| The development of pure electric vehicles is one of the most important measures to solve our country’s energy crisis,reduce environmental pollution,and achieve the great goals of carbon peak and carbon neutral.The electric drive system of electric vehicles includes an electrical system and a mechanical system.The electrical system is composed of battery,DC-DC converter,inverter,and motor.The mechanical system is composed of a reducer,a differential,and a half shaft.Both electrical system parameters and mechanical system parameters will have an impact on the dynamic performance of the entire electric drive system.The research,analysis and design of electrical and mechanical systems alone cannot accurately reflect the electromechanical coupling characteristics of the electric drive system and thus cannot optimize the performance of the electric drive system.Combined with the National Key R&D Program of China [No.2018YFB0106102]."Development of high-performance pure electric sports utility vehicles(SUV)",an SUV is used as the research object,and the integrated key of its electric drive system is established based on the bond graph theory.And than,study the influence of electromechanical parameters on the dynamic performance of the electric drive system.It can guide the optimization of electromechanical parameter design,make pure electric vehicles more reliable and stable,and provide an effective analysis method and research platform for electric vehicle design and development.The main research contents are as follows:(1)Establish an integrated bond graph model of the electric drive system.First,based on the bond graph theory,a battery bond graph model considering the electro-thermal coupling characteristics of the battery is established,and the simulation and experimental results under dynamic stress test conditions are compared to verify the accuracy of the model.Secondly,based on the bond graph theory,a bond graph model of the half-bridge DC-DC converter is established,and the effectiveness of its function is verified by simulation.Thirdly,based on the bond graph theory,establish the bond graph model of the motor system considering the iron loss,design its speed control strategy and compare it with the actual current waveform to show the effectiveness of the control and bond graph model.And than,the bond graph model of the six-degree-of-freedom gear pair is established by bond graph,and compared with the model established by the Newton method,it shows the effectiveness of the bond graph method applied to gear system modeling.Finally,based on the bond graph model of the above key components,an integrated bond graph model of the electric drive system including batteries,DC-DC converters,inverters,motors,gearboxes,differentials,axle shafts and wheels is established.And simulate and analyze its basic characteristics.(2)Analyze the influence law of the dynamic efficiency of the electric drive system.First,calculate and analyze the losses of the motor body,inverter,and reducer respectively.Then,it is substituted into the electric drive system model to analyze the factors affecting the efficiency of the motor system.Finally,based on the established electric drive system integration model,a MAP-based variable voltage control strategy is proposed to study the influence of the DC-DC converter on the efficiency of the electric drive system.(3)Study the influence of electromechanical parameters on the dynamic characteristics of the electric drive system.First,analyze the influence of electrical parameters on the dynamic characteristics of the electric drive system,including the influence characteristics of the mechanical system under the excitation of step current and pulse current,and the influence of filter capacitors and DC-DC converters on the electric drive system.Secondly,analyze the influence of mechanical parameters on the dynamic characteristics of the electric drive system,and the dynamic response characteristics of the electric drive system under different motor shaft stiffness.Finally,the influence of external loads on the dynamic characteristics of the electric drive system is analyzed,including the response characteristics of the mechanical system and the electrical system under abrupt load,and the dynamic characteristics of the electric drive system at different acceleration starting and accelerating at different speeds. |
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