Optimal synthesis of a two-stage asymmetric damper of an automotive suspension considering wheel camber variations

Abstract

The influences of damper asymmetry on the camber angle variations of a double wishbone type of suspension, together with the dynamic responses under measured urban road inputs at different vehicle velocities, were investigated. Simulation studies employing a kineto-dynamic quarter-car model comprising a bilinear damper revealed complex dependence of the dynamic and kinematic responses on the vehicle forward velocity. The study further revealed an increase in camber angle variations with an increase in damper asymmetry, while this increment showed a non-linear relationship with the suspension deflection. The camber angle variation under road inputs thus poses an additional design compromise apart from those associated with the well-established conflicting measures of ride comfort, rattle space, and road-holding properties. The study also investigated the synthesis of an optimal two-stage asymmetric damper to yield a compromise between these conflicting performance measures under road inputs at different vehicle forward velocities with consideration of minimal camber angle variations. A composite performance index, comprising the ride comfort and road-holding measures with limit constraint on camber angle variation, was formulated to seek optimal damper parameters. The results showed that an optimal asymmetric damper could be identified to yield acceptable design compromise over a wide speed range.