Research On Position Sensorless Vector Control Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor (PMSM) is widely used in industry control with theadvantages of high efficiency and small volume. Due to the application of PMSM, performance ofwashing machine gets better and better. Selecting PMSM as research object, the paper has achievedposition sensorless vector control in the full speed range.Firstly, the mathematical model of PMSM in different coordinate systems and the theory ofvector control are introduced. Based on the model, the realizing process of the vector control aregiven in detail，which incuding the built of the speed loop and current loop.Secondly, the design of sliding mode observer (SMO) is given in detail. To solve the problem ofconventional SMO, this paper designs a new continus function as sliding mode switching function,and the rotor position and speed are got by the phased-lock loop, which can effectively weaken thechattering phenomenon, improving the estimation accuracy of rotor position. A kind of no phase delayfilter is used to extract the back electromotive force, and has achieved good filtering effect. Thismethod also simplifies the structure of system. Its feasibility and effectiveness are validated throughsimulation in the environment of Matlab/Simulink.Thirdly, in order to solve the problem of the sensorless control at zero and low speed, voltagevectors injection which is based on the magnetic saturation is used to detect initial rotor position, andthe rotating current vector closed-loop control is used to start at a low speed. For the rotating currentvector closed-loop control, the self-starting strategy with speed-open-loop and current-closed-loopprocesses is studied, and the principle and steady state conditions of self-stabilization is analyzed.Finally, a PMSM sensorless system is built to verify those theroies proposed above. Theexperimental platform including hardware and software designs are based on Freescale’s56F8037DSP. The tested result has met the design requirements, and the feasibility and correctness ofproposed strategy are proved.