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18th Annual Conference on computer Graphics and Interactive Techniques, SIGGRAPH 1991

作者： Celniker, George Gossard, Dave Schlumbergcr Laboratory for Computer Science AustinTX78720 United States Department of Mechanical Engineering Computer Aided Design Laboratory Massachusetts Institute of Technology 77 Massachusetts Ave CambridgeMA02139 United States

ISBN: (纸本)0897914368

The finite element method is applied to generate primitives that build continuous deformable shapes designed to support a new free-form modeling paradigm. The primitives autonomously deform to minimize an energy functional subject to user controlled geometric constraints and loads. The approach requires less user input than conventional free-form modeling approaches because the shape can be parameterized independently of the number of degrees of freedom needed to describe the shape. Both a curve and a surface finite element arc developed. The properties of these geometric primitives have been engineered to support an interactive three phase approach for defining very fair free-form shapes as found in automobiles, ship hulls and car bodies. The shape's character lines or folds and edges are defined with deformable curve segments. These character lines are then "skinned" with a deformable surface. The final shape is sculpted interactively by applying loads to the surface to control the surface shape between character lines. Shapes created with this technique enjoy the advantage that they are already meshed for further finite element analysis. © 1991 ACM.

关键词： Finite element method

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Orientation and insertion of randomly presented parts using vibratory agitation

Orientation and insertion of randomly presented parts using ...

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ASME 1991 design Technical Conferences, DETC 1991

作者： Moncevicz, Paul H. Jakiela, Mark J. Ulrich, Karl T. Department of Mechanical Engineering Massachusetts Institute of Technology Computer-Aided Design Laboratory CambridgeMA United States Massachusetts Institute of Technology Sloan School of Management CambridgeMA United States

ISBN: (纸本)9780791807491

In this article, we propose a new approach to automated assembly. Currently, automated assembly is expensive and difficult because all of the machines required for its implementation impose organization on the parts being assembled. It is this organization that is costly. We investigate an approach that requires less organization and results in assembly as a bulk process. We describe an initial implementation of this approach with a particular parts presentation system. Experiments are performed to determine the part characteristics that promote the success of the implementation. The experimental results are described and future work is suggested. © 1991 American Society of Mechanical Engineers (ASME). All rights reserved.

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Goal orientated slicing enumeration through shape function clipping

Goal orientated slicing enumeration through shape function c...

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European Conference on design Automation

作者： G. Sigl U. Schlitchtmann Institute of Computer-Aided Design Department of Electrical Engineering Technical University Munich Munich Germany Dept. of Electr. Eng. Tech. Unvi. of Munich Germany

Two new methods for efficient enumeration of slicing structures useful for macro cell and sea-of-gates final placement are presented. Contrary to existing approaches a further preorder traversal of the slicing tree is added, which allows elimination of unnecessary shapes in an early design phase. Applying this look ahead strategy, memory and computation time requirements have been reduced drastically. Better placements have been achieved by using the saved resources to enlarge the search space for enumeration.< >

关键词： Shape Polynomials Upper bound Optimization methods design automation Printed circuits design optimization Delay Wiring Algorithm design and analysis

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A SUBSTRUCTURE TECHNIQUE FOR DYNAMICS OF FLEXIBLE MECHANICAL SYSTEMS WITH CONTACT-IMPACT

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JOURNAL OF MECHANICAL design 1990年第3期112卷 390-398页

作者： WU, SC HAUG, EJ Center for Computer Aided Design and Department of Mechanical Engineering The University of Iowa Iowa City Iowa

A substructure synthesis method is proposed to account for contact-impact effects in flexible components of mechanical systems. Components that may come into contact are divided into substructures, on each of which local deformation modes are defined to describe deformation fields of components. Constraint modes and fixed interface normal modes are used to account for elastic deformation within each substructure. A constraint addition-deletion technqiue is used to determine when contact occurs, account for the effect of contact constraints during the period of contact, and delete constraints after the completion of the contact event. Lagrange multipliers associated with the contact constraints, which represent contact forces, are used to determine the time of separation of contacting nodes. Use of the method is illustrated for longitudinal and transverse impact of elastic bars.

