A Framework for Designing Component Shapes in a Virtual Reality Environment

Despite advances in Computer-Aided Design (CAD) and the evolution of the graphical user interfaces, rapid creation, editing and visualization of three-dimensional (3D) shapes remains a tedious task. Though the availability of Virtual Reality (VR)-based systems allows enhanced three-dimensional interaction and visualization, the use of VR for ab initio shape design, as opposed to ‘importing’ models from existing CAD systems, is a relatively new area of research. Of interest are computer-human interaction issues and the design and geometric tools for shape modeling in a Virtual Environment (VE). The focus of this paper is on the latter i.e. in defining the geometric tools required for a VR-CAD system and in describing a framework that meets those requirements. This framework, the Virtual Design Software Framework (VDSF) consists of the interaction and design tools, and an underlying geometric engine that provides the representation and algorithms required by these tools. The geometric engine called the Virtual Modeler uses a graph-based representation (Shape-Graph) for modeling the shapes created by the user. The Shape-Graph facilitates interactive editing by localizing the effect of editing operations and in addition provides constraint-based design and editing mechanisms that are useful in a 3D interactive virtual environment. The paper concludes with a description of the prototype system, called the Virtual Design Studio (VDS), that is currently being implemented.1.

A Framework for Evaluating Risk in Innovative Product Development

This paper presents a novel framework for evaluating risk in innovative product design and development, and a product development methodology for risk identification and management. We define “risk” as the exposure to the chance of an unsuccessful product development outcome due to ambiguity and uncertainty. We examine uncertainties in the company’s ability to identify, design, develop, manufacture, and market products that customers desire resulting in an acceptable return for the company. Based on a basic model of innovative product development, our framework identifies three dimensions of risk in product development: Envisioning Risk, Design Risk, and Execution Risk. The risk framework points out the criticality of the engineering design activity and of the interdependencies between all facets of the organization in executing innovative product development. This paper also presents a qualitative methodology, based on the risk framework, that may be used by development teams for identification of risk and eliciting risk management solutions.

Intelligent Process Planning Implemented As an Integrated Module of CIM

In this paper we describe an architecture of a new integrative process planning system as a part of computer integrated manufacturing research system. The process planning procedure is comprised of three phases: feature completion, process selection and process sequencing. We applied a knowledge-based approach to feature completion and process selection, and the space search algorithm for process sequencing. Description of these phases is provided and underlying knowledge representation explained. Integration between the process planning, on the one side, and CAD and scheduling, on the other, is discussed. System implementation has been described and several examples of the system execution are shown.

The Process Capability Matrix: A Tool for Manufacturing Variation Analysis at the Systems Level

This paper introduces the concept of a process capability matrix — an ordered set of dimensionless parameters that capture information on a manufacturing system’s response to noises. The matrix captures information on the magnitude of noise, sensitivity to noise, and tolerance to variation. Algorithms and equations are presented that use the matrix to compute the yield of a manufacturing system. The method proves to be accurate on real engineering problems for which existing techniques are inadequate due to statistical correlation among product acceptance criteria. The process capability matrix also proves useful in a new type of block diagram of production systems. The block diagrams are shown to be useful in evaluating the effectiveness of feedforward control strategies for variation reduction. An electronics assembly process serves as an example of the algorithms and their use in design decision making.

Using Symmetry to Reduce Planning Complexity: A Case Study in Sheet-Metal Production

In this paper, we present an approach to recognize symmetries of bent sheet-metal parts at different manufacturing stages. This approach is based on Waltzman’s (Waltzman, 1987) 2D symmetry detection algorithm. 3D symmetry is recognized by considering its 2D symmetry and the associated bending transformations. We show, by recognizing that the part is symmetrical, that the planning complexity for processes in sheet-metal production can be greatly reduced. This paper is motivated by the fact that a significant percentage of sheet-metal parts are symmetrical. We have studied over 200 industrial parts and over 40% of them are symmetrical. Examples from sheet-metal nesting (layout planning), bending, stacking, product decomposition and assembly planning are discussed.

Tactile Display for a Surface Texture Sensation

The authors have developed tactile displays which have vibrating pins to convey the surface texture sensation of object surfaces to the user’s fingertip. The tactile sensation intensity scaling was performed to obtain a sensation scale of the display by means of the JND (just noticeable difference) method. One dimensional curves on the scale were displayed to investigate the human sensitivity to an intensity change rate. A tactile texture presentation method based on the image of an object surface is introduced. Two kinds of experiment were performed to discuss the feature of the method. Texture discrimination is the first one, in which the effect of texture element size to the correct separation was discussed. Then the sensations produced by the display and those by real objects were compared regarding several samples that had a major feature of vertical lines and of not containing low frequencies. The results are summarized, which is followed by the future research work.

Constraint-Based Reverse Engineering From Ultrasound Cross-Sections

This paper extends the “cross-sectional” approach for reverse engineering, used abundantly in biomedical applications, to the mechanical domain. We propose a combination of “projective” and cross-sectional algorithms for handling physical artifacts with complex topology and geometry. In addition, the paper introduces the concept of constraint-based reverse engineering, where the constraint parameters could include one or more of the following: time, storage (memory, disk-space), network bandwidth, Quality of Service (output-resolution), and so forth. We describe a specific reverse-engineering application which uses ultrasound (tilt-echo) imaging to reverse engineer spatial enumeration (volume) representations from cross-sectional data. The constraint here is time, and we summarize how our implementation can satisfy real-time reconstruction for distribution of the volume data on the internet. We present results that show volume representations computed from static objects. Since the algorithms are tuned to satisfy time constraints, this method is extendable to reverse engineer temporally-varying (elastic) objects. The current reverse engineering processing time is constrained by the data-acquisition (tilt-echo imaging) process, and the entire reverse engineering pipeline has been optimized to compute incremental volume representations in the order of 3 seconds on a network of four processors.

Design and Virtual Prototyping of Rehabilitation Aids

This paper presents a paradigm for virtual prototyping of a class of one-of-a-kind assistive devices that can be customized to the human user. This class consists of passive, articulated mechanical aids for manipulation that are physically coupled to the user. We address the mechanism synthesis, design and optimization and its evaluation in a virtual prototyping environment that consists of a CAD model of the product and a customized model of the human user. In addition, we develop the theory and methodology for designing planar serial chain mechanisms with revolute joints coupled by cable-pulley transmissions. As an illustrative example, we consider the design and prototyping of a customized feeding aid for quadriplegics.

Haptic Interfacing for Virtual Prototyping of Mechanical CAD Designs

A network-based real-time control architecture has been developed which integrates a haptic interface (the Sarcos Dextrous Arm Master) with an advanced CAD modeling system (Utah’s Alpha_1). New algorithms have been developed and tested for surface proximity testing, fast updates to local closest point on a surface, and smooth transitions between surfaces. The combination of these new algorithms with the haptic interface and CAD modeling system permits a user to actively touch and manipulate virtual parts as well as passively view them on a CRT screen.

Analytical Method for the Prediction of Reliability and Maintainability Based Life-Cycle Labor Costs

In today’s competitive marketplace, the quality of a product is becoming increasingly more important. The informed customer not only weighs the ability of the product to meet his/her requirements, and the purchase price of the product, but also the money that must be expended to maintain the function of the product. Hence, lowering the life-cycle cost of a product will increase its value and attractiveness to the customer.