Stowable Tape Spring Truss Leg for Robotic Mobility
Angelica Peña, Andrew Galassi, Hannah S. Stuart
AI summary
Problem
Wheeled robots struggle to traverse obstructed terrains like rubble and crevices, while existing transformable wheel-leg mechanisms often lack high transformation ratios or require complex active deployment systems.
Approach
The authors develop a passive leg mechanism that reinforces a single tape spring with a tensioned string, allowing it to deploy via stored spring energy and stow under the rover's weight while optimizing structural strength through adjustable string pretension.
Key results
- Achieves wheel-to-leg transformation ratios of 3.77 to 5.38
- Develops an analytical model linking string slack to transverse buckling load
- Validates a 557% increase in buckling load at optimal zero-slack tension
- Demonstrates successful obstacle traversal on a two-wheeled tail-dragging rover
Why it matters
This passive, high-ratio transformable leg design offers a lightweight, low-complexity solution for hybrid locomotion, benefiting search-and-rescue and planetary exploration robots navigating obstructed terrains.
Abstract
Obstructed terrains, such as boulders, crevices, and rubble, limit the locomotion of wheeled mobile robots. Transformable wheel-to-leg designs enable better traversal; small wheels provide driving efficiency and deployable legs enable stepping over obstructions. We propose an approach to such leg deployment utilizing a novel tape spring truss structure. It achieves large shape changes – demonstrating transformation ratios from 3.77 to 5.38 between wheel radius and leg length – in a light-weight (8 g) and compact way. Prior tape spring mechanisms have not yet used a string-tensioned truss formation. By tensioning the tape spring via a string mechanism, the wheel’s emerging deployable legs are strong enough to traverse obstacles greater than one wheel diameter. Yet, it can also be stowed using just the weight of the rover to coil the tape spring. Adjusting the string pretension allows for optimization of the leg’s transverse buckling load, resulting in a strong truss despite low mass and stowed volume. We validate the truss’s capability by incorporating it into a two-wheeled mobile rover platform, demonstrating utility in mobility across obstructed terrain.