Real-Time Deformation Sensing for Flexible Manipulators With Bending and Twisting

Wire-driven flexible manipulators are increasingly used in medical applications, such as minimally invasive surgeries, due to its ability to operate in confined space by deforming the backbone. Existing flexible manipulators are mostly controlled in open loop, as there lacks a proper real-time deformation sensing method. The deformation of a flexible manipulator includes both the backbone shape bending and backbone twist. Current sensing methods for flexible manipulators only consider the shape and neglect the twist. However, the twist is of equal importance as it affects the end-effector orientation. In this paper, we propose a real-time deformation sensing and reconstruction method for flexible manipulators. By employing the real-time position and orientation information of part of the backbone, e.g., the base and tip, we can estimate the deformation of the flexible manipulator with adequate accuracy. What's more, a vision-based high-precision off-line shape and posture sensing method for twisted flexible manipulators is also proposed to verify the proposed electromagnetic real-time shape and posture sensing method. Results show that the proposed method could well sense the deformation of the backbone with average position error root-mean-square (rms) 1.9 mm and average twist error rms 0.61°.