Vehicle Suspension Design Based on a Six-Bar Linkage

Abstract

A synthesis technique for designing novel vehicle suspension linkages based on the Watt I six-bar is presented. The goal is to maintain near vertical alignment of the wheels to the road during cornering. The complete suspension is analyzed as a symmetric planar 12-bar linkage with ground pivots located at the contact patches. The design procedure specifies the vehicle chassis orientation and the tire camber angles of the vehicle when cornering. As well, two task positions of the wheels with respect to the chassis are specified for suspension movement in straightaways. The result is 18 design equations with 18 unknowns that have a total degree of 2,097,152, though only 336 roots. An example design is presented. INTRODUCTIONThis paper presents the synthesis theory for novel automotive suspension designs based on the Watt I six-bar. The motion objectives of the synthesis are (i) to guide the chassis and wheels of the vehicle into a specified pose when cornering, and (ii) to guide the motion of the wheels through two task positions with respect to the chassis suitable for straightaways. This motion specification is equivalent to solving for four task positions of the wheel with respect to the chassis. In order to specify our motion objective we adopt two planar linkage models. They are a Watt I six-bar with base pivots b and c attached to a fixed chassis (Fig. 1), and a symmetric 12-bar with base pivots N R and N L