Speed Sensorless Control of PMSM Using An Improved Sliding Mode Observer With Sigmoid Function 51 Speed Sensorless Control of PMSM Using An Improved Sliding Mode Observer With Sigmoid Function

An improved sliding mode observer is presented to estimate the rotor position of the permanent magnet synchronous motors (PMSMs). In this observer, the discontinuous control is replaced by using the sigmoid function in order to reduce the chattering problem commonly found in the conventional sliding mode observer. When the chattering is reduced, the back emf can be obtained directly from the switching signal. Thus, the low pass filters may not be necessary to extract the low-frequency back emfs. As a result, the delay time due to low pass filters would not be appeared in this proposed observer. Then, the estimated rotor position would not necessarily be compensated as well. As a result, the proposed sliding mode observer simplifies sliding mode observer with minimal parameter adjustments. The overall system will be implemented on the TMS320F2812 based digital controller. The experimental results show that the proposed observer can reduce the chattering problem and simplify the conventional sliding mode observer.