IEEE Robotics & Automation Magazine - September 2023 - 27

It would be interesting to scale tensegristat systems down
dramatically and mimic the mechanics of biological cellular
structures, although this is not possible with currently available
electric motors. It would be best to replace the tendonmotor
tensile elements with some type of fiber that shortens
along its whole length when actuated, like muscle fiber does
[20]. Thermally actuated fibers are a currently available
option; although thermal actuation is not generally efficient,
in the future, fibers with similar behavior and higher efficiencies
might allow the small-scale cellular approach seen in real
muscular hydrostats.
CONCLUSION
We demonstrated the benefits and feasibility of a " tensegristat "
combination of tendons and fluids in which 1) actuation
is caused by tendons driven by electric motors, 2) both shape
change and motion rely primarily on buckling rather than
stretching, and 3) the total mass of fluid in the system
remains constant.
A robot constructed using these principles can reuse material
efficiently between forms with low design complexity.
This type of robot could be useful where multiple capabilities
are desired from a single robot, perhaps in wildlife observation,
search and rescue, and underground maintenance. Even
without using the capability for large-scale shape change, this
scheme can be used to construct faster, more efficient untethered
soft robots that can tune their stiffness separately from
their motion. These are important steps for soft robotics. The
supporting technology required for tensegristats (dc motors,
flexible membranes, and so on) is already well developed.
Work on optimizing the stiffness of pressurized parts, designing
joints, multipurposing motors, scaling, and reducing tendon
friction in soft robots would be helpful.
This type of design is not meant to be a " universal robot "
that can take on any form. For applications that only require a
few forms, however, tensegristats should be competitive from
centimeter through meter scales, both for creating fully morphing
robots and for creating changeable appendages on otherwise
rigid robots. If viable artificial muscle fibers are invented,
a small-scale cellular approach to tensegristat design could
yield abilities approximating biological muscular hydrostats.
ACKNOWLEDGMENT
This work was supported by the Office of Naval Research
under contract N00014-20-1-2438, and the National Science
Foundation's Graduate Research Fellowships Program. Robert
F. Shepherd is the corresponding author. This article has supplementary
downloadable material available at https://doi.
org/10.1109/MRA.2022.3204234, provided by the authors.
AUTHORS
Autumn Pratt, Department of Mechanical and Aerospace
Engineering, Cornell University, Ithaca, NY 14850 USA.
E-mail: agp76@cornell.edu.
Patrick Wilcox, Department of Mechanical and Aerospace
Engineering, Cornell University, Ithaca, NY 14850 USA.
E-mail: prw56@cornell.edu.
Caroline Hanson, Department of Mechanical and
Aerospace Engineering, Cornell University, Ithaca, NY 14850
USA. E-mail: cgh64@cornell.edu.
Robert F. Shepherd, Department of Mechanical and
Aerospace Engineering, Cornell University, Ithaca, NY 14850
USA. E-mail: rfs247@cornell.edu.
REFERENCES
[1] D. Shah, B. Yang, S. Kriegman, M. Levin, J. Bongard, and R. KramerBottiglio,
" Shape changing robots: Bioinspiration, simulation, and physical realization, "
Adv. Mater., vol. 33, no. 19, p. 2,002,882, May 2021, doi: 10.1002/
adma.202002882.
[2] E. Hawkes et al., " Programmable matter by folding, " Proc. Nat. Acad. Sci.,
vol. 107, no. 28, pp. 12,441-12,445, Jun. 2010, doi: 10.1073/pnas.0914069107.
[3] J. Davey, N. Kwok, and M. Yim, " Emulating self-reconfigurable robots -
Design of the SMORES system, " in Proc. 2012 IEEE/RSJ Int. Conf. Intell.
Robots Syst., pp. 4464-4469, doi: 10.1109/IROS.2012.6385845.
[4] W. M. Kier and K. K. Smith, " Tongues, tentacles and trunks: The biomechanics
of movement in muscular-hydrostats, " Zoological J. Linnean Soc., vol. 83, no.
4, pp. 307-324, Apr. 1985, doi: 10.1111/j.1096-3642.1985.tb01178.x.
[5] D. Shah et al., " Tensegrity robotics, " Soft Robot., vol. 9, no. 4, pp. 639-656,
Aug. 2022, doi: 10.1089/soro.2020.0170.
