Research On Position Sensorless Control Of PMSM Based On Sliding Mode Observer

Permanent Magnet Synchronous Motor(PMSM) has a wide application in the industry which includes servo drive with high performance by advantages of cost effective and high power factor.In order to achieve the closed-loop control,the traditional PMSM obtains the speed and position with the mechanical sensor,such as encoder and rotating transformer etc,mechanical sensor not only increases the overall volume and weight,but also damages the practicability and stability of system,at the same time limits the application of PMSM in some severe occasions.In order to overcome the disadvantages of mechanical sensor,the position sensorless control appears.In a large number of position sensorless control algorithms,this paper takes the position sensorless control of PMSM based on Sliding Mode Observer(SMO) as research contents emphasis,special research and analysis is focused on the rotor speed and position estimation.The main achievements of this paper are summarized as follows:Firstly,this paper describes the background of the research on position sensorless control of PMSM,reviews the home and abroad current situations,and control strategies.Through the analysis of various position sensorless control methods,the method of SMO is planned to be used as the control strategy in this paper.Secondly,this paper describes the motor structure and the principle of coordinate transformation,then gives motor model in different coordinate system,finally introduces the vector control theory and the Space Vector PWM(SVPWM).In the paper the system uses id=0 control strategy.Thirdly,this paper constructs the current observer with the motor model to obtain speed and position indirectly based on the analysis of the principle of the sliding mode variable structure.It will have a chattering phenomenon,due to switching characteristics of the SMO,the space lag and time delay etc.In this paper a saturation function replacing the traditional switch function and the low pass filter with variable cut-off frequency are used to reduce the high frequency chattering of the back electromotive force,at the same time the Phase Locked Loop (PLL) is used to estimate the rotor position,which improves the estimation accuracy of rotor position.Finally,the dead time compensation of inverter is proposed to further improve the overall estimation performance of the SMO and reduce the influence of the dead time of inverter.Therefore,in this paper,the SMO is not only has strong robustness,but also has the advantages of fast response,and small rotor position estimation error and so on.On the basis of these theories,using Simulink to build models in the Matlab,simulations verifies the feasibility of the improved SMO through the comparative analysis between traditional SMO and improved SMO.Finally,control system hardware platform is established,software process is designed.Then the relevant code is prepared to verify the proposed method,experiments verifies the effectiveness and correctness of improved SMO.