Dynamic simulation of semi-active suspension systems for durability analysis

The benefits of vehicles with semi-active suspension systems have been widely accepted, mainly for improvement in ride and handling, over the passive system. However, the durability of the suspension components resulting from this implementation received very little attention. Therefore, this research aims to examine the effect of employing a selection of semi-active control strategies on the components' durability. To achieve this early in the design cycle, accurate representations of the load histories must be generated as these histories are the prerequisite in predicting fatigue life. This requires an alternative modelling and simulation approach capable of combining the complexity of vehicle suspensions with semi-active controller models, and at the same time capable of maintaining accurate dynamic responses. In realizing this objective, a multi-body cosimulation approach has been proposed to predict these loads. Initially, efforts are centred on verifying the proposed method against conventional modelling and simulation techniques. This is followed by the evaluating the responses of vehicle suspension models of different complexities fitted with a selection of semi-active control strategies when subjected to transient and random road inputs. In an attempt to demonstrate the flexibility of MBS cosimulation, a magnetorheological damper model derived from experimental data is introduced,in which its dynamic characteristics and dynamic response are examined. It is concluded that the proposed method is capable of producing reasonably accurate load histories but at the expense of increasing solution time. Evaluation of the durability of a lower suspension arm of a multi-purpose passenger vehicle suggested that the two state semi-active strategies with skyhook damping control produced shorter fatigue life than from the conventional passives suspension systems.