Sung, Cynthia
Email Address
ORCID
Disciplines
Search Results
Now showing 1 - 10 of 19
Publication MORF: Magnetic Origami Reprogramming and Folding System for Repeatably Reconfigurable Structures with Fold Angle Control(IEEE, 2025-05-19) Unger, Gabriel; Shenoy, Sridhar; Li, Tianyu; Figueroa, Nadia; Sung, CynthiaWe present the Magnetic Origami Reprogramming and Folding System (MORF), a magnetically reprogrammable system capable of precise shape control, repeated transformations, and adaptive functionality for robotic applications. Unlike current self-folding systems, which often lack reprogrammability or lose rigidity after folding, MORF generates stiff structures over multiple folding cycles without degradation in performance. The ability to reconfigure and maintain structural stability is crucial for tasks such as reconfigurable tooling. The system utilizes a thermoplastic layer sandwiched within a thin magnetically responsive laminate sheet, enabling structures to self-fold in response to a combination of external magnetic field and heating. We demonstrate that the resulting folded structures can bear loads over 40 times their own weight and can undergo up to 50 cycles of repeated transformations without losing structural integrity. We showcase these strengths in a reconfigurable tool for unscrewing and screwing bolts and screws of various sizes, allowing the tool to adapt its shape to different bolt sizes while withstanding the mechanical stresses involved. This capability highlights the system’s potential for task-varying, load-bearing applications in robotics, where both versatility and durability are essential.Publication Design and Control of a Tunable-Stiffness Coiled-Spring Actuator(2023-05-29) Misra, Shivangi; Mitchell, Mason; Chen, Rongqian; Sung, CynthiaWe propose a novel design for a lightweight and compact tunable stiffness actuator capable of stiffness changes up to 20x. The design is based on the concept of a coiled spring, where changes in the number of layers in the spring change the bulk stiffness in a near-linear fashion. We present an elastica nested rings model for the deformation of the proposed actuator and empirically verify that the designed stiffness-changing spring abides by this model. Using the resulting model, we design a physical prototype of the tunable-stiffness coiled-spring actuator and discuss the effect of design choices on the resulting achievable stiffness range and resolution. In the future, this actuator design could be useful in a wide variety of soft robotics applications, where fast, controllable, and local stiffness change is required over a large range of stiffnesses.Publication Re-programmable Matter by Folding: Magnetically Controlled Origami that Self-Folds, Self-Unfolds, and Self-Reconfigures On-Demand(Springer, 2024-07-24) Unger, Gabriel; Sung, CynthiaWe present a reprogrammable matter system that changes shape in a controllable manner in real-time and on-demand. The system uses origami inspired fabrication for self-assembly and repeated self-reconfiguration. By writing a magnetic program onto a thin laminate and applying an external magnetic field, we control the sheet to self-fold. The magnetic program can be written at millimeter resolution over hundreds of programming cycles and folding steps. We demonstrate how the same sheet can fold and unfold into multiple shapes using a fully automated program-and-fold process. Finally, we demonstrate how electronic components can be incorporated to produce functional structures such as a foldable display. The system has advantages over existing programmable matter systems in its versatility and ability to support potentially any folding sequence.Publication Online Optimization of Soft Manipulator Mechanics via Hierarchical Control(2024) Misra, Shivangi; Sung, CynthiaActively tuning mechanical properties in soft robots is now feasible due to advancements in soft actuation technologies. In soft manipulators, these novel actuators can be distributed over the robot body to allow greater control over its large number of degrees of freedom and to stabilize local deformations against a range of disturbances. In this paper, we present a hierarchical policy for stiffness control for such a class of soft manipulators. The stiffness changes induce desired deformations in each segment, thereby influencing the manipulator’s end-effector position. The algorithm can be run as an online controller to influence the manipulator’s stable states – as we demonstrate in simulation – or offline as a design algorithm to optimize stiffness distributions – as we showcase in a hardware demonstration. Our proposed hierarchical control scheme is agnostic to the stiffness actuation method and can extend to other soft manipulators with nonuniform stiffness distributions.Publication Drag Coefficient Characterization of the Origami Magic Ball (Inproceedings)(2023-08-29) Chen, Guanyu; Chen, Dongsheng; Weakly, Jessica; Sung, CynthiaThe drag coefficient plays a vital role in the design and optimization of robots that move through fluids. From aircraft to underwater vehicles, their geometries are specially engineered so that the drag coefficients are as low as possible to achieve energy-efficient performances. Origami magic balls are 3-dimensional reconfigurable geometries composed of repeated simple waterbomb units. Their volumes can change as their geometries vary and we have used this concept in a recent underwater robot design. This paper characterizes the drag coefficient of an origami magic ball in a wind tunnel. Through dimensional analysis, the scenario where the robot swims underwater is equivalently transferred to the situation when it is in the wind tunnel. With experiments, we have collected and analyzed the drag force data. It is concluded that the drag coefficient of the magic ball increases from around 0.64 to 1.26 as it transforms from a slim ellipsoidal shape to an oblate spherical shape. Additionally, three different magic balls produce increases in the drag coefficient of between 57% and 86% on average compared to the smooth geometries of the same size and aspect ratio. The results will be useful in future designs of robots using waterbomb origami in fluidic environments.Publication Fabrication and Characterization of I-cord Knitted SMA Actuators(2021-03-13) Kim, Christopher Y; Chien, Athena; Tippur, Megha; Sung, CynthiaKnitted SMA actuators provide greater actuation stroke than single-strand SMA wire actuators by leveraging its knitted structure. However, due to short-circuiting through interlacing knit loops, existing knitted SMA sheet actuators are unsuitable for joule-heating actuation when uniform contractile actuation is desired. We explore an axially symmetric tubular i-cord knitted actuator as a