Research On Sensorless Control Of Permanent Magnet Synchronous Motor Based On Composite Sliding Mode Control

Permanent magnet synchronous motor(PMSM)are widely used in industry,agriculture,military and other fields because of its small size,high power density and simple structure.However,as a complex coupled nonlinear system,the permanent magnet synchronous motor is easily affected by uncertain factors such as internal parameter perturbation and external interference.In order to improve the control performance of the PMSM,this paper combines the sliding mode control theory with the extended state observer to study the composite sliding mode control strategy and the sensorless control technology of PMSM.The specific contents are as follows:First of all,the mathematical models of PMSM in three different coordinate systems are introduced,and the vector control system of PMSM is built on the basis of space voltage vector pulse width modulation(SVPWM),which provides a theoretical basis for the follow-up control algorithm research.Secondly,in the design of PMSM speed controller,a composite sliding mode controller is proposed.Aiming at the chattering problem in sliding mode control,a novel sliding mode reaching law is proposed,which can dynamically adjust the convergence rate according to the distance between the system state and the equilibrium point.And then an improved nonsingular fast terminal sliding mode speed controller is designed based on the reaching law to improve the dynamic performance of the system and suppress the sliding mode chattering at the same time.In addition,in order to reduce the influence of external load disturbance on the system,an internal model disturbance observer is designed for feed-forward compensation to enhance the robustness of the system.Thirdly,in the sensorless control,a rotor position and speed estimation method based on timevarying gain extended state observer(TVGESO)is proposed.Aiming at the shortcomings of traditional sliding mode observer,such as large noise and low accuracy,a time-varying gain extended state observer is designed to estimate the back EMF.Based on the current equation in the two-phase stationary coordinate system of the permanent magnet synchronous motor,the unknown back-EMF term is expanded into a new state variable,and an adaptive function is introduced to transform the fixed gain parameter in the observer into the time-varying form to suppress the occurrence of differential peaks.Then,by using the normalized phase locked loop technology,the rotor position and speed information of the motor are calculated from the estimated value of the back electromotive force to ensure the estimation accuracy.Finally,the digital control experiment platform based on DSP TMS320F28335 is built.The hardware design part mainly includes main drive circuit,power supply circuits,detection circuits,and protection circuits,etc.The software design part mainly includes the design of the main program,interrupt service subroutines,and fault protection program,and related programs are compiled to carry out experiments on the prototype of PMSM.The experimental results verify the effectiveness of the proposed algorithm.