Position Sensorless Control For Permanent Magnet Synchronous Motor Based On A New Sliding Mode Observer

With the widespread application of high-performance permanent magnetsynchronous motor (PMSM), the requirements to the control performance isbecoming increasingly high. To achieve precise vector control of PMSM, theknowledge of rotor position must be available for the closed-loop control. Generally,the rotor position is measured by a shaft position sensor such as an optical encoderand a tachogenerator. However, the utilization of these sensors will increase the sizeand volume of the motor. Besides, it will make the motor control system morecomplex, and limit the application of PMSM in a relatively harsh environment.Therefore the sensorless control method with high reliability and simple maintenanceis particularly important to the control of PMSM. A novel sensorless control strategybased on a new sliding mode observer (SMO) is proposed in this paper to achieve theposition sensorless control of PMSM.On the basis of analyzing the vector control and sliding mode variable structurecontrol strategies, the strategy of traditional SMO for position sensorless control ofPMSM is analyzed. The result shows that there are two major problems with thetraditional SMO: the chattering and inaccurate initial position estimation. To solve theaforementioned problems brought by the traditional SMO, a new SMO for thesensorless control of PMSM is proposed. The quasi-sliding mode control is applied tothe new SMO to reduce the chattering problem in the traditional SMO; andphase-locked loop (PLL) is used to extracts the rotor position, which solves the phaselag of the rotor position by eliminating the low-pass filter part.In order to verify the feasibility and effectiveness of the new sliding modeobserver, the sensorless control model of PMSM based on the new sliding modeobserver is built and the performance of the new SMO is verified through simulation.The simulation results show that: the new SMO can accurately estimate the rotorposition and have a fast dynamic response at different conditions such as constantspeed, speed step and load torque disturbance. It can achieve the position sensorlesscontrol in a wider speed range. In addition, when there is a change in the statorresistance and stator inductance, the proposed SMO can also estimate the rotorposition accurately and have a strong robustness to the parameter perturbations.