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Since the kinematic characteristics of a vehicle suspension are very complex and difficult to understand, CAE techniques must be applied to perform the suspension analysis. In this study, the influences of rear suspension geometry on the handling performances of a large-sized bus are investigated. The bus involved in this study has air spring type rigid axle suspensions with four links. Quasi-static analyses are performed to evaluate the roll characteristics of the front and rear suspension. The quasi-static responses of suspensions are evaluated in terms of roll center height and roll steer. Roll center height is mainly dependent on the vertical displacement of a panhard rod, and the vertical displacements of lower control links affect chiefly the roll steer. The parameter study with the change of rear suspension geometry is conducted to investigate the vehicle handling performance.

At the initial design stage of a new vehicle, chassis layout has the most important influence on overall vehicle performance. Most chassis designers have achieved target performances by trial and error as well as by individual know-how. Accordingly, a general procedure for automatically determining the optimum location of suspension hard points with respect to the kinematic characteristics needs to be created. In this paper, a method to optimize the toe angle in the double wishbone-type front suspension of a four-wheel-drive vehicle is presented using design of experiments, multibody dynamic simulation, and an optimum design program. The handling performances of two full vehicle models having the initial and the optimized toe angle are compared using a simulation of a single lane change maneuver. Front and rear suspensions are modeled as rigid bodies connected by kinematic joints using DADS.