On the development of a haptic system for rapid product development

This paper presents a system development that extends haptic modeling to a number of key aspects in product development. Since haptic modeling has been developed based on physical laws, it is anticipated that a natural link between the virtual world and practical applications can be established based on haptic interaction. In the proposed system, a haptic device is used as the central mechanism for reverse engineering, shape modeling, real time mechanical property analysis, machining tool path planning and coordinate measuring machine (CMM) tolerance inspection path planning. With all these features in a single haptic system, it is possible to construct a three dimensional part by either haptic shape modeling or reverse engineering, then performing real-time mechanical property analysis in which the stiffness of a part can be felt and intuitively evaluated by the user, or generating collision free cutter tool path and CMM tolerance inspection path. Due to the force feed back in all of the above activities, the product development process is more intuitive, efficient and user-friendly. A prototype system has been developed to demonstrate the proposed capabilities.     

Haptic interaction and volume modeling techniques for realistic dental simulation

We present haptic simulation and volume modeling techniques for a virtual dental training system. The system allows dental students to learn dental procedures and master their skills with realistic tactual feelings. It supports various dental procedures, such as dental probing, to diagnose carious lesions, drilling operation for cavity preparation, and filling the prepared cavities with amalgam. The system requires fast and stable haptic rendering and volume modeling techniques working on the virtual tooth. Collision detection and force computation are implemented on an offset surface in volumetric representation to simulate reasonable physical interactions between dental tools with a certain volume and the teeth model. To avoid discrete haptic feeling due to the gap between the fast haptic process (1 KHz) and much slower visual update frequency (30 Hz) during drilling and filling the cavities, we employed an intermediate implicit surface to be animated between the original and target surfaces. The volumetric teeth model is converted into a geometric model by an adaptive polygonization method to maintain sharp features in every visual frame. Volumetric material properties are represented by stiffness and color values to simulate the resistance and texture information depending on anatomical tissues. Finally, we made a dental workbench to register sensory modalities like visual, auditory and haptic sensation.     

A haptic-rendering technique based on hybrid surface representation

A novel haptic rendering technique using a hybrid surface representation addresses conventional limitations in haptic displays. A haptic interface lets the user touch, explore, paint, and manipulate virtual 3D models in a natural way using a haptic display device. A haptic rendering algorithm must generate a force field to simulate the presence of these virtual objects and their surface properties (such as friction and texture), or to guide the user along a specific trajectory. We can roughly classify haptic rendering algorithms according to the surface representation they use: geometric haptic algorithms for surface data, and volumetric haptic algorithms based on volumetric data including implicit surface representation. Our algorithm is based on a hybrid surface representation - a combination of geometric (B-rep) and implicit (V-rep) surface representations for a given 3D object, which takes advantage of both surface representations.     

Hybrid client-server architecture and control techniques for collaborative product development using haptic interfaces

In this paper, a collaborative product development and prototyping framework is proposed by using distributed haptic interfaces along with deformable objects modeling. Collaborative Virtual Environment (CVE) is a promising technique for industrial product development and virtual prototyping. Network control problems such as network traffic and network delay in communication have greatly limited collaborative virtual environment applications. The problems become more difficult when high-update-rate haptic interfaces and computation intensive deformable objects modeling are integrated into CVEs for intuitive manipulation and enhanced realism. A hybrid network architecture is proposed to balance the computational burden of haptic rendering and deformable object simulation. Adaptive artificial time compensation is used to reduce the time discrepancy between the server and the client. Interpolation and extrapolation approaches are used to synchronize graphic and haptic data transmitted over the network. The proposed techniques can be used for collaborative product development, virtual assembly, remote product simulation and other collaborative virtual environments where both haptic interfaces and deformable object models are involved.     

Five-axis pencil-cut planning and virtual prototyping with 5-DOF haptic interface

In this paper, techniques of 5-axis pencil-cut machining planning with a 5-DOF (degree of freedom) output haptic interface are presented. Detailed techniques of haptic rendering and tool interference avoidance are discussed for haptic-aided 5-axis pencil-cut tool path generation. Five-axis tool path planning has attracted great attention in CAD/CAM and NC machining. For efficient machining of complex surfaces, pencil-cut uses relatively smaller tools to remove the remaining material at corners or highly curved regions that are inaccessible with larger tools. As a critical problem for 5-axis pencil-cut tool path planning, the tasks of tool orientation determination and tool collision avoidance are achieved with a developed 5-DOF haptic interface. A Two-phase rendering approach is proposed for haptic rendering and force-torque feedback calculation with haptic interface. A Dexel-based volume modeling method is developed for global tool interference avoidance with surrounding components in a 5-axis machining environment. Hardware and software implementation of the haptic pencil-cut system with practical examples are also presented in this paper. The presented technique can be used for CAD/CAM, 5-axis machining planning and virtual prototyping.     

