CHARACTERIZATION OF AUTOMOTIVE DAMPERS USING HIGHER-ORDER FREQUENCY-RESPONSE FUNCTIONS

Automotive dampers are an important element of a vehicle's suspension system for controlling road handling and passenger ride comfort. Many automotive dampers have non-linear asymmetric characteristics to accom modate the incompatible requirements between ride comfort and road han dling, thus the ride comfort engineer requires techniques that call ch aracterize this non-linear behaviour and provide models of the dampers for use in ride performance simulations of the full suspension system . The work presented in this paper is concerned with developing a freq uency domain technique using higher order frequency response functions (HFRFs) to characterize a Monroe automotive damper. The principal dia gonals and multidimensional surfaces of the HFRFs up to third order ar e obtained. Non-linear damping coefficients for the damper are derived from the HFRFs and the energy transfer properties are investigated. T he results show that the majority of the HFRFs contain no peaks or res onances, indicating that the damper has no preferred frequencies far e nergy transfer. The accuracy of the damping coefficients determined fr om the HFRFs is poor. This is due to the inability of the technique to measure the pure HFRFs and separate the effects of non-linearities in the input actuator from those in the damper. It is concluded that the se constraints currently impose some limit on the use of the methodolo gy.