Research On The Active Front Steering Control Based On Virtual Prototyping Technology

Automotive steering system directly affects the performance of vehicle handling and stability, which is to ensure an important performance of car safety at high speed. Traditional steering system can not meet the flexibility at low speed and stability at high speed.According to vehicle driving conditions active front steering can achieve the desired steering ratio, which meets the flexibility at low speed and stability at high speed. While the system still connections machinery, so the driver can access to the true "sense of road".Taken the flexibility, comfort, stability and security of driving car as considerations, nowadays active front steering is an important research direction of the steering system.In this paper the vehicle model is built for active front steering research in ADMAS/Car.Through the swept-sine steer simulation,test results verify the correctness of the vehicle model.In the low and high friction coefficient road fish hook tests are simulated. Simulation results show that:in extreme conditions, the vehicle yaw rate and sideslip angle response can not be changed with the steering wheel angle, the vehicle is easy to lose stability.A robust nonlinear fuzzy-PID controller is adopted to control the stability of the vehicle model in this paper, taken the two degrees freedom model which has ideal steering performance as reference model. Yaw rate and sideslip angle are the control objectives and the difference of the yaw rate of actual vehicle model and the ideal yaw rate is the control variable in the fuzzy-PID controller.Tolerance zone method is used to judge the stability of the car, the co-simulation use two softwares of ADAMS/Car and MATLAB/Simulink. Simulation results show that:AFS controller can expand stability area to prevent the car ahead of time into the nonlinear and saturation region, particularly in the over-steering condition, the results relatively effective.In extreme conditions the slip forces of the tire is easily filled, it is very limited to improve vehicle stability using AFS controller.It is proposed that AFS and VTD controller is necessity to maintain vehicle stability.A fuzzy controller is designed which has a multi-variable inputs and outputs. The difference of the yaw rate of vehicle model and the ideal yaw rate and vehicle model sideslip angle are the input variables and the superposition angle and additional yaw torque angle as the output variables in the controller.It is using the methods of tolerance zone and phase plane to determine whether automobile is instability. In the low friction coefficient road the double lane change is simulated using integrated controller, simulation results show that integrated controller can maintain the car stability, which is superior to the single AFS controller, sideslip angle and yaw rate responses are controlled in an ideal range.