基于力觉交互的高速率精准操作技能训练方法

介绍了用力觉交互技术进行手眼协调高速率精准操作的动作技能训练方法。提出了记录播放和轨迹智能导引两种培训模式。在记录培训模式中,采用PD控制的方法使学员被动感受专家的运动信息。在智能导引纠正模式中,学员主动操作交互设备,计算机根据学员的操作情况控制交互设备输出导引力或纠正力。最后,采用Omega 3DOF建立了具备触觉显示和图形显示功能的“信封靶”描绘技能训练系统样机平台,分析了力模型参数对系统稳定性的影响。实验结果证明了培训方法的可行性。     

Cost-effective haptic-based networked virtual environments with high-resolution tiled display

In this paper, a haptic-based NVE (networked virtual environment) supporting high-resolution tiled display is proposed with a resource management scheme for future home applications such as a haptic-based networked game. Although NVEs with haptic interaction and immersive display have been developed in previous studies, they usually require expensive system configurations. In order to implement a cost-effective system, our proposed design includes a tiled display supporting high-resolution with several low-cost LCDs. The display nodes of the tiled display also have low processing and storage resource requirements because they only need to handle display-ready pixels received from the application node. The proposed resource management scheme, called as an object-based display scheme, reduces the resource requirements of the application node that would otherwise require significant resources to manage all the display nodes and to provide a user with haptic feedback. The proposed scheme segments graphic scenes into several pixelated virtual objects and assigns different frame rates to each object according to the interest of user. Experimental results confirm that the proposed scheme reduces the required network bandwidth and appropriately assigns the limited processing resources to graphic and haptic renderings for a high-level visual and haptic quality.     

Development scheme of haptic-based system for interactive deformable simulation

This paper aims to develop a novel scheme for interactively deformable simulation with haptic feedback. All design modules are packaged and implemented, and the experiments are conducted to study the effects of interactive deformation. The study compares the experimental results of haptic feedback by different force propagation methods, according to the Hounsfield unit (HU) of volume data. Additionally, the estimation of optimal propagation depth is illustrated by using a mass-spring model. Finally, by using the proposed scheme, a haptic-based medical simulation system for brain surgery is investigated. The integration test results with haptic feedback scenarios show that the proposed development scheme can certainly comply with the design modules, and the deformable simulation and haptic force reach a good agreement.     

Virtual DesignWorks—designing 3D CAD models via haptic interaction

Haptic devices (force feedback interfaces) show great promise for use in the design of CAD models. However, current haptic systems are used primarily to verify rather than to interact with CAD systems to design a model.The paper discusses a haptic-based CAD system—Virtual DesignWorks. It is the world's first haptic application for the design of CAD models based on component technology (COM+). With haptic devices, the system allows engineers, in virtual space, to directly touch a native B-Rep CAD model, and deform it by pushing, pulling and dragging its surfaces in a natural three-dimensional environment. Virtual DesignWorks adopts the novel COM-based haptic model, which demonstrates significant advantages compared to the traditional haptic models. Force feedback gives designers the greatest flexibility for the design of complex surfaces, and haptics has the potential to become a critical interface for design applications.     

Transparency analysis and delay compensation scheme for haptic-based networked virtual environments

Haptic-based NVEs (networked virtual environments) with CS (client/server) communication architectures support better consistency but induce larger end-to-end delays than those with P2P (peer-to-peer) communication architectures. Unfortunately, large delay severely deteriorates the transparency (i.e., reality) of haptic interaction. To improve the haptic interaction quality for haptic-based NVEs with CS communication architectures, in this paper the degradation of haptic interaction quality is analyzed according to network delays. Based on the analysis, the maximum allowable delay bound is predicted and unrealistic force feedback caused by the network delay is compensated. Experimental results confirm that the proposed analysis provides an acceptable quantification method about haptic interaction quality and that the proposed delay-compensation scheme effectively improves haptic interaction quality with respect to network delays.     

