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Research Papers: Design Automation

Optimal, Model-Based Design of Soft Robotic Manipulators

[+] Author and Article Information
Deepak Trivedi, Dustin Dienno

Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802

Christopher D. Rahn

Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802cdrahn@psu.edu

J. Mech. Des 130(9), 091402 (Aug 11, 2008) (9 pages) doi:10.1115/1.2943300 History: Received September 12, 2007; Revised April 11, 2008; Published August 11, 2008

Soft robotic manipulators, unlike their rigid-linked counterparts, deform continuously along their lengths similar to elephant trunks and octopus arms. Their excellent dexterity enables them to navigate through unstructured and cluttered environments and to handle fragile objects using whole arm manipulation. This paper develops optimal designs for OctArm manipulators, i.e., multisection, trunklike soft arms. OctArm manipulator design involves the specification of air muscle actuators and the number, length, and configuration of sections that maximize dexterity and load capacity for a given maximum actuation pressure. A general method of optimal design for OctArm manipulators using nonlinear models of the actuators and arm mechanics is developed. The manipulator model is based on Cosserat rod theory, accounts for large curvatures, extensions, and shear strains, and is coupled to the nonlinear Mooney–Rivlin actuator model. Given a dexterity constraint for each section, a genetic algorithm-based optimizer maximizes the arm load capacity by varying the actuator and section dimensions. The method generates design rules that simplify the optimization process. These rules are then applied to the design of pneumatically and hydraulically actuated OctArm manipulators using 100psi and 1000psi maximum pressures, respectively.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

OctArm VI mounted on the second link of a Talon robot arm, reaching around a ball

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Figure 2

Extensor air muscle actuators extend when pressurized as the wind angle α approaches 54deg44min from above

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Figure 3

OctArm VI: (a) semitransparent 3D view, (b) close-up photograph of the base, (c) close-up, semitransparent view of the first section, and (d) photograph of the complete arm

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Figure 4

Cross-sectional view of six and three extensor manipulator sections showing three independent control channels (blue, red, and yellow)

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Figure 5

Soft robotic manipulator model. The load capacity is defined as the maximum load that the arm can lift to y=0 at the test pressure ptest.

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Figure 6

Sections 1,2,3 of a three section robot are designed to have 360deg, 180deg, and 120deg wrap angles, respectively, to provide the desired dexterity

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Figure 7

Base section configurations for (a) fixed tube diameter ratio and (b) fixed base diameter ratio

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Figure 8

Load capacity versus arm length for optimal pneumatic two section (solid), three section (dashed), four section (dash-dotted), and five section (dotted) arms for a fixed tube diameter ratio

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Figure 9

Load capacity versus arm length for optimal hydraulic two section (solid), three section (dashed), four section (dash-dotted), and five section (dotted) arms for a fixed tube diameter ratio

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Figure 10

Load capacity versus arm length for optimal pneumatic two section (solid), three section (dashed), four section (dash-dotted), and five section (dotted) arms for an overall diameter/length ratio of 0.09

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Figure 11

Load capacity versus arm length for optimal hydraulic two section (solid), three section (dashed), four section (dash-dotted), and five section (dotted) arms for an overall diameter/length ratio of 0.09

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Figure 12

Hydraulic test case showing load capacity (triangles) and tube thickness (circles) as a function of number of sections

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Figure 13

Load capacity (dashed) and tube thickness (solid) for the optimal three section hydraulic arm versus Young’s modulus

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