Research On Active Safty Control Technologies Of In-wheel Motor Vehicle

In-wheel motor vehicle is configured as the driving motors are installed in the wheels,so the motors drive the wheels directly.It is brand new one of independent wheel drive powertrain system.As the powertrain module is compact,high transmission efficiency,short transmission chain and it is easy to be arranged,it has already been widely concerned and is considered to be an important vehicle structure.The drive torque of the drive wheels can be independently adjusted to be in a drive state and a braking state(motor regenerative braking),respectively,and thus have greater freedom and flexibility in vehicle dynamic regulation and control,enabling the car to have better safety and handling performance.In this paper,the control algorithm of the traction control and the yaw stability control of the wheel drive vehicle is studied,and the control algorithm is simulated and analyzed.The work of this paper has both theoretical and engineering practical significance.In order to analyze the dynamic characteristics of the in-wheel motor vehicle,this paper firstly analyzes the nonlinear dynamics of the in-wheel motor vehicle body,wheel and tire.On this basis,based on Matlab/Simulink simulation,the simulation model of the dynamic characteristics of the in-wheel motor vehicle is established.Based on this model,simulations of a straight-line acceleration and steering condition simulation with different adhesion coefficient are carried out.In the straight-line acceleration simulation,on the medium and low adhesion coefficient road,the wheel slip rate is larger,more than the tire slip rate.In the steering conditions,on the medium and low adhesion coefficient road,the vehicle yaw rate can not track the driver-expected yaw rate and the vehicle is lost of stability.Through above simulations,the control problem of this paper is put forward.A traction control algorithm is designed for medium and low adhesion coefficient road driving condition,when the wheel slip rate is bigger.The control model used in this section is a nonlinear wheel dynamic model.In order to make wheel slip rate track the optimum slip rate,the wheel slip is used as model state,and the motor torque is considered as the control input.In order to ensure the stability and robustness of the system,the sliding mode control algorithm is adopted.The simulation results show that the designed control algorithm can ensure that the wheel slip rate does not exceed the optimal slip modulus.When the vehicle is impacted by lateral disturbance,the yaw rate and lateral deviation of the controlled vehicle are smaller than the states of un-controlled vehicle.In order to improve the steering performance of vehicle,the vehicle yaw rate is used to track the expected yaw rate of the driver.In this paper,the yaw stability control algorithm is designed.The control model used is the 7Do F nonlinear model,which includes three wheel motion states and four wheel steering speeds,and also includes a non-linear tire model,with four drive motors as control inputs.Considering that the control object is a multi-input multi-output system,and the control input has physical constraints,a nonlinear model predictive control method is used to design the yaw stability controller.By simulation,it can be seen that the designed controller keeps the yaw rate to track the driver's desired yaw rate,the side angle is controlled to a small range,and the handling of the vehicle is improved.