Although the field of CAD has come a long way in recent years, the integration of CAD with engineering/mechanical design, especially the integration of CAD with conceptual design, has not been given enough importance. Tools which facilitate the custom development of conceptual CAD software are still not available. This is especially true in the case of intelligent CAD systems. This paper describes the philosophy and design of a framework which will facilitate the creation of knowledge-based expert systems to support conceptual design. The design of an object-oriented framework which will assist in the creation of customized expert systems for CAD applications is presented. This framework, known as the Expert Consultation Environment, provides the CAD programmer with tools to create the expert system. This framework consists of various object-oriented classes which the programmer would use during the creation of the knowledge-based expert system. A prototype of a portion of the framework was implemented. The use of this prototype framework in the creation of an expert system for a multi-disciplinary design application is discussed. The framework described in this paper would assist the programmers of CAD systems in building expert systems that are tailor-made for conceptual design. Any expert system created using an implementation of this framework will be very flexible, adaptable, and extendible.

Virtual reality is a technology which is often regarded as a natural extension to 3D computer graphics with advanced input and output devices. This technology has only recently matured enough to warrant serious engineering applications. The integration of this new technology with software systems for engineering, design and manufacturing will provide a new boost to the field of computer-aided engineering. One aspect of design and manufacturing which may be significantly affected by virtual reality is design for assembly. This paper presents the ideas behind a current research effort aimed at creating a virtual assembly design environment and integrating that environment with a commercial, parametric CAD system.

Companies are being forced to create products at a highly accelerated rate and have turned to new design techniques such as virtual prototyping. One of the newest virtual prototyping tools is the use of virtual reality for design and manufacturing analysis. Many groups have developed systems that use virtual reality techniques such as virtual fly-throughs, simulations and three-dimensional visualization. Additionally, there is an increased amount of research in the area of human-integrated techniques or human-in-the-loop analysis using virtual reality. In the field of design and manufacturing, most work has either been in simulation or in the field of human interaction without the use of virtual reality. Although these provide valuable information, a system that couples human-interaction with virtual reality can provide more information than that provided by current computer-aided design and manufacturing software. One concern, however, is the accuracy of these systems and whether the data that is obtained from these systems can be utilized. This paper presents studies performed in a virtual environment for a design and manufacturing system.

The use of virtual prototyping tools typically results in products with lower costs, better quality, and shorter development cycles. However, there are many interface/configuration problems that occur in the process of obtaining a design solution using the typical gamut of virtual prototyping tools. This paper presents the architecture, design, and implementation of a framework to support the integration of the multiple software systems used in the virtual prototyping of mechanical components. Some of the virtual prototyping software systems considered in the implementation of this framework were customer input systems, solid modeling systems, finite-element systems, knowledge-based systems, NC code generator systems, and virtual assembly systems. There is a pressing need for the different software systems to talk to each other while transferring the required data at varying levels of abstraction without compromising data integrity. Of special significance is the fact that the philosophy of the framework is widely applicable to any mechanical system, and is almost independent of specific software utilities. Thus, this design incorporates a clear path towards expansion to encompass other independent tools/systems. The architecture was designed using object-oriented methods. The framework was very successfully demonstrated for a well-defined subset of software systems being used at Isothermal Systems Research (ISR) Inc., a leader in proprietary spray cooling systems for multi-chip modules. This framework effectively supports the strong industry push towards integrated design, manufacturing, and virtual prototyping. The work presented in this paper was supported by an SBIR grant from the Department of Commerce, DOC contract 50-DKNB-5-00117.

The emergence of high performance computing has opened up new avenues for the design and analysis community. Integrated Product/Process Design techniques are allowing multi-functional teams to simultaneously optimize the design of a product. These techniques can be inhibited, however, due to software integration and data exchange issues. The work outlined in this paper focuses on these issues as they relate to the design and analysis of electro-mechanical assemblies. The first effort of this work is the creation of an open environment, called the Open Assembly Design Environment. The goal of this environment is to integrate the otherwise disparate assembly design tools using a central control system and a common set of data. These design tools include virtual reality based design systems, computer-aided design systems, design for assembly systems and process planning systems. This paper outlines the overall goals of the project, presents the architecture designed for the system, describes the interfaces developed to integrate the systems, and discusses the data representation requirements for a system integrating a virtual reality system with computer-aided design systems.

