A Sliding Mode Observer-based Permanent Magnet Motor Speed Identification Method

The permanent magnet synchronous motor(PMSM)is a superiority performance and widely-used motor. The PMSM speed regulator system adopted VVVF strategy to control the PMSM. Because of its merits such as low-dynamic, high-reliability and precise-control,it is widely used in many regions. for accurate PMSM control it's need to obtain precise rotor speed and position signal. But the sensor increases the cost and decrease the reliability. So the research to speed sensorless control becomes a hot topic.This paper introduced a new speed identification method based on sliding mode adaptive observer, taking the speed sensorless PMSM control system as the researching object. As the system is easy to be made unsteady because that the rotor changed very much by the temperature variety and the influence of environment in the practice running process, so synchronously the stator time constant which is the ratio of resistant and inductance was put forward. It may enable the system to overcome the influence of resistant uncertainty when identificating the speed, and the robustness of the system has been strengthened.As the switching function exists ,the system is prone to produce oscillations when sliding mode Variable Structure theory is used. the measures to eliminate chattering has been introduced when the identification was obtained, handling the switching function continuous to eliminate oscillations. the measures to eliminate chattering has been introduced when the identification was obtained, handling the switching function continuous to eliminate oscillations. The structure and math model of PMSM was introduced, the theory foundation of SVPWM technique and sliding mode controlling was expounded in detail, and the closed-loop vector control strategy was studied, so the speed sensorless control of PMSM can be achieved. This paper also introduced the speed identification method based POPOV theory to compare with sliding mode observer speed identification method.This paper established the math model by MATLAB/SIMULINK, and built the MATLAB model of speed sensorless vector control system of the PMSM according to the principle of SVPWM. The system constructed the sliding mode observer by sliding mode theory and calculated the rotor speed and stator time constant on line using the math model in dq axis coordinates, taking the identification speed to replace the speed sensor to form closed-loop control system. The analysis of the MATLAB results shows that this method has strong robustness and satisfied performance.