A Comparative Study of Speed Observers between Adaptive and Sliding Mode Approaches

In this paper, a comparative study of model reference adaptive system (MRAS) and sliding mode based speed observers is considered for speed sensorless induction motor drives. First, MRAS-based observer is designed and a method is introduced for its PI block design. Then, sliding mode based observer is presented in detail. Finally, a comparison is made between two observers in terms of speed tracking capability and parameters variations. The comparisons are performed through simulation studies. Furthermore, a real-time laboratory setup is constructed to evaluate some dynamic behaviors of proposed observers. The results of this study show that both observers have reasonably good speed response dynamics and acceptable tracking capability but due to their steady state errors and performance degradation dealing with parameter variation, the proposed SMO shows relatively better performance.