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Technical Paper

Factoring Nonlinear Kinematics into New Suspension Design: A CAE Approach to Vehicle Roll Dynamics

Over the past several decades, vehicle dynamics have been treated mainly on the basis of linear theories. An actual vehicle, however, also shows nonlinear properties such as roll behavior induced by movement of the roll axis. The purpose of this study was to investigate the vehicle roll dynamics in the nonlinear range. Suspensions were divided into two categories and computer-aided engineering (CAE) was used to conduct analyses of complicated kinematics. The results obtained provided theoretical support for designing the Multi-Link Beam Rear Suspension, a new type of suspension for front-wheel-drive cars.
Technical Paper

A Voxel-Based Approach to Structural Analysis That Includes Consideration of Contact Conditions

A voxel model, which consists of minute cubic cells called voxels to express the shape of an object, can now be generated automatically from CAD data. Moreover, advances in high-speed computational techniques have made it possible to perform a structural analysis using such a voxel model. This paper presents some high-speed computational techniques to realize the analysis in practice and a method to treat a contact condition on the jagged surface that characterizes a voxel model to further expand the scope of application.
Technical Paper

Application of a Control System CAD Program to a Study of an Electronic Engine Control System

Automotive electronic control systems have tended to become more complex in recent years as a result of stronger requirements for environmental friendliness and higher levels of driveability. The first step in developing a control system is to study the required logic and system configuration at the initial stage of new vehicle development. The authors have incorporated an engine-vehicle model in a control system CAD program to simulate the logic needed for various control tasks. This paper presents a typical application in which a behavior of some outputs, such as engine torque and acceleration, was analyzed, and the electronic controls needed to assure driveability were identified. The construction and operation of a controller-in-the-loop system are also described.
Technical Paper

A New CAD/CAM System for the Car Design Process

Sophisticated product designs enrich people's lives and social demands for creation of good designs are quite strong. In the automobile industry, good design quality is one of the principal factors for determining market competitiveness. In this situation where good design quality is required of every product, the authors have developed a CAD/CAM system which makes it possible to create good and accurate designs by translating designers' ideas directly and quickly into high quality CAD models, a capability that has long been desired. With this high performance system, freely formed curves and surfaces can be easily manipulated with a man-machine interface familiar to industrial designers accutomed to the conventional design process. The system also integrates photo-realistic rendering, stereography and NC milling machines for verifying differences between the realized shape and the image in the designer's mind.
Technical Paper

Development of a New Multi-Link Rear Suspension

Nissan is installing a newly developed multi-link rear suspension in its new 240SX model. This suspension achieves maximum improvement in handling and stability through unique toe control, enhanced dynamic geometry and optimized alignment. The incorporation of attitude control also works to provide flat ride characteristics by greatly mitigating jacking up and squatting motions. This paper discusses the development objectives, results of CAD/CAE analyses and experimental data obtained in tests of the new suspension installed in the 240SX.
Technical Paper

Application of the AI Technique to a CAD System for Automobiles

An expert system has been developed for use in designing exhaust tube layout. Featuring artificial intelligence (AI) techniques, this system is included in our CAD system. It provides designers with information for detecting and correcting design mistakes, based on a body of rules consisting of design standards and accumulated know-how. As a result, it shortens design time and reduces errors. This system is also useful for standardizing design procedures and transmitting techniques accurately. This paper describes the new system and application to exhaust tube layout design. It discusses various problems that must be solved in applying AI techniques to the automobile design process as well as areas and methods of application.
Technical Paper

Development of ROM Management and Evaluation System for Electronic Transmission Control Units

Electronic control of automatic transmission systems have become indispensable in order to satisfy driver expectations of comfort and vehicle response. The increasing complexity of such systems has resulted in a huge increase of control data volumes handled by electronic transmission control units (ETCUs). This paper describes the development, operation and evaluation by JATCO Corporation and Nissan Motor Co., Ltd of a Read Only Memory (ROM) management system for use with ETCUs. The system makes extensive use of computer aided design(CAD) techniques to create ROM data from standard format drawings, and vice-versa. The paper also presents the evaluation system developed for ETCU use. Making use of computer simulated testing, this increases the reliability of units and reduces testing time.
Technical Paper

Development of an Integrated Design Database System

A conventional CAD system is aimed primarily at making the work of creating design drawings more efficient. There are limits, however, to further improvement of design efficiency and design quality with such a system. What is needed is a CAD system that allows design information of various kinds to he compiled for ready access and exchange among designers. To realize a system of this sort, first of all a means was devised of putting into standard format the design information that needs to be included in product design drawings, and of storing this information in a database. These standard drawings are then used in creation of new drawings, by means of an editing process. Moreover, this integrated design database system allows designers to exchange information related to the design work online, in the form of drawing elements.
Technical Paper

Discharge Regulator of Painting Robot and Establishment of CAD Teaching System

The current spray painting system is hardly considered that the thickness is controlled enough, because the temperature greatly influence on the viscosity of paint. We noticed the problem and detected the temperature at a nozzle of a spray unit. We tried that the paint flow is controlled to get stable thickness more accurately by the temperature feedback system. We also tried to develop the new programming method of robots. This new offline programming system provided us an ideal positions and orientations of the spray gun mounted on a robot wrist, after several simulation in the CAD system. We checked and debugged the office taught date with a trial robot in a trial area, and then loaded down with the date to a target robot. We eventually provided a better production technology with the paintflow control system together with the new CAD based offline programming system.
Technical Paper

