Research On Sensorless Control Method Of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motors have many energy-saving and efficient advantages such as small size,light weight,high power factor,long service life,so it has been widely used in high-performance driving systems.PMSM adopts vector control method,which requires the position sensor to provide rotor position for accurate control.However,in some control situations,such as the motor drive of water pump and fan,there is also a tendency to transform PMSM drive from asynchronous motor.In these situations,PMSM often adopts the control mode without position sensor.Therefore,the subject of research is PMSM sensorless vector control,and two control methods are designed.One is PMSM position sensorless control method based on sliding mode observer,and the other is PMSM control method based on phase current to directly calculate the rotor position.The two methods realize the sensorless control of PMSM and provide technical support for the subsequent control of water pump and fan.The paper includes the following contents:Firstly,based on a large number of domestic and foreign literature on PMSM sensorless control,a comparative analysis was made on each control method.The mathematical model of PMSM under three different coordinate systems is established,and the PMSM vector control strategy is introduced,and the implementation process of space voltage vector pulse width modulation technology is described in detail.Secondly,the basic principle of the sliding mode variable structure is briefly described.The current observation equation of the surface-mounted PMSM sliding mode observer is designed based on the mathematical model of the??coordinate axis,and the speed and rotor angle information are estimated in real time through a phase-locked loop.Then,by analyzing the SVPWM modulation technology,a control method to directly calculate the rotor position of the phase current is designed.Through the hardware circuit model,the unique relationship between the rotor angle and the phase A and B phase current changes during thevector period is derived,and the selection of the phase current acquisition time is emphasized.Finally,three steps of I/F control are analyzed when the motor is started.Then,the hardware circuit of PMSM sensorless control system is designed,and STM32F103C8T6 is selected as the main control chip.The hardware circuit mainly includes:MCU and its peripheral circuits,phase current sampling,bus voltage sampling,flyback switching power supply,power drive,optocoupler isolation,bridge inverter,etc.Finally,based on the above theoretical analysis,two softwares without position control strategy were written on Keil MDK,including the main program,the initialization of each function module involved in STM32F103C8T6,PI regulator,SVPWM,sliding-mode observer and phase current Algorithm implementation to calculate angle directly,etc.The experimental platform was built to carry out no-load experiment of motor,sudden load experiment,load experiment,speed experiment and position comparison experiment,and the experimental results were analyzed to prove the feasibility of the two sensorless control methods.