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In many cars, ride is less comfortable on smooth roads. This is because when the hysteresis in the suspension components rises steeply, the increase of the equivalent spring constant at small amplitude deteriorates the vibration isolation of the suspension. Therefore suspension components should be designed to prevent a steep rises in hysteresis. Investigating the influence of hysteresis, component models, which can reproduce such hysteresis characteristics, should be installed with model parameters in the vehicle model. Using conventional methods, these parameters can be accurately identified if measurement data is provided; however, it is difficult at the earlier phase of vehicle development. Then, if conflicting performances, such as ride and handling, are to be improved, both should be considered concurrently as early in a phase of vehicle development as possible and the design specifications for suspension components should be determined to satisfy both performances.

This paper presents a validation method for indoor testing of a passenger car suspension. A study was done to design a supporting modular structure with comparable inertances with respect to a vehicle's actual suspension and body connection points. For the indoor test, the rear axle is positioned on a rotating drum. The suspension system is excited as the wheel passes over cleats fixed on the drum and transient wheel motions are recorded. The indoor test rig outputs (i.e., wheel and chassis accelerations) were compared with experimental data measured on an actual vehicle running at different speeds on the same set of cleats along a flat road. The comparison results validate the indoor testing method. The forces and moments acting at each suspension and chassis connection point were measured with a set of patented six-axis load cells. The forces, moments, wheel and subframe accelerations were measured up to 120 Hz.