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The ride performance potentials of a prototype torsio-elastic axle suspension for an off-road vehicle were investigated analytically and experimentally. A forestry vehicle was fitted with the prototype suspension at its rear axle to assess its ride performance benefits. Field measurements of ride vibration along the vertical, lateral, fore-aft, roll and pitch axes were performed for the suspended and an unsuspended vehicle, while traversing a forestry terrain. The measured vibration responses of both vehicles were evaluated in terms of unweighted and frequency-weighted rms accelerations and the acceleration spectra, and compared to assess the potential performance benefits of the proposed suspension. The results revealed that the proposed suspension could yield significant reductions in the vibration magnitudes transmitted to the operator's station.

The influences of fluidic X-coupling of hydro-pneumatic suspension struts on the various suspension properties are investigated for a sport utility vehicle (SUV). The stiffness and damping properties in the bounce, pitch, roll and warp modes are particularly addressed together with the couplings between the roll, pitch, bounce and warp modes of the vehicle. The proposed X-coupled suspension configuration involves diagonal hydraulic couplings among the different chambers of the four hydro-pneumatic struts. The static and dynamic forces developed by the struts of the unconnected and X-coupled suspensions are formulated using a simple generalized model, which are subsequently used to derive the stiffness and damping properties. The properties of the X-coupled suspension are compared with those of the unconnected suspension configuration, in terms of four fundamental vibration modes, namely bounce, roll, pitch and warp, to illustrate the significant effects of fluidic couplings.

The optimal damping design of roll plane interconnected hydro-pneumatic suspension is investigated, in order to improve vertical ride and road-friendliness of heavy vehicles, while maintaining enhanced roll stability. A nonlinear roll plane vehicle model is developed to study vertical as well as roll dynamics of heavy vehicles. The damping valves and gas chamber are integrated within the same suspension strut unit to realize compact design. The influence of variations in damping valve threshold velocity on relative roll stability is explored, under centrifugal acceleration excitations arising from steady turning and lane change maneuvers, as well as crosswind. The effects of damping valve design parameters on the vertical ride vibration and vehicle-road interaction characteristics are also investigated under a medium rough road input and two different vehicle speeds.

This study investigates influence of compressible hydraulic fluid and suspension floating piston dynamics of fluidic suspensions on heavy vehicle roll stability and ride dynamics. Two fluidic suspension designs, including a single-gas-chamber strut and a novel twin-gas-chamber strut, are analyzed to develop the mathematical formulations of dynamic forces, upon considerations of hydraulic fluid compressibility and floating piston dynamics. Dynamic responses of the heavy vehicle with the different suspension configurations are then performed using a nonlinear roll plane vehicle model. The excitations arise from vehicle-road interactions as well as a steady steering maneuver. The results demonstrate that the compressibility characteristic of hydraulic fluid within a hydro-pneumatic suspension could affect the vehicle roll stability and ride dynamics, while the influence of suspension floating piston dynamics on vehicle dynamic responses is negligible.