Model-based Bending Control of Magnetically-actuated Robotic Endoscopes for Automatic Retroflexion in Confined Spaces

This paper is concerned with the issue of the kinematic model-based bending control for the magnetically actuated robotic endoscope and its application for automatic retroflexion. By the utilization of the Cosserat rod theory and the transformation in the magnetic tip of the endoscope, the comprehensive kinematic model of the magnetically-actuated robotic endoscope is established. Afterward, a magnetic control scheme for the bending motion is proposed by co-developing an error feedback PID control strategy and the model-based feedback approach. Moreover, as one unique kind of bending motion, retroflexion is taken into account, and the strategy aimed at the bid of compact space retroflexion is presented by virtue of the introduction of serial waypoints pursuing the position of the magnetic tip being close to the midline as possible. Eventually, the developed modeling and bending control scheme and the compact space retroflexion strategy are examined in a magnetically actuated robotic endoscope system to manifest the effectiveness and applicability of the theoretical approach. The experimental results indicate that the designed controller can drive the endoscope to bend to the desired pose and show a reduction of about 47.01 % in the sweeping area and 79.25% in the last distance to midline achieved by conducting compact space retroflexion in comparison to "U" type one.