@conference{feshbach2024kinematicTrees,

title = {Algorithmic Design of Kinematic Trees Based on CSC Dubins Planning for Link Shapes},

author = {Daniel Feshbach and Wei-Hsi Chen and Ling Xu and Emil Schaumburg and Isabella Huang and Cynthia Sung},

year  = {2024},

date = {2024-10-08},

urldate = {2024-10-08},

booktitle = {Workshop on the Algorithmic Foundations of Robotics (WAFR)},

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 $leq pi$. 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.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{xu2024cscDubinsReparameterization,

title = {Reparametrization of 3D CSC Dubins' Paths Enabling 2D Search},

author = {Ling Xu and Yuliy Baryshnikov and Cynthia Sung},

year  = {2024},

date = {2024-10-08},

booktitle = {Workshop on the Algorithmic Foundations of Robotics (WAFR)},

abstract = {This paper addresses the Dubins path planning problem for vehicles in 3D space. In particular, we consider the problem of computing CSC paths– paths that consist of a circular arc (C) followed by a straight segment (S) followed by a circular arc (C). These paths are useful for vehicles such as fixed-wing aircraft and underwater submersibles that are subject to lower bounds on turn radius. We present a new parameterization that reduces the 3D CSC planning problem to a search over 2 variables, thus lowering search complexity, while also providing gradients that assist that search. We use these equations with a numerical solver to explore numbers and types of solutions computed for a variety of planar and 3D scenarios. Our method successfully computes CSC paths for the large majority of test cases, indicating that it could be useful for future generation of robust, efficient curvature-constrained trajectories.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{unger2024RMBF,

title = {Re-programmable Matter by Folding: Magnetically Controlled Origami that Self-Folds, Self-Unfolds, and Self-Reconfigures On-Demand},

author = {Gabriel Unger and Cynthia Sung},

url = {https://www.youtube.com/watch?v=TuIq6ykfoOA&list=PLmM-rbrIwkWXFno8GbQYxiCcA3s8SaVJW&index=1

https://repository.upenn.edu/entities/publication/18d39cb9-f453-4cc7-9a68-47ddcc4a2924},

year  = {2024},

date = {2024-07-16},

urldate = {2024-07-16},

booktitle = {8th International Meeting on Origami in Science, Mathematics, and Education},

abstract = {We 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.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{feshbach2024kinegamiPython,

title = {Kinegami: Open-source Software for Creating Kinematic Chains from Tubular Origami},

author = {Daniel Feshbach and Wei-Hsi Chen and Daniel E. Koditschek and Cynthia Sung},

url = {https://github.com/SungRoboticsGroup/KinegamiPython

https://sung.seas.upenn.edu/research/kinegami/

https://repository.upenn.edu/handle/20.500.14332/60333},

year  = {2024},

date = {2024-07-16},

urldate = {2024-07-16},

booktitle = {8th International Meeting on Origami in Science, Mathematics, and Education (8OSME)},

abstract = {Arms, legs, and fingers of animals and robots are all examples of “kinematic chains" - mechanisms with sequences of joints connected by effectively rigid links. Lightweight kinematic chains can be manufactured quickly and cheaply by folding tubes. In recent work [Chen et al. 2022], we demonstrated that origami patterns for kinematic chains with arbitrary numbers of degrees of freedom can be constructed algorithmically from a minimal kinematic specification (axes that joints rotate about or translate along). The work was founded on a catalog of tubular crease patterns for revolute joints (rotation about an axis), prismatic joints (translation along an axis), and links, which compose to form the specified design. With this paper, we release an open-source python implementation of these patterns and algorithms. Users can specify kinematic chains as a sequence of degrees of freedom or by specific joint locations and orientations. Our software uses this information to construct a single crease pattern for the corresponding chain. The software also includes functions to move or delete joints in an existing chain and regenerate the connecting links, and a visualization tool so users can check that the chain can achieve their desired configurations. This paper provides a detailed guide to the code and its usage, including an explanation of our proposed representation for tubular crease patterns. We include a number of examples to illustrate the software’s capabilities and its potential for robot and mechanism design.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{weakly2024windtunnel,

title = {A low-cost, adaptable system for lift and drag measurement in an educational wind tunnel},

author = {Jessica Weakly and Sarah Ho and Erica Feehery and Bruce Kothmann and Cynthia Sung},

url = {https://sung.seas.upenn.edu/publications/wind-tunnel-force-balance/},

doi = {10.18260/1-2--46453},

year  = {2024},

date = {2024-06-26},

urldate = {2024-06-26},

booktitle = {2024 ASEE Annual Conference and Exposition},

abstract = {Wind tunnel testing augments the undergraduate fluid dynamics curriculum by providing

hands-on application of the course material, and a low-cost version of a force balance is desirable.

