Sliding mode observers for electric machines-an overview

In electric machine control practice, it is not desirable or possible to measure all the state variables needed for control implementation. A good observer-based method to obtain state variables for use in the control law is always pursued by researchers. Observation algorithms make use of the machine model equations and allow the estimation of rotor speed and/or flux from the motor terminal measurement of current and voltage. Among different observation methods the sliding mode observer is a promising approach. This paper attempts to provide a status review and synopsis of the main approaches used in the sliding mode observer design for electric machines. Both induction machine and permanent magnet synchronous machine are covered in this paper. The research work expands from flux estimation, machine parameter estimation to sensorless control issue.