Research Papers

Wrench Capability of a Stewart Platform With Series Elastic Actuators

[+] Author and Article Information
Chawin Ophaswongse

Robotics and Rehabilitation
Laboratory (ROAR Lab),
Department of Mechanical Engineering,
Columbia University,
220 S. W. Mudd Building,
500 West 120th Street,
New York, NY 10027
e-mail: co2393@columbia.edu

Rosemarie C. Murray

Robotics and Rehabilitation
Laboratory (ROAR Lab),
Department of Mechanical Engineering,
Columbia University,
220 S. W. Mudd Building,
500 West 120th Street,
New York, NY 10027
e-mail: rcm2146@columbia.edu

Sunil K. Agrawal

Fellow ASME
Robotics and Rehabilitation
Laboratory (ROAR Lab),
Department of Mechanical Engineering,
Columbia University,
220 S. W. Mudd Building,
500 West 120th Street,
New York, NY 10027
e-mail: sunil.agrawal@columbia.edu

1Corresponding author.

Manuscript received September 21, 2017; final manuscript received December 12, 2017; published online January 29, 2018. Editor: Venkat Krovi.

J. Mechanisms Robotics 10(2), 021002 (Jan 29, 2018) (8 pages) Paper No: JMR-17-1309; doi: 10.1115/1.4038976 History: Received September 21, 2017; Revised December 12, 2017

This paper proposes a novel method for analyzing linear series elastic actuators (SEAs) in a parallel-actuated Stewart platform, which has full six degrees-of-freedom (DOF) in position and orientation. SEAs can potentially provide a better human–machine interface for the user. However, in the study of parallel-actuated systems with full 6DOF, the effect of compliance in series with actuators has not been adequately studied from the perspective of wrench capabilities. We found that some parameters of the springs and the stroke lengths of the linear actuators play a major role in the actuation limits of the system. This is an important consideration when adding SEAs into a Stewart platform or other parallel-actuated robots to improve their human usage.

Copyright © 2018 by ASME
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Grahic Jump Location
Fig. 1

Kinematic diagram of a parallel-actuated platform with SEAs

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Fig. 2

Translational workspace in the neutral orientation

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Fig. 3

Minimum potential energy field on a workspace at z = 0.165 m and in the neutral orientation

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Fig. 4

Scenarios leading to actuation limits

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Fig. 5

Example of a feasible actuation set on a translational workspace at z = 0.165 m and in the neutral orientation (ks=5.0 N/mm, ℓs,0=±10.0 mm)

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Fig. 6

Explicit analysis results of force in the positive x direction (a)–(c), and moment in the positive z direction (d)–(f), with zero prescribed moment/force at z = 0.165 m and in the neutral orientation. (a) and (d) show the upper limit of force/moment. (b) and (e) show the lower limit. (c) and (f) represent the rigid actuator case (ks=5.0 N/mm, ℓs,0=±10.0 mm).

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Fig. 7

Comparison of isotropic force and moment between two sets of spring parameters in a translational active workspace (a), (c), (e), and (g) in the neutral orientation, and a pitch-roll-yaw active workspace (b), (d), (f), and (h) at pB=[0,0,0.165]T m. The prescribed moment/force is set to zero.




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