To maximize the utility of wind tunnel-based lessons and laboratory demonstrations, there is also

a need for a setup that is easily adaptable to different tests and loading applications. This paper

provides such a force balance design, along with detailed evaluation and benchmarking to

characterize the accuracy of the force balance. Our force balance uses readily available materials

having a total cost under $125. Static load tests show that the force balance is accurate with a

mean absolute percentage error of only 2.5%. We demonstrate the system’s usefulness and

adaptability with classic examples of measuring drag on a sphere and characterizing a

NACA 0012 wing, as well as with measuring lift on a foldable wing. Finally, we pilot the force

balance in an undergraduate mechanical engineering lab setting and find that students are able to

explore the setup, understand the load cell functionality, and use the system to measure drag on a

sphere. The force balance enables students to gain hands-on learning experience related to both

fluid mechanics and statics, and our user study shows that the force balance is durable through

classroom use. The low cost, robustness, and high adaptability of the system makes it suitable for

incorporating in multiple labs or for allowing student project teams to utilize the system in their

own experiments.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{misra2024tsmb,

title = {Online Optimization of Soft Manipulator Mechanics via Hierarchical Control},

author = {Shivangi Misra and Cynthia Sung},

url = {https://youtu.be/DS2kEvccwYA?feature=shared

https://repository.upenn.edu/handle/20.500.14332/59590},

doi = {10.1109/RoboSoft60065.2024.10522004},

year  = {2024},

date = {2024-04-14},

urldate = {2024-04-14},

booktitle = {7th IEEE-RAS International Conference on Soft Robotics (RoboSoft)},

abstract = {Actively 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.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{kim2024origami,

title = {Origami-Inspired Bistable Gripper with Self-Sensing Capabilities},

author = {Christopher Kim and Lele Yang and Ashwath Anbuchelvan and Raghav Garg and Niv Milbar and Flavia Vitale and Cynthia Sung},

url = {https://www.youtube.com/watch?v=7BFJBbKCvJU

https://repository.upenn.edu/entities/publication/f2892aab-8294-4e97-bd3e-3d77590c5b1e},

doi = {10.1109/RoboSoft60065.2024.10522014},

year  = {2024},

date = {2024-04-13},

urldate = {2024-04-13},

booktitle = {IEEE-RAS International Conference on Soft Robotics (Robosoft)},

abstract = {An origami-inspired bistable gripper, featuring a dual-function custom PET linear solenoid actuator that acts both as an actuator and a sensor, is presented. Movements in the permanent magnet plunger, which is directly mounted to the gripper, create induced electromotive force (emf) in the solenoid, and these induced emf measurements are used to detect snap-through actions and light contacts on the gripper. The fabrication methods for the gripper, actuator, and a gel-free soft wearable EMG electrode are outlined, and the actuator’s self-sensing method utilizing the time-integral of the induced emf measurements are explored. Because a self-sensing actuator eliminates the need for extra sensors, it allows for further miniaturization of the robot while maintaining its compactness and lightweight design. The paper also introduces a full human-in-the-loop system, allowing users to open or close the gripper with their biceps via a wearable EMG electrode. This system bridges human intent with robotic action, offering a more intuitive interaction model for robotic control.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{chen2024design,

title = {Design and Characterization of a Pneumatic Tunable-Stiffness Bellows Actuator},

author = {Rongqian Chen and Jun Kwon and Wei-Hsi Chen and Cynthia Sung},

doi = {10.1109/RoboSoft60065.2024.10521916},

year  = {2024},

date = {2024-04-13},

urldate = {2024-04-13},

booktitle = {IEEE-RAS International Conference on Soft Robotics (RoboSoft)},

abstract = {We introduce a self-contained pneumatic actuator capable of 1.43 times stiffness gain from 1332 N/m to 1913 N/m without needing an external air source or valve. The design incorporates an air chamber bellows and a spring bellows, connected and sealed. Stiffness modulation is achieved by altering the air chamber volume. We present an approach for computing the volume, pressurized force, and stiffness of a single bellows component, as well as methods for composing single bellows models to predict the change in stiffness of the dual bellows actuator as a function of air chamber compression. We detail the fabrication of the actuator and verify the models on the fabricated prototype. This actuator holds promise for future integration in tunable stiffness robots demanding high strength and adaptability in dynamic scenarios.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{feshbach2023curvequad,

