A new sliding mode observer for the sensorless control of a PMLSM

In order to achieve sensorless control for permanent magnet linear synchronous motor (PMLSM) direct drive system, speed and position of the motor must be estimated. A new high speed sliding mode observer (SMO) is proposed for a PMLSM based on the sliding mode variable structure theory. A Sigmoid function is used for the SMO as a switching function of the control law, eliminating sliding mode chattering and improving its response rate. Simulation results show that the proposed SMO based on Sigmoid function is capable of estimating speed and position of the motor accurately and rapidly, and the proposed PMLSM sensorless control system has a good dynamic response.