20th Design Automation Conference: Volume 1 — Dynamic Mechanical Systems; Geometric Modeling and Features; Concurrent Engineering
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Published By American Society Of Mechanical Engineers

9780791897676

Author(s):  
Shyam V. Narayan ◽  
Zhi-Kui Ling

Abstract Feature based modeling has been used as a means to bridge the gap between engineering design and manufacturing. Features can represent an artifact with higher level entities which relate directly to its design functionalities and manufacturing characteristics, such as surface finish, manufacturability, fits, tolerance etc. In this study, a heuristic based feature recognition approach is proposed by using the graph representation of a design. The process consists of two steps: subgraph construction, and subgraph to feature identification. In this study, the subgraph construction is accomplished by using a set of heuristic rules. The process of subgraph to feature identification is carried out with a set of integers and characters which represent the geometric, topological, and semantic characteristics of the corresponding feature. This feature recognition scheme is used for the identification of machine features in a design.


Author(s):  
Faydor L. Litvin ◽  
Jui-Sheng Chen ◽  
Thomas M. Sep ◽  
Jyh-Chiang Wang

Abstract Computerized investigation of the influence of alignment errors on the transmission errors and the shift of the bearing contact is proposed. The investigation is performed for an imaginary hypoid gear drive with conjugate tooth surfaces. It is proven that the transmission functions caused by misalignment are periodic discontinues almost linear functions with the frequency of cycle of meshing. The above functions can be totally absorbed by a predesigned parabolic function. The shift of the bearing contact caused by misalignment has been determined as well. The performed investigation is based on computerized simulation of meshing and contact of gear tooth surfaces. The machine-tool settings for the generation of the designed gear drive have been determined. Numerical example that illustrates the developed theory is given. The performed investigation allows to determine the influence of gear misalignment on transmission errors, and design a low-noise hypoid gear drive by a properly predesigned parabolic function of transmission errors.


Author(s):  
Vassilios E. Theodoracatos ◽  
Xiaogang Guan

Abstract This paper presents a new Computer-Aided Design (CAD) synthesis model which uses Plex Grammar as structural relationship descriptors and NURBS surface representation for constructing standard and non-standard solid entities. Here, the designer uses a syntactic design methodology for early topological and geometrical definition of the structure of concept alternatives resulting from the design process. This syntactic scheme provides the capability of describing a large set of complex structures by using a small set of simple entities. The recursive nature of the grammar and the hierarchical representation of the structure makes the description of complex structures simple and under the direct control of the designer. An object structure constructive tree is generated and subsequently translated into Plex Grammar production rules in order to form an Interconnection Matrix (ICM) expressing. The resulting Plex structure defined in the ICM expresses the topological information among entities which form the specific types of objects. By modifying the Plex grammar rules, various objects with different geometry and topology can easily be reconstructed. Compared to conventional solid modeling techniques, this approach provides more systematic object generation, easy manipulation and modification, control over congruity and the ability to represent sculptured shapes. Several examples of syntactic solid modeling applied in design synthesis will be presented for further usage in downstream applications.


Author(s):  
James K. Coles ◽  
Richard H. Crawford ◽  
Kristin L. Wood

Abstract A new feature recognition method is presented that generates volumetric feature representations from conventional boundary representations of mechanical parts. Recognition is accomplished by decomposing the known total feature volume of a part into a set of smaller volumes through analytic face extension. The decomposed volumes are combined to generate an initial set of features. Alternative sets of features are generated by maintaining and evaluating information on intersections of the initial feature set. The capabilities of the method are demonstrated through both a hypothetical and a real world design example. The method’s ability to locate features despite interactions with other features, and its ability to generate alternative sets of features, distinguishes it from existing recognition techniques.


