Endoscope Geometrical Analysis and Kinematic Control

Abstract

Endoscopes are used in medical practice to effect minimally invasive diagnostics and treatments through a natural or surgical orifice. The endoscope is a snakelike device with a two degree-of-freedom articulated tip that bends in any direction using internal cables actuated by knobs. In this paper we use a serial robot model of the tip to show that the tip motions are not decoupled with respect to the knob inputs nor do they have constant gains. Further in a geometrical analysis it is shown that the articulated tip always lies along a circle. A tip kinematic control strategy is developed based on small motions that is able to decouple the output motions from the input motions and provide a constant gain functions. This allows the surgeon to control the endoscope in an intuitive and efficient manner.