Tele-echography using a two-layer teleoperation algorithm with energy scaling

Performing ultrasound procedures from a remote site is a challenging task since both a stable behavior, for the safety of the patient, and a high-level of usability, to exploit the sonographer's expertise, need to be guaranteed. Furthermore, a teleoperation system that provides such requirements has to deal with communication delays as well. To address this issue, we use the two-layer algorithm: a passivity-based bilateral teleoperation architecture able to guarantee stability despite unknown and time-varying delay. Its flexibility allows to implement different kinds of control laws. In a Tele-Echography system, the slave manipulator has to apply significant forces needed by the procedure whereas the haptic device at the master side should be very light to avoid tiring the operator. Therefore, the energy needed by these two robots to perform their movements is very different and the energy injected into the system by the operator is often not sufficient to implement the desired action at the slave side. Methods to overcome this problem require to perfectly know the dynamical models of the robots. The solution proposed in this paper does not require such knowledge and is based on properly scaling the energy exchanged between the master and the slave side. We show the effectiveness of this approach in a real setup using a TOUCH haptic device and a WAM Barrett robot holding an ultrasound probe.