Multi-objective optimisation of quarter-car models with linear or piecewise linear suspension dampers

A systematic methodology is applied leading to optimum selection of the suspension damping and stiffness parameters for two degree of freedom quarter-car models, subjected to road excitation. First, models involving passive damping with constant or dual rate characteristics are considered. Then, models where the damping coefficient of the suspension is selected so that the resulting system approximates the performance of an active suspension system with sky-hook damping are also examined. For all these models, appropriate methodologies are first employed for locating the motions of the vehicle resulting from passing over roads of a given geometric profile with constant horizontal speed. Three suitable performance indices are then defined, whose optimisation yields the most important suspension stiffness and damping parameters. Since these indices are conflicting, a suitable multi-objective optimisation methodology is set up and applied. As a result, a series of diagrams with typical numerical results are obtained and presented in both the corresponding objective spaces (in the form of classical Pareto fronts) and parameter spaces, for vehicle models running over roads involving an isolated or a distributed geometric irregularity.