A FIXED PARAMETER OPTIMAL CONTROLLER-DESIGN FOR AN ACTIVE SUSPENSION SYSTEM - A SENSITIVITY ANALYSIS

The function of an automotive suspension system is to maintain passeng er comfort and vehicle road handling capabilities whilst supporting th e body mass of the vehicle and operating within the constraints of the suspension working space. In order to satisfy these criteria the over all suspension system is required to be 'tuned' to provide a satisfact ory compromise: the point at which this compromise is made is an impor tant design parameter and varies from vehicle to vehicle depending upo n its application and may also be required to vary depending upon oper ating conditions. The paper presents results of an extensive sensitivi ty analysis aimed at assessing the effectiveness of an optimal control law design which is based on a low order generalised minimum variance approach applied to a low bandwidth slow active suspension system. Th e control law design is assessed when subjected to an increase in the body mass of the vehicle as well as variations in the tyre spring rate and the conventional suspension elements: the base vehicle under cons ideration being a large luxury saloon car. The results of the sensitiv ity analysis highlight the need for flexibility in the controller cost weightings and reinforce the appropriateness and practicability of us ing a fixed low order model structure in order to achieve further impr ovements in overall ride quality.