Sensorless PMSM Control with Sliding Mode Observer Based on Sigmoid Function

It is impossible to install or apply position sensors appropriately in some special applications of PMSM. Sensorless PMSM control is an appropriate choice to solve some problems in the control of PMSM. It is necessary to acquire an estimated position precisely and avoid the chattering phenomenon for sensorless PMSM control. This paper proposes an algorithm for estimating position with sliding mode observer (SMO) based on sigmoid function, and a sufficient condition that leads SMO into a sliding surface is acquired using Lyapunov stabilization analysis. The outcome of this study shows that SMO based on sigmoid function for sensorless PMSM control can estimate position with high precision and avoid chattering phenomenon under the condition of different velocity and load. However, the estimated position needs to be compensated for according to load, and the compensating value is in proportion to the value of the current.