Non-speed Sensor Permanent Magnet Synchronous Motor Control Based On Back-EMF Observation

The third generation tombarthite permanent magnet synchronous motors(PMSM)have high power density,torque inertia ratio as well as a quick dynamic response,making it widely used.But the speed control performance of the PMSM depends on the rotor position feedback,and the existence disadvantages of mechanical position sensors made the sensorless control technique was widely studied.So far,the middle-high speed sensorless control strategies were matured,however,with the non-ideal conditions,the middle-low speed control methods were relatively less.In this paper,basing on the surface-mounted PMSM model and the id equals zero vector control pattern,striving to realize the accurate middle-low range speed control,a sliding mode back-EMF observer sensorless control stratagem was proposed,the main achievement follows:1.Three mathematical models were built in different coordinate system.The principle of vector control was explained through the dq coordinate system,and a PI current loop together with PI speed loop vector control model was built by chosen the d axis ampere equals zero,confirming the models' effectiveness.2.The sliding mode theory was analyzed and used into PMSM sensorless control,then designed a sliding mode rotor position and revolution observer.Aiming at the inevitable defect in sliding mode chattering,chattering was weakened in three follow aspects: Firstly,using quasi-sliding mode by saturation function;Secondly,using phase-locked loop replaced the arc tan function to extract position and revolution information;Thirdly,filtering the chattering via a special low-pass direct current filter.3.Considering the PMSM starting performance,in order to overcome the condition that non-ideal terms and the back-EMF was to low to detect,as the motor starts.This paper has adopted a current frequency ratio open loop starting pattern,making the motor start smoothly and reducing the system start overshoot high current impact.At last,on the basis of the paper,simulation models were built in the Matlab/Simulink platform,completing the simulation analyze about all the strategy that the paper mentioned.By means of the combination of the respective advantages,a middle low range PMSM sensorless control finally achieved.