Vision and Contact based Optimal Control for Autonomous Trocar Docking

Abstract

Future operating theaters will be equipped with robots to perform various surgical tasks including, for example, endoscope control (Fig. 1b). Fully automated surgery is likely to be part of the distant future [1]. However, human-in-the-loop supervisory control architectures where the surgeon selects from several autonomous sequences is already being successfully applied in preclinical tests, e.g. autonomous bowel anastomoses was recently carried out in animals [2]. Inserting an endoscope into a trocar or introducer is a key step for every keyhole surgical procedure – hereafter we will only refer to this device as a ``trocar’’. Our goal is to develop a controller for autonomous trocar docking. Autonomous trocar docking is a version of the peg-in-hole problem. Extensive work in the robotics literature addresses this problem, e.g. [3], [4], [5]. The peg-in-hole problem has been widely studied in the context of assembly [6] where, typically, the hole is considered static and rigid to interaction. In our case, however, the trocar is not fixed and responds to interaction. Within the scope of surgical robotics, a recent article addressed autonomous trocar docking for retinal surgery [7]. A vision-based system tracks the trocar and aligns the robot with the estimated pose prior to insertion. This work assumes the robot accurately aligns with the estimated pose, prior to insertion, and does not utilize contact information. In contrast, we consider procedures on a larger scale, e.g. endoscopic lumbar discectomy/decompression, and cholecystectomy. For these cases, often, surgeons will utilize contact between the endoscope and trocar in order to complete the insertion successfully. To the best of our knowledge, we have not found literature that explores this particular generalization of the problem directly. Our primary contribution in this work is an optimal control formulation for automated trocar docking. We use a nonlinear optimization program to model the task, minimizing a cost function subject to constraints to find optimal joint configurations. The controller incorporates a geometric model for insertion and a force-feedback (FF) term to ensure patient safety by preventing excessive interaction forces with the trocar. Experiments, demonstrated on a real hardware lab setup, validate the approach (Fig. 1b). Our method successfully achieves trocar insertion on our real robot lab setup, and simulation trials demonstrate its ability to reduce interaction forces.

Publication
12th Conference on New Technologies for Computer and Robot Assisted Surgery