Mechanism Analysis And Feature Extraction Of Coupling Faults In Electric Vehicle Range Extender

Diesel engine/generator-type extended-range electric vehicles are the most viable electric vehicle products currently in development and market,which has aroused widespread concern in society.The research on extended-range electric vehicles mainly focused on power matching and energy management,and there were few researches on fault diagnosis,which leads to the lack of supporting fault diagnosis technology for extended-range electric vehicles.As the auxiliary power component of the incremental electric vehicle,the stability of the extended-range electric vehicle depends on its running state.Therefore,the fault diagnosis research of the range extender can provide theoretical basis and scientific guidance for the maintenance of such electric vehicles.This thesis takes a certain type of range extender as the research object,realizes the electromechanical joint simulation of the extender by establishing the rigid-flexible mixed multi-body dynamics model and control model,studies the variation of the state parameters of the range extender when coupled fault occurs,and uses harmonic spectrum analysis method to extract fault features.The research completed is as follows:(1)Established an electromechanical joint simulation model.The multi-body dynamics,finite element analysis and virtual prototyping technology are applied to the joint simulation modeling of the extender.Firstly,the dynamic multi-body dynamics model of the range extender is established by using the dynamic analysis software,and then the crankshaft is imported into the finite element analysis software.The flexible treatment is carried out to replace the rigid crankshaft to complete the construction of the rigid-flexible multi-body dynamics model of the range extender.Meanwhile,the physical model of the generator under normal state and inter-turn short-circuit fault of stator windings is built,complete the generator modeling according to the equations of voltage,current,flux linkage,etc..Finally,the rigid-flexible multi-body dynamics model of range extender is exported to MATLAB,and the joint simulation model of range extender is realized according to the speed control principle.(2)Extract the single fault characteristic parameter of the range extender.Firstly,the single harmonic sub-phase analysis method is used to decompose the periodic excitation torque into a simple harmonic function and study the harmonic response,andanalyze the mechanism of misfire failure.Secondly,the Lagrangian energy method is used to write out the misalignment of the extender shaft system.Study equations to study the dynamic response of different types of misalignment faults;then,transform the three-phase coordinate system according to the park vector method,analyze the relationship between the frequency response of the electromagnetic torque and the inter-turn short-circuit fault;The simulation model simulates three single faults,and the simulation analysis results are compared with theoretical research to extract the single fault characteristic parameters of the range extender.(3)Extracted the fault characteristic parameters of the extender.The electromechanical joint simulation model of the extender is used to simulate misfire-misalignment coupling fault and misfire-turn-to-turn short-circuit coupling fault of the range extender.Simulation experiments are carried out under the conditions of different misfire fault degrees,different misalignment fault types and amounts,and different turn-to-turn short circuit fault degrees.Harmonic spectrum analysis method is used to process parameters such as engine rotation speed,angular acceleration signal,generator three-phase current,electromagnetic torque and axial force of shaft diameter,etc.And extracted coupled fault characteristic parameters by comparing the change rules of single fault state parameters with theoretical analysis results.Based on the study of the single fault and coupling fault of the range extender,the electromechanical joint simulation model of the range extender is established.The mechanism of misfire fault,misalignment fault and interturn short circuit fault is analyzed.The instantaneous crankshaft speed and generator spindle displacement are obtained.The variation law of the state parameters such as generator current and electromagnetic torque is used to extract the fault characteristic parameters of the range extender.The project research results realize the mechanism analysis and feature extraction of the range extender coupling fault,which helps the range extender to carry out reasonable and scientific maintenance,and provides theoretical support for the diagnosis of extended-range electric vehicles.