Four-Wheel Steering And Differential Braking Joint Realization Of Vehicle Stability Control

With the vigorous development of the auto industry,the problems of vehicle in safe driving,control stability and energy conservation and environmental protection caused further study of scholars both at home and abroad.New drive-by-wire technology has better response rate and response effect,therefore applied in the vehicle active safety and handling stability has great research value.In this article,through combining four-wheel steering-by-wire and brake-by-wire system achieve the stability of vehicle control.Compared with the front wheel steering,four-wheel steering has the good characteristic of low speed turning flexibility and high speed turning stability.Brake-by-wire system overcomes the limitation of the traditional braking system on the structure and principle.Four-wheel steering system through the angle output,can amendment the vehicle's over steer or under steer,the same as braking system by braking force output.So combining four-wheel steering and brake-by-wire has the very vital significance.First of all,analyze the vehicle steering instability reason and why choosing side-slip angle and yaw rate as the vehicle stability control variables,and calculate their expected values.Then use the road adhesion coefficient,vehicle speed and steering wheel angle rate designing fuzzy controller to calculate the vehicle stability variables threshold to determine whether the vehicle is in stable condition,if not,implement stability control.Secondly,the four-wheel steering,differential braking individual and combined control are studied.The differential braking kinetics model was established,the differential braking alone vehicle stability control is analyzed,using the linear quadratic optimal control method,to calculate the vehicle directly yawing moment needed to restore a stable state,and through the EHB single wheel braking implementation of the system.For output sliding mode variable structure control of braking torque choice lay a foundation on which wheel.Four-wheel steering dynamics model is established,using the linear quadratic optimal control method to the rear wheel angle control strategy are studied.Analyzes the deficiency of four-wheel steering and differential braking individual control,illustrates the necessity of joint control.In addition,based on the four-wheel steering vehicle nonlinear dynamic model is designed based on linear quadratic controller and integral function switching adaptive sliding mode controller,through the four-wheel steering and differential brake joint realization of vehicle stability control.Finally,a Car Sim and Simulink joint simulation is carried out,four-wheel steering control and differential braking control individually controlling under the double lane change condition of dry and snow road,the simulation verified the deficiency of the four-wheel steering and differential braking control alone,illustrates the necessity of joint control.Four-wheel steering and differential braking joint realization of vehicle stability control simulation is carried out under the dry and snow pavement sharp turn,emergency avoidance and lane change 6 kinds of working conditions.The simulation results demonstrate that the proposed joint control strategy achieve a better performance in lateral stability control than that lonely control.The joint control based on the integral function switching adaptive sliding mode controller has better stability control effect compared with the ordinary sliding mode controller.