A Comprehensive Method for Computing Non-Linear Elastokinematic Properties of Passenger Car Suspension Systems: Double Wishbone Case Study

Suspension and steering design play a major role in ensuring the correct dynamic behaviour of road vehicles. Passenger
cars are especially demanding from this point of view: NVH and ride comfort requirements often collide with active
safety-related requirements such as road holding in steady-state conditions and stability in transients. Driving pleasure is
also important for market success, therefore accurate steering feedback and predictable handling properties are additional
priorities.
Since flexible bushings are used as interface between the suspension arms and the chassis, extra degrees of freedom make
the design process a complex task. While the use of a multibody software is common practice in the industry, a dedicated
computational tool can be more practical and straightforward, especially when undertaking the design of a new suspension
concept ground-up.
The paper presents a computational methodology for the design of an independent suspension with the associated
kinematic and compliance attributes. Typical elastokinematic properties like toe, camber, wheelbase, and track variations
vs tyre forces and moments can be computed by means of a dedicated software tool. A sort of validation was performed
either by means of a comparison with a MathWorks Simscape® Multibody based model. Finally, a sensitivity analysis is
given as an example.
Computationally, the method proposed is intuitively based on the equilibrium equations. The nonlinear equations are then
solved with Newton-Raphson algorithm. The method can be also optimized for computational efficiency and is
thoroughly described so that the reader can easily replicate it in the desired programming environment.