Hydraulically Interconnected Vehicle Suspension: Optimization and Sensitivity Analysis

Abstract

This paper extends recent research on vehicles with hydraulically interconnected suspension (HIS) systems. Such suspension schemes have received considerable attention in the research community over the last few years. This is due, in part, to their reported ability to provide stiffness and damping rates dependent on the suspension mode of operation (i.e. the bounce, roll, pitch, or articulation of the unsprung masses relative to the sprung mass), rather than relying on the stiffness and damping characteristics of the single wheel stations. In this paper, the optimization of such a system is considered. Use is made of a previously derived four-degree-of-freedom model of a roll-plane half-car fitted with a typical antiroll HIS system. Objective functions are then developed, based on the desire to improve ride comfort and to minimize suspension working space and tyre normal force fluctuations. With this formulation, a large number of optimal solutions are found and presented graphically, and the performance limitations and trade-offs between the desired objectives are illustrated. To contextualize these results, a similar optimization process is applied to a half-car with a conventional independent suspension. Four optimal parameter combinations are then selected as base points for further examination of the HIS vehicle. This is done by way of a basic sensitivity analysis, based on the local method, which involves single-parameter perturbations about a base point. The objective of the paper is to outline the dynamic performance, trade-offs, and limitations of an HIS-equipped vehicle, and to identify the system's most important parameters.