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Biomimetics 2018, 3(3), 16;

Capability by Stacking: The Current Design Heuristic for Soft Robots

School of Engineering, The Institute for Integrated Micro and Nano Systems, The University of Edinburgh, The King’s Buildings, Edinburgh EH9 3LJ, UK
Engineering and Physical Sciences Research Council (EPSRC) Centre for Doctoral Training (CDT) in Robotics and Autonomous Systems, School of Informatics, The University of Edinburgh, Edinburgh EH9 3LJ, UK
Department of Computer Science and Engineering, University of Michigan, 2260 Hayward St. BBB3737, Ann Arbor, MI 48109, USA
Author to whom correspondence should be addressed.
Received: 1 June 2018 / Revised: 8 July 2018 / Accepted: 10 July 2018 / Published: 13 July 2018
(This article belongs to the Special Issue Soft Robotics)
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Soft robots are a new class of systems being developed and studied by robotics scientists. These systems have a diverse range of applications including sub-sea manipulation and rehabilitative robotics. In their current state of development, the prevalent paradigm for the control architecture in these systems is a one-to-one mapping of controller outputs to actuators. In this work, we define functional blocks as the physical implementation of some discrete behaviors, which are presented as a decomposition of the behavior of the soft robot. We also use the term ‘stacking’ as the ability to combine functional blocks to create a system that is more complex and has greater capability than the sum of its parts. By stacking functional blocks a system designer can increase the range of behaviors and the overall capability of the system. As the community continues to increase the capabilities of soft systems—by stacking more and more functional blocks—we will encounter a practical limit with the number of parallelized control lines. In this paper, we review 20 soft systems reported in the literature and we observe this trend of one-to-one mapping of control outputs to functional blocks. We also observe that stacking functional blocks results in systems that are increasingly capable of a diverse range of complex motions and behaviors, leading ultimately to systems that are capable of performing useful tasks. The design heuristic that we observe is one of increased capability by stacking simple units—a classic engineering approach. As we move towards more capability in soft robotic systems, and begin to reach practical limits in control, we predict that we will require increased amounts of autonomy in the system. The field of soft robotics is in its infancy, and as we move towards realizing the potential of this technology, we will need to develop design tools and control paradigms that allow us to handle the complexity in these stacked, non-linear systems. View Full-Text
Keywords: soft robots; stacking; hierarchy; functional blocks; complexity; capability; design soft robots; stacking; hierarchy; functional blocks; complexity; capability; design

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Mahon, S.T.; Roberts, J.O.; Sayed, M.E.; Chun, D.H.-T.; Aracri, S.; McKenzie, R.M.; Nemitz, M.P.; Stokes, A.A. Capability by Stacking: The Current Design Heuristic for Soft Robots. Biomimetics 2018, 3, 16.

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