Research Of The Rotor Position Estimation Schemes For Switched Reluctance Motor With Embedded Sensing Coils

Switched reluctance motor(SRM)is a novel motor with a double salient structure.It has been employed widely in many fields such as aerospace,electric vehicle drive and other fields due to its simple structure,low cost,flexibility in control and so on.The signal of rotor position plays an essential role for driving SRM.Position sensor installed with the motor is the traditional position estimation technology.The position sensor easily affected by environmental factors such as high temperature or oil pollution.Therefore,the sensorless technology or indirect position estimation technology research of SRM has high necessity.This thesis proposes a indirect position estimation method.Injecting high frequency pulse into sensing coils and acquiring the current enveloping lines through the detection circuit to obtain indirectly phase inductance.The target of accurately estimating the rotor position of the SRM is achieved.The main content can be summarized as the following:(1)For the issues of mutual inductance influence between main windings and sensing coils or adjacent sensing coils,according to the method of calculating mutual electromotive force,the ability of different structure sensing coils to eliminate the mutual inductance of the main winding is analyzed.The magnetic field distribution of the different main windings'combination is analyzed based on the finite element analysis,and the differences in the magnetic field distribution of different combinations are compared.The mutual inductance characteristics between sensing coils and main windings in the different magnetic field distribution are analyzed,and the optimal structure of sensing coils is determined.(2)According to the basic principle of sensing coils method,the sensing circuit is designed and the relevant parameters of the signal generation circuit,the detection circuit and the low-pass filter circuit are determined.A simulation model is built up by finite element analysis software Ansoft,injecting square wave pulse into sensing coils and the enveloping lines which reflects the trend of phase inductance is obtained.The phase inductance is calculated by enveloping lines,and the influence of the sensing coils' inductance characteristics is analyzed in detail by Ansoft when the main magnetic circuit is saturated.(3)This thesis proposes a position estimation scheme.The simulation model is established based on Simulink software,and the simulation results verifies the correctness of the scheme above.The calculation error caused by phase shift when the motor operating at high speed is analyzed,and a compensation strategy is proposed to ensure the accuracy of the estimation.(4)The experiment platform of the 12/8 SRM including main control chip,drive circuit current conditioning circuit is built.The pulse injection experiment,the position estimation experiment during different load conditions and different operation conditions of the motor,the experiment of actual position and the estimated position with the phase shift compensation are carried out separately.The experimental results validate the correctness of the a position estimation scheme proposed in this thesis.The rotor position estimation schemes for switched reluctance motor with embedded sensing coils proposed in this thesis is feasible by simulation analysis and experimental verification.The target of estimating the rotor position during the full speed range is achieved.