Lab Papers (GRASP)

Document Type

Conference Paper

Subject Area


Date of this Version


Publication Source

2023 IEEE International Conference on Robotics and Automation (ICRA)

Bib Tex

@ARTICLE{tunable_stiffness_spring, author={Misra, Shivangi and Mitchell, Mason and Chen, Rongqian and Sung, Cynthia}, JOURNAL={IEEE International Conference on Robotics and Automation (ICRA)}, title={Design and Control of a Tunable-Stiffness Coiled-Actuator}, year={2023}}


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.

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© 2023 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.


tunable-stiffness, actuator design, modeling, manipulator, soft robotics

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Robotics Commons



Date Posted: 06 March 2023

This document has been peer reviewed.