Research On Indirect Rotor Position Detection Technique Of SRM Based On Searching Coils

Position sensor is the important part of switched Reluctance motor drive(SRD).Different SRD choose suitable position sensor according to the application background.SRM sensorless technology is still in the research stage as a whole,and it’s difficult to replace position sensor in the industrial situation.This paper mainly studies the SRM indirect rotor position detection technology based on searching coils.The searching coils and phase winding are wounded on the stator teeth,and it has excellent environmental adaptability.The basic idea of position detection is to estimate rotor position from the inductance of searching coil.The influence of mutual inductance and saturation will make the nonlinearity of the searching coil inductance more serious.Therefore,the position estimation based on the symmetry and periodicity of the searching inductance has obvious errors.In this paper,the influence of mutual inductance and saturation on SRM rotor position estimation is analyzed,and the position estimation method is proposed to eliminate mutual inductance and saturation.It is found that the mutual inductance effect between phase windings and searching coils can be neglected,while the mutual inductance among searching coils can not be neglected using multi-phase searching coils to estimate the rotor position of SRM.On this basis,two methods to eliminate the mutual inductance effect among searching coils are proposed.The first method is that two searching coils are used to realize intial positioning and start the SRM,and the single searching coil is used to detect the position of SRM after starting.The second proposed method is to estimate the rotor position by injecting staggered pulse in order to eliminating mutual inductance.Because the main magnetic circuit and the searching coil magnetic circuit share the core of SRM,the saturation of the main magnetic circuit will seriously distort the searching coil inductance.In order to eliminate the influence of saturation on the position estimation of seaching coil,the minimum inductance position of each phase can be detected from the saturated seaching coil inductance,and the estinated discrete rotor position signal is identical to the position signal obtained from position sensor.The maximum position detection error is 0.254 degree at no load in a wide speed range,while 0.348 degree at full load in a wide speed range,and the position detection accuracy is high.