title = {CurveQuad: A centimeter-scale origami quadruped that leverages curved creases to self-fold and crawl with one motor},

author = {Daniel Feshbach and Xuelin Wu and Satviki Vasireddy and Louis Beardell and Bao To and Yuliy Baryshnikov and Cynthia Sung},

url = {https://www.youtube.com/watch?v=RnSHG5F2Iek&ab_channel=SungRoboticsGroup

https://sung.seas.upenn.edu/publications/curvequad/},

doi = {10.1109/IROS55552.2023.10342339},

year  = {2023},

date = {2023-10-01},

urldate = {2023-10-01},

booktitle = {IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS)},

abstract = {We present CurveQuad, a miniature curved origami quadruped that is able to self-fold and unfold, crawl, and steer, all using a single actuator. CurveQuad is designed for planar manufacturing, with parts that attach and stack sequentially on a flat body. The design uses 4 curved creases pulled by 2 pairs of tendons from opposite ends of a link on a 270deg servo. It is 8 cm in the longest direction and weighs 10.9 g. Rotating the horn pulls the tendons inwards to induce folding. Continuing to rotate the horn shears the robot, enabling the robot to shuffle forward while turning in either direction. We experimentally validate the robot’s ability to fold, steer, and unfold by changing the magnitude of horn rotation. We also demonstrate basic feedback control by steering towards a light source from a variety of starting positions and orientations, and swarm aggregation by having 4 robots simultaneously steer towards the light. The results demonstrate the potential of using curved crease origami in self-assembling and deployable robots with complex motions such as locomotion.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{chen2023electronics,

title = {Electronics Design and Verification for Robots With Actuation and Sensing Requirements},

author = {Dongsheng Chen and Zonghao Huang and Cynthia Sung},

url = {https://repository.upenn.edu/entities/publication/20eeddb9-8163-44c4-bec4-ed47f62d8f4b},

doi = {10.1115/DETC2023-115313},

year  = {2023},

date = {2023-08-29},

urldate = {2023-08-29},

booktitle = {ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference (IDETC/CIE)},

pages = {DETC2023-115313},

abstract = {Robot design is a challenging problem involving a balance between the robot's mechanical design, kinematic structure, and actuation and sensing capabilities. Recent work in computational robot design has focused on mechanical design while assuming that the given actuators are sufficient for the task. At the same time, existing electronics design tools ignore the physical requirements of the actuators and sensors in the circuit. In this paper, we present the first system that closes the loop between the two, incorporating a robot's mechanical requirements into its circuit design process. We show that the problem can be solved using an iterative search consisting of two parts. First, a dynamic simulator converts the mechanical design and the given task into concrete actuation and sensing requirements. Second, a circuit generator executes a branch-and-bound search to convert the design requirements into a feasible electronic design. The system iterates through both of these steps, a process that is sometimes required since the electronics components add mass that may affect the robot's design requirements. We demonstrate this approach on two examples -- a manipulator and a quadruped -- showing in both cases that the system is able to generate a valid electronics design.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{wilson2023impact,

title = {The Impact of Robotics Expertise on Iterative Robot Design Decisions and Vulnerability to Anchoring Bias},

author = {Cristina Wilson and Kallahan Brown and Cynthia Sung},

url = {https://youtu.be/hFHxWawZ4_w},

doi = {10.1115/DETC2023-116874},

year  = {2023},

date = {2023-08-28},

urldate = {2023-08-28},

booktitle = {ASME International Design Engineering Technical Conferences and Computers and Information in Engineering Conference (IDETC/CIE)},

pages = {DETC2023-116874},

abstract = {Robot design is a complex cognitive activity that requires the designer to iteratively navigate multiple engineering disciplines and the relations between them. In this paper, we explore how people approach robot design and how trends in design strategy vary with the level of expertise of the designer. Using our interactive Build-a-Bot software tool, we recruited 39 participants from the 2022 IEEE International Conference on Robotics and Automation. These participants varied in age from 19 to 56 years, and had between 0 and 17 years of robotics experience. We tracked the participants' design decisions over the course of a 15~min. task of designing a ground robot to cross an uneven environment. Our results showed that participants engaged in iterative testing and modification of their designs, but unlike previous studies, there was no statistically significant effect of participant's expertise on the frequency of iterations. We additionally found that, across levels of expertise, participants were vulnerable to anchoring-and-adjustment, in which they latched onto an initial design concept and insufficiently adjusted the design, even when confronted with difficulties developing the concept into a satisfactory solution. 

