Lab Papers (GRASP)

Document Type

Conference Paper

Subject Area


Date of this Version


Publication Source

International Design Engineering Technical Conferences & Computers and Information in Engineering Conference

Bib Tex

@inproceedings{chen2023drag, title = {Drag coefficient characterization of the origami magic ball}, author = {Guanyu Chen and Dongsheng Chen and Jessica Weakly and Cynthia Sung}, 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)}}


The 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.

Copyright/Permission Statement

© 2023 ASME. Personal use of this material is permitted. Permission from ASME 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.


Origami, magic ball, drag coefficient

Included in

Robotics Commons



Date Posted:16 May 2023

This document has been peer reviewed.