The suspension is an important mechanical system in road vehicles. A typical suspension system consist in links, control arms, bushing, spring, damper and bump-stop. The rigid parts, i.e. links and control arms determine the kinematic of the suspension and the force elements, i.e. spring, damper and bump-stop define the forces that the suspension, with a generalize motion (road irregularities), will apply to the chassis. We can see on Fig. 1, some common suspension systems in passenger cars.
The function of a suspension system can be categories into:
- Ensure the maximum contact between the tires and the road,
- Mantain the wheel in a proper alignment,
- Carry the car and passengers weight.
- Limit the travel distance of the chassis,
- Reduce the vertical accelerations,
- Absorb the impacts of the road (irrugularities, obstacles and holes).
 Rill, G.: Road Vehicle Dynamics - Fundamentals and Modeling, Taylor & Francis, Boca Raton, 2011.