Visual feedback control for endoscopes using tension estimation

This paper introduces a visual feedback control technique in order to robotize endscopes which are used in medical or industrial devices. Generally, endoscope consists of small-diameter tubes and two pairs of wires. The tubes are used as links and the wires are connected to the interior of the terminal link, which pass through the interior of every other link and it is used to transfer driving force via the wire tensions. The near terminal of wires are connected to operational unit. In order to robotize it, the operational unit should be replaced motor drive unit. Furthermore, a compact CCD camera is mounted on the terminal to observe target parts. But to robotize it, visual feedback control function should be implemented. One pair of the wires is for side-to-side motion while the other pair is for up-and-down motion. The control system consists of a visual feedback control loop and a minor loop that directly controls the tension estimation of the wires. The minor loop is designed based on the disturbance observer. Further, the outer visual feedback control loop is designed to track a target point using CCD camera. This control method is evaluated experimentally.