Research On Longitudinal Dynamics Control Of Four-Wheel Independent Drive Electric Vehicle

Since petroleum and some other fuels are non-renewable energy,and car ownership has been showing a growing trend,electric vehicle technology has become an inevitable trend to solve the energy and environmental crisis.Compared with the centralized drive electric vehicle,the distributed drive electric vehicle obviously shows better dynamic maneuverability,high transfer efficiency and simplified system structure,so the distributed drive electric vehicle has gradually become a research hotspot.In this paper,based on the four-wheel independent drive electric vehicle,design the strategy for longitudinal dynamics control.The four-wheel torque of distributed drive vehicle can be independently controlled,so considering dynamic characteristics of tire and actuator of braking system,and based on the concept of hierarchical control,use advanced control allocation technology to achieve vehicle stability control and improve control performance.The main completed research work is as follows:(1)Build vehicle dynamics model and establish the CarSim/Simulink co-simulation platform.Build vehicle dynamics model by CarSim software.Then,according to the requirements of the control model to configure the I/O interface between the CarSim and the MATLAB/Simulink software,connect the vehicle model with the controller model.(2)Based on the inverse tire model,design the slip rate control strategy which is used for the stabilizing state condition.Firstly,allocate the target longitudinal tire force based on the constrained optimal allocation method.Then calculate the target slip rate by the Dugoff inverse tire model,and use the Sliding Mode Control(SMC)method to track the target slip rate.Finally,compare the tire force control distribution results which are based on the inverse tire model with that without considering the dynamic characteristics of the tire by simulation.The results show that the control accuracy of the tire force is effectively improved by the strategy designed in this paper,and the absolute error of tire force is reduced by at least 51.10%.(3)Based on the actuator dynamic control allocation method,design the slip rate control strategy which is used for limiting driving control.Firstly,regulate the slip rate by the sliding mode control method to prevent the wheel from slipping and locking,obtaining the Acceleration Slip Regulation(ASR)torque and Anti-lock Braking System(ABS)torque.When the vehicle brakes,considering the dynamic characteristics of the motor and hydraulic brake system,allocate torque for the motor and mechanical braking system based on the Model Predictive Control(MPC)dynamic allocation method.Finally,compare the control effect of the model predictive dynamic control allocation algorithm with that pure hydraulic static control allocation algorithm by simulation.The results shows that the dynamic control allocation method can help the slip rate control system respond faster,and the tracking effect of the system to the target slip rate and the target braking torque is better.(4)Based on the NI real-time simulation system and VeriStand software,establish a joint real-time simulation platform of the CarSim vehicle model and controller model,including real-time monitoring,data acquisition and the interactive control system.Use real-time simulation to test the control algorithm designed in this paper to verify the real-time and effectiveness of the control strategy.