State of the art CAD/CAM technology enables the capture of user design intent through the use of assembly constraints, features, parameters, etc. However, due to the large size of the CAD models, engineers are using other virtual prototyping methods for visualization and complete assembly analysis. Constraint and parameter information is lost in the transfer of models from the CAD system to the virtual prototyping systems. In virtual prototyping systems, users typically have tools to modify the location of an assembly component. In order to maintain model validity, procedures need to be developed to transfer these modifications back to the CAD system while maintaining the design intent of the original CAD user. In other words, how do we take information about changes to absolute or relative location and orientation of a component and transform this to updated constraint and parametric information in the original CAD model? In this paper, we address this need to update the constraints and parametric information of a CAD model based on location and orientation changes communicated from a virtual prototyping system. After analyzing and categorizing the assembly constraints in a typical feature-based CAD system, we propose a methodology to decide what information needs to be updated, and a procedure to update the information — all based on the original design intent captured in the constraints. The results of a test case to validate the methodology are also presented.

A 3D menu, also called a virtual menu, is now an accepted method of interaction between the user and the computer in an immersive environment. It adds functionality and allows interactions that are usually difficult to specify through direct interaction. We present the design and methodology of a support system for 3D menu creation and interaction in an immersive environment. Three kinds of virtual menus are supported — a paddle, a static billboard, and a dynamic billboard. These are distinguished by different spatial presentation and interaction paradigms in the virtual environment. The integration of the support system into an immersive environment is presented in the context of engineering applications research at Washington State University. Problems encountered and future planned enhancements are also examined. A clean separation between the virtual menu support system and the application in which the virtual menu will be created and displayed has been maintained.

Virtual prototyping is a relatively new field which is significantly changing the product development process. In many applications, virtual prototyping relies on virtual reality tools for analysis of designs. This paper presents an architecture for a virtual prototyping system which was created for the analysis of automotive interiors. This flexible and open architecture allows the integration of various virtual reality software and hardware tools with conventional state-of-the-art CAD/CAM tools to provide an integrated virtual prototyping environment. This architecture supports the automatic transfer of data from and to parametric CAD systems, human modeling for ergonomic evaluations (first person and third person perspectives), design modifications in the virtual environment, distributed evaluations of virtual prototypes, reverse transfer of design modifications to the CAD system, and preservation of design intent and assembly intent during modifications in the virtual environment.

Virtual Prototyping (VP) is a relatively new technology which involves the use of Virtual Reality (VR) and other computer technologies to create digital prototypes. Recently, this rapidly expanding technology has matured enough to warrant serious consideration as part of the engineering design and manufacturing process. Virtual prototyping has extended beyond the specific use of virtual reality to now include the use of next-generation Computer Aided Engineering (CAE) technologies including advanced visualization systems, human modeling systems, and CAD/CAM systems. The emergence of these systems has raised significant concern regarding the integration and concurrent use of these tools. As the use of next-generation CAE systems becomes more prevalent, engineers will continue to grapple with how, when, and where to properly use these tools in the engineering design cycle. The abundance of data generated and used by these systems places considerable burden on the engineer, who often ends up spending more time on data and process management (e.g. transferring data from system to system, version control, system integration, etc.) rather than on the actual design problem. As these systems continue to become mainstream, the burden placed upon the engineer using these systems must be alleviated. The effective use of these tools in an integrated, synergistic fashion has not yet been realized. This paper discusses a number of distinct approaches for creating a collaborative, distributed architecture for virtual prototyping. The architectural philosophies discussed include: Product Development Approach, CAE Tool Integration Approach, User-session Approach, Functional Approach, and Black-box Approach. A final architecture, created from the value-added features of each of the discussed philosophies, was created. A prototype implementation of this architecture and its underlying technological infrastructure is briefly discussed.

Swept volumes are the volumes created by a part moving in space during the process of assembly, disassembly, service, etc. Swept volumes represent important manufacturing, maintainability, and serviceability data. Several graphical and implicit modeling techniques are currently available to create and represent swept volumes as three-dimensional polygonal blobs. In this paper, we present a method for generating swept volumes from trajectory data created in a virtual graphics environment during an assembly/disassembly scenario. The individual instances can be edited in the virtual environment by swept instance removal and modification of position and orientation of instances. Using a synchronous link between the virtual environment and the CAD system, the trajectory information from the virtual environment is used along with the parametric model in the CAD system to create swept volume geometry directly in a parametric CAD system as a feature of the assembly. In addition, using the synchronous link, this swept volume (not just instances along the trajectory) can then be exported back to the original virtual environment and displayed. This method can handle any sweeping trajectory and does not restrict the geometry or the topology requirement of the sweeping object. The swept volumes generated this way are accurate, concise, and can be easily processed by CAD systems.

