Elastokinematic modeling and study of five-rod suspension with subframe

Multibody, elastokinematic model of a car rear axle composed of two five-rod suspensions with the suspension subframe is studied. A substitute mechanism with rigid links and compliant joints is assumed. Equations of the system static equilibrium and kinematic constraints are written using joint and absolute coordinates, and screw calculus. Elastomeric bushings, installed in the suspension rods and subframe, are included in the model together with the suspension springs, and radial elasticities of the tires. Subsequent stages of the model development and verification, from geometric to elastokinematic models with 1, 6, and 22 degrees of freedom, are illustrated with numerical examples. Issues of the mechanism direct position problem, instantaneous kinematics, screw displacements, and static equilibrium are presented. Verification of the models is based on measurements of the real mechanism disassembled from the car and installed at a kinematic and compliance test stand.