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Research Papers

A Cable Based Active Variable Stiffness Module With Decoupled Tension

[+] Author and Article Information
Xiaobo Zhou

Automation Robotics
and Mechatronics Laboratory,
Mechanical Engineering,
State University of New York at Buffalo,
Buffalo, NY 14260
e-mail: xzhou9@buffalo.edu

Seung-kook Jun

Automation Robotics
and Mechatronics Laboratory,
Mechanical Engineering,
State University of New York at Buffalo,
Buffalo, NY 14260
e-mail: seungjun@buffalo.edu

Venkat Krovi

Automation Robotics
and Mechatronics Laboratory,
Department of Mechanical
and Aerospace Engineering,
State University of New York at Buffalo,
Buffalo, NY 14260
e-mail: vkrovi@buffalo.edu

1Corresponding author.

Contributed by the Mechanisms and Robotics Committee of ASME for publication in the JOURNAL OF MECHANISMS AND ROBOTICS. Manuscript received September 25, 2014; final manuscript received December 1, 2014; published online December 31, 2014. Assoc. Editor: Thomas Sugar.

J. Mechanisms Robotics 7(1), 011005 (Feb 01, 2015) (5 pages) Paper No: JMR-14-1259; doi: 10.1115/1.4029308 History: Received September 25, 2014; Revised December 01, 2014; Online December 31, 2014

Variable stiffness modules add significant robustness to mechanical systems during forceful interactions with uncertain environments. Most existing variable stiffness modules tend to be bulky—by virtue of their use of solid components—making them less suitable for mobile applications. In recent times, pretensioned cable-based variable stiffness modules have been proposed to reduce weight. While passive, these modules depend on significant internal tension to provide the desired stiffness—as a consequence, their stiffness modulation capability tends to be limited. In this paper, we present design, analysis, and testing of a cable-based active-variable stiffness module which can achieve large stiffness modulation range with low tension. Controlled changes in structural parameters (independent of cable length actuation) now permit independent modulation of both the desired tension and the perceived stiffness. This capability is now systematically evaluated via simulation as well as on a hardware-in-the-loop experimental setup.

FIGURES IN THIS ARTICLE
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Copyright © 2015 by ASME
Topics: Cables , Stiffness , Tension
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Figures

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Fig. 1

Different realizations of VSA

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Fig. 2

Variable stiffness module: (a) low stiffness configuration; (b) conventional passive module to achieve higher stiffness; and (c) active module to achieve higher stiffness with lower tension

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Fig. 3

Antagonistic joint configuration

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Fig. 4

Cable tension comparison

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Fig. 5

Tension measurement setup

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Fig. 6

Antagonistic joint setup

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Fig. 7

Stiffness verification setup

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Fig. 8

Increase stiffness while holding load

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Fig. 9

Trajectory tracking without load

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Fig. 10

Trajectory tracking with load

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