A load torque compensation scheme under the speed measurement delay

The average speed detection method involves a measurement delay, which can cause a serious instability problem to the unknown load torque observer. The instability can be cured by inserting an artificial delay into the torque-filtering path of the observer. Also, by utilizing the concept of the phase lead compensator, we propose a method of designing an arbitrary high-order low-pass filter (Q filter). Through the results of simulation and experiments, we show that our proposed method yields more robust and improved results than the conventional load torque observer.