analyzed in detail, and optimization algorithm of current input is developed to improve the power efficiency and the fault tolerance capability of system. Simulation is then carried out to validate the proposed method and algorithm in this study. The simulation results indicate that by using the trajectory planning, the given torque values and the torque model, optimal current could be obtained to drive the rotor to achieve desired motions.