Research Of Sensorless Control Algorithm For PMSM Based On SMO

The high performance AC servo systems need to realize closed-loop control of motor speed, the speed feedback signal comes from motor shaft coaxial connected.In order to acquire accurate,reliable speed and position signal, the senor must be accurately installed, maintained properly. The installation of high-precision sensor, not only increases maintenance requirement and cost of the system, but also the ability of adaptation to environment becomes worse, which in the high reliability requirements of the applications will be limited. Therefore, cancelling the sensor and making the system with good control performance will become an important issue in the field of motor speed.Sensorless control is by measuring the motor voltage, current and other measurable physical quantity to estimate the rotor position and speed information of permanent magnet synchronous motor (PMSM) through special observer strategy to complete the closed-loop control. The key to control technology is the acquirement of speed information, the estimated accuracy of the rotation speed the directly determines the performance of speed control system. In a method of the PMSM sensorless vector control system, this thesis adopts the sliding mode variable structure control principle to realize real-time online estimate the speed and position of motor rotor.Firstly, this thesis compares several methods of rotor position detection of the sensorless PMSM, among them, we select a kind of rotor position estimation base on sliding mode observer (SMO), which has advantage of easy implementation, fast response and simple control algorithm of engineering application.Sencondly, we make a detailed discussion for PMSM structure, the mathematical model and coordinate transform. This thesis determines to use id=0 current vector control strategy of PMSM through to researching the mathematical model of PMSM thoroughly. Thirdly, we design for the SMO for observing rotor information with the correct theoretical guidance through to analyses basic principle of sliding mode variable structure control and the design process of sliding mode controller.Finally, According to the permanent magnet synchronous motor mathematical model, the vector control strategy and the sliding mode observer design principles the thesis discussed as above, we make use of MATLAB/Simulink to build a simulation model of PMSM sensorless vector control system based on SMO. The simulation results show that the SMO to estimates the rotor information accurately, the sensorless vector control strategy in this thesis is feasible, has good robustness and satisfied performance.