possible solution. The fabrication process of an i-cord knitted SMA actuator and its electrical, thermal, and mechanics models are presented. After modifying existing models for single-strand SMA wire and adjusting their parameters, the proposed electrical, thermal, and mechanics models were verified with experimental results. Acknowledgements Support for this project has been provided in part by NSF REU EEC-1659190 and by the GeorgiaTech Stamps President's Scholars program.Publication Push-On Push-Off: A Compliant Bistable Gripper with Mechanical Sensing and Actuation(2021-03-13) McWilliams, Jessica; Yuan, Yifan; Sung, Cynthia; Friedman, JasonGrasping is an essential task in robotic applications and is an open challenge due to the complexity and uncertainty of contact interactions. In order to achieve robust grasping, systems typically rely on precise actuators and reliable sensing in order to control the contact state. We propose an alternative design paradigm that leverages contact and a compliant bistable mechanism in order to achieve "sensing" and "actuation" purely mechanically. To grasp an object, the manipulator holding our end effector presses the bistable mechanism into the object until snap-through causes the gripper to enclose it. To release the object, the tips of the gripper are pushed against the ground, until rotation of the linkages causes snap-through in the other direction. This push-on push-off scheme reduces the complexity of the grasping task by allowing the manipulator to automatically achieve the correct grasping behavior as long as it can get the end effector to the correct location and apply sufficient force. We present our dynamic model for the bistable gripping mechanism, propose an optimized result, and demonstrate the functionality of the concept on a fabricated prototype. We discuss our stiffness tuning strategy for the 3D printed springs, and verify the snap-through behavior of the system using compression tests on an MTS machine. Acknowledgements Support for this project has been provided in part by NSF Grant No. 1138847 and DGE-1845298. We also thank Terry Kientz, Jeremy Wang, Peter Szczesniak, and Joe Valdez for their assistance with the fabrication, and Neal Tinaikar for assistance with initial prototypes. We are grateful.Publication Kinegami: Algorithmic Design of Compliant Kinematic Chains From Tubular Origami(2022-10-12) Chen, Wei-Hsi; Yang, Woohyeok; Peach, Lucien; Koditschek, Daniel E; Sung, Cynthia ROrigami processes can generate both rigid and compliant structures from the same homogeneous sheet material. In this article, we advance the origami robotics literature by showing that it is possible to construct an arbitrary rigid kinematic chain with prescribed joint compliance from a single tubular sheet. Our “Kinegami” algorithm converts a Denavit–Hartenberg specification into a single-sheet crease pattern for an equivalent serial robot mechanism by composing origami modules from a catalogue. The algorithm arises from the key observation that tubular origami linkage design reduces to a Dubins path planning problem. The automatically generated structural connections and movable joints that realize the specified design can also be endowed with independent user-specified compliance. We apply the Kinegami algorithm to a number of common robot mechanisms and hand-fold their algorithmically generated single-sheet crease patterns into functioning kinematic chains. We believe this is the first completely automated end-to-end system for converting an abstract manipulator specification into a physically realizable origami design that requires no additional human input.Publication Reconfiguring Non-Convex Holes in Pivoting Modular Cube Robots(2021-07-07) Feshbach, Daniel Adam; Sung, CynthiaWe present an algorithm for self-reconfiguration of admissible 3D configurations of pivoting modular cube robots with holes of arbitrary shape and number. Cube modules move across the surface of configurations by pivoting about shared edges, enabling configurations to reshape themselves. Previous work provides a reconfiguration algorithm for admissible 3D configurations containing no non-convex holes; we improve upon this by handling arbitrary admissible 3D configurations. The key insight specifies a point in the deconstruction of layers enclosing non-convex holes at which we can pause and move inner modules out of the hole. We prove this happens early enough to maintain connectivity, but late enough to open enough room in the enclosing layer for modules to escape the hole. Our algorithm gives reconfiguration plans with O(n^2) moves for n modules.Publication Supplementary Materials: Algorithmic Design of Kinematic Trees Based on CSC Dubins Planning for Link Shapes(2024-10-08) Feshbach, Daniel Adam; Chen, Wei-Hsi; Xu, Ling; Schaumburg, Emil; Huang, Isabella; Sung, CynthiaSupplementary materials for the paper "Algorithmic Design of Kinematic Trees Based on CSC Dubins Planning for Link Shapes", presented at The 16th International Workshop on the Algorithmic Foundations of Robotics (WAFR), 2024. Paper abstract: Computational tools for robot design require algorithms moving between several layers of abstraction including task, morphology, kinematics, mechanism shapes, and actuation. In this paper we give a linear-time algorithm mapping from kinematics to mechanism shape for tree-structured linkages. Specifically, we take as input a tree whose nodes are axes of motion (lines which joints rotate about or translate along) along with types and sizes for joints on these axes, and a radius r for a tubular bound on the link shapes. Our algorithm outputs the geometry for a kinematic tree instantiating these specifications such that the neutral configuration has no self-intersection. The algorithm approach is based on understanding the mechanism design problem as a planning problem for link shapes, and arranging the joints along their axes of motion to be appropriately spaced and oriented such that feasible, non-intersecting paths exist linking them. Since link bending is restricted by its tubular radius, this is a Dubins planning problem, and to prove the correctness of our algorithm we also prove a theorem about Dubins paths: if two point-direction pairs are separated by a plane at least 2r from each, and the directions each have non-negative dot product with the plane normal, then they are connected by a radius-r CSC Dubins path with turn angles <= pi. We implement our design algorithm in code and provide a 3D printed example of a tubular kinematic tree. The results provide an existence proof of tubular-shaped kinematic trees implementing given axes of motion, and could be used as a starting point for further optimization in an automated or algorithm-assisted robot design system.