Induced Vertex Motion As a Performance Measure for Surgery in Confined Spaces

While in the design phase of a robotic system for the procedures performed in surgical confined spaces or hard-to-reach-deep surgical fields, designers can leverage a systematic method to compare the design alternatives for tele-surgical manipulators quantitatively. Unlike most of the work in the literature, we propose an approach for comparing design alternatives by considering the spurious motions along the length of the manipulator in lieu of existing approaches looking at only the end-effector dexterity measures. We propose a performance measure quantifying these spurious motions while the end-effector executes the application-critical tasks such as suturing and tying a knot. A good manipulator design should yield minimal swept volume along its length portions within the confined space. If informed about these spurious motions, that design would lead to reduced force on the internal organs, reducing the pain and discomfort as well as occurrences of extracorporeal inter-manipulator collisions. To validate the proposed approach, we present two illustrative simulation case studies: (1) two planar rigid link serial robots performing the task of following a desired trajectory and (2) two different architectures of tele-surgical manipulators performing the task of passing a circular suture needle under the fulcrum constraints. The results show the applicability of the proposed performance measure in determining the suitability of a particular design alternative for a given task. Although results are promising, using this measure alone for design optimization may compromise overall device dexterity. Therefore, this measure needs to be incorporated into a weighted optimization framework for robot design.