|
The vast majority of suspension systems widely used in road vehicles by all major manufacturers are passive. They have a unique force - displacement or speed - force characteristic, imposed by the characteristics of the constructive elements used. However, for the suspension system of the vehicles, to optimally perform on the widest possible areas of the road unevenness, adaptive suspension systems have been developed. These systems can be either semi-active or active. The main problem that these suspension systems have to answer is the maximization of traction. This involves maintaining permanent contact between tire and road, while also ensuring increased passenger comfort. Passenger comfort, on the other hand, requires smooth damping, with as little chassis acceleration as possible. Under these conditions, it is impossible for passive systems to meet these requirements, and a compromise between comfort and safety is always necessary. For these reasons, adaptive systems have been developed that allow the shortcomings of passive systems to be eliminated, being able to ensure optimal behavior for the entire frequency range offered by runway irregularities. Semi - active systems usually use dampers with variable parameters, dictated by various controllers such as proportional, derivative, integrative or various combinations thereof. This paper aims to simulate and analyze a passive suspension by referring to the characteristics of a semi-active. The study evaluates the vertical movements of a vehicle with known parameters over different shapes of the cross section of the road. The study involves the use of the Matlab-Simulink environment in which a physical study model for the quarter machine model is made, using the predefined blocks found in Simscape. According to the obtained results, there is a substantial change in the damping characteristic when using the semi-active suspension, in order to reduce the oscillations and shorten the time to reach equilibrium.
|