Evaluation of an Open-grill Vehicle Aerodynamics Simulation Method Considering Dirty CAD Geometries

In open-grille vehicle aerodynamics simulation using computational fluid dynamics, in addition to basic flow characteristics, such as turbulent flow with a Reynolds number of several million on the bluff body, it is important to accurately estimate the cooling air flow introduced from the front opening. It is therefore necessary to reproduce the detailed geometry of the entire vehicle including the engine bay as precisely as possible. However, there is a problem of generating a good-quality calculation grid with a small workload. It usually takes several days to a week for the pretreatment process to make the geometry data ‘clean’ or ‘watertight’. The authors proposed a computational method for complex geometries with a hierarchical Cartesian grid and a topology-independent immersed boundary method with dummy cells that discretize the geometry on a cell-by-cell basis and can set an imaginary point arbitrarily.
Technical Paper

Color Shading Technology for Design CAD Systems

ONE ISSUE IN NEW VEHICLE DEVELOPMENT that has become increasingly more important is the need to put attractive vehicles on the market at the right time. In recent years vehicle design has become a very crucial factor in this effort. Automakers are required to create vehicles having a higher quality design in a shorter period of time and supply them to the market in a timely fashion. As part of the effort to meet these requirements the automakers have developed a variety of CAD/CAM systems, which counterparts in Industry in general. Although most CAD/CAM systems are currently being used primarily at the design and manufacturing stages, the full potential of CAD systems has yet to be realized at the design stage. At Nissan, we have developed a CAD styling system called the Digitized Image Modeling System (DIMS), which serves as a support tool for the creation of new vehicle designs.
Technical Paper

Application of CAP to Analyze Mechanisms Producing Dummy Injury Readings under U.S. Side Impact Test Conditions

Evaluations of dummy injury readings obtained in regulatory crash tests and new car assessment program tests provide indices for the development of crash safety performance in the process of developing new vehicles. Based on these indices, vehicle body structures and occupant restraint systems are designed to meet the required occupant injury criteria. There are many types of regulatory tests and new car assessment program tests that are conducted to evaluate vehicle safety performance in side impacts. Factoring all of the multiple test configurations into the development of new vehicles requires advanced design capabilities based on a good understanding of the mechanisms producing dummy injury readings. In recent years, advances in computer-aided engineering (CAE) tools and computer processing power have made it possible to run simulations of occupant restraint systems such as side airbags and seatbelts.
Technical Paper

Method of Fatigue Life Estimation for Arc–Welded Structures

Two working groups in the JSAE Committee of Fatigue–Reliability Section1 are currently researching the issue of fatigue life by both experimental and the CAE approach. Information regarding frequent critical problems on arc–welded structures were sought from auto–manufacturers, vehicle component suppliers, and material suppliers. The method for anti–fatigue design on arc–welded structures was established not only by a database created by physical test results in accordance with the collected information but also with design procedure taking Fracture–Mechanics into consideration. This method will be applied to vehicle development as one of the virtual laboratories in the digital prototype phase. In this paper, both the database from bench–test results on arc welded structures and FEA algorithm unique to JSAE are proposed some of the analysis results associated with the latter proposal are also reported.
Technical Paper

Application of CAE Technology to the Development of Plastic Automotive Components

The use of CAE software in developing plastic components has advanced rapidly in recent years. This progress has been supported by the development of practical analytical tools, based on the finite element and boundary element methods, and on the dramatic improvements seen in computer performance. Following the introduction of a flow analysis program in 1982, Nissan has developed and implemented advanced programs for use in developing plastic components and has integrated the programs into a unified in-house system. This system is being utilized at the design and manufacturing stages of interior and exterior trim parts and has produced concrete results in different phases of component development. Work is now proceeding on the development of a system that can simultaneously analyze both the component performance and the factors that need to be considered in the manufacturing process.
Technical Paper

Evaluation of Equivalent Temperature in a Vehicle Cabin with a Numerical Thermal Manikin (Part 2): Evaluation of Thermal Environment and Equivalent Temperature in a Vehicle Cabin

In the previous paper (Part 1), measurements of equivalent temperature (teq) using a clothed thermal manikin and modeling of the clothed thermal manikin for teq simulation were discussed. In this paper (Part 2), the outline of the proposed mesh-free simulation method is described and comparisons between teq in the calculations and measurements under summer cooling with solar radiation and winter heating without solar radiation conditions in a vehicle cabin are discussed. The key factors for evaluating teq on each body segment of the clothed thermal manikin under cooling and heating conditions are also discussed. In the mesh-free simulation, even if there is a hole or an unnecessary shape on the CAD model, only a group of points whose density is controlled in the simulation area is generated without modifying the CAD model. Therefore, the fluid mesh required by conventional CFD code is not required, and the analysis load is significantly reduced.