Research Papers

Designing Compliant Spine Mechanisms for Climbing

[+] Author and Article Information
Alan T. Asbeck

 Artificial Intelligence Laboratory,Department of Computer Science,Stanford University, Stanford, CA 94305aasbeck@gmail.com

Mark R. Cutkosky

 Biomimetics and Dexterous Manipulation Laboratory,Department of Mechanical Engineering,Stanford University, Stanford, CA 94305cutkosky@stanford.edu

J. Mechanisms Robotics 4(3), 031007 (Jun 08, 2012) (8 pages) doi:10.1115/1.40066591 History: Received August 31, 2011; Revised March 30, 2012; Published June 07, 2012; Online June 08, 2012

This paper presents design principles for compliant mechanisms used to support and load spines used in climbing rough vertical surfaces. The design principles ensure that constraints associated with spine/surface interactions are satisfied and that when multiple spines are placed in contact with a surface they share the load without premature failures or spine overloading. The design principles are demonstrated with a compliant mechanism that has been used for robotic and human climbing on surfaces such as brick, stucco and concrete.

Copyright © 2012 by American Society of Mechanical Engineers
Topics: Force , Design , Mechanisms , Stress
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Figure 1

From left to right, Perching UAV (0.4 kg, 10 spines), RiSE (3.8 kg, 192 spines), Human (84 kg, 1200 spines) hanging with spines. Far right shows a closeup of a group of spines, some of which have engaged on a roofing paper surface.

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Figure 2

Schematic description of typical spine attachment and loading trajectories (left) and corresponding normal and tangential forces and constraints in force space (right). The upper figures are for a single spine; the lower figures are for three spines on a common foot.

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Figure 3

Stretchable stalk model of a compliant spine mechanism

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Figure 4

RiSE spine mechanism and equivalent mechanism. Element 5 and rotating element 2 provide normal compliance; elements 3 and 4 provide shear compliance. Element 6 is a pin in a cutout that provides overload protection. Approach volume shows range of approach directions.

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Figure 5

Each column shows the RiSE mechanism during a different phase of use. Arrows show motions applied to the base. As spines contact the surface (a), the mechanism rotates around pin (2) seen in Fig. 4. As spine engages an asperity (b), the mechanism stretches. As it reaches maximum extension (c), the overload pin hits the cutout, triggering release and reattachment.

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Figure 6

Plot of forces from the RiSE toes on a prepared surface (solid lines) and simulated forces (dashed lines) using the stalk model. The three pairs of lines show results for preload depths of 0.0, 3.0, and 6.0 mm, respectively, from left to right.

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Figure 7

Measured linkage behavior for the RiSE spines (solid lines) as compared to the stalk model (dashed lines). Preloads of 0.0, 3.0, and 6.0 mm were applied, followed by a drag of 8 mm parallel to the surface. Spine cartesian stiffness matrices are shown at various points using the stalk model.

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Figure 8

Top, trajectory used when loading spines and associated times for a test on roofing paper reinforced with cyanoacrylate glue. The lower two plots show the forces as the group of ten spines engages the surface. Solid lines indicate preload and loading phases; dashed lines indicate the pull-off phase.

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Figure 9

Empirical measurement of the safe region for a group of ten spines on a roofing paper surface. Blue dots are for paper reinforced with cyanoacrylate glue, and show the same adhesion limit as unreinforced paper (red + symbols) but with a larger Fmax limit.




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