A disturbance torque compensation scheme considering the speed measurement delay [in PM synchronous motors]

The average speed detection method involves a speed measurement delay, and the delay may cause a serious stability problem to the unknown load torque observer. The instability can be cured by inserting an artificial delay into the input filtering path of the observer. Also, by utilizing the phase lead compensator concept, the authors propose a method of designing an arbitrary high order Q-filter. Through simulation and experimental results, they have shown that their proposed method yields more stable and improved results than the conventional load torque observer