The use of virtual environments to plan and evaluate assembly processes has been gaining significant acceptance in the engineering community. The prohibitive costs of immersive virtual environments and the availability of the internet have brought to the forefront the need for methods for sharing the virtual environment during the assembly evaluation process. This will support true collaborative engineering. This paper presents the design and implementation of a CORBA-based distributed virtual assembly environment. The architecture is based on capturing key states and events in the virtual assembly process. This collaborative environment is based on the VADE system created at Washington State University. Test cases were conducted using this system and the results are presented in this paper.

In recent years, the world economy has seen expansive market growth in the area of Micro-Electro Mechanical Systems (MEMS). It is predicted that the MEMS market could reach more than $34 billion by the year 2002. Today, commercially available MEMS products include accelerometers for airbags and inkjet printer heads. These products require little or no assembly because a monolithic integrated circuit process is used to develop the devices. However, future MEMS will be more elaborate. Monolithic integration is not feasible when incompatible processes, complex geometry, or different materials are involved. For these cases, new and extremely precise micro-manipulation capabilities will be required for successful product realization. This paper outlines the design and implementation of a computer aided simulation of Micro Electro Mechanical Systems (MEMS) assembly utilizing force feedback devices for display of forces of interaction. The system described in this paper solves boundary element equations for electrostatic forces between MEMS components and then displays this solution in near real time with the help of the PHANToM force feedback device. Issues discussed in this paper include: boundary element solutions of electrostatic forces, interpolation of a six degree of freedom solution grid, scaling up of electrostatic forces to human scale, and use of the PHANToM device for haptic display of electrostatic and contact forces.

Current virtual assembly environments primarily allow assembly operations involving pick and place manipulations with hands. In some applications, assembly tools snap onto screws and are constrained. Some non-immersive systems create tool motion script models for the tool to execute the assembly operation. The inclusion of tools and realistic tool operations is a significant step in creating a better virtual assembly environment. We propose a technique to model hand held tools and the corresponding assembly operations in a virtual environment. Intermediate-location constraints and tool engagement constraints obtained from the CAD model are used to model the intermediate positions and engagements of a fastener tool, tool-part, and base-part. In addition, tool-based motion dependent on the rotation of the tool and the pitch of the thread has been achieved for a fastener part This allows us to simulate the physical reality of these interactions without using expensive collide, penetrate, correct, and align methods. The tools and tool/hand/part interactions have been modeled and tested in a virtual assembly and design environment successfully. This capability also allows tool accessibility and tool operability to be verified.

Virtual assembly is a promising application of virtual reality in design and manufacturing and has drawn much attention from industry and research institutes. Physically based modeling has been an important research topic in computer graphics and virtual reality. In this paper, physically based modeling issues in virtual assembly are investigated. The specific requirements and characteristics of physically based modeling in virtual assembly versus those in traditional computer graphics are analyzed and studied. The mass properties of the assembly models are extracted from the Computer Aided Design (CAD) system while the design models are transferred from the CAD system to the virtual assembly environment. This added information allows the assembly models to be categorized using human strength survey data. The interaction of parts, environment objects, and the human are analyzed. In the fully immersed virtual environment, it is discovered that certain presentations of gravitational acceleration needs to be scaled down to achieve maximum realistic feeling. Finally the benefits and limitations of physically based modeling in virtual environments are discussed.

The mechanical engineering department at Washington State University has just completed a 6 year program in offering a modern sequence of design/manufacturing electives. Using theoretical foundations, site visits, guest lectures, IT based labs, and hands-on manufacturing exercises students learn about the role of information technology and electronic data in modern manufacturing enterprise systems, design for manufacture concepts, design automation, and also hands-on machining using advanced programming concepts of CNC code and CNC machines that are integrated with CAD/CAM systems. In this paper, two key courses of this sequence will be discussed and the innovations that they have enabled in engineering design education of the students will be presented. What is significant is that thru these courses we have achieved a dynamic interplay between the new and the old — we have been able to leapfrog into concepts of modern industry where IT and modern computing tools play a critical role in the manufacturing enterprise system and bring about considerable design and manufacturing automation; at the same time we have also retained and enhanced traditional concepts from before where design engineers had considerable hands-on knowledge with machining and manufacturing processes.

