Samir Garbaya

The affect of contact force sensations on user performance in virtual assembly tasks

The development of a realistic virtual assembly environment is challenging because of the complexity of the physical processes and the limitation of available VR technology. Many research activities in this domain primarily focused on particular aspects of the assembly task such as the feasibility of assembly operations in terms of interference between the manipulated parts. The virtual assembly environment reported in this research is focused on mechanical part assembly. The approach presented addresses the problem of part-to-part contacts during the mating phase of assembly tasks. The system described calculates contact force sensations by making their intensity dependent on the depth of penetration. However the penetration is not visible to the user who sees a separate model, which does not intersect the mating part model. The two 3D models of the part, the off-screen rendered model and the on-screen rendered model are connected by a spring-dumper arrangement. The force calculated is felt by the operator through the haptic interface when parts come in contact during the mating phase of the assembly task. An evaluation study investigating the effect of contact force sensation on user performance during part-to-part interface was conducted. The results showed statistically significant effect of contact force sensation on user performance in terms of task completion time. The subjective evaluation based on feedback from users confirmed that contact force sensation is a useful cue for the operator to find the relative positions of components in the final assembly state.

The development of a physics and constraint based haptic virtual assembly system

Purpose – This paper aims to report the development and key features of a novel virtual reality system for assembly planning and evaluation called Haptic Assembly and Manufacturing System (HAMS). The system is intended to be used as a tool for training, design analysis and path planning. Design/methodology/approach – The proposed system uses the physics-based modelling (PBM) to perform assemblies in virtual environments. Moreover, dynamic assembly constrains have been considered to reduce the degrees of freedom of virtual objects and enhance the virtual assembly performance. Findings – To evaluate the effectiveness and performance of HAMS, the assembly of various mechanical components has been carried out, and the results have shown that it can be effectively used to simulate, evaluate, plan and automatically formalise the assembly of complex models in a more natural and intuitive way. Research limitations/implications – The collision detection performance is the bottleneck in any virtual assembly system....

Modeling Dynamic Behavior of Parts in Virtual Assembly Environment

Physically-based behavior of parts and subassemblies provides the user with realistic virtual assembly planning environment. Parts’ mating is an important phase of the assembly operation. It determines the feasibility of the operation and affects the assembly sequence generated from the interaction with virtual parts. Haptic sensation of forces generated by the contacts between parts, during the mating phase, is a perception cue which assists the operator in locating the parts in their final assembly positions and orientations [1]. The research work reported in this paper focuses on modeling the dynamic behavior of mechanical parts during the execution of virtual assembly operation. The concept of spring-damper model was adopted to preclude the interpenetration of parts during the mating phase. The concept of “visual dynamic behavior” representing the manipulation of real parts was developed. More investigations are required to extend this concept to include the manipulation of subassemblies.Copyright

Virtual Assembly Environment Modelling

In this paper, we present the virtual environment of assembly sequence generation of a product at the design stage. The interaction technique developed for the manipulation of virtual parts includes visual and haptic feedback limited to force sensation in the fingertips and weight and inertia parts sensation. At this stage of development, the parts and subassemblies have kinematics behaviour in the virtual scene. We present some guidelines for modeling a generic virtual environment for performing assembly tasks. Virtual parts modeling and connections modeling is based on characteristics of real parts and connections. The mating phase of assembly is based on the Snap-Fitting technique, which is improved by the addition of vectors in the symmetry axis of virtual parts. An XML modeling allows the environment to be generic and supporting different products.Copyright

A new methodology to evaluate the performance of physics simulation engines in haptic virtual assembly

Purpose – In this study, a new methodology to evaluate the performance of physics simulation engines (PSEs) when used in haptic virtual assembly applications is proposed. This methodology can be used to assess the performance of any physics engine. To prove the feasibility of the proposed methodology, two-third party PSEs – Bullet and PhysXtm – were evaluated. The paper aims to discuss these issues. Design/methodology/approach – Eight assembly tests comprising variable geometric and dynamic complexity were conducted. The strengths and weaknesses of each simulation engine for haptic virtual assembly were identified by measuring different parameters such as task completion time, influence of weight perception and force feedback. Findings – The proposed tests have led to the development of a standard methodology by which physics engines can be compared and evaluated. The results have shown that when the assembly comprises complex shapes, Bullet has better performance than PhysX. It was also observed that the...

