Research On Sensorless Control Technology Of Permanent Magnet Synchronous Motor Based On Sliding Mode Variable Structure Control

At present most Permanent Magnet Synchronous Motor(PMSM)adopts vector control technology with mechanical sensors at present,which not only increases the volume and cost of the motor drive system,but also the operation performance is easily affected by the working environment.Position-free vector control technology can effectively avoid the above problems,so it has become a research hotspot in the field of motor control.Among them,the sliding mode observer(SMO)has fast dynamic response speed and strong robustness,which makes it an important research branch in the field of position sensorless vector control.However,there are some problems in traditional SMO,such as chattering,low observation accuracy and poor effect in medium and low speed range,which seriously affects the further application and control performance of SMO in PMSM.Therefore,the above problems are solved in this paper.The main research contents are as follows:(1)In order to study PMSM position-free vector control technology,mathematical models of PMSM in stationary and synchronous rotation coordinate systems are constructed in this paper.The space vector pulse width modulation(SVPWM)model is established,and its advantages over sine pulse width modulation are analyzed.And different vector control methods of PMSM are analyzed.(2)Based on sliding mode variable structure control theory,the influence on the performance of traditional SMO is analyzed from three aspects: basic principle,parameter design and linear system running trajectory.The numerical relationship of different parameters in the trajectory of traditional SMO is analyzed by the phase-plane control method.It is pointed out that the convergence rate of traditional SMO in sliding mode motion is affected by the motor parameters,and the system observation accuracy is affected by the sliding mode gain coefficient.And the traditional SMO position-free vector control simulation system of PMSM is constructed to verify the correctness of the conclusion.(3)On the one hand,in order to solve the chattering problem of traditional SMO,the integral sliding mode surface function combined with the designed variable power reaching law algorithm is adopted to weaken chattering and improve robustness of the SMO control system.On the other hand,in order to improve the accuracy of the observer,the influence of sliding mode gain coefficient and sampling current error on the location information acquisition by SMO are analyzed.Based on the adaptive control,an adaptive sliding mode gain coefficient control method is designed to improve the observation accuracy by adjusting the sliding mode gain in real time.(4)The experimental platform of PMSM position sensorless vector control system is built based on DSP28035.And the correctness and effectiveness of the proposed theory in this paper are verified.