Optimal Workload Actuator Balancing and Dynamic Reference Generation in Active Vehicle Control

This paper addresses the problem of vehicle attitude control by means of active front steering and rear torque vectoring in the presence of saturating actuators. A novel approach of actuation balancing is proven to be the optimal way to keep the vehicle off saturation or, at least, to postpone the saturation occurrences as much as possible. To this end, a control law is proposed, achieving the tracking goal while keeping the balancing among the actuators. Exponential tracking is shown in nominal (non-saturated) conditions, where the optimality guarantees that the actuators remain as far as possible from their bounds. However, in hard conditions, saturations may still occur and tracking may be lost. Hence, it is shown how to modify dynamically the reference signals in order to compensate the lack of control action of actuators entering a possible saturation condition. As a consequence, less strict references are obtained and the tracking goal is recovered, while keeping the actuators within their saturation bounds. On top of the formal results, the method is validated by means of simulations performed in a non-ideal setting, including parameter uncertainties and unmodeled actuation delays.