Improved Performance of Motor-Drive Systems by SAW Shaft Torque Feedback

The use of SAW (surface acoustic wave) shaft-torque feedback sensor for improving the dynamic tracking performance of servo-motor drive systems is discussed. As the SAW torque sensor exhibits a high sensitivity and bandwidth, and is unaffected by electromagnetic noise, the sensor is directly integrated into an electrical machine assembly without affecting the mechanical stiffness of the system. The use of sensor allows assignment of the closed-loop zeros, and thus enabling the rejection of a specific periodic load disturbance, and independent tuning of tracking and regulation dynamics. The integration of the SAW sensor inside a servo-motor has led to a compact unit suitable for industrial sevo-control applications.