Research Papers

Pneumatic Torsional Actuators for Inflatable Robots

[+] Author and Article Information
Siddharth Sanan

Graduate Student
The Robotics Institute,
Carnegie Mellon University,
Pittsburgh, PA 15213
e-mail: sanan@cmu.edu

Peter S. Lynn

Research Engineer
Otherlab Inc.,
San Francisco, CA 94110
e-mail: pete@otherlab.com

Saul T. Griffith

Chief Scientist
Otherlab Inc.,
San Francisco, CA 94110
e-mail: saul@otherlab.com

1Corresponding author.

Contributed by the Mechanisms and Robotics Committee of ASME for publication in the JOURNAL OF MECHANISMS AND ROBOTICS. Manuscript received April 24, 2013; final manuscript received January 18, 2014; published online April 3, 2014. Assoc. Editor: Anupam Saxena.

J. Mechanisms Robotics 6(3), 031003 (Apr 03, 2014) (7 pages) Paper No: JMR-13-1081; doi: 10.1115/1.4026629 History: Received April 24, 2013; Revised January 18, 2014

This paper discusses a variety of novel fluidic actuators to generate rotary motion. While pneumatic artificial muscles (PAMs) that can generate linear motion have been researched and developed fairly extensively, little effort has been devoted to develop simple actuators that can provide rotary motion. A variety of possible designs and principles are discussed to achieve such rotary motion, along with accompanying analysis to understand motion and torque characteristics of each actuator. Experiments with prototype actuators validate performance expectations of each design.

Copyright © 2014 by ASME
Topics: Actuators , Torque
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Fig. 1

The PneuArm inflatable manipulator prototype [9]

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Fig. 2

The two oppositely oriented helix that make up the rotary shape actuator. Each leaf of the helices is wrapped around the common central axis of the actuator of length l, as helix with a pitch circle radius r. Note that one leaf of the right helix has been shown transparent for illustrative purposes.

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Fig. 3

Physical realization of the torsion shape actuator. The relative arrangement of the two helix can be seen as labeled in the two pictures.

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Fig. 8

Geometric parameters of the rotary Peano actuator

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Fig. 7

Tubes of the Peano actuator are arranged helically to form the main cylinder of the actuator. The main cylinder is closed at both its ends to form a closed volume. One of the tubes has been highlighted for illustration.

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Fig. 6

Schematic showing the contraction principle used in the Peano actuators and the serial arrangement of tubes that makes up a Peano actuator. (a) Contraction principle used in Peano actuators. It is assumed that the tube inflates so that its cross-section is comprised of two symmetric circular arcs that can be parameterized by either l, r, or φ as shown. Only one parameter is needed if the tube fabric is assumed to be inextensible in hoop. (b) The linear Peano actuator consists of a number of tubes arranged serially as shown in the schematic above. The actuator length decreases as the tubes are inflated due to contraction of each individual tube in the actuator.

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Fig. 5

Example torque displacement characteristics for the right helix of a torsion shape actuator

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Fig. 4

Flat development of helix during actuator motion. The two black arrows on the edges of each flat development are used to indicate the edges that are folded together to form a cylindrical surface.

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Fig. 9

Peano skin type twist actuator

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Fig. 10

Example torque displacement characteristics for Peano torque actuators

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Fig. 11

Arrangement of fibers on the McKibben linear actuator and the torsion weave actuator. The two large arrows are used to indicate the two edges that are folded together to make the flat fabric surface into a cylindrical surface. (a) Symmetric arrangement of inextensible fibers on the surface of a McKibben type actuator. Flat development of the cylindrical surface of the actuator is shown. (b) Asymmetric arrangement of inextensible fibers on the surface of the torsion weave actuator. Flat development of the cylindrical surface of the actuator is shown.

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Fig. 12

The geometry of a single block of the helical weave pattern fabric used for the torsion weave actuator

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Fig. 13

Example torque displacement characteristics for the torsion weave actuator

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Fig. 14

Prototyped torsion weave actuator in its nominal and inflated configuration



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