Evaluation of a Bilateral Tele-Echographic Architecture in Presence of Time Delay

Tele-ecography with force-feedback aims at remotely reproducing ultrasound examination. Current state-of-the-art tele-echography systems have been tested on phantoms or humans, but in non-realistic conditions. In fact, most of them do not consider the presence of time delay (that is a source of instability in all teleoperation tasks) or they do not establish sufficient contact forces according to ultrasound requirements. Moreover, none of these architectures take advantage of a robotic solution to relieve doctor's fatigue, which has been demonstrated source of work-related musculoskeletal disorders (WRMSD). This paper aims to evaluate the performance of a proposed tele-echography architecture under realistic working conditions, which are the presence of time delay and ultrasound-required contact forces. To deal with instability, two separate transmission networks were implemented and the teleoperation one was passivated according to Time Domain Passivity Approach. Moreover, a user-dependent scaling factor on the force-feedback is proposed to deal with WRMSD. The system has been tested by a single user contacting a custom-made gelatin phantom to identify an immersed screw. The architecture was found successful in the task exhibiting a stable behaviour in presence of 400 ms round trip delay and with contact of 20 N.