Development of a permanent magnet slotless limited-angle torque motor with a moving coil for optical scanning system

This paper presents a permanent magnet (PM) slotless limited-angle torque motor (LATM) with a moving coil for optical scanning system, which possesses the characteristic of both linearizing torque versus rotor position angle and rapid dynamic response. A magnetic equivalent circuit (MEC) for the proposed LATM is derived and implemented in the design process to estimate torque coefficient, moment of inertia, electromechanical time constant and other relative parameters of the LATM. Coil parameters have also been optimized by simple analytical method so that a less electromechanical time constant can be achieved. Then, 3-D finite element method (FEM) is employed to validate the analytical method and to analyze accurately electromagnetic performance of this slotless LATMs. Finally, a prototype machine is established which experimental results well agree with theoretical and simulation analysis. In addition, a simple linear control system based on conventional PID controller is established, which shows better control characteristic of the proposed slotless LATM.