Mathematical Model for Kinematic Analysis of McPherson Strut Suspension

Kinematic inputs such as camber, caster variation are very important for design of any suspension setup. Usual procedure is to get these inputs from kinematic software. But every designer cannot have this software & one has to learn them too. We have developed a method for kinematic analysis of McPherson strut type suspension which can be implemented on easily available and familiar software like MS Excel. Results obtained are in correlation with results from commercially available mechanism tools such as Pro mechanism. All links in suspension layout are considered as rigid. Vector calculus and other mathematical methods have been used to come up with final solution. Inputs required for mathematical program are suspension hardpoints, Lower arm angle from design orientation as wheel travel input and Rack stroke as steering input. Suspension characteristics which can be derived by using proposed mathematic model are curves for camber, caster, toe change &curves for bump and rebound steer. Also we can get changed position of hardpoints for any given wheel and rack travel. Designer can play with hardpoints using this tool to get desired wheel motion & to tweak camber, caster and bump steer curves as per vehicle level targets.