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.