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Energy optimal control theory (EOC) is applied to the energy flow control of a hybrid electric vehicle. Since the differential equation is solved analytically, the control law can be easily implemented in real time. Because the objective function is described in power form that permits negative value, not only the energy consumption is minimized but also the energy regeneration by the motor is maximized. In the simulation for the 10-mode driving, it is shown that the fuel cost of EOC is 15% lower than the rule based control (RBC).

Characteristics analysis of hydraulically damped rubber mount (HDM) for vibration isolation in automotive powertrain is very important at the design and development stage of HDM. Fluid-structure interaction (FSI) between rubber parts and fluid flow in chambers in HDM is critical to the frequency-and amplitude-dependent characteristics of HDM. In this paper, an arbitrary-Lagrangian-Eulerian (ALE) based coupling finite element (FE) method is developed to solve fully coupling problem of FSI in HDM. A typical kind of HDM in a vehicle powertrain mounting system composed of rubber spring, two fluid chambers, fluid track and decoupler is selected to investigate performance prediction of HDM. Dynamic characteristic analysis under typical working condition are calculated and compared with experiment results. The agreeable comparison results verify the effectiveness of the presented FSI formulation and characteristic prediction approach of HDM.

To predict dynamic characteristics of hydraulically damped rubber mount (HDM), some key parameters in lumped-parameter model of HDM, such as volumetric elastic characteristics of fluid chambers and equivalent piston cross-section area of upper chamber, must be determined in some special ways because of difficulty in experimental measurement. In this paper, a kind of simulation approach of volumetric elasticity is developed by using finite element (FE) code of ABAQUS on the basis of hydrostatic fluid-rubber interaction modeling method. Contributions of different rubber parts to volumetric elastic characteristics are revealed. Predications of dynamic characteristics and frequency response analysis of a typical HDM with fixed-decoupler verify the effectiveness of the proposed parameter identification method.

In this study, the genetic algorithm so called GA is newly applied for the optimization of many engine mounting parameters, calculations of stiffness matrix and inverse matrix to obtain 6 degrees of freedoms displacements at mounting points and a center of gravity. As a result, the optimized result could be shortly obtained in a minute, and an inexperienced engineer could easily make the optimum engine mounting layout, which can satisfy the vibration isolation and the non-interference in an engine compartment.

This study is motivated from the investigation of vehicle suspension system with changeable damping and variant stiffness parameters. Such suspension system can be modeled as a dynamic polytope based on the mapping of affinely changed parameters. According to the polytopic dynamics decomposition, knowledge of linear time invariant system can be applied to each polytope vertex and the time variant system is solved by the polytope convex synthesis method. For time variant vehicle suspension system, the different model structures for control purposes are formulated. A quarter-car is taken as the example for demonstration in observer design and nonlinear control design.

The design of automobile human safety is a very important design factor, which the car manufacturers have recently focused. Crash tests have provided information on dummy response measurements such as the maximum chest acceleration head injury criteria (HIC) value and femur loading. The subject of this research is an optimal design of the seat belt in consideration of the deformation behavior of a vehicle cabin with the aim of reducing the human injury. The research focuses on the optimization method of taking the comprehensive trade off between the global approximation and computational cost. The optimization approach called Most Probable Optimal Design (MPOD) proposed by the authors is modified to be applicable to the optimization of cabin crash deformation behavior and safety belt with the mixed discrete and continuous design variables. The application example of the Hybrid III dummy model shows that the MPOD technique is effective in saving the computational cost.

This paper presents the polytopic modeling method and state variable observer design approach for semi-active suspension with changeable damping and variant stiffness elements. And such semi-active suspension system is suitable to be modeled as a dynamic polytopic system where the extreme vertices of damping and stiffness values are taken as the convex vertices of polytope. Thus, a dynamic polytopic model is the convex synthesis with all the vertex system dynamics and linear system theory can be applied to the system at each vertex. Herein, the conventional Kalman filter theory is utilized to design the observer for each vertex system, then the polytopic observer is formulated by a convex synthesis. The proposed observer design approach is testified by numerical study and vehicle test.

As an important class of nonlinear system, polytopic bilinear system is investigated. Combined with the properties of convex polytope, the nonlinear control for polytopic bilinear system is formulated by synthesizing nonlinear H∞ controller which is designed for polytopic bilinear system at vertices. For a semi-active suspension system with controllable damping and variant stiffness elements, it is easily modeled as a polytopic bilinear system model. In this case, the desired nonlinear control properties are pursued in making effective use of the changeable damping property while the variant stiffness is taken as the affine parameter of polytopic model. Therefore, polytopic bilinear system model could be reduced to a feasible problem by polytopic convex decomposition. Then the control problem of bilinear system model is to find a solution of nonlinear H∞ control.

