Synthesis of a Vehicle Suspension with Constrained Lateral Space using a Roll-plane Kineto-dynamic Model

The larger chassis space requirements of hybrid vehicles necessitates considerations of the suspension synthesis with limited lateral space, which may involve complex compromises among performance measures related to vehicle ride and handling. This study investigates the influences of suspension linkage geometry on the kinematic and dynamic responses of the vehicle including the wheel load in order to facilitate synthesis of suspension with constrained lateral space. A kineto-dynamic half-car model is formulated incorporating double wishbone suspensions with tire compliance, although the results are limited to kinematic responses alone. An optimal synthesis of the suspension is presented to attain a compromise among the different kinematic performance measures with considerations of lateral space constraints. In the kineto-dynamic model, the struts comprising linear springs and viscous dampers are introduced as force elements. Kinematic formulations of the proposed model are derived using displacement matrix method. The kinematic responses, particularly the variations in the camber angles and the wheel track width are investigated under wheel vertical displacement, chassis roll, and simultaneous inputs of wheel center displacement and chassis roll. The results attained from a sensitivity analysis suggested that variations in the joint coordinates could yield reduction in the lateral space, while these would involve complex compromises among the kinematic responses of the suspension. A composite objective function of camber angle and track width measures under wheel vertical displacement and chassis roll excitations is subsequently formulated and solved with constraints on variations in the roll center height and the suspension lateral packaging space to seek optimal joint coordinates. The proposed synthesis with optimal joint coordinates could yield nearly 10% reductions in the lateral packaging space, and camber angle and wheel track variations with only minimal increase in the peak roll camber.