Research Papers

Synthesis and Analysis of Soft Parallel Robots Comprised of Active Constraints

[+] Author and Article Information
Jonathan B. Hopkins

Mechanical and Aerospace Engineering,
University of California, Los Angeles,
420 Westwood Plaza,
46-147F Engineering IV. Bldg.,
Los Angeles, CA 90095
e-mail: hopkins@seas.ucla.edu; jonathanbhopkins@gmail.com

Jordan Rivera

Mechanical Engineering,
Bucknell University,
701 Moore Ave.,
Lewisburg, PA 17837
e-mail: jar055@bucknell.edu

Charles Kim

Mechanical Engineering,
Bucknell University,
701 Moore Ave.,
Lewisburg, PA 17837
e-mail: charles.kim@bucknell.edu

Girish Krishnan

Industrial and Enterprise Systems Engineering,
Illinois at Urbana-Champaign,
314 Transportation Bldg. 104 S. Mathews,
Urbana, IL 61801
e-mail: gkrishna@illinois.edu

1These are co-first authors due to their equal level of contribution to this paper.

2Corresponding author.

Contributed by the Mechanisms and Robotics Committee of ASME for publication in the JOURNAL OF MECHANISMS AND ROBOTICS. Manuscript received September 24, 2014; final manuscript received December 2, 2014; published online December 31, 2014. Assoc. Editor: Carl Nelson.

J. Mechanisms Robotics 7(1), 011002 (Feb 01, 2015) (13 pages) Paper No: JMR-14-1255; doi: 10.1115/1.4029324 History: Received September 24, 2014; Revised December 02, 2014; Online December 31, 2014

In this paper, we introduce a new type of spatial parallel robot that is comprised of soft inflatable constraints called trichamber actuators (TCAs). We extend the principles of the freedom and constraint topologies (FACT) synthesis approach to enable the synthesis and analysis of this new type of soft robot. The concepts of passive and active freedom spaces are introduced and applied to the design of general parallel systems that consist of active constraints (i.e., constraint that can be actuated to impart various loads onto the system's stage) that both drive desired motions and guide the system's desired degrees of freedom (DOFs). We provide the fabrication details of the TCA constraints introduced in this paper and experimentally determine their appropriate FACT-based constraint model. We fabricate a soft parallel robot that consists of three TCA constraints and verify and validate its FACT-predicted performance using finite element analysis (FEA) and experimental data. Other such soft robots are synthesized using FACT as case studies.

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Fig. 1

TCA. Inflation of combinations of three internal chambers leads to extension (a) or bending (b).

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Fig. 2

Parallel system consisting of inflatable TCAs

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Fig. 3

Desired DOFs (a), freedom and constraint spaces (b), and constraints lie within the space (c)

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Fig. 4

Parameters necessary to define the system's twist–wrench stiffness matrix

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Fig. 5

Resulting twist produced by actuating wire (1) (a), system's AFS (b)

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Fig. 6

AFS (a), PFS that satisfies conditions (b), its constraint space (c), topology selected from that space (d), and tuned parameters (e)

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Fig. 7

AFS (a), PFS that satisfies conditions (b), its constraint space (c), and topology selected (d)

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Fig. 8

Cross section of a TCA (a), transverse linear stiffness test (b), axial stiffness test (c), torsional stiffness test (d), and calculating the TCA's material properties (e)

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Fig. 9

6DOFs achieved by hexapod robot—three rotations (a)–(c), and three translations (d)–(f)

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Fig. 10

Geometric parameters for the three-legged soft robot

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Fig. 11

Twist vectors that describe the analytical and FEA results drawn to scale (a), and FEA verification (b)

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Fig. 12

Experimental setup (a), and twist vectors that describe the analytical and experimental results drawn to scale (b)




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