A Starter's Kit for Concentric Tube Robots

TL;DR

An educational kit aimed at lowering the barriers to entry into concentric tube robot research and having the potential to help early-stage graduate students get rapidly started with CTR research is presented.

Abstract

Concentric Tube Robots (CTRs) have garnered significant interest within the surgical robotics community because of their flexibility, dexterity, and ease of miniaturization. However, mastering the unique kinematics and design principles of CTRs can be challenging for newcomers to the field. In this paper, we present an educational kit aimed at lowering the barriers to entry into concentric tube robot research. Our goal is to provide accessible learning resources for CTRs, bridging the knowledge gap between traditional robotic arms and these specialized devices. The proposed kit includes (1) An open-source design and assembly instructions for an economical (cost of materials $\approx$ 700 USD) modular CTR; (2) A set of self-study materials to learn the basics of CTR modeling and control, including automatically-graded assignments. To evaluate the effectiveness of our educational kit, we conducted a human subjects study involving first-year graduate students in engineering. Over a four-week period, participants -- none of whom had any prior knowledge of concentric tube robots -- successfully built their first CTR using the provided materials, implemented the robot's kinematics in MATLAB, and conducted a tip-tracking experiment with an optical tracking device. Our findings suggest that the proposed kit facilitates learning and hands-on experience with CTRs, and furthermore, it has the potential to help early-stage graduate students get rapidly started with CTR research. By disseminating these resources, we hope to broaden participation in concentric tube robot research to a wider a more diverse group of researchers.

Figures (10)

• Figure 1: Authors of this manuscript measuring the position of the tip of a concentric tube robot (CTR) with an optically-tracked probe. The CTR pictured here is part of an educational kit developed by our team with the goal of providing accessible resources to learn CTR kinematics and acquire hands-on experience with these devices.
• Figure 2: In our educational kit, we refer to the kinematic modeling proposed in webster_mechanics_2009, where (a) the shape of a Concentric Tube Robot is partitioned into a sequence of constant curvature arcs called links. The geometry of each link is uniquely described by three parameters, namely the arc length $\ell$, the curvature $\kappa$ (or, alternatively, the radius of curvature $R$), and a rotation $\phi$ about the link's base. (b) The curvature of each link is a weighted superposition of the natural curvatures of the tubes present in the link, as captured by Eq. \ref{['eq: in-plane-bending']}. (c) If two (or more) concentric tubes do not share the same bending plane, the corresponding link will bend in the middle, as described by Eqs. \ref{['eq:out-of-plane-bending-1']} and \ref{['eq:out-of-plane-bending-2']}.
• Figure 3: Proposed open-source concentric tube robot. Each tube is attached to a motorized cart moving on a system of rails. Each cart is equipped with two motors, respectively responsible for tube translation and rotation. Translation uses a rotating ball nut mechanism, with a fixed lead screw shared by all carts.
• Figure 4: Procedure for installing a tube into a cart. (a) First, the cube lock at the base of a tube is inserted into the green pulley. (b) The tube is rotated by 45$^\circ$ in either direction. A tube lock is inserted to hold the cube in place. (c) The tube is now securely fastened. Tubes can be quickly removed or swapped by reversing this procedure.
• Figure 5: Experimental setup for the characterization of the motion accuracy of the proposed actuation unit. An optical tracker, the Polaris Vega, is used to track the movement of the carts relative to a fixed frame of reference (the robot base frame). A rotation verification tool is used in place of a tube to track rotation.