Stroke-based modeling and haptic skill display for Chinese calligraphy simulation system

The goal of this paper is to study haptic skill representation and display in a Chinese calligraphy training system. The challenge is to model haptic skill during the writing of different strokes in Chinese characters and to achieve haptic rendering with high fidelity and stability. The planning of the writing process is organized at three levels: task, representation and device level to describe the haptic handwriting skill. State transition graph (STG) is proposed to describe switches between tasks during the handwriting. Chinese characters are modeled using 39 typical strokes, which are further grouped into basic and compound strokes. The compound stroke is considered to be sequential combination of the basic strokes. Straight and curve strokes are modeled using line segment and the Bezier curve, respectively. Information from STG is used for real-time collision detection and haptic rendering. Ambiguity of the collision detection at stroke-corner points is prevented using active stroke combined with local nearest point computation. A modified virtual fixture method is developed for haptic rendering. The approach is tested on a prototype training system using Phantom desktop. Initial experiments suggest that the proposed modeling and rendering method is effective.     

A reverse engineering method based on haptic volume removing

This paper presents a new reverse engineering methodology that is based on haptic volume removing. When a physical object is to be digitized, it is first buried in a piece of virtual clay that is generated with the help of a fixture. Now digitizing the physical object is by simply chipping away the virtual clay with a position tracker that is attached to a haptic device PHANToM^®. While chipping away the clay, the user can see on the computer monitor what is emerging and at the same time feel the chipping force from the haptic device. By so doing, reverse engineering is seamlessly integrated into haptic volume sculpting that is now widely used for conceptual design. Furthermore, the proposed method has eliminated the need to merge point clouds that are digitized from different views using current digitizers. The virtual clay volume is represented by a spatial run-length encoding scheme. A prototype system has been developed to demonstrate the feasibility of the proposed new method through a case study. The strengths and weaknesses of the presented method are analyzed and the applicability is discussed.     

Haptic sculpting of multi-resolution B-spline surfaces with shaped tools

In this paper, we first propose an implicit surface to B-spline surface haptic interface, which provides both force and torque feedback. We then present a new haptic sculpting system for B-spline surfaces with shaped tools of implicit surface. In the physical world, people touch or sculpt with their fingers or tools, instead of just manipulating points. Shaped virtual sculpting tools help users to relate the virtual modeling process to physical-world experience. Various novel haptic sculpting operations are developed to make the sculpting of B-spline surfaces more intuitive. Wavelet-based multi-resolution tools are provided to let modelers adjust the resolution of sculpture surfaces and thus the scale of deformation can be easily controlled. Moreover, sweep editing and 3D texture have been implemented by taking advantage of both the wavelet technique and haptic sculpting tools.     

Haptic modeling in the conceptual phases of product design

The paper presents the results of a research project aimed at developing an innovative system for modeling industrial products based on haptic technology. The system consists of a Computer Aided Design (CAD) system enhanced with intuitive designer-oriented interaction tools and modalities. The system integrates innovative six degrees of freedom (DOF) haptic tools for modeling digital shapes, with sweep operators applied to class-A surfaces and force computation models based on chip formation models. The system aims at exploiting designers’ existing skills in modeling products, improving the products design process by reducing the necessity of building several physical models for evaluating and testing the product designs. The system requirements have been defined observing designers during their daily work and translating the way they model shapes using hands and craft tools into specifications for the modeling system and the haptic tool. The system prototype has been tested by designers who have found it intuitive and effective to use.     

