A Programmably Compliant Origami Mechanism for Dynamically Dexterous Robots

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 −1 using 8 mil thick polyester-coated paper. Accordingly, we design origami energy-storing springs with a stiffness of 1035 N m −1 each and incorporate them into a three degree-offreedom (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 shotput 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.

A Tendon-Driven Origami Hopper Triggered by Proprioceptive Contact Detection

“…We construct the origami bellow out of 8 mil thick Durilla synthetics paper with polyester finish (CTI Paper, USA) and glued into a closed cylinder with the 3M 467MP adhesive transfer tape. Our previous work [30] shows that these REBO bellows exhibit the compliance (force-extension) properties of a Hooke's law spring when compressed up to 2/3 of its travel. Data presented in [30] demonstrate that varying the cone angle β varies the REBO's stiffness, K s , according to a roughly affine function K s (N m −1 ) = 16.1β( • ) − 43.7.…”

“…Our previous work [30] shows that these REBO bellows exhibit the compliance (force-extension) properties of a Hooke's law spring when compressed up to 2/3 of its travel. Data presented in [30] demonstrate that varying the cone angle β varies the REBO's stiffness, K s , according to a roughly affine function K s (N m −1 ) = 16.1β( • ) − 43.7. Furthermore, concentric arrangement of two REBOs as depicted in the right hand image of Fig.…”

“…Origami Robots: Origami structures, meta-materials formed by folding flat sheets, exhibit compliance and resilience properties distinct from those of the planar constituent material as a result of the folding pattern and geometric constraints [28], [29]. Origami designs reported in the literature, prior to our recent origami juggler [30], store energy only in the folds and can achieve dynamic manipulation either with very small loads [31], [32] or through the use of additional springs [33]. Our juggler [30] and its (essentially merely inverted) operation as the hopper reported here (along with a highly resilient single shot leaping machine [34]) perform considerably larger work due to the new Reconfigurable Expanding Bistable Origami (REBO) pattern [2] that recruits bending energy from the faces, which would have previously been considered rigid plates.…”

“…Our prior work [30] demonstrated that a REBO structure could be used to juggle (repeatedly loft and catch) a 1kg load. Here, we modify that design to achieve actual locomotion: translation of the mechanism's mass center through a two degree-of-freedom workspace.…”

“…4 However, it was not clear whether the consequently diminished proprioceptive transparency [42], [45] would necessitate the introduction of toe contact sensors to ensure an adequate reaction time. More critically, prior kinematic analysis [30] showed that the range of motion and tracking error of the juggler's end effector was not adequate for the stepping control underlying fully planar locomotion via fore-aft hopping [8]. Together, these three design improvements -careful regearing; increase of workspace volume; and improved tracking control -yield the following new contributions:…”