Tele-echography of moving organs using an Impedance-controlled telerobotic system

A novel impedance-controlled teleoperation system is developed for robot-assisted tele-echography of moving organs such as heart, chest and breast during their natural motions (beating and/or breathing). The procedure of devising the two impedance models for the master and slave robots is developed such that (a) the slave robot holding the ultrasound (US) probe follows the master trajectory but complies with the oscillatory interaction force of the moving organ, and (b) the sonographer receives feedback from the non-oscillatory portion of the slave-organ interaction force via the master robot similar to the haptic feedback received in echography of a stationary organ. These goals are achieved via appropriate parameter adjustment in the desired impedance models without requiring any direct measurement and/or online prediction of the organ's motions. The stability and tracking convergence of the teleoperation system in the presence of communication delays and modeling uncertainties are proven in a Lyapunov-based framework. The performance of the proposed tele-echography system is evaluated experimentally using a master-slave telerobotic system, a US imaging system and a mechanical moving-organ simulator.