A Novel Sliding Mode Observer With Optimized Constant Rate Reaching Law for Sensorless Control of Induction Motor

A novel sliding mode observer (SMO) with optimized constant rate reaching law for speed estimation in sensorless induction motor drives is proposed in this article to balance the dilemma between the requirement of fast reaching transient and the chattering reduction on sliding mode surface. By considering the reaching way to the sliding mode surface, a widely used reaching law called constant rate reaching law (CRRL) is introduced into SMO. However, SMO with CRRL cannot satisfy the rapidity of transient performance and the low chattering level simultaneously. To solve this problem, an optimized constant rate reaching law (OCRRL), which is based on the options of an exponential term that adapts to the variations of sliding mode surface and system states, is introduced into SMO. The proposed SMO with OCRRL is able to decrease the reaching time and suppress the chattering problem simultaneously. Simulation and experimental results both show the validity of the proposed approach.