The floating hub: An innovative device to improve vehicle comfort

摘要

The ride and NVH performance of small and medium cars is becoming increasingly important due to the fact that today's customers expect ride and handling performance of a level previously required from larger vehicles and at a lower cost. To respond to these market demands, as regards suspension system design, it is usually necessary to intervene on the Longitudinal Wheel Compliance (LWC) and the Geometrical Wheel Center Locus (GWCL). In simpler suspension configurations, modifying the GWCL necessarily has a significant impact on the overall chassis layout due to the need to raise the forward attachments to the body structure. Correspondingly, for such suspension architectures, attention is currently focusing on the LWC, the challenge being to manage the handling/comfort compromise effectively due to the fact that increased LWC can be detrimental to handling performance through the introduction of compliance-toe effects. While needing to restrict the scope of modification to the LWC, Centro Ricerche Fiat (CRF) has developed an innovative device which can enable the application of simpler types of suspensions, designed to effectively decouple comfort from handling performance. This device, the so-called Floating Hub, aims to manage the principal ride performance characteristics by essentially introducing an additional longitudinal degree of freedom. Excitation due to road surface roughness is filtered without introducing adverse compliance-toe effects due to lateral or longitudinal loads. This article describes the activities performed to develop this solution starting from a twist-beam rear suspension, the objective being to maintain all the advantages related to costs, dimensions, production feasibility, etc., while improving ride and comfort. Tests on a vehicle equipped with the Floating Hub have demonstrated a significant enhancement of ride performance on both uneven roads and during passage over obstacles, without altering the overall handling performance.