Author(s):  
David E. Montgomery ◽  
Robert L. West

Abstract Experimental spatial dynamics modeling involves using scanning lasers to sample surface shape and dynamic response of structures in order to verify structural dynamics design intent. Formation of accurate spatial models from laser-based measurements requires that laser position and orientation be registered relative to a fixed coordinate system. A three point direct registration procedure is defined for shape modeling using laser range and mirror deflection angles. Surface velocity measurements with a portable laser Doppler vibrometer (LDV) also require registration, but range information is unavailable. A multiple point indirect registration algorithm for the LDV is described that involves minimizing three nonlinear equations. A simulated laser rangefinder (LRF) was developed for demonstrating three point direct registration. The 3-D geometry of a compressor housing was modeled by combining range data from multiple laser positions. The multiple point indirect registration was applied to 3-D velocity response field reconstruction of a composite plate from velocity measurements scanned at three separate positions.


Author(s):  
Heming Yang ◽  
Xinfang Zhang ◽  
Ji Zhou ◽  
Jun Yu

Abstract Collision and interference detection among 3-D moving objects is an important issue in the simulation of their behavior. This paper presents a new model for representing 3-D objects and a corresponding effective algorithm for detecting collisions and interferences among moving objects. Objects can be represented for efficient collision and interference detection by a hierarchy of oct - sphere model (HOSM). Algorithms are given for building the HOSM and for detecting collisions and interferences between moving objects. On the basis of HOSM, the algorithm checks only intersections between the nodes of the models which are on the surfaces of the objects. Furthermore, because a node of HOSM represents a spherical region, the collision between the two nodes can be easily found just by calculating the distance between the centers of the two spheres corresponding to them no matter how the objects move. Finally, we discuss the efficiency of the algorithm through an example.


Author(s):  
Yong Fang ◽  
F. W. Liou

Abstract In this paper, the implementation of a modeling system for the simulation of three dimensional mechanical assemblies with elastic components is presented. A mechanical assembly is modeled as a multi-body system with changing topologies. The elastic behavior can be automatically modeled using finite element method. With this simulation tool, a designer can interactively create an assembly of mechanical components ready for dynamic and elastic analysis. This paper presents a prototype of the modeling system.


Author(s):  
Meyer Nahon

Abstract The determination of the interference distance between objects is a problem encountered in the off-line simulation of robotic systems. It is similar to the problem of finding the minimum separation distance between two bodies — a problem which, at present, is commonly solved using optimization techniques. This paper presents an analogous optimization formulation for the quick and accurate determination of the interference distance between two interfering objects. The optimization problem consists of finding the maximum amount by which the boundaries of two interfering object can be moved back while still maintaining a non-empty interference volume. Since the approach used is similar to that used in the minimum separation problem, a single algorithm has been implemented which, given the position and orientation of two objects, will return the separation or interference distance between the objects, as appropriate.


Author(s):  
Jeong-Soo Ahn ◽  
Kyihwan Park ◽  
Richard H. Crawford

Abstract Design activities consists not only of product design, but also of development of the process by which the product will be designed. However, development and documentation of computational design processes are largely unsupported by commercial CAD systems. This paper proposes a new computational architecture for procedural representation of embodiment design processes. A design actor is defined as an independent computational unit of the design process. The proposed architecture models a design process as a sequence of design tasks by representing individual parameters and tasks as design actors, and the sequence of design tasks as a network of design actors assembled according to their functional dependencies. The use of design actors promotes modularity in representing design problems and solution processes. Iterative design processes can be represented since the architecture provides explicit feedforward and feedback information exchange between design actors. The paper describes an object-oriented implementation of the design actor architecture, and demonstrates the approach with an example design of an air-core solenoid in an optical disk drive.


Author(s):  
Wei Chen ◽  
Janet K. Allen ◽  
Farrokh Mistree

Abstract In this paper, we introduce a concurrent approach to preliminary system design by using a modification of Taguchi’s method of robust design. It is possible to model interactions among component concept selections and synthesis of system variables. This approach also can improve computational efficiency and provide more design knowledge for the conceptual design of complex engineering systems. This technique is effective in dealing with both discrete and continuous variables simultaneously in design. We illustrate our approach by the preliminary design of a solar powered irrigation system. The selections of critical component concepts are integrated with the determination of system variables, i.e., the thermodynamic operating parameters.


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