Pulsating torque modeling and compensation for high precision positioning control

AC machines with PM (permanent magnet) are used with preference for applications in high performance positioning systems. The actuated servo drive of ball-screw-driven system which has been used in many industrial applications for fast and precise positioning in the microscopic displacement range is an AC PM motor. This servo drive generates parasitic pulsating torque caused by the power supply and the machine construction resulting speed oscillations which, although small in magnitude, affect the performance of the mechanism. Pulsating torque effects are analyzed and modeled using a mathematical approach and then used for compensation. The experimental results after pulsating torque compensation demonstrate the effectiveness of pulsating torque compensation to accomplish high precision positioning performance of the ball-screw-driven system in the microscopic displacement range.