关键词： Dynamics (Mechanics) Separation (Technology) Deformation

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A recursive dynamic formulation for flexible mechanisms

A recursive dynamic formulation for flexible mechanisms

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ASME 1990 design Technical Conferences, DETC 1990

作者： Souh, Byung Yil Kim, S.S. Department of Mechanical Engineering Center for Computer Aided Design The University of Iowa Iowa CityIA United States

ISBN: (纸本)9780791805213

This paper presents a recursive dynamic formulation for modeling and simulation of spatial mechanisms with elastic beams. In order to circumvent some difficulties in the convential assumed mode approach, each flexible link is modeled with finite elements. The motion of the flexible link comprises the rigid body motion and elastic deformation. The elastic deformations are represented by nodal coordinates relative to the moving coordinate system fixed to the link. Recursive kinematic relationships are derived between finite beam elements. Using variational equations of motion for the one beam element and recursive relationships, the equations of motion for the open-chain flexible bodies are derived in terms of relative joint and nodal coordinates. For closed-loop systems, Lagrange multipliers are used to generate the equations of motion with kinematic constraints. The proposed method models geometric nonlinear effects and axial tensioning effects automatically. Also, the difficulties of the mode selection in the assumed mode approach is avoided. Numerical examples illustrate the effectiveness of this approach. © 1990 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Equations of motion

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Workstation-based man-in-the-loop simulation for multibody systems

Workstation-based man-in-the-loop simulation for multibody s...

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ASME 1990 design Technical Conferences, DETC 1990

作者： Chang, J.L. Kim, S.S. Department of Mechanical Engineering Center for Computer Aided Design The University of Iowa Iowa CityIA United States

ISBN: (纸本)9780791805213

This paper presents a general approach to achieving real-time man-in-the-loop simulation for multibody dynamic systems. Emerging real-time dynamic simulation methods are used to demonstrate the potential for creating interactive design workstations with a human operator in the control loop. The recursive formulation of multibody system dynamics with relative coordinates is employed for efficient numerical analysis and implementation on parallel computer. A workstation-based simulator is developed by integrating the real-time dynamics program, a realistic graphics display, and the operator's control interface. High speed computer graphics techniques are employed to create realistic visual cues for the simulator. Real-time man-in-the-loop simulation is analyzed, as regards the goal of real clock time, not only with respect to dynamic simulation but also with respect to graphics display and the operator interface. Synchronization of the simulation is found to be most important for realism of the simulator. A backhoe simulation is implemented to demonstrate the capability for man-in-the-loop simulation. The backhoe simulator is developed by modeling backhoe dynamics and hydraulic systems with the recursive formulation to achieve real-time simulation, developing an interactive graphics program for visual cues, and interfacing the operator's control action with the dynamic simulation through a pair of joysticks. © 1990 American Society of Mechanical Engineers (ASME). All rights reserved.

关键词： Simulators

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An accurate model for ambiguity delay simulation

An accurate model for ambiguity delay simulation

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1990 European design Automation Conference, EDAC 1990

作者： Krodel, Thomas H. Antreich, Kurt J. Institute of Computer Aided Design Department of Electrical Engineering Technical University of Munich MunichD-8000 Germany

ISBN: (纸本)0818620242

This paper presents a new approach for the accurate computation of ambiguously delayed waveforms which is implemented in the event-driven logic simulation system LDSIM. Six logic values are defined to be sets of up to four basic values. The mapping function representing the ambiguity delay model only manipulates these basic values. This principle results in a powerful and versatile ambiguity delay model that is clearly presented, easy to implement and guarantees correct delay computation of arbitrary six-valued waveforms with respect to the concept of superposition and causality. © 1990 IEEE.

