Low Speed Control of Permanent Magnet Synchronous Motor Based on Instantaneous Speed Estimation

Incremental-type encoder is widely used for speed detection in servo system. However, the speed controller of the system usually becomes unstable at low speed range using average speed estimation method. An instantaneous speed estimation scheme for low speed control of permanent magnet synchronous motor is proposed. The speed estimation adopts a full order state observer to calculate feedback speed. The method can achieve good response because it is possible to detect the speed exactly without detection dead time. The observer design considerations for application are analyzed. Furthermore, inertia identification based on recursive extended least square algorithm is presented to reduce sensitivity of the speed estimation. Experimental results show that low speed control performance using the instantaneous speed estimation with inertia identification is superior to that of conventional one