Fundamental issues in suspension design for heavy road vehicles

Heavy road vehicles play an important role in the economy of many countries by providing an efficient means of transporting freight. Such vehicles can also have a significant impact on safety, the infrastructure and the envir onment. The design of the suspension affects the performance of the vehicle in terms of ride, infrastructure damage, suspension working space, energy consumption, rollover stability, yaw stability, braking and traction. The p ublished literature on suspension design for heavy road vehicles is reviewe d. It is found that extensive knowledge exists, but that there are areas wh ere improved understanding is needed. Areas identified as fundamental issue s requiring attention include ride discomfort criteria, secondary suspensio ns, and controllable suspensions. Two issues in particular are examined in detail: suspension tuning and suspension configuration. In the tuning of suspension parameter values for vibration performance, num erical optimisation techniques have been used extensively, but generic tuni ng strategies have not been widely developed. Modal analysis is proposed as a technique for gaining the insight into vehicle vibration behaviour neces sary to enable tuning strategies to be devised. As an example, the techniqu e is applied to the pitch-plane vibration of a tractor-semitrailer. In analyses of new suspension configurations or concepts, comparison with a lternative concepts is not always made. Lack of such comparisons makes the selection of an optimum concept difficult. Analysis of alternative concepts using simple mathematical models, and comparison of their performance usin g common criteria, is advocated for enabling informed selection of an optim um. An example involving two alternative roll control systems is used to de monstrate the issue.