Harmonizing interoperability - Emergent Serious Gaming in Playful Stochastic CAD Environments

Computer-Aided Design (CAD) applications often promote memorable experiences for the wrong reasons. Coupled with complex functionality and poor user experience the learning curve is often steep and overwhelming. Invoking design creativity remains limited to conveying established geometry. Gameplay conversely excels in memorable and formative experiences and could spur intuition and natural creativity. If games are profoundly imbued for purposeful play, thriving on tacit and explicit user knowledge, a CAD system carefully stylized with ludic mechanisms could potentially be highly productive. An emergent serious game (SG) and CAD system may then hold promise. Preliminary feedbacks suggest a game-CAD environment incorporating interoperable mechanisms of CAD and SG systems to exchange creation improves user interactions resulting in better evolution of the workflow. The emerging scenarios presented reports a transformative approach to understanding of relationships in CAD use, learning and play mechanisms that enhance creativity and innovation.

From virtual to augmented reality in financial trading: a CYBERII application

Abstract Digital media technology is becoming an integral part of our daily activities, with widespread penetration in various application domains including arts, medicine, education, and commerce. The purpose of this paper is to discuss the horizon of emerging digital media technologies in electronic financial trading with reference to a novel application drawing expertise from two important fields of study, namely: digital media (video and image) processing and augmented reality. The paper presents an ergonomic study that considers the potential utility and usability of augmented reality (AR) in finance. In order to justify the outcome of this ergonomic study, the authors describe the technology under study (CYBERII) and its implementation in finance. This ergonomic study is based on a comparative analysis of the use of AR with a counterpart virtual reality (VR) approach used for the same application. The comparative analysis highlights an added value in the shift from the use of VR to AR in electronic financial trading. This added value is gained from augmented realism and less constrained interaction. The paper discusses the challenges and rewards of the emerging digital mediatechnologies in meeting the needs of electronic commerce applications, particularly in electronic financial trading. The main considerations taken into account are the realism of rendering, systemportability, and widespread usability. This study motivates further ergonomic studies involving the evaluation of augmented reality integration including CYBERII technology, in the field of electronic commerce.

Towards a Model for Predicting Intention in 3D Moving-Target Selection Tasks

Novel interaction techniques have been developed to address the difficulties of selecting moving targets. However, similar to their static-target counterparts, these techniques may suffer from clutter and overlap, which can be addressed by predicting intended targets. Unfortunately, current predictive techniques are tailored towards static-target selection. Thus, a novel approach for predicting user intention in moving-target selection tasks using decision-trees constructed with the initial physical states of both the user and the targets is proposed. This approach is verified in a virtual reality application in which users must choose, and select between different moving targets. With two targets, this model is able to predict user choice with approximately 71% accuracy, which is significantly better than both chance and a frequentist approach.

An evaluation of physics engines and their application in haptic virtual assembly environments

