Design of first- and second-order sliding mode observers for induction motors using a stator-flux model

Abstract

We extend current research in the area of ‘sensorless’ control of induction motors by presenting two observers based on first- and second-order sliding mode control theories for the simultaneous estimation of flux and speed. We base the observers on the stator-flux model of the motor instead of the usual rotor-flux model mainly because of the uncertain rotor resistance that plays a significant role in the latter. By designing the observers as if they are sliding mode controllers, we lend the properties of parameter insensitive closed-loop dynamics and finite time convergence to the stator flux and speed estimation schemes. We also present simulation and experimental results to validate the operation of the observers.

Keywords:

• induction motors
• observers
• sliding mode control
• stator-flux model
• super twisting algorithm

Acknowledgements

This research was supported in part by the Deutsche Forschungsgemeinschaft (German Research Foundation), for which the authors are grateful. Our thanks also go to Mr Michael Fall who helped in conducting the IM tests to determine its electrical parameters.