Position Detection Method And Implementation Of PMSLM Based On Linear Hall-effect Sensors

Permanent magnet synchronous linear motor(PMSLM)is a kind of motor which combines the advantages of linear motor and permanent magnet synchronous motor.It has the advantages of simple mechanical structure,large thrust,high efficiency,good dynamic response and easy maintenance.It has become the application hotspot in many fields like aviation equipment,high-speed and high-precision machine tools and so on.The pole position detection of PMSLM is the key factor of the whole linear motor closed-loop control system,and its position estimation accuracy will directly affect the control performance and dynamic response speed of PMSLM.At present,there are many linear motor position sensors,such as magnetic grid sensor,grating sensor and hall-effect sensor.Although the detection accuracy of magnetic grid sensor and grating sensor is high,there are many problems,such as large structure size,high cost and high requirements for the working environment.Low resolution hall-effect sensors of switch type and lock-in type have low cost,but the accuracy of position estimation is limited.Therefore,considering the factors of position detection accuracy,cost and engineering application,this project uses linear hall-effect sensor as the pole position detection element,and focuses on the PMSLM pole position detection method based on linear hall-effect sensor.In order to optimize the position detection accuracy of the whole stroke of the motor,a reasonable installation layout of hall-effect sensors and an improved detection algorithm are designed.In this paper,the position detection models of different numbers of the linear halleffect sensors are analyzed specifically.By using the vector control strategy of PMSLM,the waveform signal is obtained through the linear hall-effect sensors detection of orthogonal placement,and then the pole position and speed information of the motor are obtained through the operation.As the feedback input of PMSLM closed-loop control,the vector control of PMSLM with speed and current double closed-loop which is based on linear Hall is established.In order to study the installation layout principle of linear hall-effect sensor relative to PMSLM,the specific model of linear hall-effect sensor is selected.Taking15 slot 20 pole motor as an example,the horizontal installation layout is analyzed from the control principle first.And then combined with Ansoft Maxwell software carries out two-dimensional and three-dimensional quantitative analysis on the magnetic field distribution of motor poles,the best installation position parameter of linear hall-effect sensor in three directions of motor is given.Additionally,the general law of installation position of linear hall-effect sensors is summarized.In order to solve the problem that the estimation error of the detection position increases due to the magnetic field distortion at the pole of the motor’s moving end when the PMSLM is running in full stroke,a vector tracking position observer method based on linear hall-effect sensor is proposed.The linear hall-effect sensor detection signal is mainly used to compensate the linear hall-effect sensor detection signal combined with the back EMF parameters of the motor itself.The position detection model based on linear hall-effect sensor and the observer detection model based on linear hall-effect sensor are built in Matlab/Simulink,and the simulation results of the two models are compared to verify that the detection model of the latter can effectively improve the control accuracy of the motor in the whole stroke.Finally,the corresponding experimental platform is designed to verify the linear hall-effect sensor installation strategy and the improved position estimation algorithm.The experimental results verify the accuracy of the linear hall-effect sensor installation layout,and the dynamic operation test results have high anastomosis with the simulation results,which proves the effectiveness of the improved position estimation algorithm.