Rotor Position Detection Of Sensorless Permanent-Magnet Synchronous In-Wheel Motor Based On Carrier Phase-Shifted Technology

Permanent magnet synchronous motors have the advantages of wide speed range,small size,and high efficiency,so that they are widely used in drive control systems such as rail transit trains,new energy vehicles,and energy-saving transformations in the industrial field.The sensorless control technology on permanent magnet synchronous motor can not only simplify the system structure design and reduce costs,but also improve the reliability of the system.It has important significance and value in some special applications such as aerospace,new energy vehicles and rail vehicles.However,the precision of the rotor position detection at standstill and very-low speed operation state is not high,in view of the above problems,this dissertation proposes a rotor position detection method based on carrier phase-shifted motor,which is researched and verified on theoretical calculation,simulation analysis,software implementation and prototype experiments.The main researches of this dissertation are as follows:(1)A rotor position detection method based on the phase-shifted method is proposed.First,the equivalent state model corresponding to the pulse signals is established,so that the equivalent inductance is calculated.The ratio of the winding inductance to the equivalent inductance determines the range of the rotor position relative to the axis of the phase A winding,and sections the position range of the rotor.Then,a certain proportion of voltage is injected into the winding,and the magnetic saturation is taken into account for inductance characteristic analysis,and the polarity of the rotor position is identified according to the inductance characteristic.Finally,in the three-phase coordinate system,the three-phase waveform of the neutral point voltage is sampled,and the three adjacent intersections of two consecutive phases are used as vertices to construct a reference triangle.According to the triangle similarity theorem,the neutral point voltage values are used to directly calculate the rotor position angle.(2)Carry out analysis of related factors affecting motor winding inductance.Set up an experimental test platform for the stator core,rotor permanent magnets and windings,and study the influence of different injected currents on the inductance through experiments to provide a theoretical basis for the injection voltage of the windings.Verify the rotor position detection method of the carrier phase-shifted method through the result of the equivalent inductance ratio.(3)The angle smoothing method is compared and studied between rotor position detection methods at different speeds.A simulation mathematical model is established to compare and study the detection accuracy of back-EMF(Electro-Motive Force)position detection and carrier phase-shifted rotor position detection methods in the full speed domain.The angle smoothing method between two different rotor position detection methods is found by comparing the direct switching method,average switching method and weighted average smoothing method of the two rotor position detection strategies.(4)A permanent magnet synchronous motor system control experimental device based on the carrier phase-shifted rotor position detection method is built,and the hardware design,software programming logic and control realization method of the control system are given.In the static state,the open-loop and closed-loop control methods are used to verify the rotor position detection accuracy,and the closed-loop control method is used to verify the rotor position detection accuracy in the ultra-low and high-speed state.Finally,the smoothness of the weighted average method from low speed to high speed is verified through experiments.