摘要:

Smooth motion generation is an important issue in the computer animation and virtual reality (VR) area. In general, the motion of a rigid body consists of translation and orientation. The former is described by a space curve in 3-dimensional Euclidean space, while the latter is represented by a curve in the unit quaternion space. Although there are well-known techniques for smoothing the translation curve in the Euclidean space, few results have been reported for smoothing motion as a whole. This paper improves the previous study and provides a more robust algorithm, which seeks to minimize the weighted sum of the strain-energy and the sum of the squared errors.

ISSN:0740-817X    

DOI:10.1080/07408179808966503

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In a manufacturing enterprise, virtual environments can improve productivity by allowing employees to train without taking production equipment out of service. As a demonstration of this capability, we have developed a virtual environment to simulate overhead crane operation. This virtual environment was developed by combining 3-D factory drawings with 3-D simulation models of crane and load motion. The crane simulator allows an operator to maneuver a crane and load in three dimensions. Implemented on a PC with an update rate of 14.3 Hz, the simulator runs in real-time interaction that approximates live machinery.

ISSN:0740-817X    

DOI:10.1080/07408179808966504

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An approach to automatically extract three dimensional (3D) models (that is, geometries and topologies) of physical objects in a facility is described. The rationale for this work is its repeated use in efficiently developing databases of 3D objects for applying virtual reality (VR) tools in detailed layout decision support. Obtaining 3D object models can be a challenging task. Sometimes they are available, for example, in a Computer-Aided Design (CAD) database and these can be readily imported into a VR database. But on many occasions one is not so fortunate and these object models have to be created in correlation to an existing or proposed facility, which can be an extremely tedious and time consuming task. A time efficient and economical alternative is to use video camera images, but quickly and accurately capturing the depth information from 2D camera images has so far remained elusive because the existing methodologies are too general purpose and operate at a lower level of abstraction, namely digitized images. We have developed a method for directly inputting 3D objects into VR-aided facility layout models, by integrating the strengths of previously tried and tested technological components: (i) camera calibration; (ii) image processing; (iii) stereo vision; and (iv) Delaunay triangulation. The techniques described here are embedded in a prototype architecture and toolkit called MIRRORS (Methodology for Inputting Raw Recordings into 3D Object Renderings for Stereo). The primary contribution of this paper is that it has been able to design an integrated system to build 3D object models from 2D images. The MIRRORS system has been primarily designed for objects without free-form surfaces and whose shape can be recovered from a relatively nondense set of points.

ISSN:0740-817X    

DOI:10.1080/07408179808966505

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Most software packages available for particle tracing focus on visualizing steady or unsteady vector fields by using massless particle trajectories. For many applications, however, the use of massed and evaporating particles would provide a model of physical processes that could be used in product testing or design. In this article we describe the TrackPack toolkit, which provides an integrated interface for computing massless, massed, and evaporating particle trajectories in steady flow. In all cases, we assume a noncoupled model and compute particle trajectories through an existing vector field by numerically integrating with forward Euler, fourth-order Runge-Kutta, or an analytic streamline calculation. The TrackPack software effort was motivated by an industrial application to model pollution control systems in industrial boilers. We briefly describe the project and the visualization environment, and we demonstrate the necessity for massed, evaporating models in the application.

