Stability Control of a Passenger Car by Combined Additional Steering and Unilateral Braking

SUMMARY To investigate the combined control of the side slip angle and yaw velocity of a vehicle in critical driving situations a complex vehicle model (developed in ADAMS) with ABS and adequate tyre characteristics are used. The control loop includes an observer to estimate the side slip angle of the vehicle and a ‘sliding mode controller’ based on a simplified 2-wheel and 4-wheel vehicle model respectively. The output of the controller is one of the three combinations containing two of the possible actuator actions: additional steering at the front, at the rear and in combination with unilateral braking, an additional yaw moment. This yaw moment has to be transformed via corresponding longitudinal slip values into braking moments. Simulation results for a severe steering step input and braking during cornering very well illustrate the advantages of all three investigated control strategies. Only for heavy braking during cornering (for more than 0.7g longitudinal deceleration on a dry surface) the combination unilateral braking with additional steering of the front wheels is less favourable as a result of the control limitations due to the dominant ABS.