Study On The Electromechanical Coupling Dynamic Characteristics And Active Control Of Torsional Vibration Of Electric Vehicle’s Electric Drive Assembly

With the increasingly high performance requirements for electric vehicles,the electric drive system has been developed from the simple coupling system to three-in-one electric drive assembly composed of motor,reducer and control system.The traditional coupling joint is replaced with integrated structure which the motor is directly coupled to the gearbox in this kind of three-in-one electric drive system.The integrated design and manufacturing of electric drive assembly has greatly improved the efficiency and power density of the drive system and reduced the volume and weight.Meanwhile,it causes torsional vibration of the motor shaft.Therefore,the establishments of electromechanical coupling model and the study of its coupled vibration mechanism have important guiding significance for the study on system torsional vibration suppression.Firstly,according to the structure of electric drive assembly,the dynamic electromechanical coupling model of gear transmission system,dynamic motor and motor control is established.The dynamic equations of electromechanical coupling are derived considering load,motor torque input,meshing error,tooth clearance and other internal and external excitations.The motor output characteristics under two different control modes are analyzed.Then the state space equation of the system is established by the electromechanical coupling dynamics equation,and the transfer function of the system is obtained.According to the transfer function,the zero-pole diagram and Bode diagram of the system are obtained,and the vibration mechanism of the system is analyzed.Dynamic simulation was carried out for the models with and without transmission system,and the influence of gear transmission system on motor characteristics was studied by comparing their dynamic characteristics comprehensively.The vibration characteristics and dynamic meshing force of the model were obtained,and the influence of each frequency on the electromechanical characteristics was obtained by Fourier transform.Based on the original control system,the effects of speed loop bandwidth,current loop bandwidth on the electromechanical coupling vibration characteristics are studied.Finally,a hybrid ADRC(active disturbance rejection control)is proposed based on the advantages and disadvantages of linear and nonlinear functions.According to the analysis of vibration characteristics mentioned above,the motor shaft speed difference(35)? is selected as the observation target of the controller.A control strategy based on ADRC current compensation whose control target is(35)?=0 is proposed.The torsional vibration characteristics of the system before and after vibration suppression are compared,and the effectiveness and feasibility of the current compensation control strategy are verified by simulation under step load and impact load respectively.