The results raise interesting questions for how future engineers can avoid design bias and how design tools can assist in both efficient assessment and optimization of design workflow for complex design tasks.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{misra2023design,

title = {Design and Control of a Tunable-Stiffness Coiled-Spring Actuator},

author = {Shivangi Misra and Mason Mitchell and Rongqian Chen and Cynthia Sung},

url = {https://repository.upenn.edu/grasp_papers/72/

https://youtu.be/52WVMEeGxUk

},

doi = {10.1109/ICRA48891.2023.10161218},

year  = {2023},

date = {2023-05-30},

urldate = {2023-05-30},

booktitle = {IEEE International Conference on Robotics and Automation (ICRA)},

abstract = {We 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.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{huang2022evorobogami,

title = {EvoRobogami: Co-designing with Humans in Evolutionary Robotics Experiments},

author = {Zonghao Huang and Quinn Wu and David Howard and Cynthia Sung},

url = {https://arxiv.org/abs/2205.08086

https://sung.seas.upenn.edu/publications/evorobogami-gecco-2022/},

doi = {10.1145/3512290.3528867},

year  = {2022},

date = {2022-07-09},

urldate = {2022-07-09},

booktitle = {Genetic and Evolutionary Computation Conference (GECCO)},

abstract = {We study the effects of injecting human-generated designs into the initial population of an evolutionary robotics experiment, where subsequent population of robots are optimised via a Genetic Algorithm and MAP-Elites. First, human participants interact via a graphical front-end to explore a directly-parameterised legged robot design space and attempt to produce robots via a combination of intuition and trial-and-error that perform well in a range of environments. Environments are generated whose corresponding high-performance robot designs range from intuitive to complex and hard to grasp. Once the human designs have been collected, their impact on the evolutionary process is assessed by replacing a varying number of designs in the initial population with human designs and subsequently running the evolutionary algorithm. Our results suggest that a balance of random and hand-designed initial solutions provides the best performance for the problems considered, and that human designs are most valuable when the problem is intuitive. The influence of human design in an evolutionary algorithm is a highly understudied area, and the insights in this paper may be valuable to the area of AI-based design more generally. },

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{misra2022forward,

title = {Forward kinematics and control of a segmented tunable-stiffness 3-D continuum manipulator},

author = {Shivangi Misra and Cynthia Sung},

url = {https://repository.upenn.edu/grasp_papers/69/

https://youtu.be/P-vg3Hiuk4M

https://youtu.be/lc6W61xCWuQ},

doi = {10.1109/ICRA46639.2022.9812098},

year  = {2022},

date = {2022-05-23},

urldate = {2022-05-23},

booktitle = {IEEE International Conference on Robotics and Automation (ICRA)},

abstract = {In this work, we consider the problem of controlling the end effector position of a continuum manipulator through local stiffness changes. Continuum manipulators offer the advantage of continuous deformation along their lengths, and recent advances in smart material actuators further enable local compliance changes, which can affect the manipulator's bulk motion. However, leveraging local stiffness change to control motion remains lightly explored. We build a kinematic model of a continuum manipulator as a sequence of segments consisting of symmetrically arranged springs around the perimeter of every segment, and we show that this system has a closed form solution to its forward kinematics. The model includes common constraints such as restriction of torsional or shearing movement. Based on this model, we propose a controller on the spring stiffnesses for a single segment and provide provable guarantees on convergence to a desired goal position. The results are verified in simulation and compared to physical hardware.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{sun2022repeated,

title = {Repeated jumping with the REBOund: Self-righting jumping robot leveraging bistable origami-inspired design},

