Research On Rotor Position Detection Technology Of PMSM Based On Fluxgate

In the closed-loop control system of permanent magnet synchronous motor,rotor position information is a very important physical quantity,which is mainly obtained by rotor position sensor.At present,the commercial rotor position sensors mainly include photoelectric,hall,resolver and so on.Aiming at the existing problems of position sensors,this paper studies a fluxgate position sensor with high resolution,strong anti-interference ability,which can be used in harsh environments and has the possibility of miniaturization.It provides a reference value for the future development of position sensors.Firstly,the mathematical model of permanent magnet synchronous motor(PMSM)and its common control methods are introduced.Taking i_d=0 control as an example,the mathematical model of PMSM with rotor position deviation is established,and the influence of rotor position deviation on PMSM control system is analyzed.Secondly,the working principle of fluxgate sensor is introduced,and the mathematical models of single core and double core fluxgate sensors are deduced.Two-dimensional simulation model of single-core fluxgate and two-dimensional simulation model of ring double-core fluxgate are established in Ansoft Maxwell simulation software,and they are analyzed by finite element method.The mathematical model and simulation results of the sensor show that the probe of fluxgate position sensor should adopt the ring double-iron core structure.Then,the influence of excitation frequency and space magnetic field intensity on the output signal of the fluxgate probe is studied.The harmonic analysis of the output signal of the ring double-core fluxgate is carried out.The rationality of using the second harmonic signal to detect the external magnetic field intensity is verified.The range of the designed ring double-core fluxgate to detect the external magnetic field intensity is given.The manufacturing process of the probe for ring double-core fluxgate is introduced.According to the characteristics of fluxgate probe output signal,the signal processing system of fluxgate sensor is designed.The design process of driving circuit and band-pass filter of the system is introduced.Then the phase sensitive detection technology is introduced in detail,and the influence of the phase difference between the reference signal and the measured signal in the phase sensitive detector on the output signal is analyzed.A signal conditioning circuit is designed to adjust the amplitude and DC offset of the output signal of the phase sensitive detection circuit.The method of fluxgate sensor detecting motor rotor position is studied.Two detection methods are introduced,one is the indirect detection method of the fluxgate type magnetic encoder,and the other is the detection method based on the rotor leakage flux.In the indirect detection method,the spatial magnetic field distribution of the auxiliary permanent magnets with two magnetizing directions is studied.The magnetizing direction of the auxiliary permanent magnets and the installation position of the fluxgate probe are determined by finite element analysis.In the rotor leakage detection method,taking the printed PMSM designed in the laboratory as an example,the finite element simulation model of printed PMSM is established,and the leakage of printed PMSM in different positions is simulated.The advantages of fluxgate sensor over other magnetic sensors in the installation position of motor are analyzed,and the problems in magnetic flux leakage detection method are pointed out.Finally,the hardware system of fluxgate sensor is tested.Taking i_d=0 control as an example,two methods of motor rotor position detection proposed in this paper are experimented to verify the feasibility of fluxgate sensor to detect motor rotor position in motor control system,and the existing problems of the two methods are analyzed.