Ride＆Handling Analysis And Optimization Of Commercial Vehicle With Three Axles

Commercial vehicle with multiaxle has been playing a more and more important rolein national economy due to economic development, booming of transportation andlogistics industry. However, dynamic performance of multi-axle vehicle has not beensufficiently studied so far. With this research background, tri-axle commercial vehicle isstudied by dividing it into two categories: tri-axle vehicle with tandem suspension andtri-axle vehicle with double-front-axle steering system. Both ride and handlingcharacteristics of the two kinds are investigated. The contents of this dissertation can beconcluded as follows:(1) Ride and handling characteristics of the two kinds of vehicle are analysed. Motionequations describing ride behaviour are derived by building half-vehicle model. Based onthe equations, influences of Olley tuning rule on responses of pitch vibration of the vehicleand matching method of natural frequency of front and rear suspension are researched.Next, ratio of sprung to unsprung mass, ratio of tire vertical rate to suspension spring rateand damping ratio, etc are selected as variable parameters to study the influences on RMSof vertical acceleration, suspension travel and dynamic load of the tire.3-freedomsimplified model considering rolling motion of the car body is established to investigatehandling behaviour. Thus equations of motion are derived, considering the influence ofvertical load transfer between left-side and right-side tires on the cornering stiffness.Understeer gradient of both the two kinds are obtained and then, influences of corneringstiffness and axle load on understeer gradient are investigated.(2) Tri-axle vehicle with tandem suspension is taken as an object of study to domulti-objective optimization, which aims to improve both handling and ride performances.After the optimization, feasible Pareto solutions are obtained and illustratedstraightforwardly with ‘spider graph’. According to multi-objective theory,4differentcriteria are employed to select different schemes for the whole vehicle design.The completion of this paper provides a way to analyze dynamic characteristicsqualitatively and quantitatively to some extent. It also has referential significance toresearch on commercial vehicle with more than three axles.