author = {Yuchen Sun* and Joanna Wang* and Cynthia Sung},

url = {https://repository.upenn.edu/grasp_papers/70/

https://youtu.be/LoCXcwIxCgU

https://youtu.be/JXWAp-rVOxg},

doi = {10.1109/ICRA46639.2022.9812232},

year  = {2022},

date = {2022-05-23},

urldate = {2022-05-23},

booktitle = {IEEE International Conference on Robotics and Automation (ICRA)},

abstract = {Repeated jumping is crucial to the mobility of jumping robots. In this paper, we extend upon the REBOund jumping robot design, an origami-inspired jumping robot that uses the Reconfigurable Expanding Bistable Origami (REBO) pattern as its body. The robot design takes advantage of the pattern's bistability to jump with controllable timing. For jump repeatedly, we also add self-righting legs that utilize a single motor actuation mechanism. We describe a dynamic model that captures the compression of the REBO pattern and the REBOund self-righting process and compared it to the physical robot. Our experiments show that the REBOund is able to successfully self-right and jump repeatedly over tens of jumps.},

note = {* = co-first author},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{qin2022trussbot,

title = {TrussBot: Modeling, design and control of a compliant, helical truss of tetrahedral modules},

author = {Yuhong Qin* and Linda Ting* and Celestina Saven* and Yumika Amemiya and Michael Tanis and Randall Kamien and Cynthia Sung},

url = {https://repository.upenn.edu/grasp_papers/71/

https://youtu.be/bcvFMq40EzI

https://youtu.be/mGf1qmQVNmg},

doi = {10.1109/ICRA46639.2022.9812295},

year  = {2022},

date = {2022-05-23},

urldate = {2022-05-23},

booktitle = {IEEE International Conference on Robotics and Automation},

abstract = {Modular and truss robots offer the potential of high reconfigurability and great functional flexibility, but common implementations relying on rigid components often lead to highly complex actuation and control requirements. This paper introduces a new type of modular, compliant robot: TrussBot. TrussBot is composed of 3D-printed tetrahedral modules connected at the corners with compliant joints. We propose a truss geometry, analyze its deformation modes, and provide a simulation framework for predicting its behavior under applied loads and actuation. The TrussBot is geometrically constrained, thus requiring compliant joints to move. The TrussBot can be actuated through a network of tendons which pinch vertices together and apply a twisting motion due to the structure's connectivity. The truss was demonstrated in a physical prototype and compared to simulation results. },

note = {*=co-first author},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{yuan2021programmable,

title = {Programmable Stiffness and Applications of 3D Printed TPU Diamond Lattices},

author = {Yifan Yuan and Cynthia Sung},

doi = {10.1115/DETC2021-69826},

year  = {2021},

date = {2021-11-17},

urldate = {2021-11-17},

booktitle = {International Design Engineering Technical Conferences & Computers and Information in Engineering Conference},

number = {DETC2021-69826, V08AT08A016},

abstract = {Additive manufacturing provides a rapid manufacturing method for a variety of materials with different applications. Thermoplastic Polyurethane (TPU) is a soft polymer material that can be 3D printed. In this work, we explore the mechanical properties of a 3D printed grid pattern structure with TPU. By changing the pattern's cell size and wall thickness parameters, we control the density of the grid lattice and, as a result, the bulk elastic modulus of the structure. We compare simulation and physical compression tests and conclude that the bulk elastic modulus of a print is related to the infill percentage according to a cubic relationship, with higher infill percentage samples resulting in higher elastic moduli. The precise cell size and wall thickness parameter values are minor influences comparatively. The elastic moduli of the resulting samples span from 0.36 MPa with 23.44% infill to 21.83 MPa with 75% infill, compared to an elastic modulus of 64.31 MPa when printing at 100% density. We also explore other factors such as the sample size, the printer, the build orientation, and the sample geometry. The results have uses in a variety of applications, including a custom linear spring, a bistable gripper, or a soft robot finger. },

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{li2021hav,

title = {Soft hybrid aerial vehicle via bistable mechanism},

author = {Xuan Li* and Jessica McWilliams* and Minchen Li and Cynthia Sung and Chenfanfu Jiang},

