Real-time motion control of a multi-degree-of-freedom variable reluctance spherical motor
Presents high-precision control strategies and bearing support mechanisms for real-time motion control of a multiple degree-of-freedom (DOF) variable-reluctance (VR) spherical motor. In particular, a resultant magnetic force model is derived which, along with the torque model, is used to develop a reaction-free control strategy to establish a non-contact support mechanism through magnetic levitation to achieve high performance motion. An equivalent angle-axis based control is also designed and implemented for real-time applications. The designed control strategy only requires limited knowledge of system dynamics, and therefore is robust and practical. A look-up table based on-line nonlinear optimization scheme is devised to facilitate the control strategy for a prototype VR spherical motor. Control experimental results verify the reaction-free control strategy and demonstrate the motion capability of the multi-DOF VR spherical motor. The concepts, methodologies, and experimental techniques developed in the paper establish an essential analytical and engineering basis for real-time motion control of VR spherical motors.