Research On Sensorless Control Of Segmented Bilateral Linear SRM

As one of the optional motors for linear drive systems,Linear Switched Reluctance Motor(LSRM)has gained rapid development in recent years due to its simple and robust structure,low manufacturing and maintenance costs,no permanent magnets,ability to operate in harsh environments,and high fault tolerance.LSRM needs to detect the position of the moving element in real-time during operation.The position sensor increases the volume,cost,and maintenance cost of the control system,and becomes a weak link in the reliable operation of the motor.Therefore,studying the sensorless control of LSRM can reduce the cost of the driving system and improve the reliability of the system.Based on the structure and magnetic flux distribution of the segmented bilateral LSRM,this article uses the magnetic circuit segmentation method to select four special position points of the motor rotor,builds a magnetic circuit model for LSRM single side excitation,and analyzes the impact of motor rotor lateral displacement on winding inductance.By utilizing the characteristics of mutual independence between phases and strong coupling between windings in the motor,a position sensorless control method based on coupling voltage is proposed by combining the pulse injection method and mutual inductance method in traditional SRM position sensorless control methods.Study the variation law of coupling voltage with the relative position of the mover under the condition of symmetrical air gap,and analyze the variation relationship of coupling voltage on both sides of the winding with position under the condition of asymmetric air gap.This article presents the initial position judgment strategy of bilateral LSRM and the commutation control process after starting operation.Digital filtering and delay modules are added to the control process to reduce the impact of bus voltage fluctuations on the proposed sensorless control method.Secondly,using the mutual inductance formula of the phase winding,a nonlinear simulation model of the bilateral LSRM sensorless MATLAB/Simulink control system is constructed,and the variation curves of the coupling voltage on both sides of the motor with position are calculated and obtained under normal and offset fault conditions of the motor rotor.Study the relationship between the excitation current of the winding and the lateral displacement under the condition of lateral displacement of the rotor,and analyze the influence of different conduction and turn off positions on the winding current.The simulation results verify the feasibility of the proposed bilateral LSRM sensorless control method.Finally,LSRM prototype was produced and a testing platform was built.Among them,the hardware system mainly consists of a controller,power converter,driving circuit,current sensor,voltage sensor,isolation circuit,clamp circuit,and auxiliary power supply.The program flowchart of the control system is provided.Completed LSRM sensorless control tests under three conditions:no lateral displacement of the motor rotor,lateral sequential displacement,and lateral extreme displacement.The experimental results show that the LSRM position sensorless control method based on coupling voltage proposed in this article can achieve accurate initial position judgment,smooth starting operation,and chopping speed regulation operation without or without lateral displacement of the motor rotor.