Integrated vehicle control through the coordination of longitudinal/lateral and vertical dynamics controllers: Flatness and LPV/H ∞ based design
Résumé
This paper deals with Global Chassis Control (GCC) of ground vehicles. It focuses on the coordination of suspensions and steering/braking vehicle controllers based on the interaction between the vertical and lateral behaviors of the vehicle. Indeed, the roll motion of the car can generate increasing load transfers that affect considerably the suspension system and vehicle stability. The load transfers can be described using the lateral acceleration. Then, the coordination is highlighted, in this work, through the relationship between the suspension behavior and the lateral acceleration in the framework of the Linear Paramter Varying (LPV) approach. The proposed control law is designed in hierarchical way to improve the overall dynamics of the vehicle. This global control strategy includes two types controllers. The first one is the longitudinal/lateral nonlinear Flatness controller. Based on the adequate choice of the flat outputs, the flatness proof of a 3DoF two wheels nonlinear vehicle model has been established. Then, the combined longitudinal and lateral vehicle control is designed. The algebraic estimation techniques have been used in order to have an accuracy estimation of the derivatives and filtering of the reference flat outputs. Such control strategy is developed in order to cope with coupled driving maneuvers like obstacle avoidance via steering control and stop-and-go control via braking or driving wheel torque. The second part of the proposed strategy consists of the LP V /H∞ suspension controller. This controller uses the lateral acceleration as a varying parameter to take into account the load transfers that affects directly the suspension system and therefore to achieve the desired performance. The coordination between the vehicle vertical and lateral dynamics is highlighted in this study, and the LP V /H∞ framework ensures a specific collaborative coordination between the suspension and the steering/braking controllers. Simulations on a complex full vehicle model have been validated using experimental data obtained on-board vehicle, with an identification procedure on a real Renault Mégane Coupé.
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