Priority-based haptic event filtering for transmission and error control in networked virtual environments

A data filtering scheme is proposed for transmission and error control of haptic events in haptic-based network virtual environments; this scheme is called as priority-based haptic event filtering. Because a high update rate of approximately 1 kHz is required for haptic rendering, sophisticated transmission rate control and reduction schemes are necessary for the haptic events. Although existing schemes can reduce the transmission rate without any perception impairment, they are very sensitive to packet losses. In this paper, we prioritize the haptic events according to the delay and loss effects. Utilizing the proposed haptic event prioritization, the proposed filtering scheme adapts the transmission rate and updates the predicted loss rate according to the current network state. Our simulation and experiment results confirm that the proposed scheme can effectively select important haptic events and guarantee an improved haptic interaction quality over a bandwidth-limited lossy network than existing transmission schemes tailored for networked haptics.     

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.     

Vision-assisted control for manipulation using virtual fixtures

We present the design and implementation of a vision-based system for cooperative manipulation at millimeter to micrometer scales. The system is based on an admittance control algorithm that implements a broad class of guidance modes called virtual fixtures. A virtual fixture, like a real fixture, limits the motion of a tool to a prescribed class or range of motions. We describe how both hard (unyielding) and soft (yielding) virtual fixtures can be implemented in this control framework. We then detail the construction of virtual fixtures for point positioning and curve following as well as extensions of these to tubes, cones, and sequences thereof. We also describe an implemented system using the JHU Steady Hand Robot. The system uses computer vision as a sensor for providing a reference trajectory, and the virtual fixture control algorithm then provides haptic feedback to implemented direct, shared manipulation. We provide extensive experimental results detailing both system performance and the effects of virtual fixtures on human speed and accuracy.     

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。     

Haptic rendering for dental training system

Immersion and interaction are two key features of virtual reality systems, which are especially important for medical applications. Based on the requirement of motor skill training in dental surgery, haptic rendering method based on triangle model is investigated in this paper. Multi-rate haptic rendering architecture is proposed to solve the contradiction between fidelity and efficiency requirements. Realtime collision detection algorithm based on spatial partition and time coherence is utilized to enable fast contact determination. Proxy-based collision response algorithm is proposed to compute surface contact point. Cutting force model based on piecewise contact transition model is proposed for dental drilling simulation during tooth preparation. Velocity-driven levels of detail haptic rendering algorithm is proposed to maintain high update rate for complex scenes with a large number of triangles. Hapticvisual collocated dental training prototype is established using half-mirror solution. Typical dental operations have been realized including dental caries exploration, detection of boundary within dental cross-section plane, and dental drilling during tooth preparation. The haptic rendering method is a fundamental technology to improve immersion and interaction of virtual reality training systems, which is useful not only in dental training, but also in other surgical training systems. Supported by National Natural Science Foundation of China (Grant Nos. 60605027, 50575011), National High-Tech Research & Development Program of China (Grant No. 2007AA01Z310)     

NC painting robot for narrow areas

Giving a natural operational feeling to a human via a haptic interface requires not only a sophisticated and intuitive mechanical design, but also an appropriate control system design. Most haptic systems, however, implicitly demand that the human gets used to manipulation of the haptic devices before he/she can get the feel of the virtual space and/or telepresence beyond the haptic device. Based on a new concept of a human-in-the-loop system called Human Adaptive Mechatronics (HAM), an assist-control for a force/vision interactive haptic system is discussed in this paper. The proposed assist-control scheme includes online estimation of a operator's control characteristics, and a 'force assist' function implemented as a change in the support ratio according to the identified skill level. We developed a HAM haptic device test system, performed evaluation experiments with this apparatus and analyzed the measured data. It was confirmed that the operator's skill could be estimated sufficiently and that operator's performance was enhanced by the assist-control.     

Whole-hand kinesthetic feedback and haptic perception in dextrous virtual manipulation

One of the key requirements for a Virtual Reality system is the multimodal, real-time interaction between the human operator and a computer simulated and animated environment. This paper investigates problems related particularly to the haptic interaction between the human operator and a virtual environment. The work presented here focuses on two issues: 1) the synthesis of whole-hand kinesthetic feedback, based on the application of forces (torques) on individual phalanges (joints) of the human hand, and 2) the experimental evaluation of this haptic feedback system, in terms of human haptic perception of virtual physical properties (such as the weight of a virtual manipulated object), using psychophysical methods. The proposed kinesthetic feedback methodology is based on the solution of a generalized force distribution problem for the human hand during virtual manipulation tasks. The solution is computationally efficient and has been experimentally implemented using an exoskeleton force-feedback glove. A series of experiments is reported concerning the perception of weight of manipulated virtual objects and the obtained results demonstrate the feasibility of the concept. Issues related to the use of sensory substitution techniques for the application of haptic feedback on the human hand are also discussed.     

Effects of feedback type and modality on motor skill learning and retention

ABSTRACT

Two types of feedback, including knowledge of results (KR) and knowledge of performance (KP) are typically delivered as part of motor training using different sensory modalities. Twenty-four right-handed individuals performed a computer-based psychomotor training task using a contemporary haptic interface. Results revealed that KP was superior to KR for overall task performance retention, whereas KR was good for training specific aspects of performance. A combination of KP and KR through the same modality did not produce an additive positive learning effect for task performance. Auditory and haptic feedback improved retention over visual, but only with the use of multiple information cues. Design guidelines are provided for training systems for motor skill development and/or rehabilitation.     

Effect of Dual-rate Sampling on the Stability of a Haptic Interface

Conventional controllers in impedance-based haptic interfaces are sampled data systems that utilize position and velocity information for the necessary force feedback. In a canonical virtual wall simulation, this feedback force is generated based on interaction with the wall simulating certain stiffness and damping. Increasing the sampling rate of the controller increases the stable range of virtual wall stiffness. However, an increased sampling rate exacerbates the velocity information, decreasing the stable range of virtual wall damping. In this work, the authors propose a dual-rate sampling scheme in which the position and velocity loops of a haptics controller are decoupled and sampled at different rates. The scheme enables independent sampling of the position data at higher rates, while simultaneously sampling the velocity data at appropriate rates. In this paper, the authors provide experimental and theoretical implications of the effect of dual-rate sampling on the stability of a haptic interface. Experiments with a single degree-of-freedom (DOF) haptic interface reveals an enhanced region of stable virtual wall stiffness for a particular range of virtual wall damping, compared to the values with conventional uniform-rate scheme. Virtual wall stiffness ranging from 150 - 360 Nm/rad was stably implemented over a range of 0 - 1 Nms/rad of virtual wall damping using the proposed scheme at position loop sampling rate of 20kHz and velocity loop sampling rate of 2kHz. Whereas in the conventional scheme, the stable range of virtual stiffness dropped considerably (～ 0 Nm/rad) for the virtual wall damping above 0.1 Nms/rad when the uniform rate sampling of 20kHz was used for both the position and velocity sampling loops. Theoretical stability analyzes using classical control tools and simulations justified the effectiveness of the proposed scheme. The scheme is easy to implement and extensible to multi-DOF haptic interfaces as well.     

Influences of haptic communication on a shared manual task

With the advent of new haptic feedback devices, researchers are giving serious consideration to the incorporation of haptic communication in collaborative virtual environments. For instance, haptic interactions based tools can be used for medical and related education whereby students can train in minimal invasive surgery using virtual reality before approaching human subjects. To design virtual environments that support haptic communication, a deeper understanding of humans′ haptic interactions is required. In this paper, human′s haptic collaboration is investigated. A collaborative virtual environment was designed to support performing a shared manual task. To evaluate this system, 60 medical students participated to an experimental study. Participants were asked to perform in dyads a needle insertion task after a training period. Results show that compared to conventional training methods, a visual-haptic training improves user′s collaborative performance. In addition, we found that haptic interaction influences the partners′ verbal communication when sharing haptic information. This indicates that the haptic communication training changes the nature of the users′ mental representations. Finally, we found that haptic interactions increased the sense of copresence in the virtual environment: haptic communication facilitates users′ collaboration in a shared manual task within a shared virtual environment. Design implications for including haptic communication in virtual environments are outlined.     

一种基于物理意义的快速力反馈形变模型及实时力觉响应算法

虚拟物体在受力作用时的形变建模是虚拟环境中力/触觉人机交互的关键.文中提出了一种新的基于物理意义的形变建模方法,不仅计算速度快,满足力反馈的实时性要求,而且能够同时保证接触力和形变的计算具有较高的精度,适用于具有较大变形量的柔性物体的力反馈计算,满足精细作业对虚拟现实系统的要求.     

Simultaneous remote haptic collaboration for assembling tasks

Stand-alone virtual environments (VEs) using haptic devices have proved useful for assembly/disassembly simulation of mechanical components. Nowadays, collaborative haptic virtual environments (CHVEs) are also emerging. A new peer-to-peer collaborative haptic assembly simulator (CHAS) has been developed whereby two users can simultaneously carry out assembly tasks using haptic devices. Two major challenges have been addressed: virtual scene synchronization (consistency) and the provision of a reliable and effective haptic feedback. A consistency-maintenance scheme has been designed to solve the challenge of achieving consistency. Results show that consistency is guaranteed. Furthermore, a force-smoothing algorithm has been developed which is shown to improve the quality of force feedback under adverse network conditions. A range of laboratory experiments and several real trials between Labein (Spain) and Queen’s University Belfast (Northern Ireland) have verified that CHAS can provide an adequate haptic interaction when both users perform remote assemblies (assembly of one user’s object with an object grasped by the other user). Moreover, when collisions between grasped objects occur (dependent collisions), the haptic feedback usually provides satisfactory haptic perception. Based on a qualitative study, it is shown that the haptic feedback obtained during remote assemblies with dependent collisions can continue to improve the sense of co-presence between users with regard to only visual feedback.     

An approach to human motor skill training for uniform group performance

Prior research has focused on designing training approaches for novice operators to support maximum motor skill development. However, in production operations, workers must be trained to uniform performance levels to prevent ‘bottlenecks’ or work-in-process inventory accumulation. This study introduces a new approach to support assignment of training protocols to operators to achieve comparable levels of motor performance. Thirty-six participants performed a computer-based motor test. Based on performance classification results, each participant was assigned to a specific haptic virtual reality training condition. Results revealed participants identified as ‘medium’ or ‘low’ performers achieved levels of motor performance comparable to ‘high’ performers through 1-h training.Relevance to IndustryFindings can be applied to operator training in manual assembly operations, promoting a group of novice workers to achieve uniform performance levels and mitigating production bottlenecks.     

Force modeling for tooth preparation in a dental training system

Feedback force is very important for novices to simulate tooth preparation by using the haptic interaction system (dental training system) in a virtual environment. In the process of haptic simulation, the fidelity of generated forces by a haptic device decides whether the simulation is successful. A force model computes feedback force, and we present an analytical force model to compute the force between a tooth and a dental pin during tooth preparation. The force between a tooth and a dental pin is modeled in two parts: (1) force to resist human’s operation and (2) friction to resist the rotation of the dental engine. The force to resist the human’s operation is divided into three parts in the coordinates that are constructed on the bottom center of the dental pin. In addition, we also consider the effects of dental-pin type, tooth stiffness, and contact geometry in the force model. To determine the parameters of the force model, we construct a measuring system by using machine vision and a force/torque sensor to track the human’s operations and measure the forces between the dental pins and teeth. Based on the measuring results, we construct the relation between the force and the human’s operation. The force model is implemented in the prototype of a dental training system that uses the Phantom as the haptic interface. Dentists performing virtual operations have confirmed the fidelity of feedback force.     

The implementation and evaluation of a virtual haptic back

A virtual haptic back (VHB) model has been developed by a cross-disciplinary team of researchers at Ohio University. Haptics give the human the sense of touch and force from virtual computer models. The objective is to create a tool for medical and related education whereby students can train in the difficult art of palpation using virtual reality before approaching human subjects. Palpation is the art of medical diagnosis through the sense of touch. Haptic anatomy could be a key area in the future of medical school training; our goal is to add science to the art of palpation to improve osteopathic, physical therapy and massage therapy training for students and practitioners. Modelling of the VHB took place in two steps. First, Cartesian back data was collected via the Metrecom Skeletal Analysis System (SAS) digitiser. The back of a prone human subject was digitised, giving an array of three-dimensional points. Several methods were considered to smooth out the back data. Spline fitting with matched first and second derivates was the chosen method. Once an acceptable graphical model was created, haptic feedback was added using the PHANToM haptic interface, allowing the human user to explore and feel the virtual back. Experienced and novice palpators formally evaluated the VHB to give us feedback for improvements. In addition, four Doctors of Osteopathy informally interacted with our model and gave verbal feedback. Our experts all suggested modelling underlying muscles and skeletal structure in addition to the skin layer for more realism. Once this is accomplished we will further program somatic dysfunction of various types in the VHB for students to diagnose. This article contributes to the state of the art in virtual haptic anatomy. While other research groups are working in this area, our work is the first specifically aimed towards osteopathic medicine, physical therapy, and massage therapy students and practitioners.