Contact and Deformation Modeling for Interactive Environments

Contact and deformation modeling for interactive environments has seen many applications, from surgical simulation and training, to virtual prototyping, to teleoperation, etc., where both visual feedback and haptic feedback are needed. High-quality feedback demands a high level of physical realism as well as a high update rate in rendering, which are often conflicting requirements. In this paper, we present a unique approach to modeling force and deformation between a rigid body and an elastic object under complex contacts, which achieves a good compromise of reasonable physical realism and real-time update rate (at least 1 kHz). We simulate contact forces based on a nonlinear physical model. We further introduce a novel approximation of material deformation suitable for interactive environments based on applying Bernoulli-Euler bending beam theory to the simulation of elastic shape deformation. Our approach is able to simulate the contact forces exerted upon the rigid body (that can be virtually held by a user via a haptic device) not only when it forms one or more than one contact with the elastic object, but also when it moves compliantly on the surface of the elastic object, taking friction into account. Our approach is also able to simulate the global and local shape deformation of the elastic object due to contact. All the simulations can be performed in a combined update rate of over 1 kHz, which we demonstrate in several examples.     

Haptic function evaluation of multi-material part design

Recently haptic shape modeling has got a momentum in industrial and conceptual design. In this paper, a real-time haptic interface of synthesized shape modeling and haptic function evaluation of product design for multi-material part is presented. Due to the advancement of manufacturing technologies, multi-material is increasingly employed by industrial designers as a means for increasing the appeals of a product while also adding functional capability. Multi-material part manufacturing processes allow designers to select different materials for different portions of a product in order to improve the material-function compatibility for the overall product. For quick design verification, the shape design and function evaluation are implemented in the same haptic environment where a load can be applied to a part design using a haptic device and at the same time the combined reaction of the part in terms of displacement and reaction can be visualized and felt by the user. The intuitive correlation between the applied force and incurred displacement (or deflection) provides an instant evaluation of the stiffness of a part design. The proposed methodology is illustrated through a case study: the design of a toothbrush.     

Layered rhombus-chain-connected model for real-time haptic rendering

The modeling and simulation of deformable objects is a challenging topic in the field of haptic rendering between human and virtual environment. In this paper, a novel and efficient layered rhombus-chain-connected haptic deformation model based on physics is proposed for an excellent haptic rendering. During the modeling, the accumulation of relative displacements in each chain structure unit in each layer is equal to the deformation on the virtual object surface, and the resultant force of corresponding springs is equivalent to the external force. The layered rhombus-chain-connected model is convenient and fast to calculate, and can satisfy real-time requirement due to its simplicity. Experimental study in both homogenous and non-homogenous virtual human liver and lungs based on the proposed model are conducted, and the results demonstrate that our model provides stable and realistic haptic feeling in real time. Meanwhile, the display result is vivid.     

Touch and design: novel haptic interfaces for the generation of high quality surfaces for industrial design

This paper presents the results of a research project aimed at developing haptic tools for virtual shape modelling resembling real tools like rakes and sandpaper used by modelers and designers in the real workshop. The developed system consists of a CAD (computer aided design) system enhanced with intuitive designer-oriented interaction tools and modalities. The system requirements have been defined on the basis of the observation of designers during their daily work, and translating the way they model shapes using hands and craft tools into specifications for the modelling system based on haptic tools.     

Bridging the HASM: An OWL ontology for modeling the information pathways in haptic interfaces software

Haptics technology has received enormous attention to enhance human computer interaction. The last decade has witnessed a rapid progress in haptic application software development due to the fact that the underlying technology has become mature and has opened up novel research areas. In an attempt to organize the path between cause and effect we envision a need for a standard for haptic application software modeling. In order for the software to better enhance the tactile information sensation, flow and perception and also make interaction between humans and haptics more efficient and natural, we need a formal representation of the haptics domain. This article proposes the use of HASM, a haptic applications software modeling ontology to formally model the haptics domain in order to be used during the specifications and design phases of developing software applications for haptic interfaces. The presented ontology captures the existing knowledge in haptics domain, using OWL, and defines the pathways that the haptic information follows between the human and the machine haptic system, using SWRL rules. The haptic ontology that has been developed will be used as a basis to design effective user interfaces and assist the development of software modeling for haptic devices. A case study is demonstrating how this haptic ontology can be used to design a software model that analyzes the perception of a haptic property of an object by interacting with a haptic device.     

Haptic Cooperative Virtual Workspace: Architecture and evaluation

The Haptic Cooperative Virtual Workspace (HCVW), where users can simultaneously manipulate and haptically feel the same object, is beneficial and in some cases indispensable for training a team of surgeons, or in application areas in telerobotics and entertainment. In this paper we propose an architecture for the haptic cooperative workspace where the participants can kinesthetically interact, feel and push each other simultaneously while moving in the simulation. This involves the ability to manipulate the same virtual object at the same time. A set of experiments carried out to investigate the haptic cooperative workspace is reported. A new approach to quantitatively evaluate the cooperative haptic system is proposed, which can be extended to evaluate haptic systems in general.     

