An effective multibody and genetic algorithm approach to active tyre-suspension-seat system design

The factors contributing to the arousal of the feeling of comfort perceived by passengers travelling on a vehicle are multiple and subjectively variable. In a strictly vibrational field, however, this feeling can be rigorously made dependent on the tyre-suspension-seat dynamic system, driveline and engine vibrations. Over the years, many different criteria and models have been developed to enable the optimal estimation of the design parameters for these systems. It is widely accepted that acceleration and its variation are the most detrimental parameters that impact the physical comfort of passengers. In conventional passive suspension systems, the spring-damper characteristics may be adjusted to emphasise only one of several conflicting objectives, such as passenger comfort, road holding, and suspension deflection. In active suspension systems, on the other hand, the feedback-controller actuator assembly allows the designer to balance these objectives in a more efficient manner. Some limitations of this approach are related to the extremely wide spectrum of magnitude and frequency of external forces that the tyre-suspension-seat system must be able to control and mitigate. The numerous models and systems of optimisation that have been developed do not generally consider time exposure limits established by unification agencies and road authorities. This paper presents an active tyre-suspension-seat system control for passenger cars, utilising both a non-linear multibody model and Genetic Algorithm (GA) controls. The developed active tyre-suspension-seat system control also allows various time exposure limits and an active damping element to be considered. The minimisation of seat acceleration in the entire frequency spectrum has been obtained by considering an active control and passive mechanical parameters concurrently as design variables, using 3 degrees-of-freedom (DoF) multibody model of a quarter car body and wheel assembly. Road Roughness is used to determine vertical component acceleration, treated as the input variable in the GA control. The results of simulations and experimental data drawn from a case study verified that the proposed active system is very effective at isolating passengers from vibration.