Global chassis control using coordinated control of braking/steering actuators

International audienceAutomotive light vehicles are complex systems involving many different dynamics. On one side, vertical, roll and pitch behaviours are often related to comfort performances (indeed, roll is also linked to safety characteristics [23]). On the other hand, safety performances are mainly characterized by the longitudinal, lateral and yaw dynamics [38, 14]. In practice, these two behaviours are often treated in a decoupled may (the first dynamics are often related to suspensions systems while the second one to steering and braking systems). This chapter focuses on the safety problem, and more specifically, on lateral and yaw dynamics. It presents two close techniques to design robust gain-scheduled H∞ MIMO VDSC (Vehicle Dynamic Stability Controller), involving both steering and rear braking actuators. Both approaches aim at restoring the yaw rate of the vehicle as close as possible to the nominal motion expected by the driver. The specific framework of each of that approaches is given below. First, a methodology allowing to synthesize such a controller while taking into account the braking actuator limitations and use the steering actuator only if it is necessary, is presented. The proposed solution is coupled with a local ABS strategy to guarantee slip stability and make the solution complete. The originality relies on the LPV formulation of the saturation-like function of the allowable braking force directly during the synthesis step. Secondly, the control design methodology aims at using the steering action to control the yaw rate and at limiting the use of the braking actuator only when the vehicle goes toward instability. Judging the vehicle stability region is done from the phase-plane of the side-slip angle and its time derivative, which is used to monitor the car dynamical behaviour. These controllers are both treated in an original way by the synthesis of a parameter dependent controller built in the LPV framework and by the solution of an LMI problem. Nonlinear time and frequency domain simulations, performed on a complex full vehicle model (which has been validated on a real car), subject to critical driving situations, show the efficiency and robustness of the proposed solutions