Sensorless Hybird Control For Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor(PMSM) has been widely used in various field such as robot and new energy vehicles due to its simple structure and high power density. In order to achieve high-precision control, closed-loop control of PMSM needs high-precision mechanical sensor, which raise the cost of system, deteriorate the reliability of system and limit the applications of PMSM. The sensorless control of PMSM gives up the mechanical sensor and get the position of rotor from electrical signal.Firstly, this paper has presented the research situation of the sensorless control and the control strategies suitable in low and high speed-range in detail, respectively. Secondly, the key point of the vector control of PMSM is introduced, and then provided the voltage equation, flux equation, torque equation and mechanical motion equation under two phases frame. Thirdly, modeled the vector control system of PMSM based on the space vector pulse-width modulating method.In high speed-range, a sliding-mode observer(SMO) is applied. Firstly, the basic principle of sliding variable structure is introduced. Secondly, in order to overcome the chattering problem and long response time of the conventional SMO, improvement has been made. The improved SMO has three aspects transformation included use sigmoid function instead of sign function, variable switch gain instead of fixed gain and phase-locked loop replace direct calculation method. Finally, simulations of the Matlab/Simulink show the proposed method has good effect on restrain chattering and reduce the response time.The pulsing high frequency voltage signal injection(PHFSI) is applied in low speed-range included zero speed. In the first place, explain the reason for use PHFSI, moreover, the theory and implementation of PHFSI are introduced in detail. In the end, the simulation model of PHFSI is established and the results of simulation are analyzed.For the reason that one method cannot achieve high-precision control in the whole speed-range, this paper combined the improved SMO with PHFSI, and the weight function is used to switch the two methods at proper speed, the results of simulation indicate that there is no obvious velocity perturbation and achieve the purpose of smooth transition. Finally, based on the simulations, the work of the establishment of the experimental platform and the software design of the main modules has been done.