ISSN:0740-817X    

DOI:10.1080/07408179808966506

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

It is generally acknowledged that existing computer-aided design systems have inefficient user interfaces. Especially during the concept shape design stage, these systems prove to be cumbersome because of two reasons: (i) they require the usage of two-dimensional (2D) input devices, while the designs are typically three-dimensional (3D); and, (ii) CAD systems require the specification of dimensions, which may not be precisely known at the concept stage. To overcome these limitations, this research proposes the use of virtual reality (VR) devices to provide a physically intuitive interface for concept shape creation. The intuitiveness of the interface arises from the use of natural hand gestures and voice commands that emulate the way in which designers discuss concept shapes. In this scenario, the interface between the human and computer plays a central role with respect to usability, usefulness and accuracy. The focus of this research is on using two modalities: (i) hand input; and, (ii) voice driven commands, or a combination of these modalities to accomplish typical CAD tasks. Based on experience with a conventional CAD system, a set of typical CAD tasks are identified. A series of tests are then performed to determine the relative efficiency of the different modality combinations to achieve each task. The interface test results indicate that while voice commands are intuitive in initiating operations such as viewpoint zooming in/out and object creation/deletion, hand inputs are effective in performing spatial tasks such as interactive dimensioning and re-location of shapes. It was also found that a combination of voice and hand input can be used for accomplishing certain tasks more effectively such as, zooming in/out a particular direction (hand orientation indicates direction and voice is used for indicating zoom in/out operation). Based on the experience with the prototypical system developed it is concluded that voice and hand input are effective ways of building three-dimensional shapes in a virtual reality environment. To verify the efficiency of the VR-CAD interface, sample injection molded parts are built on the current VR-based CAD system and a traditional CAD system, and the times taken to build these parts are compared. The test results indicate that building geometry shapes containing canonical forms, such as block, cylinder, sphere, ⃛ etc, using a VR interface results in a speedup of five to ten times over traditional CAD systems.

ISSN:0740-817X    

DOI:10.1080/07408179808966507

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper studies static complexity in manufacturing systems. We enumerate factors influencing static complexity, and define a static complexity measure in terms of the processing requirements of parts to be produced and machine capabilities. The measure suggested for static complexity in manufacturing systems needs only the information available from production orders and process plans. The variation in static complexity is studied with respect to part similarity, system size, and product design changes. Finally, we present relationships between the static complexity measure and system performance.

ISSN:0740-817X    

DOI:10.1080/07408179808966508

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In manufacturing facilities, shipping and receiving traditionally have been concentrated in one or two areas of the building. The widespread introduction of just-in-time shipping policies in US manufacturing companies during the past 15 years, as well as the common use of decentralized receiving in the Japanese automobile industry, has motivated the consideration (and occasionally the adoption) of dock configurations to support decentralized receiving (also known as perimeter receiving). By providing multiple access points along the perimeter of the building, decentralized receiving generally reduces the time and cost associated with moving purchased parts to the locations within the facility where they are used, but also results in increased cost of construction, maintenance, and operation for docks and associated truck access/egress, as well as additional interior floorspace requirements. We develop an optimization-based procedure to determine which of several possible dock areas to construct, how many doors or gates each should have, how many unloading and internal material handling staff should be assigned to each group, and which inbound materials each group should handle. We consider the amortized cost of constructing and equipping the docks, the amortized cost of material handling equipment to support the unloaders and material handlers, the cost of operating the material handling equipment, and labor costs for both unloading and internal material handling.

ISSN:0740-817X    

DOI:10.1080/07408179808966509

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A flexible manufacturing system (FMS) is highly capital-intensive and FMS users are concerned with achieving high system utilization. The production planning function for setting up an FMS prior to production should be developed in order to make the most of the potential benefits of FMSs. We consider two production planning problems of grouping and loading a flexible flow system, which is an important subset of FMSs where the routing of parts is unidirectional. We show that considering this routing restriction as well as limited machine flexibility strongly affects both the solution techniques and the quality of the solutions. Because of the complexity of the problem, we present a heuristic approach that decomposes the original problem into three interrelated subproblems. We show that the proposed approach usually finds a near-optimum solution and is superior to an approach that exists in the literature of FMS production planning. We also introduce effective heuristic methods for two new subproblems that arise because of the unidirectional flow precedence and flexibility constraints. Computational results are reported and future research issues are discussed.

ISSN:0740-817X    

DOI:10.1080/07408179808966510

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0740-817X    

DOI:10.1080/07408179808966511

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0740-817X    

DOI:10.1080/07408179808966512

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor