Liya Ni

Design and implementation of a collaborative virtual haptic surgical training system

The high level design of a hapto-visual telementoring virtual environment consisting of two networked stations allowing two users to collaborate within the learning environment is outlined. The physical implementation and the operation of the system are described. This system is designed to be used for remote surgical training. It would allow surgeons to remotely train students in a networked hapto-visual virtual environment to perform simple tasks. Moreover, the system provides a platform for studying many aspects of collaborative virtual environment (CVE) systems and their applications.

The effect of time delays on tele-haptics

Information technology has reached a limit in what can be done in training and doing remote tasks with only sight and sound. The next critical step is to add the sense of touch over network connections, otherwise known as tele-haptics. In this paper, an experimental demonstration involving a simple identification task has been developed, using a custom two degree-of-freedom haptic interface. The experiment shows quantitatively that haptics can be employed to greatly enhance user performance but the addition of simulated network time delay and sensor noise quickly degrades performance. It is demonstrated that time-delay compensation techniques can aid in situations where the time-delay and sensor noise make the equipment unusable. In addition, another experiment demonstrating tele-haptics using two MPB Freedom 6S haptic devices is discussed. Key issues in the implementation of such an experiment are presented and a description of the results is given.

A Gain-Switching Control Scheme for Position-Error-Based Bilateral Teleoperation: Contact Stability Analysis and Controller Design

To lower the cost of a force-reflecting teleoperation system, position errors instead of direct measurements from force/torque sensors can be used for force feedback. An investigation on transparency shows that position-error-based teleoperation provides poor transparency when using constant controller gains, and this can be overcome by gain switching. The scenario studied in this paper is a position-errorbased bilateral teleoperation system when the slave robot is either in free motion or colliding with a stationary stiff environment. A contact stability analysis is presented for teleoperation systems with constant controller gains and then extended to a gain-switching teleoperation system. Issues on the design of a gain-switching control scheme are discussed. The effectiveness of the proposed gain-switching control scheme is evaluated experimentally.

A heterogeneous scalable architecture for collaborative haptics environments

The purpose of this research effort is to design a generic architecture for collaborative haptic, audio, visual environments (C-HAVE). We aim to develop a heterogeneous scalable architecture for large collaborative haptics environments where a number of potential users participate with different kinds of haptic devices. This paper begins with a brief overview of C-HAVE and then proceeds to describe a generic architecture that is implemented over HLA/RTI (High Level Architecture/Run Time Infrastructure), an IEEE standard for distributed simulations and modeling. A potential electronic commerce application over C-HAVE is discussed.

A gain-switching control scheme for position-error-based force-reflecting teleoperation

To lower the cost of a force-reflecting teleoperation system, position errors instead of direct measurements from force/torque sensors can be used for force feedback. However, the position-position architecture with fixed PD controllers provides poor transparency. A gain-switching control scheme is developed in this paper to solve this problem. Based on the detection of the impedance change at the slave site, the master and slave PD controller gains are switched accordingly. Experimental results are shown to demonstrate the effectiveness of this method.

Contact transition stability analysis for a bilateral teleoperation system

A bilaterally controlled teleoperation system usually involves contact tasks at a remote location. Dynamic interaction between the slave robot and the environment may cause severe chattering instability. This paper presents a contact transition stability analysis for a position-error-based bilateral teleoperation system. The scenario studied is when the slave robot collides with a stationary stiff environment. Under a few assumptions and conditions, the teleoperation system is shown to be asymptotically stable. The analysis includes the dynamics of the human arm and of the environment.

Conducting a real-time remote handshake with haptics

Summary form only given. A demonstration has been developed that illustrates a bilateral telehaptics platform to enable a local user and a remote user to shake hands in real time over a telecommunications network. The platform has been developed around an off-the-shelf six DOF haptic manipulator and a real time operating system. Only the first three DOF of the device are enabled with haptics. The demonstration shows two devices connected in a bilateral telehaptic configuration on a local network with a network traffic simulator in between the two devices.

A Human-to-human Force-reflecting Teleoperation System Using Fuzzy Logic Controller Tuning

A new application of teleoperation is to provide the sense of force to human-to-human interaction over computer networks. This is also known as Telehaptics. To lower the cost of such systems, position errors instead of direct force/torque measurements can be used for feedback. To improve the performance in terms of transparency, it is desirable to adjust the position controller gains on-line. In this paper, fuzzy logic is applied to the on-line controller tuning, based on the detection of changes in the dynamics, using power and inertia information. With this method, the communication between two users with force feedback becomes more transparent and natural.

Implementation issues for bilateral tele-mentoring applications

Recent advances in the area of tele-haptics - the ability to transmit the sense of touch over communications channels - has enabled the implementation of tele-mentoring of tasks where a remote expert user guides a local student by literally holding his/her hand via a network connection. A demonstration of tele-haptics was successfully conducted between Geneva and Ottawa in October, 2003 using a mannequin in lieu of a virtual environment for a medical training simulation. In this paper, the results of that demonstration are extended to include a virtual environment. The task is that of guiding a user through a haptic simulation of a bifurcation of an artery in a medical training simulator. Two commercial six degree of freedom haptic devices (three degrees actuated) are employed in this experimental setup. It is demonstrated that, in the presence of time delays, this simple task is rendered unusable due to the appearance of instability. A time-delay compensation technique is used to restore stability. Two implementation issues have been found to greatly impact both stability and performance. The first issue is that of the sampling period used by the haptic devices at both the local and remote locations. The second is that of slight differences in the sampling times of the controllers at both local and remote haptic devices, which ultimately impacts the synchronization of the controllers at the two locations. The impact of these two implementation issues will be studied for this particular application through experimental verification.

A Pilot Study of Video Compression Techniques for Stereoscopic Telepresence Applications

This paper focuses on evaluating and quantifying the effects of a novel foveated stereo video compression algorithm for visual telepresence applications. In a typical telepresence application, a user at the local site views real-time stereo video captured and transmitted from a telerobotic camera platform located at a remote site. The telerobotic camera platform tracks the users head motion, producing the sensation of being present at the remote site. Three valuable factors were examined: foveation, disparity compression, and global motion compensation. The algorithm was analyzed by introducing the above-mentioned components separately. It was found that each component increased the compression rate significantly.