[6] S. Seok, C. Onal, K.-J. Cho, R. Wood, D. Rus, and S. Kim, " Meshworm: A
peristaltic soft robot with antagonistic nickel titanium coil actuators, " IEEE/
ASME Trans. Mechatronics, vol. 18, no. 5, pp. 1485-1497, Oct. 2013, doi: 10.1109/
TMECH.2012.2204070.
[7] R. Skelton and M. Oliviera, Tensegrity Systems. New York, NY, USA:
Springer-Verlag, 2009.
[8] F. Ilievski, A. D. Mazzeo, R. F. Shepherd, X. Chen, and G. M. Whitesides,
" Soft robotics for chemists, " Angew. Chem. Int. Ed., vol. 50, no. 8, pp. 1890-1895,
Feb. 2011, doi: 10.1002/anie.201006464.
[9] L. Shui, L. Zhu, Z. Yang, Y. Liu, and X. Chen, " Energy efficiency of mobile
soft robots, " Soft Matter, vol. 13, no. 44, pp. 8223-8233, Nov. 2017, doi: 10.1039/
C7SM01617D.
[10] M. Wehner et al., " Pneumatic energy sources for autonomous and wearable
soft robotics, " Soft Robot., vol. 1, no. 4, pp. 263-274, Dec. 2014, doi: 10.1089/
soro.2014.0018.
[11] T. Ren, Y. Li, M. Xu, Y. Li, C. Xiong, and Y. Chen, " A novel tendon-driven
soft actuator with self-pumping property, " Soft Robot., vol. 7, no. 2, pp. 130-139,
Apr. 2020, doi: 10.1089/soro.2019.0008.
[12] B. Mosadegh et al., " Pneumatic networks for soft robotics that actuate rapidly, "
Adv. Functional Mater., vol. 24, no. 15, pp. 2163-2170, Jan. 2014, doi:
10.1002/adfm.201303288.
[13] H. Alexander, " Tensile instability of initially spherical balloons, " Int. J. Eng.
Sci., vol. 9, no. 1, pp. 151-160, Jan. 1971, doi: 10.1016/0020-7225(71)90017-6.
[14] M. Tolley et al., " A resilient, untethered soft robot, " Soft Robot., vol. 1, no. 3,
pp. 213-223, Sep. 2014, doi: 10.1089/soro.2014.0008.
[15] P. Cavallaro, A. Sadegh, and C. Quigley, " Contributions of strain energy
and PV-work on the bending behavior of uncoated plain-woven fabric air
beams, " J. Eng. Fibers Fabr., vol. 2, no. 1, pp. 1-15, Apr. 2007, doi: 10.1177/
155892500700200102.
[16] N. S. Usevitch, Z. M. Hammond, M. Schwager, A. M. Okamura, E. W.
Hawkes, and S. Follmer, " An untethered isoperimetric soft robot, " Sci. Robot.,
vol. 5, no. 40, p. eaaz0492, Mar. 2020, doi: 10.1126/scirobotics.aaz0492.
[17] W. Davids, H. Zhang, A. Turner, and M. Peterson, " Beam finite-element
analysis of pressurized fabric tubes, " J. Structural Eng., vol. 133, no. 7, pp. 990-
998, Jul. 2007, doi: 10.1061/(ASCE)0733-9445(2007)133:7(990).
[18] S. M. Spearing, " Micro devices and micro systems, materials for, " in
Encyclopedia of Materials: Science and Technology, 2nd ed. 2001, pp.
5580-5587.
[19] K. Dermitzakis, J. Carbajal, and J. Marden, " Scaling laws in robotics, " in
Proc. Eur. Future Technol. Conf. Exhib., Budapest, Hungary, 2011, pp. 250-252.
[20] R. Baughman, " Playing nature's game with artificial muscles, " Science,
vol. 308, no. 5718, pp. 63-65, Apr. 2005, doi: 10.1126/science.1099010.
SEPTEMBER 2023 IEEE ROBOTICS & AUTOMATION MAGAZINE
27
IEEE Robotics & Automation Magazine - September 2023

Table of Contents for the Digital Edition of IEEE Robotics & Automation Magazine - September 2023
