Nonlinear Vibration And Control Of The Vehicle Suspension System Under The Consecutive Speed-control Hump Excitation

Speed control humps (SCH) is a traffic safety facility for vehicle speed limit anddriving safety by causing vehicle vibrations so that force drivers to lower their speedactively via increase road irregularities. The vehicle and road vibrations will happenwhile the vehicle is passing over the SCH, in particular, since the vehicle contains a lotof nonlinear components, nonlinear vehicles under the consecutive SCH excitationsmay cause complicate nonlinear phenomenon such as bifurcation and chaoticvibrations. These nonlinear behaviors could cause vehicles vibration intensified, noiseincreasing, components wear or road early fatigue damage, which will induce thethreat of ride comfort and driving safety. Therefore, the study on nonlinear dynamicssuch as bifurcation and chaos and its suppression methods based on mechanicalmechanism will be an important subject.This thesis aims at the severe vibration phenomenon induced by the consecutiveSCH and roadside humps on highway, investigating the nonlinear dynamics problemsin the nonlinear vehicle suspension under the coupling excitations between consecutiveSCHs in the form of periodic laid and speed of vehicle. The coupling SCH-speed roadexcitation is established, and the geometric structure of consecutive SCHs is simulatedas the synthetic waveform of a trapezoidal wave and a square wave. Nonlinear halfvehicle suspension model (1/2vehicle suspension model with Four degree of freedom(DOF)) will be studied by analyzing the structures and nonlinearity of the vehiclesuspension. The nonlinear dynamics characteristics are investigated by simulation, andthen the effects of the different nonlinear states on system vibrations are discussed.Two effective approaches to eliminate the influence of nonlinear states on vehiclevibrations are investigated, based on nonlinear active suspension, sliding mode control(SMC) strategy is designed for controlling nonlinear vibration in the vehiclesuspension.Based on the relative studies about nonlinear vibrations occurred in nonlinearvehicles with the excitation of the consecutive SCHs road surfaces, the studied topicwill provide helpful experience for the nonlinear mechanical problems about nonlinearvehicle suspension model under complex road excitation, and it will also deepen ourunderstanding of chaotic vibrations in actual mechanical systems, rich the knowledge of chaotic vibration and control theory, which has two aspects of value both on thetheory and the actual.