Combining physical constraints with geometric constraint-based modeling for virtual assembly

The research presented in this dissertation aims to create a virtual assembly environment capable of simulating the constant and subtle interactions (hand-part, part-part) that occur during manual assembly, and providing appropriate feedback to the user in real-time. A virtual assembly system called SHARP System for Haptic Assembly and Realistic Prototyping is created, which utilizes simulated physical constraints for part placement during assembly.;The first approach taken in this research attempt utilized Voxmap Point Shell (VPS) software for implementing collision detection and physics-based modeling in SHARP. A volumetric approach, where complex CAD models were represented by numerous small cubic-voxel elements was used to obtain fast physics update rates (500--1000 Hz). A novel dual-handed haptic interface was developed and integrated into the system allowing the user to simultaneously manipulate parts with both hands. However, coarse model approximations used for collision detection and physics-based modeling only allowed assembly when minimum clearance was limited to ∼8-10%.;To provide a solution to the low clearance assembly problem, the second effort focused on importing accurate parametric CAD data (B-Rep) models into SHARP. These accurate B-Rep representations are used for collision detection as well as for simulating physical contacts more accurately. A new hybrid approach is presented, which combines the simulated physical constraints with geometric constraints which can be defined at runtime. Different case studies are used to identify the suitable combination of methods (collision detection, physical constraints, geometric constraints) capable of best simulating intricate interactions and environment behavior during manual assembly. An innovative automatic constraint recognition algorithm is created and integrated into SHARP. The feature-based approach utilized for the algorithm design, facilitates faster identification of potential geometric constraints that need to be defined. This approach results in optimized system performance while providing a more natural user experience for assembly

A low cost Virtual Reality interface for CAD model manipulation and visualization

The human-computer interface technology provided in modern CAD systems makes the use of two dimensional (2D) computer interfaces, e.g. a keyboard and mouse, to generate and interact with CAD models. In addition, all CAD systems project complex 3D CAD models on a two dimensional computer screen, and the designer has to understand the spatial relationship of the different parts in the assembly by visualizing it in his/her mind. Because of the 2D nature of the keyboard and mouse, his/her interaction with complex 3D CAD models is restrictive and unintuitive. As compared to the traditional computer interface, VR provides a more interactive and intuitive interface for interacting with complex 3D CAD models; however, the high cost related to the VR equipment and the high level of technical skill required for implementing these technologies have restricted the widespread acceptance of such useful technologies. With the development of low-cost VR technologies in recent years, VR solutions have become more accessible. The objective of the research presented in this thesis is to implement the currently available low-cost VR technology for providing solution to the human-computer interaction problems present in today\u27s CAD applications. The thesis first reviews and analyzes some of the low-cost VR applications which are available in the market for interacting with CAD models. It then elucidates the development and implementation of a low-cost VR human-computer interface, the VR CAD Model Viewer, which is capable of importing and rendering stereo views of CAD models made in CAD systems like Pro/Engineer. The application developed also provides the user with the 3D 6-degree of freedom Data Glove device to interact with CAD models using his/her hands. A human subjects study is also performed which aims at recording the interface performance and user feedback about the use and intuitiveness of the interface. Studying this new type of learning experience and charting its strengths and limits is an important frontier for cognitive science research, scientific modeling, and constructive pedagogy

Coexistent Brugada Syndrome and Wolff-Parkinson-White Syndrome: What is the Optimal Management?

AbstractCoexistent Brugada syndrome and Wolff-Parkinson-White (WPW) syndrome is rare, and as such poses management challenges. The overlap of symptoms attributable to each condition, the timing of ventricular stimulation after accessory pathway ablation and the predictive value of programmed stimulation in Brugada syndrome are controversial. We describe a case of coexistent Brugada syndrome and WPW syndrome in a symptomatic young adult. We discuss our treatment approach and the existing literature along with the challenges in management of such cases

Inappropriate mode switching clarified by using a chest radiograph

AbstractAn 80-year-old woman with a history of paroxysmal atrial fibrillation and atrioventricular node disease status post-dual chamber pacemaker placement was noted to have abnormal pacing episodes during a percutaneous coronary intervention. Pacemaker interrogation revealed a high number of short duration mode switching episodes. Representative electrograms demonstrated high frequency nonphysiologic recordings predominantly in the atrial lead. Intrinsic pacemaker malfunction was excluded. A chest radiograph showed excess atrial and ventricular lead slack in the right ventricular inflow. It was suspected that lead–lead interaction resulted in artifacts and oversensing, causing frequent short episodes of inappropriate mode switching

A Low Cost Virtual Reality Human Computer Interface for CAD Model Manipulation

Interactions with high volume complex three-dimensional data using traditional two-dimensional computer interfaces have, historically, been inefficient and restrictive. However, during the past decade, virtual reality (VR) has presented a new paradigm for human-computer interaction. This paper presents a VR human-computer interface system, which aims at providing a solution to the human-computer interaction problems present in today’s computer-aided design (CAD) software applications. A data glove device is used as a 3D interface for CAD model manipulation in a virtual design space. To make the visualization more realistic, real-time active stereo vision is provided using LCD shutter glasses. To determine the ease of use and intuitiveness of the interface, a human subject study was conducted for performing standard CAD manipulation tasks. Analysis results and technical issues are also presented and discussed