Intuitive Telemanipulation of Hyper-Redundant Snake Robots within Locomotion and Reorientation using Task-Priority Inverse Kinematics

TL;DR

This work tackles intuitive telemanipulation of hyper-redundant snake robots for minimally invasive tasks, where a $6$-DoF end-effector input must drive a long, highly articulated chain. The authors propose SnakeTTP, a task-priority inverse kinematics framework that places the end-effector pose task at the highest priority and performs backbone shaping in the null space with two formulations: point-to-point correspondences and a Fréchet-distance–based shape fitting. The approach achieves real-time performance (approximately $1.5$ ms per iteration) and demonstrates via a $14$-person user study that online locomotion with macroscopic path tracking is feasible; pivot reorientation within a target area shows the Fréchet-based method reduces shape change by up to $20.1\%$ compared to conventional correspondences. Overall, the method enables intuitive, safe, and efficient telemanipulation of snake robots for MIS without requiring full a priori shape specifications or intraoperative imaging, offering a practical route to improved tissue access and maneuverability.$

Abstract

Snake robots offer considerable potential for endoscopic interventions due to their ability to follow curvilinear paths. Telemanipulation is an open problem due to hyper-redundancy, as input devices only allow a specification of six degrees of freedom. Our work addresses this by presenting a unified telemanipulation strategy which enables follow-the-leader locomotion and reorientation keeping the shape change as small as possible. The basis for this is a novel shape-fitting approach for solving the inverse kinematics in only a few milliseconds. Shape fitting is performed by maximizing the similarity of two curves using Fréchet distance while simultaneously specifying the position and orientation of the end effector. Telemanipulation performance is investigated in a study in which 14 participants controlled a simulated snake robot to locomote into the target area. In a final validation, pivot reorientation within the target area is addressed.

Figures (7)

• Figure 1: (a) Intuitive telemanipulation with SnakeTTP using an input device (frames: base ${\mathscr{F}}_{\mathrm{B}}$, stylus ${\mathscr{F}}_{\mathrm{S}}$). The snake's tip is controlled by orientation input ${}_{\mathrm{}}^{\mathrm{B}}{\boldsymbol{R}}^{\mathrm{}}_{\mathrm{S}}$. A camera at the distal end provides visual feedback. Buttons activate the feeder for locomotion ($b_1$) or realize pivot reorientation ($b_2$). Green spheres indicate a desired curvilinear path to be followed. (b) Less shape change is realized during reconfiguration compared to a reference.
• Figure 2: Kinematic chain with $n$ rotational actuators of height $h$, linear feeder $q_1$, frames ${\mathscr{F}}_{i}$ and arbitrary tool transformation $^{n{+}1}\boldsymbol{T}_\mathrm{E}$
• Figure 3: Convergence of shape and pose errors averaged for 100 random desired shapes. One iteration takes on average $1.5ms$.
• Figure 4: (a) Normalized shape error at the end of the telemanipulation run using SnakeTTP compared to the shape-fitting method with knowledge of the entire path (Initial). (b)--(d) Spatial visualization of the three paths, the final configurations of an exemplary study participant (SnakeTTP) and the shape fitting results given knowledge of the entire paths (Initial). (e) Results of the reorientation experiment for shape fitting using Fréchet distance, point-to-point correspondences and with disabled shape fitting for three paths. The opening angle of the viewing cone $\theta$ was increased equidistantly.
• Figure : Compute Jacobian $\boldsymbol{J}_{\mathrm{F}}$ for Fréchet task