Study On Stability Control Strategy Of 4WID Electric Vehicle Driven By Hub Motor

The development of new energy automobile industry with electric vehicles as the main body has become an important measure to improve the environment and save costs.As a typical mechatronics integrated system,automobile is developing rapidly in such directions as electricalization,intelligence,network connection,lightweight and sharing.Four-wheel independent drive hub motor electric vehicle is the mainstream development direction of electric vehicle in the future.After omitting the traditional mechanical transmission parts,the four wheel drive / braking force of electric vehicle is controlled separately.So there is a broad space for research on flexibility and stability.At present,the research on the stability of drive control at home and abroad is still not yet mature.Researching more safe,efficient,and stable control systems is the focus of research.Therefore,this thesis is based on the characteristics of the four-wheel independent drive hub motor electric vehicle,focusing on the control strategy of the drive control system.The main research contents include:The CarSim vehicle simulation software based on parametric modeling is used to build the whole vehicle model.The CarSim is improved as the independent driving form of the motor and the interface is configured.The permanent magnet brushless DC motor model is built in the Matlab/Simulink software.The motor parameters are matched based on the vehicle dynamics index.The hierarchical control structure is adopted,and the upper layer is the torque decision layer.First,the instability determination module is designed based on the phase plane method,and the yaw moment controller based on the second-order sliding mode control theory is constructed,which integrates the yaw angular velocity a nd the side deflection angle of the center of mass.The yaw moment is determined by weighted control algorithm.Secondly,the driving anti-slip controller is designed by using fuzzy PID control theory and feedforward plus feedback method,and PI speed following controller is designed according to PI control theory.And introduce pedal opening to coordinate the speed and drive anti-slip torque;based on the safety as the goal,designed the coordinated control strategy of driving stability.The lower layer combines tire "friction ellipse" characteristics,based on a constrained optimal distribution theory,formulates an optimal driving force distribution algorithm,and at the same time designs a braking force distribution controller based on the stability boundary.The braking force is selectively distributed to the hydraulic brake cylinder of the wheel by PID combined with the understeer and excessive steering of the vehicle.According to the typical working conditions,the off-line simulation analysis of the control strategy is carried out.The simulation results show that compared with the fuzzy PID algorithm without feedforward,the deviation of wheel slip rate is controlled within 0.02.The control effect of yaw velocity and side deflection angle of mass center is increased by 80% and 50% respectively by combined distribution of driving and braking.In addition,a real-time simulation experiment platform is built with dSPACE,and the experimental results are compared with the off-line simulation results.The results show that the execution time of the algorithm is less than that of 550 ?s,which is smaller than the specified cycle period of 1 ms,and the verification meets the real-time requirements.