Functional vehicle dynamics simulation differs from the regular multi-body simulation especially by means of modeling parameters. The models are usually parametric, involving suspension properties that are commonly used by OEM's. Input data for a multi-body simulation (MBS) is, normally, raw information about suspension hard points coordinates, flexible elements stiffness (such as bushing and springs), etc. As for a functional simulation, the input data can be one outcome of a multi-body one, such as K&C data or even measured data of a bench test. However, the results of both ways of simulation must be the similar.
Functional simulation software does not solve the multi-body equations for each integration step as any regular MBS software and, as such, can run the model in a faster way. In this way, software-in-the-loop and hardware-in-the-loop starts to become a clear advantage of these art of simulation. However, even at early stages of a project, functional simulation plays also an important role in the sense of building up models in a fast way, not requiring much engineering time to get results from CAE models.
Using functional simulation approach, a mathematical vehicle model was developed based mainly on the kinematic and compliance data of the both front and rear suspensions. Different maneuvers were validated against measured data in order to certify the modeling for different conditions. Using this model, a sensitivity analysis was done identifying the main steering parameters (scrub radius, caster trail, lateral and longitudinal offset) that influence the most a few dynamic characteristics such as steering returnability, dynamic torque and on center feeling of the vehicle. Using a functional simulation, the sensitivity analysis can reveal information not possible for a multi-body analysis, since such steering parameters cannot be change individually, without changing K&C properties. This information represents strategical advantage on pre-project stages, since it will lead the suspension conception choice for a given set of attributes demand for vehicle dynamics.