Most of the existing control techniques applied to automobiles are based on a linear model of the relevant dynamic system. However, in spite of the increasing demand for more sophisticated vehicles, very little research is being directed toward understanding and predicting the nonlinear response caused by non-predictable operating conditions such as the variation of suspension characteristics due to wear and tear or the frictional coefficient of the road. In this research, we used a neural network based identification technique to predict the structural response of dynamic systems and validated the technique through comparison with experimental data obtained with a cantilever beam. This identification technique is further extended to forecast the frictional coefficient μ of roads. Numerical results indicate promising future applications.

The shape and topology optimization method using a homogenization method is a powerful design tool because it can treat topological changes of a design domain. This method was originally developed in 1988 [1] and have been studied by many researchers. However, their scope of application in real vehicle design works has been limited where a design domain and boundary conditions are very complicated. The authors have developed a powerful optimization system by adopting a general purpose finite element analysis code. A method for treating vibration problems is also discussed. A new objective function corresponding to a multi-eigenvalue optimization problem is suggested. An improved optimization algorithm is then applied to solve the problem. Applications of the optimization system to design the body and the parts of a solar car are presented.

Since interior noise has a strong effect on vehicle salability, it is particularly important to be able to estimate noise levels accurately by means of simulation at the design stage. The use of sensitivity analysis makes it easy to determine how the analytical model should be modified or the structure optimized for the purpose of reducting vibration and noise of the structural-acoustic systems. The present work focused on a structural-acoustic coupling problem. As the coefficient matrices of a coupled structural-acoustic system are not symmetrical, the conventional orthogonality conditions obtained in structural dynamics generally do not hold true for the coupled system. To overcome this problem, the orthogonality and normalization conditions of a coupled system were derived by us. In this paper, our sensitivity analysis methods are applied to an interior noise problem of a cabin model.

The occurrence of various vibrations and noises in an automobile, such as idling vibration, boom noise and road noise, is greatly affected by the natural vibration modes and could be developed for controlling the body strength and weight these problems could be solved and a high-performance vehicle realised. This paper presents an analytical method developed by the authors to solve these problems and gives examples of its application. In developing this method, the problems of natural vibration mode and static stiffness control were addressed. Perturbation and sensitivity analysis methods have already been proposed for mode control. Four typical methods were examined and the best one was chosen in terms of accuracy and calculation time when handling large-scale problems. For static sensitivity analysis, we proposed a nevi method which is like natural mode sensitivity analysis.

In order to calculate efficiently the characteristics of car body vibration and the acoustic characteristic of the passenger compartment, a structural-acoustic analysis system, ‘CAD-B’, was developed. This system divides the body into three components - front body, main cabin and rear body. The characteristics of front and rear body vibration are expressed in modal parameters. The vibration characteristic throughout the car body is then calculated through the building block approach, while the main cabin remains in finite elements. A good agreement in eigen pairs was seen between this approach and the conventional finite element method. As for the passenger compartment, it is divided into finite elements and its eigen pairs are calculated. Then by linking body vibration with the acoustic characteristic of the passenger compartment, sound pressure in the passenger compartment is calculated.

With the increasing demand for smaller automobiles that will conserve natural resources and save energy, and the need to systematize the development of such vehicles by shortening their developmental period and by reducing the number of required experimental vehicles, the analysis of automotive collisions has become increasingly important for us. The analysis of automotive collisions was first conducted by a lumped-mass method, although it has some shortcomings, e.g., it is difficult to make models and it is inappropriate for three-dimensional analysis. Consequently, a finite element method is also presently in use. From the finite element method currently in use, for the purpose, however, a practical level of analysis duration and deformation analysis cannot be expected. Therefore, we have developed a hybrid program called “FEMASS”, which is a combination of the lumped-mass method and the finite element method programs.

This paper describes a non-linear analysis of automobile body structure by the finite element method. Numerical calculations were made for both the roof crush resistance and seat belt anchorage strength of a body structure and were compared with test results. Dynamic analysis was also made by an incremental method similar to that used for the static case. Results calculated for both situations indicate correspondence well with experimental results.