Synchronous Constant Elapsed Time Speed Estimation Using Incremental Encoders

This paper proposes a high-performance speed measurement method for variable speed electric drives using incremental encoders. It is based on the well-known constant elapse time (CET) method. However, the principle of speed estimation is changed from event driven to ready on demand. This helps to remove the jitter effect, caused by the asynchronous nature of the CET method, and make the speed estimation time constant regardless of the current speed. The proposed method can be implemented on modern motion control microcontrollers. Experimental results using a vector controlled permanent magnet synchronous motor (PMSM) are provided to confirm the performance of the proposed algorithm and the improvements with respect to conventional methods. Synchronous the CET method of speed estimation allows to double the accuracy compared to the original CET method for the same behavior of the speed loop, or to increase the speed response time twice for the same accuracy.