url = {https://arxiv.org/abs/2011.00426

https://www.youtube.com/watch?v=fnTyAVVzJMc},

doi = {10.1109/ICRA48506.2021.9561434},

year  = {2021},

date = {2021-05-01},

urldate = {2021-05-01},

booktitle = {IEEE International Conference on Robotics and Automation (ICRA)},

abstract = {Unmanned aerial vehicles have been demonstrated successfully in a variety of tasks, including surveying and sampling tasks over large areas. These vehicles can take many forms. Quadrotors' agility and ability to hover makes them well suited for navigating potentially tight spaces, while fixed wing aircraft are capable of efficient flight over long distances. Hybrid aerial vehicles (HAVs) attempt to achieve both of these benefits by exhibiting multiple modes; however, morphing HAVs typically require extra actuators which add mass, reducing both agility and efficiency. We propose a morphing HAV with folding wings that exhibits both a quadrotor and a fixed wing mode without requiring any extra actuation. This is achieved by leveraging the motion of a bistable mechanism at the center of the aircraft to drive folding of the wing using only the existing motors and the inertia of the system. We optimize both the bistable mechanism and the folding wing using a topology optimization approach. The resulting mechanisms were fabricated on a 3D printer and replaced the frame of an existing quadrotor. Our prototype successfully transitions between both modes and our experiments demonstrate that the behavior of the fabricated prototype is consistent with that of the simulation.},

note = {*=co-first author, best paper in mechanisms and design},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{mcwilliams2021push,

title = {Push On, Push Off: A compliant bistable gripper with mechanical sensing and actuation},

author = {Jessica McWilliams and Yifan Yuan and Jason Friedman and Cynthia Sung},

url = {https://www.youtube.com/watch?v=z50dYYzYvls

https://repository.upenn.edu/meam_papers/307/},

doi = {10.1109/RoboSoft51838.2021.9479209},

year  = {2021},

date = {2021-04-01},

urldate = {2021-04-01},

booktitle = {IEEE International Conference on Soft Robotics (RoboSoft)},

pages = {622-629},

abstract = {Grasping 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. },

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{kim2021sma,

title = {Fabrication and characterization of I-cord knitted SMA actuators},

author = {Christopher Kim and Athena Chien and Megha Tippur and Cynthia Sung},

url = {https://www.youtube.com/watch?v=Czoy5NctBtY

https://repository.upenn.edu/meam_papers/308/

},

doi = {10.1109/RoboSoft51838.2021.9479207},

year  = {2021},

date = {2021-04-01},

urldate = {2021-04-01},

booktitle = {IEEE International Conference on Soft Robotics (RoboSoft)},

pages = {379-386},

abstract = {Knitted 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.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{carlson2020rebound,

title = {REBOund: Untethered origami jumping robot with controllable jump height},

author = {Jaimie Carlson and Jason Friedman and Christopher Kim and Cynthia Sung},

url = {https://sung.seas.upenn.edu/wp-content/publications/carlsonICRA2020_jumper.pdf},

doi = {10.1109/ICRA40945.2020.9196534},

year  = {2020},

date = {2020-06-01},

urldate = {2020-06-01},

booktitle = {IEEE International Conference on Robotics and Automation (ICRA)},

pages = {10089-10095},

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.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{chen2020tendon,

title = {A tendon-driven origami hopper triggered by proprioceptive contact detection},

author = {Wei-Hsi Chen and Shivangi Misra and J. Diego Caporale and Daniel E. Koditschek and Shu Yang and Cynthia Sung},

url = {https://repository.upenn.edu/ese_papers/866/

https://youtu.be/3fx-vVZki5c},

doi = {10.1109/RoboSoft48309.2020.9116040},

year  = {2020},

date = {2020-05-26},

urldate = {2020-05-26},

booktitle = {IEEE International Conference on Soft Robotics (RoboSoft)},

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.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{yuan2018programmable,

title = {Programmable 3-D surfaces using origami tessellations},

author = {Hang Yuan and James Pikul and Cynthia Sung},

url = {https://sung.seas.upenn.edu/wp-content/publications/yuan_7OSME_2018_programmable.pdf},

year  = {2018},

date = {2018-09-19},

urldate = {2018-09-19},

booktitle = {7th International Meeting on Origami in Science, Mathematics, and Education},

pages = {893-906},

abstract = {We present an origami-inspired approach to reconfigurable surfaces. A circular origami tessellation with the ability to extend and flatten was designed to approximate radially symmetric 3-D surfaces. The pattern exhibits snap-through effects, allowing desired 3-D shapes to be maintained indefinitely without additional infrastructure or energy input. We characterize the geometry of the fold pattern and its resulting 3-D shape, present a strategy for reconfiguration, and demonstrate this strategy for surfaces with positive, negative, and zero Gaussian curvature.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{deng2018leveraging,

title = {Leveraging compliance in origami robot legs for robust and natural locomotion},

author = {Xiang Deng and Cynthia Sung},

url = {https://sung.seas.upenn.edu/wp-content/publications/deng_7OSME_2018_leveraging.pdf},

