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A theoretical approach is presented to the quantificaiton of potential cross-country performance limits of an active suspension system. A pitch-plane representation of a wheeled vehicle is used along with the assumption of ideal actuators and perfect terrain knowledge. The geometrical constraints on possible chassis motion imposed by the vehicle and terrain geometry are formulated. Algorithms are developed to determine the optimal (in terms of vehicle ride) chassis vertical and pitch motion trajectories as well as vehicle ride limiting speed as a function of both terrain roughness and allowable suspension travel. Finally, possible active suspension implementation schemes for approaching these ideal performance limits are discussed.

This paper discusses the evolution of commercial active suspension systems and the recent adaptation of this potential dual-use technology to military applications. It contrasts the commercial automotive industry's focus on enhancing on-road ride, stability and handling with the military's objective of increasing off-road mobility. The specific adaptation of a commercially developed active suspension system to the Army's High Mobility Multi-purpose Wheeled Vehicle (HMMWV) is described along with changes required to accommodate this 3000 kg, 4x4 all-terrain vehicle. Resulting design and installation are presented, followed by a brief synopsis of the vehicle's performance. The desire for even greater cross-country performance is discussed as the motivation for pursuing the development of more effective off-road control strategies and the progress in this arena is presented.