Torque model and drive method for developing closed-loop orientation control of spherical brushless direct current motor

Abstract

This paper presents a novel multi-degree of freedom actuator driven by three-phase inputs, referred to here as a spherical brushless direct current motor (SBLDC), and its closed-loop control system. The SBLDC can simultaneously generate both spinning and tilting torque for the orientation control of a rotating rotor using two independent BLDC drivers commercially available. The mathematical torque model is derived by three-phase inputs and rotor orientation. A drive method is developed based on the torque model to achieve desired three-dimensional torque. The closed-loop orientation control system based on cascade PID control is designed to validate the torque model and drive method. Finally, the performance of the SBLDC is demonstrated through the numerical simulation, which shows the compact three-phase spherical actuator's potential for precise three-dimensional orientation control.