Multi-objective qLPV H∞/ H2 control of a half vehicle

The main role of suspensions is to improve comfort by isolating the vehicle chassis to an uneven ground and to provide a good road holding to ensure passenger safety. Suspension control of quarter vehicle have been widely explored the past few years to improve vertical movements either by applying LQ [9], Skyhook [11], H∞ control [7], [16], LPV [4] or mixed synthesis [1], [14]. Roll dynamic is catched by the half vehicle model and is directly linked to suspension behavior. Separated synthesis on each suspension can’t guarantee global performances. The aim of the mixed H∞/ H2 control synthesis is to treat the standard H2 and H∞ optimal control problems as separate problems but in a unified state-space framework. This method yields a compensator that combines the H2 quadratic performance criterion for disturbance rejection with the H∞ performance criterion for maximum robustness against destabilizing uncertainties. It means, the controller which minimizes the H2 performance index is selected from the suitable H∞ controllers, thus the desired criteria are met by creating a balance between H2 and H∞ norms [3]. The mixed qLPV H∞/ H2 method is proposed here for the design of active suspension system, in which different optimization criteria are applied to guarantee the performance specifications and the nonlinearity of the suspension system. The nonlinearity in the suspension system is caused by the changes in the spring and damping coefficients. It is assumed that the nonlinear dynamics of road vehicles is approximated by LPV (qLPV) models, in which nonlinear terms are hidden with newly defined scheduling variables and they are available from calculated signals. The active suspension based on the LPV model takes the nonlinear dynamics of the system into consideration. Performance