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Ride Confort Analysis and Optimization for a Heavy Commercial Vehicle

Author: JuChengChao
Tutor: HanXu
School: Hunan University
Course: Vehicle Engineering
Keywords: Ride Comfort Heavy Commercial Vehicle Theory of Multi-body System Dynamic Optimization Leaf Spring
CLC: U461.4
Type: Master's thesis
Year: 2009
Downloads: 365
Quote: 6
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Abstract


In this dissertation, heavy commercial vehicles are selected as the research object. The dynamics simulation model of the whole vehicle is constructed based on Multi-Body System Dynamics theories and inverse techniques. Vehicle ride comfort performances are studied by analyzing this model. The influences of suspension system on the vehicle ride comfort performances are also investigated. Then, the performances are improved by optimizing the suspension system.A standard road model is studied and some disadvantages of frequency domain road model are discussed. In order to avoid these disadvantages, a time domain B-level random road model is created by the harmonics superposition theory and the model is validated according to the national criterion of Vehicle vibration-Describing method for road surface irregularity. The root mean square of power spectral density of x-axis, y-axis and z-axis acceleration at the driver’s seat is selected to access the vehicle ride performances.This dissertation proposes a new method to build the leaf spring model combining genetic algorithm and inverse techniques. Leaf spring is built based on the discrete beam theory. Consequently, multi-leaf spring model can be modeled by little piece leaf spring model and the stiffness of the leaf spring can be controlled by the discrete beam parameters. Genetic algorithm is employed as an inverse operator to determine the parameters of the discrete beams. This method has three advantages. First, it simplifies the process of creating the leaf model. Second, it decreases the degrees of freedom of the model. The last but not least, the high accuracy of the model can be maintained.Some aspects of the whole vehicle such as F/R suspension system, steering system, the cab suspension system, tire, frame and body, etc. are analyzed through software ADAMS. The structural form of the subsystems and its parameters are confirmed. The relationships of those parts are defined. Based on the above analysis, a dynamic model of the whole vehicle is established and validated.The simulations of the whole vehicle model under random input running test and pulse input running test are executed. The effect of different speeds, different roads and the main vehicle parameters is investigated. Finally, in order to optimize the vehicle ride comfort performance, the stiffness and damper of the suspension system and the root mean square value of power spectral density at the driver’s seat are selected as the design variables and objective function, respectively. Genetic algorithm is employed to solve this optimization problem. The results show that the vibration responses of the model after optimization are lower than those before optimization. The vehicle ride comfort performance is improved obviously.The research concentrates on the exploration and application of virtual prototyping technology. The designs for vehicle ride comfort performance can be processed on computers. It makes a practical sense for saving the manufacture and time cost in new vehicle developments.

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CLC: > Transportation > Road transport > Automotive Engineering > Car theory > Car ride and comfort
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