Kevin W. Lyons

Virtual assembly using virtual reality techniques

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 a research effort aimed at creating a virtual assembly design environment.

VADE: a Virtual Assembly Design Environment

Virtual Assembly Design Environment (VADE) resulted from a research and development project started in 1995, sponsored by the National Institute of Standards and Technology (NIST). The main purpose of this project was to explore the potential and the technical challenges in using VR technologies for design and manufacturing by creating a VE for assembly planning and evaluation. In this article, we describe the overall system, the important features, and examples of using VADE. We also discuss the benefits and limitations of virtual assembly systems. In addition, we compare virtual assembly and automated assembly planning systems.

A Virtual Assembly Design Environment

The Virtual Assembly Design Environment (VADE) is a virtual reality (VR) based engineering application which allows engineers to evaluate, analyze, and plan the assembly of mechanical systems. This system focuses on utilizing an immersive virtual environment tightly coupled with commercial computer aided design (CAD) systems. Salient features of VADE include: data integration (two-way) with a parametric CAD system; realistic interaction of the user with parts in the virtual environment; creation of valued design information in the virtual environment; reverse data transfer of design information back to the CAD system; significant interactivity in the virtual environment; collision detection; and physically-based modeling. This paper describes the functionality and applications of VADE. A discussion of the limitations of virtual assembly and a comparison with automated assembly planning systems are presented. Experiments conducted using real-world engineering models are also described.

Function-to-form mapping: model, representation and applications in design synthesis

Design of a new artifact begins with incomplete knowledge about the final product and the design evolves as it progresses from the conceptual design stage to a more detailed design. In this paper, an effort has been made to give a structural framework, through a set of generic definitions, to product specification, functional representation, artifact representation, artifact behavior and tolerance representation. A design synthesis process has been proposed for evolution of a product from the product specification. The proposed design synthesis method is a mapping from the functional requirements to artifacts, with multi-stage constrained optimization during stages of design evolution. Provisions have been kept to augment and/or modify the product specification and domain knowledge during stages of development to guide the design process. The effectiveness of the proposed design process has been illustrated with a simple design example based on a sample artifact library. An overall design scheme has been presented.

A Model for Capturing Product Assembly Information

The important issue of mechanical assemblies has been a subject of intense research over the past several years. Most electromechanical products are assemblies of several components, for various technical as well as economic reasons. This paper provides an object-oriented definition of an assembly model called the Open Assembly Model (OAM) and defines an extension to the NIST Core Product Model (NIST-CPM). The assembly model represents the function, form, and behavior of the assembly and defines both a system level conceptual model and associated hierarchical relationships. The model provides a way for tolerance representation and propagation, kinematics representation, and engineering analysis at the system level. The assembly model is open so as to enable plug-and-play with various applications, such as analysis (FEM, tolerance, assembly), process planning, and virtual assembly (using VR techniques). With the advent of the Internet more and more products are designed and manufactured globally in a distributed and collaborative environment. The class structure defined in OAM can be used by designers to collaborate in such an environment. The proposed model includes both assembly as a concept and assembly as a data structure. For the latter it uses STEP. The OAM together with CPM can be used to capture the assembly evolution from the conceptual to the detailed design stages. It is expected that the proposed OAM will enhance the assembly information content in the STEP standard. A case study example is discussed to explain the Usecase analysis of the assembly model.

Framework and indicators for a sustainable manufacturing mapping methodology

Increasing numbers of companies in the manufacturing industry have identified market potential for implementing sustainable and green manufacturing. Yet, current sustainability assessment tools for companies are complicated, requiring vast amounts of data and technical expertise to use them. Value Stream Mapping (VSM) is founded on lean practices, and it uses a simple method to analyze various types of material, energy, and information flow needed to bring products and services to the end-customer. The objective of this paper is to introduce and illustrate the application of a VSM-based assessment, termed as Sustainable Manufacturing Mapping (SMM). SMM takes chosen sustainability indicators into consideration and is based on VSM, Life Cycle Assessment (LCA), and Discrete Event Simulation (DES). The main phases of SMM include goal definition, identification of the sustainability indicators, and modeling the current and future state process maps. In this paper, some example indicators were identified and an SMM process map was generated for illustrative purposes.

Industry case studies in the use of immersive virtual assembly

In this paper, we report on two engineering case studies that have been conducted as part of a Virtual Assembly Technology Consortium. The objectives of the case studies were to determine if immersive virtual assembly capabilities allow industry assembly situations to be modelled and studied realistically, and to demonstrate the downstream value of the virtual assembly capabilities in areas such as ergonomics, assembly installation, process planning, installation, and serviceability. What is of special significance is that instead of modelling simplified problems or perceived representative situations, the case studies were constructed from actual assembly floor projects and situations encountered at industry member sites and with considerable participation from industry engineers and manufacturing shop floor personnel. Based on the success of the case studies, the consortium members inferred that virtual assembly methods are poised to move out of the realm of special projects and test scenarios to deployment in the actual design and manufacturing cycle. However, in order to be truly accepted in industry, there are still issues to be addressed in terms of ease of use, portability of the applications, and preparation of the models for the evaluations. Thus, the case studies added a new dimension to the exploration and understanding of how this new technology could be of practical value in industry.

Sustainability characterisation for manufacturing processes

Manufacturing industries lack the measurement science and the needed information base to measure and effectively compare environmental performances of manufacturing processes, across resources and associated services with respect to sustainability. The current use of ad hoc methods and tools to assess and describe sustainability of manufactured products does not necessarily account for manufacturing processes explicitly, and hence results in inaccurate and ambiguous comparisons. Such comparisons do not proactively contribute to sustainability improvement. Further, we identified that there are no formal methods for acquiring and exchanging information that help establish a consolidated sustainability information base. Our ultimate goal is to develop the needed measurement science and methodology to evaluate sustainability of fundamental manufacturing processes to ensure reliable and consistent comparisons. As a precursor, based on a literature study, this paper identifies the required elements to evaluate sustainability performance for manufacturing with a focus on the environmental impact. Societal and economic impacts, although equally important, are beyond the scope of discussion in this paper. In this paper, we first discuss identified manufacturing process classifications, sustainable manufacturing indicators and computable metrics, relevant information models and software tools, a conceptual model for sustainability characterisation, and finally, conclude with an overview of the future research directions.

Object-oriented representation of electro-mechanical assemblies using UML

The important issue of representing mechanical assemblies has been a subject of intense research over the past several years. Most electromechanical products are assemblies of several components. This paper presents an object-oriented definition of an assembly model called Open Assembly Model (OAM). The assembly model has function, form, and behavior. It defines both a system level conceptual model and the associated hierarchical relationships. The model provides a way for representing tolerance representation and propagation, kinematics representation, and engineering analysis at the system level. The assembly model is open so as to enable plug-and-play with various analysis and applications modules. A case study example is discussed to explain the Usecase analysis of the assembly model.

Smoothing haptic interaction using molecular force calculations

This paper presents a new method for smoothing haptic interaction with molecular force calculations that uses Lennard-Jones forcefield. The gradient of the forcefield is used unaltered when the distance between two atoms is greater than the sum of their van der Waals radii. However, when they are smaller, a hard-surface wall implemented using a spring model is used to repel two atoms. This eliminates the instability when two atoms are in contact in the presence of forcefields that have strong gradients. This method is tested on rigid hydrocarbon molecules with no bond creation or breaking. Published by Elsevier Science Ltd.