Research On Sensorless Control System Of Permanent Magnet Synchronous Motor In Full Speed Range

The traditional motor control method is to use the position sensor to detect the rotor position information,but the installation of the sensor will increase the volume of the motor,increase the manufacturing cost of the motor,and is susceptible to electromagnetic interference,which limits the use conditions of the permanent magnet synchronous motor(PMSM).Therefore,the use of position sensorless control method to observe and track rotor position in real time has become one of the current research hotspots.In this dissertation,a sliding mode observer position-free control method with fast dynamic response and strong anti-interference ability is proposed.The observer can extract the rotor position information through the back-EMF.However,when the motor is running at low speed,the back-EMF is too small.The rotor information cannot be accurately obtained,so the sliding mode observer method is not suitable for low-speed conditions.In order to solve this problem,this dissertation uses the high frequency signal injection method to obtain the rotor information at low speed,and considers the composite control method of the two algorithms in the full speed domain,thus significantly improving the rotor estimation accuracy.(1)Aiming at the chattering problem and rotor phase delay problem of traditional sliding mode observer in medium and high speed domain,this dissertation mainly adopts the following improvement measures:(1)The traditional sign function is changed into sigmoid function,which makes the control smoother and weakens the chattering better;(2)the traditional exponential reaching law steady-state chattering does not approach zero,so the power reaching law is used to control the sliding mode motion,which makes the reaching process smoother and the steady-state chattering smaller;(3)using double low-pass filter instead of the traditional first-order low-pass filter to filter out the high-order harmonics in back electromotive force more effectively,and using phase compensation to correct the rotor angle;(4)Using phase-locked loop technology to improve rotor error estimation accuracy.(2)Aiming at the problem that the sliding mode observer cannot correctly estimate the rotor position in the low speed domain,a rotor position estimation method based on pulsating high frequency injection is proposed.The high frequency signal is injected into the d-axis,and the rotor position is extracted by the generated current response.At the same time,in order to make the two estimation methods proposed between low speed and medium-high speed switch smoothly,a composite controller based on weighted hysteresis average algorithm is designed.Finally,the simulation platform is used to build the models of improved sliding mode observer,high frequency injection method and composite controller.The simulation results show that the design has good rotor information estimation performance in the full speed range,and meets the static and dynamic performance requirements of the speed control system.(3)This dissertation builds a permanent magnet synchronous motor drive control experimental platform with TMS320F28335 as the core,and develops a set of permanent magnet synchronous motor sensorless speed control system suitable for full speed range.The experimental results under different speed / torque operating conditions are analyzed and compared to verify the effectiveness and superiority of the proposed rotor position estimation method.