Minimal visual occlusion redundancy resolution of continuum robots in confined spaces

Minimally invasive surgery in confined spaces often requires the coordinated use of endoscopes and surgical tools while minimizing visual occlusions. In a robotic system such visual occlusion avoidance has to be achieved autonomously while keeping the surgical end-effector as close as possible to the center of the field of view of the endoscope. This paper presents an investigation of use of redundancy resolution to solve the problem of visual occlusion. Specifically, the paper addresses hard cases where a continuum robot or an ablation catheter emanate from a narrow access channel containing an endoscope. A redundancy resolution method accounting for the kinematics of the continuum robot and allowing for rotation of an angled lens endoscope is presented. A potential field method is used to guide all portions of the continuum arm outside of the visualization cone of the endoscope and a gradient descent method is used to guide the rotation of the endoscope to keep the end-effector as close as possible to the center of the visual field of the endoscope. A simulation case study demonstrates the utility of our method using a recently designed transurethral bladder cancer surgery system as a demonstration platform. Although the context of the problem is bladder surgery utilizing a continuum robot, the method can be generalized to any redundant robot that requires to accomplish a task with minimal visual occlusion.