Modeling and animation of fracture of heterogeneous materials based on CUDA

Existing techniques for animation of object fracture are based on an assumption that the object materials are homogeneous while most real world materials are heterogeneous. In this paper, we propose to use movable cellular automata (MCA) to simulate fracture phenomena on heterogeneous objects. The method is based on the discrete representation and inherits the advantages from both classical cellular automaton and discrete element methods. In our approach, the object is represented as discrete spherical particles, named movable cellular automata. MCA is used to simulate the material and physical properties so as to determine when and where the fracture occurs. To achieve real-time performance, we accelerate the complex computation of automata’s physical properties in MCA simulation using CUDA on a GPU. The simulation results are directly sent to vertex buffer object (VBO) for rendering to avoid the costly communication between CPU and GPU. The experimental results show the effectiveness of our method.     

用于实时柔性触觉再现的平行菱形链连接模型

精度高且实时性好的柔性触觉变形模型是实现触觉再现系统的关键。提出了一种新的基于物理意义的平行菱形链连接触觉变形模型,系统中各个链结构单元相对位移的叠加对外等效为物体表面的变形,与之相连的弹簧弹性力的合力等效为物体表面的接触力。使用Delta 6-DOF手控器,建立了触觉再现实验系统,对柔性体的接触变形和实时虚拟触觉反馈进行仿真, 实验结果表明所提出的模型不仅计算简单,而且能够保证触觉接触力和形变计算具有较高精度,满足虚拟现实系统对精细作业和实时性的要求。     

Real-time area-based haptic rendering and the augmented tactile display device for a palpation simulator

Although people usually contact a surface with some area rather than a point, most haptic devices allow a user to interact with a virtual object at one point at a time and likewise most haptic rendering algorithms deal with such situations only. In a palpation procedure, medical doctors push and rub the organ's surface, and are provided the sensation of distributed pressure and contact force (reflecting force) for discerning doubtable areas of the organ. In this paper, we suggest real-time area-based haptic rendering to describe distributed pressure and contact force simultaneously, and present a haptic interface system to generate surface properties in accordance with the haptic rendering algorithm. We represent the haptic model using the shape-retaining chain link (S-chain) framework for a fast and stable computation of the contact force and distributed pressure from a volumetric virtual object. In addition, we developed a compact pin-array-type tactile display unit and attached it to the PHANToM^TM haptic device to complement each other. For the evaluation, experiments were conducted with non-homogenous volumetric cubic objects consisting of approximately 500 000 volume elements. The experimental results show that compared to the point contact, the area contact provides the user with more precise perception of the shape and softness of the object's composition, and that our proposed system satisfies the real-time and realism constraints to be useful for a virtual reality application.     

Haptic rendering: introductory concepts

Haptic rendering allows users to "feel" virtual objects in a simulated environment. We survey current haptic systems and discuss some basic haptic-rendering algorithms. In the past decade we've seen an enormous increase in interest in the science of haptics. Haptics broadly refers to touch interactions (physical contact) that occur for the purpose of perception or manipulation of objects. These interactions can be between a human hand and a real object; a robot end-effector and a real object; a human hand and a simulated object (via haptic interface devices); or a variety of combinations of human and machine interactions with real, remote, or virtual objects. Rendering refers to the process by which desired sensory stimuli are imposed on the user to convey information about a virtual haptic object.     

Handling of Virtual Contact in Immersive Virtual Environments: Beyond Visuals

This paper addresses the issue of improving the perception of contact that users make with purely virtual objects in virtual environments. Because these objects have no physical component, the user's perceptual understanding of the material properties of the object, and of the nature of the contact, is hindered, often limited solely to visual feedback. Many techniques for providing haptic feedback to compensate for the lack of touch in virtual environments have been proposed. These systems have increased our understanding of the nature of how humans perceive contact. However, providing effective, general-purpose haptic feedback solutions has proven elusive. We propose a more-holistic approach, incorporating feedback to several modalities in concert. This paper describes a prototype system we have developed for delivering vibrotactile feedback to the user. The system provides a low-cost, distributed, portable solution for incorporating vibrotactile feedback into various types of systems. We discuss different parameters that can be manipulated to provide different sensations, propose ways in which this feedback can be combined with feedback of other modalities to create a better understanding of virtual contact, and describe possible applications.