Stiffness Synthesis of a Five-Rod Suspension for Given Load-Displacement Characteristics

Abstract

The paper describes a novel algorithm for solving the synthesis problem of a multi-link wheel-guiding mechanism with a known topology and dimension. The synthesis objectives contain the elastokinematical specifications, described by a set of spatial displacements that the wheel carrier should undergo from a design position under specified loads corresponding to typical car manoeuvres. Radial spring rates of cylindrical elastomeric bushings, embodied in the suspension rods, are considered as design variables. Relations between the design variables and the objectives are established using the first-order kinematics and screw calculus, under assumptions about small displacements and linear force-deflection characteristics of the flexible elements. The problem is solved by using a constrained linear least-squares algorithm. Depending whether the input data is provided by a designer or acquired during suitable experiments, the algorithm can be used for synthesis or estimation of the stiffness parameters. Numerical examples are solved for two five-rod suspensions, with the same topology but different configuration and dimension, installed at rear-driven axles of actual cars. Static spring rates of the five rod-bushings are determined, for which both suspensions satisfy the formulated ride/handling criteria in the best way. Fundamental characteristics and limitations of the suspensions are described.