Torque Ripple Suppression Strategy of Permanent Magnet Servo System with Cascaded Gain-Compensated Filter

Torque ripple is a primary disturbance in motion control systems, such as in high-precision CNC machine tools, where mid-to-low frequency torque ripple arises from motor mechanical design and servo control systems. To address this issue in permanent magnet synchronous motor (PMSM) servo drives, this paper proposes a suppression scheme utilizing a speed observer and a cascaded gain-compensated filter. To avoid compromising the speed loop's tracking performance, the speed observer estimates the rigid speed component. The cascaded filter is designed to extract the mid-to-low frequency vibrational component from the difference between the actual and observed speeds. This extracted component is then compensated back into the speed feedback loop. Experimental results demonstrate that the proposed scheme effectively suppresses mid-to-low frequency torque ripple, consequently mitigating speed fluctuations within the corresponding frequency band and enhancing servo motor control precision.