Research On Sensorless Permanent Magnet Synchronous Motor Control Strategy Based On Sliding Mode Observer

Permanent magnet synchronous motor drive system is widely used in transportation,aerospace,industrial production and other fields due to its high power density and high control precision.The use of position sensorless drive technology reduces costs and increases system reliability in harsh environments while reducing system size.However,Vector control requires high accuracy and robustness of position sensorless signals.In order to improve the robustness of the observer,the position sensor of the permanent magnet synchronous motor based on the sliding mode control law is applied to the conventional method.However,the robustness improvement of the observer is accompanied by the system chattering problem,thus reducing the observation accuracy.The main research work of this paper is as follows:Aiming at the problem that the system speed fluctuation is too large due to sudden increase of external disturbance load,the expansion torque observer is designed based on the mathematical model of permanent magnet synchronous motor.Based on this,the speed controller with feedforward torque is designed based on the active disturbance rejection control technology.By introducing the sliding mode control theory,the observer control law is designed to improve the observer robustness and load torque observation ability and convergence rate.Compared with the conventional extended observer with linear control law and PI speed controller,the experimental results show that the proposed method is improved in the field of the load torque disturbance.To attenuate chattering,a rotor position observer that combines a quasi-sliding mode with a sliding mode is typically employed.Firstly,the analysis is carried out for the observer in the quasi-sliding mode.It is proved theoretically that the method of weakening the chattering at the cost of weakening the robustness will cause the stator current observation error,which leads to the error of the back EMF observation,which causes phase lag.In order to solve the above problems,a variable integral rotor position observer with error compensation function is designed.Firstly,the sliding mode surface and control law of the conventional method are improved.Then,the rotor position filter without phase delay is proposed.The experimental results show that the proposed method has a significant effect on hysteresis inhibition.The root cause of the observer's chattering problem based on sliding mode control law is analyzed.The integral sliding mode observer is designed to eliminate the chattering phenomenon as much as possible.Firstly,the integral sliding mode surface is designed.Then the gain adaptive sliding mode control law is designed according to the back-EMF mathematical model.Finally,the first-order low-pass filtering link is analyzed,and the rotor angle quantitative compensation link is designed to weaken the low-pass filtering.The phase lag caused by the link.The experimental results show that the proposed method can largely suppress chattering.The conventional full-order sliding mode position observer is analyzed.The theoretical deduction proves that the method cannot guarantee the absolute finite time convergence of the observation error,and the internal chattering phenomenon of the observer still exists.Aiming at problems mentioned above,the concept of terminal sliding mode and high-order sliding mode control law in sliding mode control theory is introduced firstly.The state model of back-EMF is analyzed,and the full-order observer modeling process is given.Then the high-order terminal is designed.The sliding surface and the control law are proved by the Lyapunov stability theorem.The necessary and sufficient conditions for the stability of the proposed observer are theoretically analyzed.Then the observer's ability to suppress the buffeting and the observation error of finite time convergence to zero is analyzed theoretically.The specific digital discrete process of the designed high-order sliding surface is given.The experimental results demonstrate the effectiveness of the proposed method in the above two aspects.