HAPTIC SCULPTING AND 5-AXIS PENCIL-CUT PLANNING IN VIRTUAL PROTOTYPING AND MANUFACTURING

ABSTRACT In this paper, a Two-phase approach to tool collision detection and local gouging elimination is proposed for haptic pencil-cut of sculptured surfaces. Pencil-cut is a special kind of machining operation, whose purpose is to use relatively smaller tools to remove rest material on the corners or highly curved regions that are inaccessible by bigger tools. Tool orientation determination and tool collision avoidance are critical issues for 5-axis pencil-cut tool path planning. Detailed techniques of haptic rendering and tool interference avoidance are discussed for haptic-aided 5-axis pencil-cut tool path generation. Hardware and software implementation of the haptic pencil-cut system with practical examples are also presented in this paper

The addition of the haptic modality to the virtual reality modeling language

Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1998.Includes bibliographical references (p. 40-43).by Evan F. Wies.S.B.and M.Eng

Haptic rendering of continuous parametric models

Haptic rendering is the process of computing restoring forces that are required to generate a perception of touch between a user and a virtual environment. The realism of haptic rendering depends mainly on haptic rendering algorithms and the modeling of virtual objects in a virtual environment. Friction and texture rendering also play an important role in increasing the realism of the experience between a user and a virtual environment. The state of the art haptic and friction rendering algorithms in the literature are developed for polygonal models. These approaches can not benefit from the advantages of continuous parametric surfaces such as compact representation, higher order continuity and exact computation of surface normals. In this thesis, a feedback-stabilized closest point tracking based haptic rendering algorithm is extended by introducing a direct friction rendering method for continuous parametric surfaces. Unlike the existing approaches, the proposed friction rendering method is direct and does not rely on the algorithms introduced for polyhedral surfaces. This algorithm implements the stiction model of friction for haptic rendering of parametric surfaces. It can directly operate on parametric models and can handle surfaces with high curvature. Furthermore, the algorithm allows transitions from sticking to sliding and sliding to sticking, as well as surface to surface transitions, without introducing discontinuous force artifacts. The algorithm also allows for tuning of the friction coefficient during the mode transitions to enable rendering of the Stribeck effect. Thanks to its feedback-stabilized core, it is robust against drift and numerical noise. The algorithm is computationally efficient (with respect to time and space); its applicability and effectiveness to simulate friction are verified through simulations and real-time implementations. In particular, the friction rendering algorithm is tested using pre-determined trajectories that demonstrate successful rendering of static friction at a corner, the mode changes from static-to-dynamic and dynamic-to-static friction

Types of Digital Visuals in E-Learning

This session explores the various types of digital visuals used in e-learning, with examples covering one-dimensional to four-dimensional imagery. Examples will demonstrate how the addition of live data, time elements, image overlays, digital-enabled effects, and interactivity add value to electronic learning. Samples from live courses and sites will be shown. There will be a discussion of how the various types of images can be developed

Haptic rendering of parametric surfaces using a feedback stabilized extremal distance tracking algorithm

A new extremal distance tracking algorithm is presented for convex parametric curves and surfaces undergoing rigid body motion. The geometric extremization problem is differ-entiated with respect to time to produce a dynamical system that incorporates dependence on both surface shape and rigid body motion. Extremization then takes place by in-tegrating these dynamical equations, but with a feedback controller in place to stabilize the solution. A controller design using feedback linearization is developed that si-multaneously accounts for surface shape and motion while asymptotically achieving (and maintaining) the extremal pair. Collision detection then takes place in a framework fully analogous to that used for multibody simulation. Lo-cal stability results are extended to provide global stability for body shapes composed of pieced-together convex para-metric surface patches using a switching algorithm

Modeling and rendering for development of a virtual bone surgery system

A virtual bone surgery system is developed to provide the potential of a realistic, safe, and controllable environment for surgical education. It can be used for training in orthopedic surgery, as well as for planning and rehearsal of bone surgery procedures...Using the developed system, the user can perform virtual bone surgery by simultaneously seeing bone material removal through a graphic display device, feeling the force via a haptic deice, and hearing the sound of tool-bone interaction --Abstract, page iii

Design and development of a VR system for exploration of medical data using haptic rendering and high quality visualization

[no abstract

Collision Detection and Merging of Deformable B-Spline Surfaces in Virtual Reality Environment

This thesis presents a computational framework for representing, manipulating and merging rigid and deformable freeform objects in virtual reality (VR) environment. The core algorithms for collision detection, merging, and physics-based modeling used within this framework assume that all 3D deformable objects are B-spline surfaces. The interactive design tool can be represented as a B-spline surface, an implicit surface or a point, to allow the user a variety of rigid or deformable tools. The collision detection system utilizes the fact that the blending matrices used to discretize the B-spline surface are independent of the position of the control points and, therefore, can be pre-calculated. Complex B-spline surfaces can be generated by merging various B-spline surface patches using the B-spline surface patches merging algorithm presented in this thesis. Finally, the physics-based modeling system uses the mass-spring representation to determine the deformation and the reaction force values provided to the user. This helps to simulate realistic material behaviour of the model and assist the user in validating the design before performing extensive product detailing or finite element analysis using commercially available CAD software. The novelty of the proposed method stems from the pre-calculated blending matrices used to generate the points for graphical rendering, collision detection, merging of B-spline patches, and nodes for the mass spring system. This approach reduces computational time by avoiding the need to solve complex equations for blending functions of B-splines and perform the inversion of large matrices. This alternative approach to the mechanical concept design will also help to do away with the need to build prototypes for conceptualization and preliminary validation of the idea thereby reducing the time and cost of concept design phase and the wastage of resources

Virtual reality based creation of concept model designs for CAD systems

This work introduces a novel method to overcome most of the drawbacks in traditional methods for creating design models. The main innovation is the use of virtual tools to simulate the natural physical environment in which freeform. Design models are created by experienced designers. Namely, the model is created in a virtual environment by carving a work piece with tools that simulate NC milling cutters. Algorithms have been developed to support the approach, in which the design model is created in a Virtual Reality (VR) environment and selection and manipulation of tools can be performed in the virtual space. The desianer\u27s hand movements generate the tool trajectories and they are obtained by recording the position and orientation of a hand mounted motion tracker. Swept volumes of virtual tools are generated from the geometry of the tool and its trajectories. Then Boolean operations are performed on the swept volumes and the initial virtual stock (work piece) to create the design model. Algorithms have been developed as a part of this work to integrate the VR environment with a commercial CAD/CAM system in order to demonstrate the practical applications of the research results. The integrated system provides a much more efficient and easy-to-implement process of freeform model creation than employed in current CAD/CAM software. It could prove to be the prototype for the next-generation CAD/CAM system