A Tunably Compliant Origami Mechanism for Dynamically Dexterous Robots

TL;DR

This paper introduces a tunable origami-based mechanism that enhances the dynamic dexterity of robots by allowing adjustable stiffness, enabling stable juggling and precise trajectory control in a compact form.

Contribution

It presents a novel origami design with adjustable stiffness, integrated into a multi-DOF robotic mechanism for improved dynamic performance and dexterity.

Findings

Achieved a tunable axial stiffness range of 200-1500 N/m.

Demonstrated trajectory tracking with less than 15% rms error.

Enabled stable juggling with high-energy collisions.

Abstract

We present an approach to overcoming challenges in dynamical dexterity for robots through tunable origami structures. Our work leverages a one-parameter family of flat sheet crease patterns that folds into origami bellows, whose axial compliance can be tuned to select desired stiffness. Concentrically arranged cylinder pairs reliably manifest additive stiffness, extending the tunable range by nearly an order of magnitude and achieving bulk axial stiffness spanning 200-1500 N/m using 8 mil thick polyester-coated paper. Accordingly, we design origami energy-storing springs with a stiffness of 1035 N/m each and incorporate them into a three degree-of-freedom (DOF) tendon-driven spatial pointing mechanism that exhibits trajectory tracking accuracy less than 15% rms error within a ~2 cm^3 volume. The origami springs can sustain high power throughput, enabling the robot to achieve asymptotically stable juggling for both highly elastic (1~kg resilient shot put ball) and highly damped ("medicine ball") collisions in the vertical direction with apex heights approaching 10 cm. The results demonstrate that "soft" robotic mechanisms are able to perform a controlled, dynamically actuated task.