year  = {2018},

date = {2018-09-12},

urldate = {2018-09-12},

booktitle = {7th International Meeting on Origami in Science, Mathematics, and Education},

pages = {965-980},

abstract = {We present an origami-inspired compliant robot leg design with three degree of freedom compliance. Using the proposed leg, we created a full quadrupedal robot that can walk robustly with adaption to non-flat terrains and external perturbations. We can reconfigure the design to change the stiffness. According to systematic locomotion tests, we demonstrate unique advantages of the proposed leg design over a rigid counterpart of the same dimension and weight in terms of enhancing locomotion stability},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{sung2017self,

title = {Self-folded soft robotic structures with controllable joints},

author = {Cynthia Sung and Rhea Lin and Shuhei Miyashita and Sehyuk Yim and Sangbae Kim and Daniela Rus},

doi = {10.1109/ICRA.2017.7989072},

year  = {2017},

date = {2017-05-29},

urldate = {2017-05-29},

booktitle = {IEEE International Conference on Robotics and Automation (ICRA)},

pages = {580-587},

abstract = {This paper describes additive self-folding, an origami-inspired rapid fabrication approach for creating actuatable compliant structures. Recent work in 3-D printing and other rapid fabrication processes have mostly focused on rigid objects or objects that can achieve small deformations. In contrast, soft robots often require elastic materials and large amounts of movement. Additive self-folding is a process that involves cutting slices of a 3-D object in a long strip and then pleat folding them into a likeness of the original model. The zigzag pattern for folding enables large bending movements that can be actuated and controlled. Gaps between slices in the folded model can be designed to provide larger deformations or higher shape accuracy. We advance existing planar fabrication and self-folding techniques to automate the fabrication process, enabling highly compliant structures with complex 3-D geometries to be designed and fabricated within a few hours. We describe this process in this paper and provide algorithms for converting 3-D meshes into additive self-folding designs. The designs can be rapidly instrumented for global control using magnetic fields or tendon-driven for local bending. We also describe how the resulting structures can be modeled and their responses to tendon-driven control predicted. We test our design and fabrication methods on three models (a bunny, a tuna fish, and a starfish) and demonstrate the method's potential for actuation by actuating the tuna fish and starfish models using tendons and magnetic control.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{spielberg2017functional,

title = {Functional co-optimization of articulated robots},

author = {Andrew Spielberg and Brandon Araki and Cynthia Sung and Russ Tedrake and Daniela Rus},

doi = {10.1109/ICRA.2017.7989587},

year  = {2017},

date = {2017-05-29},

urldate = {2017-05-29},

booktitle = {IEEE International Conference on Robotics and Automation (ICRA)},

pages = {5035-5042},

abstract = {We present parametric trajectory optimization, a method for simultaneously computing physical parameters, actuation requirements, and robot motions for more efficient robot designs. In this scheme, robot dimensions, masses, and other physical parameters are solved for concurrently with traditional motion planning variables, including dynamically consistent robot states, actuation inputs, and contact forces. Our method requires minimal user domain knowledge, requiring only a coarse guess of the target robot configuration sequence and a parameterized robot topology as input. We demonstrate our results on four simulated robots, one of which we physically fabricated in order to demonstrate physical consistency. We demonstrate that by optimizing robot body parameters alongside robot trajectories, motion planning problems which would otherwise be infeasible can be made feasible, and actuation requirements can be significantly reduced.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}

@conference{sung2015automated,

title = {Automated fabrication of foldable robots using thick materials},

author = {Cynthia Sung and Daniela Rus},

doi = {10.1007/978-3-319-51532-8_16},

year  = {2015},

date = {2015-09-09},

booktitle = {International Symposium on Robotics Research},

pages = {253-266},

abstract = {Designing complex machines such as robots often requires multiple iterations of design and prototyping. Folding has recently emerged as a method to both simplify fabrication and accelerate assembly of such machines. However, the robots so far produced by folding have often been made of thin, flexible materials that limit their size and strength. We introduce a folding-based fabrication process that uses thick materials layered with flexible film to enable folding while maintaining high stiffness in the folded structure. We use this process to fabricate multiple solid bodies, as well as two hexapods, one of which can carry up to 2.50 kg payloads. Each folded structure took less than 3 h to construct. Our results indicate that folding using thick materials can be a viable method for rapidly fabricating and prototyping larger and sturdier robots.},

keywords = {},

pubstate = {published},

tppubtype = {conference}

}