Road Transport Vehicle Coupling Vibration Analysis And The Multi-objective Optimization

The vibration problems regarding the road transport vehicle focuses on two aspects: the ride comfort and the cargo safety.The ride comfort has been investigated carefully and improved greatly due to the character of the road transport: long-time driving.Comparing to the ride comfort,the vibration at the carriage should be considered as important as that of the cab since the vibration reduction of the carriage could guarantee the safety of the packages,and the benefit effect would be more significant for the spectial tranportations such as the medical treat and the spectial euquipment deliever.In this thesis,the vibration problem of the whole car and the subsystem of a threeaxle road transport vehicle was investigated through multibody dynamic simulation and field measurement.In the study on the mathematical modelling and solving method of the whole vehicle dynamics,the power density spectra of several sorts of road roughness were generated based on the ISO standard,dynamic models of a quarter car,a half car and a whole car were derived,the equations of motion were solved using Newmark-?,Runge-Kutta,Hamming and Finite differential methods.Considering the research demand,the response precision and the computational cost,comparisons between various models and solving methods indicate that the 7 degrees-of-freedom model combined with Hamming or Runge-Kutta method provide the most precise result.These two combinations show similar performance in the calculation of the dynamic load coefficient,however,the Runge-Kutta method show a higher accuracy in the prediction of the vertical acceleration of the car body.To analyse the vibration coupling and attenuation between different subsystems of the vehicle.Based on the state space theory,a simuation method of the vibraton coupling and attenuation of a multi-support system was proposed and applied in a three-axle vehicle.The dynamic model was developed through consider the whole vehicle as a typical single base and multiple upper bodyies system consisted of a cab,a carriage and a chassis.After the verification of the dynamic model of the vehicle according to the vertical accelerations at the driver seat rail and at the carriage centre recorded in a field test,a design of experiment was conducted using the Latin Hypercube sampling method in which the mass properties,the stiffness and damping coefficients of the mounts and suspensions,and the geometries were taken as the design parameters.The sensitivities of the dynamic response with respect to the design parameters were identified and the main effect that how the design parameter affect the response was also investigated.To minimise the vibraton coupling effects between the subsystems and to maximise the vibration attenuations between the subsystems,multi-objective optimisations were carried out using four algorithms: the multi-objective particle swarm optimisation,the adaptive simulated annealing algorithm,the neighborhood cultivation genetic algorithm,and the non-dominated sorting genetic algorithm in order to compromise between the trade-off of the vibration coupling and the vibration attenuation.The four optimal designs from differet algorithms all show better vibration performance comparing with the baseline vehicle.The r.m.s.accelerations of the vertical vibration are decreased 60% at least at different vehicle speeds.