Automated stability testing of elastic rods with helical centerlines using a robotic system

TL;DR

This paper presents an automated robotic system for stability testing of elastic rods with helical centerlines, enabling precise manipulation and detection of instabilities, which advances experimental mechanics automation.

Contribution

It introduces a novel robotic manipulation scheme for exploring stability of helical elastic rods, integrating vision-based instability detection, and validating results against numerical simulations.

Findings

Good agreement between experimental and numerical results

Automated system effectively explores stability space of helical rods

Method facilitates automation in experimental mechanics

Abstract

Experimental analysis of the mechanics of a deformable object, and particularly its stability, requires repetitive testing and, depending on the complexity of the object's shape, a testing setup that can manipulate many degrees of freedom at the object's boundary. Motivated by recent advancements in robotic manipulation of deformable objects, this paper addresses these challenges by constructing a method for automated stability testing of a slender elastic rod -- a canonical example of a deformable object -- using a robotic system. We focus on rod configurations with helical centerlines since the stability of a helical rod can be described using only three parameters, but experimentally determining the stability requires manipulation of both the position and orientation at one end of the rod, which is not possible using traditional experimental methods that only actuate a limited number of degrees of freedom. Using a recent geometric characterization of stability for helical rods, we construct and implement a manipulation scheme to explore the space of stable helices, and we use a vision system to detect the onset of instabilities within this space. The experimental results obtained by our automated testing system show good agreement with numerical simulations of elastic rods in helical configurations. The methods described in this paper lay the groundwork for automation to grow within the field of experimental mechanics.