关键词： computation theory

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INTEGRATING PROLOG AND CADAM TO PRODUCE AN INTELLIGENT CAD SYSTEM

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SOFTWARE-PRACTICE & EXPERIENCE 1990年第10期20卷 1049-1076页

作者： BOND, AH SOETARMAN, B Computer Aided Design Laboratory 3066 Engineering 1 MANE Department University of California Los Angeles California 90024 U.S.A.

A discussion is presented of system issues in integrating an artificial intelligence system with a conventional computer-aided design system. Two different schemes for integration, and experience in implementing a combined VM/PROLOG and CADAM, are described. Both Prolog and CADAM are separately interactively systems, and it was necessary to provide an interactive interface to each, and to be able to move between them. Since CADAM is not reentrant, a coroutining relationship was required. It was necessary to specify a Prolog form for drawings and to be able to transform drawings in the CADAM workspace in Fortran array form into Prolog clauses, representing the same information and residing in the Prolog workspace, and vice versa. The problems of linking to CADAM, and of storage management in a VM virtual machine had to be dealt with. Finally, error recovery had to be considered. Examples of the use of the system are presented, including examples of CAD graphics, and the setting of goals, with the corresponding system responses. The main practical application area was the design and manufacture of assemblies made of sheet metal and extrusions, such as components of aircraft. Several application programs, implemented using the intelligent CAD system, are described.

关键词： System integration Prolog Artificial intelligence CADAM CAD VM

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An accurate model for ambiguity delay simulation

An accurate model for ambiguity delay simulation

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European design Automation Conference

作者： T.H. Krodel K.J. Antreich Institute of Computer Aided Design Department of Electrical Engineering Technical University Munich Munich Germany

关键词： Circuit simulation Propagation delay Predictive models Timing computational modeling Logic design Discrete event simulation Power system modeling Integrated circuit modeling Quantum computing

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CAD CAM MANUFACTURING OF PROTOTYPE SHIPBOARD COMPONENTS

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NAVAL ENGINEERS JOURNAL 1990年第3期102卷 93-99页

作者： CALVERT, TE RODRIGUEZ, FA SLEBZAK, JS Thomas E. Calvert P.E.: is a senior project engineer with the Propulsion and Auxiliary Systems Department David Taylor Research Center Annapolis Md. His interests include application of computers to all aspects of engineering with particular emphasis on utilization of small computers. Mr. Calvert is a licensed professional engineer in Maryland. He received a BSEE from Drexel University in 1969 and since that time has completed a number of graduate courses related to machinery acoustics. Francisco A. Rodriguez:is an engineer with the Propulsion and Auxiliary Systems Department David Taylor Research Center. He was formerly with the Computer-Aided Design/Interactive Graphics Group of the Division of Engineering and Weapons U.S. Naval Academy. His interests include interfacing the computer aided design to the computer aided manufacturing along with related software and hardware development. Mr. Rodriguez received a BSEEfrom the University of Virginia in 1968. James S. Slebzak:is a mechanical engineering technician with the Propulsion and Auxiliary Systems Department David Taylor Research Center. He received his machinists papers in 1971 after serving his apprenticeship at David Taylor Research Center. He continued his education and became the senior numerical control programmer at the Annapolis Laboratory. He completed his mechanical technology degree from Anne Arundel Community College in 1986. His interests are in the application of numerically controlled manufacturing techniques to prototype machinery components.

The machine shop at the Annapolis Laboratory of the David Taylor Research Center (DTRC) provides model making and prototype support to a large variety of naval ship related engineering projects. In order to meet these challenging requirements, computer aided design/computer aided manufacturing (CAD/CAM) techniques are being used to produce “one of a kind” prototypes or very low volume production parts. The use of computer aides in these cases is to facilitate the accurate manufacture of a difficult part, rather than to improve manufacturing efficiencies. In addition, the approach provides the flexibility required to support research and development projects. Several examples of prototype shipboard components manufactured using CAD/CAM techniques are presented in this paper. The hardware and software that facilitated these projects are discussed. The examples described have met the requirements to produce a wide variety of prototype shipboard machinery components quickly and accurately.

关键词： Ship Equipment

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