Methodology to Determine Optimum Suspension Hard Points at an Early Design Stage for Achieving Steering Returnability in Any Vehicle

Steering returnability while driving is one of the most important parameter which affects the drive pleasure and handling of a vehicle. Steering returnability refers to the automatic returning response of the steering wheel after taking a full turn while vehicle is being steered during driving. Evaluating steering response characteristics of any vehicle in a virtual environment at early stage of a product development saves significant development time and cost. Through this paper an attempt has been made to develop a methodology for selection of suspension hard points which influences steering returnability characteristics of a vehicle at an early product design stage. Conventionally, suspension kinematic parameters such as Caster angle, Steering axis inclination (SAI), etc. are iterated during vehicle design stage to achieve desired Steering returnability. However, at times vehicle level trials indicate that increasing caster angle or SAI does not guarantee a desirable increase in steering returnability. In this new methodology a set of iterative trials are done to vary hard points (X, Y, Z co-ordinates) of Lower ball joint of an independent front suspension to create desired Jacking effect [2] or differential vertical lifting [1, 2] at front wheel end of the vehicle during steer condition to facilitate and impart self-returning motion at steering wheel. Vehicle level test results conducted on a vehicle indicates an improvement in steering returnability by around 50% with reference to the base vehicle in which hard point modifications were incorporated to validate this methodology. This methodology can be applied to other vehicles during their early design stage for faster and first time right approach.