This paper presents a practical method and a new haptic model to support manipulations of bones and their segments during the planning of a surgical operation in a virtual environment using a haptic interface. To perform an effective dental surgery it is important to have all the operation related information of the patient available beforehand in order to plan the operation and avoid any complications. A haptic interface with a virtual and accurate patient model to support the planning of bone cuts is therefore critical, useful and necessary for the surgeons. The system proposed uses DICOM images taken from a digital tomography scanner and creates a mesh model of the filtered skull, from which the jaw bone can be isolated for further use. A novel solution for cutting the bones has been developed and it uses the haptic tool to determine and define the bone-cutting plane in the bone, and this new approach creates three new meshes of the original model. Using this approach the computational power is optimized and a real time feedback can be achieved during all bone manipulations. During the movement of the mesh cutting, a novel friction profile is predefined in the haptical system to simulate the force feedback feel of different densities in the bone.Whether from internal sources or arising from environmental sources, thermal error in most machine tools is inexorable. Out of several thermal error control methods, electronic compensation can be an easy-to-implement and cost effective solution. However, analytically locating the optimal thermally sensitive points within the machine structure for compensation has been a challenging task. This is especially true when complex structural deformations arising from the heat generated internally as well as long term environmental temperature fluctuations can only be controlled with a limited number of temperature inputs. This paper presents some case study results confirming the sensitivity to sensor location and a new efficient offline method for determining localized thermally sensitive points within the machine structure using finite element method (FEA) and Matlab software. Compared to the empirical and complex analytical methods, this software based method allows efficient and rapid optimization for detecting the most effective location(s) including practicality of installation. These sensitive points will contribute to the development and enhancement of new and existing thermal error compensation models respectively by updating them with the location information. The method is shown to provide significant benefits in the correlation of a simple thermal control model and comments are made on the efficiency with which this method could be practically applied.Virtual Reality (VR) applications are employed in engineering situation to simulate real and artificial situations where the user can interact with 3D models in real time. Within these applications the virtual environment must emulate real world physics such that the system behaviour and interaction are as natural as possible and to support realistic manufacturing applications. As a consequence of this focus, several simulation engines have been developed for various digital applications, including VR, to compute the physical response and body dynamics of objects. However, the performance of these physics engines within haptic-enabled VR applications varies considerably. In this study two third party physics engines - Bullet and PhysXtm- are evaluated to establish their appropriateness for haptic virtual assembly applications. With this objective in mind five assembly tasks were created with increasing assembly and geometry complexity. Each of these was carried out using the two different physics engines which had been implemented in a haptic-enabled virtual assembly platform specifically developed for this purpose. Several physics-performance parameters were also defined to aid the comparison. This approach and the subsequent results successfully demonstrated the key strengths, limitations, and weaknesses of the physics engines in haptic virtual assembly environments.Communicating the knowledge and science of product engineering, analysis and manufacturing planning is an area of continued research driven by the digital economy. Virtual Reality (VR) is a generally accepted interactive digital platform which industry and academia have used to model engineering workspaces. Interactive services that generate a sense of immersion, particularly the sense of touch to communicate shape modelling and manipulation, is increasingly being used in applications that range from Design For Manufacturing and Assembly (DFMA) and Process Planning (PP) to medical applications such as surgical planning and training. In simulation, the natural way for solid modelling is the use of primitive geometries, and combinations of them where complex shapes are required, to create, modify or manipulate models. However, this natural way makes use of Booleans operands that require large computational times which make them inappropriate for real time VR applications. This work presents an insight on new methods for haptic shape modelling focused on Boolean operands on a polygon mesh. This is not meant as a contrast to point/mesh- editing methods, instead it is focused on idealising polygonal mesh modelling and manipulation for use with haptics. The resulting models retain a high level of geometric detail for visualisation, modelling, manipulation and haptic rendering.

Effect of weight perception on human performance in a haptic-enabled virtual assembly platform

Virtual assembly platforms (VAPs) provide a means to interrogate product form, fit and function thereby shortening the design cycle time and improving product manufacturability while reducing assembly cost. VAPs lend themselves to training and can be used as offline programmable interfaces for planning and automation. Haptic devices are increasingly being chosen as the mode of interaction for VAPs over conventional glove-based and 3D-mice, the key benefit being the kinaesthetic feedback users receive while performing virtual assembly tasks in 2D/3D space leading to a virtual world closer to the real world. However, the challenge in recent years is to understand and evaluate the addedvalue of haptics. This paper reports on a haptic enabled VAP with a view to questioning the awareness of the environment and associated assembly tasks. The objective is to evaluate and compare human performance during virtual assembly and real-world assembly, and to identify conditions that may affect the performance of virtual assembly tasks. In particular, the effect of weight perception on virtual assembly tasks is investigated.