Category Archives: Publications

Congratulations to Jessica McWilliams and Christopher Kim, whose papers were accepted to RoboSoft 2021!

Jessica McWilliams, Yifan Yuan, Jason Friedman, Cynthia Sung: Push On, Push Off: A compliant bistable gripper with mechanical sensing and actuation. IEEE International Conference on Soft Robotics (RoboSoft), 2021, (to appear).
Christopher Kim, Athena Chien, Megha Tippur, Cynthia Sung: Fabrication and characterization of I-cord knitted SMA actuators. IEEE International Conference on Soft Robotics (RoboSoft), 2021, (to appear).

ICRA and RoboSoft publications: Jumping and Hopping Origami Robots

Our papers on using origami for energy storage in dynamic robot locomotion were accepted to ICRA and RoboSoft!

REBOund: Untethered Origami Jumping Robot with Controllable Jump Height” (ICRA 2020)

Abstract: Origami robots are well-suited for jumping maneuvers because of their light weight and ability to incorporate actuation and control strategies directly into the robot body. However, existing origami robots often model fold patterns as rigidly foldable and fail to take advantage of deformation in an origami sheet for potential energy storage. In this paper, we consider a parametric origami tessellation, the Reconfigurable Expanding Bistable Origami (REBO) pattern, which leverages face deformations to act as a nonlinear spring. We present a pseudo-rigid-body model for the REBO for computing its energy stored when compressed to a given displacement and compare that model to experimental measurements taken on a mechanical testing system. This stored potential energy, when released quickly, can cause the pattern to jump. Using our model and experimental data, we design and fabricate a jumping robot, REBOund, that uses the spring-like REBO pattern as its body. Four lightweight servo motors with custom release mechanisms allow for quick compression and release of the origami pattern, allowing the fold pattern to jump over its own height even when carrying 5 times its own weight in electronics and power. We further demonstrate that small geometric changes to the pattern allow us to change the jump height without changing the actuation or control mechanism.

A tendon-driven origami hopper triggered by proprioceptive contact detection” (RoboSoft 2020)

Abstract: We report on experiments with a laptop-sized (0.23m, 2.53kg), paper origami robot that exhibits highly dynamic and stable two degree-of-freedom (circular boom) hopping at speeds in excess of 1.5 bl/s (body-lengths per second) at a specific resistance O(1) while achieving aerial phase apex states 25% above the stance height over thousands of cycles. Three conventional brushless DC motors load energy into the folded paper springs through pulley-borne cables whose sudden loss of tension upon touchdown triggers the release of spring potential that accelerates the body back through liftoff to flight with a 20W powerstroke, whereupon the toe angle is adjusted to regulate fore-aft speed. We also demonstrate in the vertical hopping mode the transparency of this actuation scheme by using proprioceptive contact detection with only motor encoder sensing. The combination of actuation and sensing shows potential to lower system complexity for tendon-driven robots.

RA-L publication: Programmably Compliant Origami

Our paper “A programmably compliant origami mechanism for dynamically dexterous robots” was accepted to RA-L. This was a collaborative project with Prof. Dan Koditschek and Prof. Shu Yang’s groups.

Abstract: We present an approach to overcoming challenges in dynamical dexterity for robots through programmably compliant origami mechanisms. 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 programmable range by nearly an order of magnitude and achieving bulk axial stiffness spanning 200-1500 Nm-1 using 8 mil thick polyester-coated paper. Accordingly, we design origami energy-storing springs with a stiffness of 1035 Nm-1 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 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.