New Sliding Mode Observer For Position Sensorless Control Of Permanent Magnet Synchronous Motor

In the high-performance control system of permanent magnet synchronous motor, the rotor position and speed are essential feedback, usually the mechanical sensors (such as optical encoder and resolver) are needed to detect the information of rotor position and speed. However, the use of sensors not only increases the system cost and the volume of motor, but limits the application of permanent magnet synchronous motor in some special occasions. Therefore, the sensorless technology is particularly important in the control system of permanent magnet synchronous motor. In this paper, the sliding mode observer is used to achieve the estimation of rotor position and speed of permanent magnet synchronous motor, the theoretical analysis is verified through simulation and experimental.Firstly, the mathematical models of permanent magnet synchronous motor in different coordinate systems are introduced, and the vector control theory is studied, on this basis, the dual closed-loop vector control system of permanent magnet synchronous motor is built. Then, the theory of sliding mode observer is studied in detail, based on the mathematical model of permanent magnet synchronous motor in ?-? coordinate system the sliding mode observer is built to achieve estimating rotor position and speed. The inherent chattering problem of sliding mode observer is analyzed, and the sliding mode current observer is improved. Typically, the equivalent back EMF signal contains high frequency components, and a low pass filter is needed to extract the required continuous signal, however, the use of low-pass filter will bring the phase delay and amplitude attenuation, to solve this problem, an observer is built based on the back EMF model to substitute for low-pass filter to extract back EMF signal, in this way not only the phase compensation part is eliminated, but also the estimation accuracy is improved.The sensorless control model of permanent magnet synchronous motor is built, and the performance of improved sliding mode observer is verified through simulation, the results demonstrate that the proposed method can effectively reduce the impact of chattering and has good static and dynamic performance. An 11kW permanent magnet synchronous motor is chosen as control object, with the digital signal processor TMS320F28335 as the main controller, a control platform of permanent magnet synchronous motor is built. The correctness and validity of the proposed method is testified by experiment at different experimental conditions such as constant speed with load, speed step and load disturbance, the results show that the proposed method can effectively estimate the rotor position and speed and has strong robustness and feasibility.