W. Edward Red

Model Consistency and Conflict Resolution With Data Preservation in Multi-User Computer Aided Design

Simultaneous multi-user computer aided design (CAD) allows multiple designers to contribute to the same model at the same time. The resulting parallel design workflow shortens product development cycles. In a replicated, simultaneous multi-user CAD system, modeling data must be kept consistent between clients. This paper presents a method that keeps independent copies of the models in sync between distributed CAD clients. This is accomplished by enforcing modeling operations to occur in the same order on all the clients. In case of conflict, a resolution method preserves conflicting operations locally for later reuse or resolution by the user. These methods are implemented in a commercial CAD system which has been enhanced to enable simultaneous multi-user. Validation tests are run to demonstrate that the methods implemented ensure model consistency and resolve conflicts while preserving conflicting operation data.

Collaborative Design Principles From Minecraft With Applications to Multi-User CAD

Real-time simultaneous multi-user (RSM) computer-aided design (CAD) is currently a major area of research and industry interest due to its potential to reduce design lead times and improve design quality through enhanced collaboration. Minecraft, a popular multi-player online game in which players use blocks to design structures, is of academic interest as a natural experiment in collaborative 3D design of very complex structures. Virtual teams of up to forty simultaneous designers have created city-scale models with total design times in the thousands of hours. Using observation and a survey of Minecraft users, we offer insights into how virtual design teams might effectively build, communicate, and manage projects in an RSM CAD design environment. The results suggest that RSM CAD will be useful and practical in an engineering setting with several simultaneous contributors. We also discuss the potential effects of RSM CAD on team organization, planning, design concurrency, communication, and mentoring.Copyright

Direct Process Control Using n-Dimensional NURBS Curves

AbstractDirect control allows CAD/CAM applications to pass native part geometry directly to a machine tool for part processing. Although highly efficient for 3-axis machines, one of direct control’s advantages is in implementing new algorithms for 5 and 6-axis machining, where the tool orientation is a more complex function of the surface geometry. This paper introduces a new extended n-dimensional NURBS vector that incorporates tool orientation into control parameters. By including state control parameters such as feed rate and spindle rpm, the n-D NURBS becomes the first mathematical representation to incorporate all required machining information.

The local calibration method for robot inaccuracy compensation

This article presents a local calibration method that is philosophically different from the more contemporary global calibration methods. Local methods seek models of robot performance at the robot distal link measured relative to parts in localized part regions. In contrast, global methods seek to model various sources of robot inaccuracy internal to the robot. For example, a significant global research area is the determination of the actual robot arm structural parameters. Given more accurate estimates of these parameters, global compensation methods propose perturbation techniques or improved kinematic models that can be used to control the as-manufactured robot. To implement local calibration methods, calibration procedures have been developed to locate tool and sensor tool control frames (TCFs) and to measure robot inaccuracy in localized regions. Using the measured position and orientation (pose) data obtained by hardware sensors, the components of operational inaccuracy are integrated into compensation models. This article discusses compensating model effectiveness and considers the interactions between hardware sensors and part features necessary to extract robot pose measurements automatically and effectively. Applying the relative calibration methodologies presented in this article to a GMF S-200 six-axis robot, robot repeatability was reduced by 39% and average localized robot inaccuracy was reduced from 3.4 mm (0.134 inch) to less than 0.86 mm (0.034 inch). The compensated robot inaccuracy is near the unstructured robot repeatability.

Collaborative Design Principles From Minecraft With Applications to Multi-User Computer-Aided Design

Synchronous collaborative (“multi-user”) computer-aided design (CAD) is a current topic of academic and industry interest due to its potential to reduce design lead times and improve design quality through enhanced collaboration. Minecraft, a popular multiplayer online game in which players can use blocks to design structures, is of academic interest as a natural experiment in a collaborative 3D design of very complex structures. Virtual teams of up to 40 simultaneous designers have created city-scale models with total design times in the thousands of hours. Using observation and a survey of Minecraft users, we offer insights into how virtual design teams might effectively build, communicate, and manage projects in a multi-user CAD design environment. The results suggest that multi-user CAD will be useful and practical in an engineering setting with several simultaneous contributors. We also discuss the effects of multi-user CAD on team organization, planning, design concurrency, communication, and mentoring.

Enhancements for Improved Topological Entity Identification Performance in Multi-user CAD

ABSTRACTMulti-user CAD allows designers to simultaneously work on a model, allowing designs to be realized at a much faster rate than ever before. In a replicated, simultaneous multi-user CAD system, it is critical that models be consistent between clients. A major component of model consistency is ensuring references to topological objects be the same on all clients in the same part. Previous methods are inefficient for models with a large number of faces and edges. This paper presents enhancements over previous methods which more efficiently identify faces and edges through lazy naming as well as caching and normalizing topological entity data. The implementation and results of these enhancements show significant time savings compared to an eager naming method.

Development of a Variational Part Model Using In-Process Dimensional Measurement Error

AbstractTo improve the precision of CNC machined parts, the dynamic machining errors due to tool deflection, tool wear, heat deformation, etc. should be accounted for. This paper presents a systematic approach for automatically compensating for these errors based on a new closed-looped machining scheme. The new scheme introduces a Variational Part Model which inherently possesses the dynamic machining error. To create the Variational Part Model, the machined part is measured on the machine (in-process inspection) and compared to the CAD model’s theoretical data. The data is then used in conjunction with modeling functions contained in Unigraphics’ Application Programming Interface (API) to interact with the CAD model and modify it’s surface geometry. The validity and effectiveness of the methods are presented as well as results from experimental testing.

Part Relative Robot Inaccuracy Compensation Using Kinematic and Stochastic Modeling

In spite of its programming limitations, most robot tasks are planned using teach pendent programming. Off-line simulation enhances robot programmability, but it has one residual flaw: most industrial robots are too inaccurate to precisely follow paths generated off-line. Robot inaccuracy results in position deviation between the simulated path and the implemented path. An efficient and practical methodology to significantly improve robot accuracy of paths planned off-line has yet to be devised. The purpose of this paper is to describe a methodology for practical robot calibration intended to reduce robot inaccuracy. Calibrated models of robot position are determined by measuring robot poses in relation to a calibrated table or plate. Pose measurements are obtained with a vision-system camera and touch probe mounted adjacent to the robot end-effector. Kinematic and stochastic models of robot position are derived from the pose measurements. These models are incorporated into simulation software to provide inaccuracy compensation for paths planned off-line.

Off-Line Integration Techniques for Robot Path Planning

Off-line programming techniques are not developed to the stage of practical application because of robot inaccuracy, difficulty in precise robot calibration,and difficulty in interfacing to CAD data bases. In this paper we present a practical approach to off-line programming of robots used in microelectronics assembly by integrating an off-line simulation program with data base preprocessing, robot calibration and robot inaccuracy correction. The calibration algorithms and the integration techniques described in this paper were verified in an environment of microelectronics assembly using a cylindrical robot.

Multi-user collaborative tool path planning using process decomposition

ABSTRACTSingle-user computer-aided engineering applications force a strictly serial design process, which ultimately lengthens time to market. We created multi-user tool path planning software, which allows the work to be done in parallel by several users who are experts in various processes. Key to decreasing the time spent developing tool paths is the decomposition of the various operations needed to manufacture a part among various users. By observing the use of other multi-user applications as well as observing users developing tool paths using current CAM software, we developed a method to decompose the paths among the users. Finally, we estimate the process time saved.