Research Of Position Sensorless Of Permanent Magnet Synchronous Motor Based On Sliding Mode Observer

At present,more and more permanent magnetic materials have been explored,and the research on power electronics is becoming more mature,makeing many fields use permanent magnet synchronous motor for driving.So stricter requirements of the control precision and dynamic response performance such as rotational speed and torque are needed.Meanwhile,the control accuracy and dynamic performance of PMSM are also improved.The technology of position sensorless control overcomes some problems which due to the installation of sensors,such as simplifying the structure,reducing cost and so on.So,it has become an important part of people's research in recent years.Based on the research of position sensorless,this paper analyzes some problems of traditional sliding mode observers,introduces some commonly used estimation methods and improves it.In order to verify the position sensorless reliability used in this paper,then we draw the system control chart to simulate in the environment of Matlab/Simulink.Finally,a hardware experimental platform is designed to verify it.First,this topic introduces the commonly used methods of rotor position measurement for PMSM under position sensorless condition and the related theories of sliding mode variable structure are emphasized.The working principle and classification structure of the motor are introduced in detail.The dynamic equations in different coordinate are also explained.The control strategy uses the technology of voltage space vector SVPWM.On this basis,the control concept based on sliding mode observer without position sensor is introduced in detail.The core of this method is to establish the sliding surface to estimate the back electromotive force.However,due to the obvious "bounce" problem in traditional sliding mode observers,we need to improve the switching function and set up the boundary layer.This paper proposes that the smaller the “average slope” of the switching function in the boundary layer,the smaller the “bounce”.After simulation on the Matlab/Simulink platform,saturation function is used finally.The phase-locked loop technique is then used when estimating rotor position and speed,instead of the low-pass filter,preventing the error caused by the low-pass filter due to phase compensation and other factors.Finally we build the experimental platform,and a permanent magnet synchronous motor sensorless control system is designed based on TMS320F28335 chip of TI company.The hardware circuits of current protection circuit,driving circuit and control circuit are introduced.After that,we use C language to program in the CCS5.0 environment,and introduce the system flow chart of the main program modules.In order to facilitate debugging,the internal operation amount is displayed on the oscilloscope in the form of analog data by TLC5620 conversion chip.The results show that when the motor reaches a certain speed,the estimated value of the back EMF is close to the actual value,while the rotor position and speed estimation are more accurate.Moreover,when the load torque is abrupt,the dynamic response of the system is also good.