| With the development of society and the improvement of science technology, automobile industry in the world has been gained remarkable achievements, which is going forward to the direction of safety and comfort and environmental friendliness and energy-efficient, among them, comfort of automobiles specially cars and heavy-duty trucks is important indication and means of people's high quality life and gaining profits of economy. Ride comfort affects directly comfort of automobile. However, research in ride comfort of cars and heavy-duty trucks is fallen behind developed countries, which are not satisfied with increasing fierce competition of auto-technology.For test method applied to prototype automobile has long cycle and wastes plenty of human resources and material resources and financial resources, it is not satisfied with requirements of rapid renovation of modern automobile and short cycle of production and competition among auto manufacturers, modeling and simulation of automobile ride comfort is becoming more and more important.Therefore, the problems of studying ride comfort of cars and heavy-duty trucks have become respectively one part of chassis matching and performance optimization of cars and heavy-duty trucks, which are sub-projects of integration and exploitation of advanced technology of cars (2006AA110102) and heavy-duty trucks (2006AA110104), both are national 863 high-tech research and development projects. Relying on them, new studies of modeling and simulation of automobile ride comfort are carried out and applied in the analysis of ride comfort of cars and heavy-duty trucks in the dissertation. Works in the dissertation are as following.New methods have been given for modeling and simulation of automobile ride comfort. They are frequency field simulation of pseudo-excitation method and the method of mathematical modeling for automobile vibration structure based on ideas of finite element method and the numerical simulation method of time field based on variation theories. They have been applied to study modeling and simulation of automobile ride comfort, good conclusions have been gained.Background and significance are dissertated for automobile ride comfort research. With requirements of cars and heavy-duty trucks increasing, research of ride comfort becomes more and more important for cars and heavy-duty trucks, therefore, research of modeling and simulation is very important for automobile ride comfort. Domestic and overseas status of modeling and simulation is introduced to study of automobile ride comfort, and main contents are defined in the dissertation.Stationary random vibration pseudo-excitation method is a new method for simulation of time-frequency field, but it is seldom applied in auto domain. Based on different characteristics of pseudo excitation, pseudo excitation can be noted as single-point pseudo excitation and generalized-point pseudo excitation and multi-point pseudo excitation. Basic theories of stationary random vibration pseudo-excitation method are discussed from simple to more difficult ones, rigorous derivations are given, which further enrich and perfect theory of pseudo-excitation method.Stationary random vibration pseudo-excitation method is applied to simulation analysis of automobile ride comfort. Steps of pseudo-excitation method applied are introduced for simulation of automobile ride comfort. Different characteristics are compared between pseudo- excitation method and Fourier analysis method. Effectiveness of pseudo- excitation method is discussed for simulation of full automobile ride comfort. Results show that pseudo-excitation method is equal to Fourier analysis method for simulation of automobile ride comfort, but it is better than Fourier analysis method.Based on ideas of finite element method,automobile vibration structure is divided, element and global analysis are done, bind disposals were disposed as forced displacements, then, matrixes of factors for mathematical model of automobile vibration structures, assembly method of matrixes of factors is introduced. Mathematical model of automobile vibration structures is assembled by hand, and effectiveness of method is tested for mathematical modeling. Modules are programmed for element analysis and global analysis and bind disposals. Results show that matrixes of factors of mathematical model can be assembled not only by hand but also by program, flexibility of method is indicated, the problems are resolved for complex of mathematical model of automobile vibration structures and making wrong easily.In order to give a new numerical method for responses of structure system, mathematical foundation is given for deduction of theories. Convolution integral function is obtained for any structure system that mass matrix and damping matrix and stiffness matrix are symmetrical. By formula deduction, its stationary condition is equal to balance equation of balance equation of system vibration. Interpolation functions of vibration response of structure and force on structure are constructed by polynomial interpolation method. Based on Convolution integral function of structure system, a universal step-by-step recursion formula is give. Three-point time element step-by-step recursion formula is given by application of the universal step-by-step recursion formula. The accuracy and precision are proved by stability analysis and practical examples.For nine-degree of freedom vibration structure of full car and thirteen-degree of freedom vibration structure of heavy-duty truck, they are divided by the method of modeling, and mathematical models are constructed. Pseudo road excitations are constructed for the two automobile vibration structure systems. The method is given for statistical characteristics of automobile vibration response variables by time field numerical method.The simulation of time field and frequency field are given based on pseudo road excitations by the combination of three new methods for modeling and simulation. The feasibility and accuracy are proved by modeling and simulation.The creative works in this dissertation are:(1)Basic theories of stationary random vibration pseudo excitation method are discussed deeply, which further enrich and perfect theories of pseudo excitation method. Basic theories of stationary random vibration pseudo excitation method are applied to different automobile structures, the results are same with Fourier analysis method, but it is easier than Fourier analysis method. Pseudo excitation method is applied not only to stationary random vibration analysis but also non-stationary random vibration analysis, therefore, it is better than Fourier analysis method, it is worth studying in auto domain.A new method of mathematical modeling is studied for automobile vibration structures based on ideas of element finite method. It is easy not only to assemble by hand but also to carry out by program. It is easy to apply for engineering staffs. New ideas of modeling are given for structures with vibration of rigid bodies such as torsion vibration of automobile power train. Convolution integral function is obtained for any structure system that mass matrix and damping matrix and stiffness matrix are symmetrical. Its stationary condition is equal to balance equation of balance equation of system vibration. Interpolation functions are constructed for vibration response of structure and force on structure, a universal step-by-step recursion formula of time field numerical method is given by the combination of interpolation functions and convolution integral function.Nine-degree of freedom vibration structure of full car and six-wheel excitations of heavy-duty truck and thirteen-degree of freedom vibration structure with balance suspensions are constructed, a new element is added, which perfects the method of modeling for mathematical model of automobile vibration. Pseudo excitation method and the method of modeling and numerical method are combined, the simulation of cars and heavy-duty trucks are done with them, new and feasible methods are given for automobile ride comfort.
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