Virtual reality (VR) technologies and systems have the potential to play a key role in assisting disabled inhabitants of smart home environments with instrumental activities of daily living (IADLs). While immersive environments have useful applications in the fields of gaming, simulation, and manufacturing, their capabilities have been largely untapped in smart home environments. We have developed an integrated CAD and virtual reality system which assists a smart home resident in locating and navigating to objects in the home. Using the methods presented in this paper, a room modeled in a CAD system is imported into a virtual environment, which is linked to an audio query-response interface. The user’s head and room objects are fitted with the sensors which are part of a six DOF motion tracking system. Methods have been created to allow the inhabitant to move objects around in the room and then later issue an audio query for the location of the object. The system generates an audio response with the object’s position relative to the person’s current position and orientation. As he approaches the object, information is derived from the virtual models of both the room and the objects within the room to provide better guidance. The ability of the VR-SMART system to guide a resident to an object was tested by mounting a head mounted display (HMD) on a user located in a room. This allowed the user to navigate through the virtual world that simulated the room he occupied, thereby providing a way to test the positional accuracy of the virtual system. Results of the testing in the immersive environment showed that although the overall system shows promise at a 30% success rate, the success of the system depends on the accuracy and calibration of the tracking system. In order to improve the success of the system, we explored the precision of a second motion capture system, with more accurate results. Results confirmed that the VR-SMART system could significantly improve the assistance of disabled people in finding objects easily in the room when implemented only as an assistive system without the head-mounted display.

Much of the work in ontologies for product engineering has focused on the modeling of these ontologies. A key characteristic of an ontology model is that it uses a logic-based and formal specification to represent the information model, thus allowing querying and reasoning. In order to take advantage of this, we seek to move past ontology modeling and focus on developing meaningful reasoning mechanisms that are applicable for the domain of product engineering — a) to allow the user to make basic inferences such as checking consistency for definitions of concepts, b) to query and retrieve existing product data information, and c) to derive new product data information not explicitly expressed in knowledge bases. A typical semantic application architecture consisting of knowledge base layer, logic reasoning layer, and application interface layer is adopted. Reasoning units are deployed in the logic reasoning layer of this architecture. These reasoning units act on the knowledge base for product engineering, specifically, the domain of product assembly constraint. SWRL & SQWRL are used to define the retrieval specifications and inference rules. User interfaces are also developed to help users submit the reasoning tasks, view the results, and thus assess the knowledge base indirectly and transparently. It is concluded that the reasoning mechanism exploits and extends the semantic representation made possible through ontology and holds promise for improved knowledge discovery and understanding.

Training for assembly simulations can be provided using a wide range of technologies — from a simple computer-based training (CBT) approach to a complex immersive training (IMT) approach. The CBT approach allows user interactions through traditional keyboard and mouse while the IMT approach immerses the user in a virtual environment for a more realistic experience. Typically, for a particular scenario, tools for each of these are developed completely independently. Consequently, there is much duplication of data and effort and a lack of synchronization between them. In this paper, we focus on ontologies for the assembly simulation and training domain. Ontologies provide an opportunity to capture and manage common data and map concepts from one application to another in a logical and measured manner. Methods are developed to enable knowledge in these ontologies to be used and shared in a comprehensive and effective manner between CBT and IMT tools. Both tools are also well integrated with the Sharable Content Object Reference Model (SCORM) so that the progress during training can be recorded, tracked and evaluated by Learning Management System (LMS).

In this paper we present a detailed exploration of ontology-driven approaches and strategies for integrating product data between CAD/CAE applications. We structure the ontology model into three layers: General Domain Ontology, Domain Specific Ontology, and Application Specific Ontology. In particular, Application Specific Ontologies are built for PRO/E, CATIA, and a virtual assembly design tool called VADE. This allows the integration processes to be demonstrated for a) two applications in the common domain of product design, and b) two applications in different domains, one in the product design domain and the other in an assembly simulation domain. In addition, these ontology-driven strategies are compared with two other approaches. The first study focuses on the knowledge modeling aspect and compares the ontology approach with a standard modeling language, UML. The second study focuses on data integration and translation aspect and compares the ontology-driven approach with a traditional one. It is concluded that an ontology-driven approach is superior for solving heterogeneous data problems involving multiple applications by managing data on semantic level.

This paper presents our continuing work to develop methods to exchange product knowledge in the semantic level in the CAD/CAE domains. We present an approach based on a shared ontology, in which a higher level of ontologies are shared among lower levels of ontologies. Key mapping strategies, such as Equivalency, Attribute Similarity, Composition Similarity, and Inheritance Similarity are defined to map concepts and properties defined in a product design domain and an assembly simulation domain. In addition, a Bridge Ontology is designed to store information obtained from mapping processes and construct a link between different knowledge repositories. An Ontology Mapping Application (OMA) which brings together all these elements has been designed and implemented. It is a Java-based application that allows the user to load source and target ontologies, calculate concept and property similarities between them, display the mapping results, and output a corresponding Bridge Ontology .