A 500 Hz predictive visual servoing scheme to mechanically filter complex repetitive organ motions in robotized surgery

Periodic deformations of organs and soft tissues are complex, repetitive disturbances for surgeons manipulating robotic interfaces in computer-assisted surgery. They are due to respiratory movements or heart beats, and they have to be manually compensated for by the surgeon whenever accurate gestures are needed, as it is the case in cardiac or robotized laparoscopic surgery. This work presents a repetitive model predictive control scheme for the cancellation of fast periodic motions by a robot arm, which is controlled by visual servoing at 500 Hz by means of a high-speed camera. The problem we address is to keep a constant distance in the camera images from a surgical tool´s tip to the organ surface. Contributions of the control input to reference tracking and to the fast-disturbance rejection are split and computed separately to ensure that the surgeon´s interaction on the robot bas no influence on the cancellation performance. The system is tested in a laboratory experiment with an experimental surgical arm and in in vivo conditions on a living pig with a standard surgical robot. Results show the effectiveness and the potential of the proposed control scheme.