On some geometric control properties of active suspensions systems

The geometric control properties of vehicles with active suspensions are analyzed. A special attention is devoted to the problem of disturbance decoupling. Active suspensions of advanced vehicles allow the active rejection of external disturbances exerted on the sprung mass of the vehicle and caused by road surface irregularity. We focus on the road irregularity disturbances with the purpose of isolating the chassis from vibrations transmitted through suspensions. The paper is aimed at the synthesis of a decoupling control law of the regulated outputs, i.e., roll, pitch and chassis height, from the external disturbances. The paper emphasizes that disturbance decoupling can be thought as a structural property of road vehicles with active suspensions. The framework throughout is the geometric approach to the control of dynamic systems. It is shown that a controlled and conditioned invariant subspace exists such that it allows the geometric disturbance localization. The decoupling problem with stability and the algebraic feedback of suspension heights, i.e. the system measurements, are considered. Simulations with real data are included to validate theoretical results. Saturating actuators are also considered in order to model a more realistic case.