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Research Papers

Optimizing Stiffness and Dexterity of Planar Adaptive Cable-Driven Parallel Robots

[+] Author and Article Information
Saeed Abdolshah

Department of Management and
Engineering (DTG),
University of Padua,
Padova 35131, Italy
e-mail: Saeed.abdolshah@studenti.unipd.it

Damiano Zanotto

Mem. ASME
ROAR Lab,
Columbia University,
New York, NY 10027
e-mail: dz2265@columbia.edu

Giulio Rosati

Department of Management and
Engineering (DTG),
University of Padua,
Padova 35131, Italy
e-mail: giulio.rosati@unipd.it

Sunil K. Agrawal

Fellow ASME ROAR Lab,
Department of Mechanical Engineering,
Columbia University,
New York, NY 10027
e-mail: sunil.agrawal@columbia.edu

1Corresponding author.

Manuscript received April 26, 2016; final manuscript received December 18, 2016; published online March 20, 2017. Assoc. Editor: Venkat Krovi.

J. Mechanisms Robotics 9(3), 031004 (Mar 20, 2017) (11 pages) Paper No: JMR-16-1119; doi: 10.1115/1.4035681 History: Received April 26, 2016; Revised December 18, 2016

Adaptive cable-driven parallel robots are a special subclass of cable-driven systems in which the locations of the pulley blocks are modified as a function of the end-effector pose to obtain optimal values of given performance indices within a target workspace. Due to their augmented kinematic redundancy, such systems enable larger workspace volume and higher performance compared to traditional designs featuring the same number of cables. Previous studies have introduced a systematic method to optimize design and trajectory planning of the moving pulley-blocks for a given performance index. In this paper, we study the motions of the pulley blocks that optimize two performance indices simultaneously: stiffness and dexterity. Specifically, we present a method to determine the pulley blocks motions that guarantee ideal dexterity with the best feasible elastic stiffness, as well as those that guarantee isotropic elastic stiffness with the best feasible dexterity. We demonstrate the proposed approach on some practical cases of planar adaptive cable-driven parallel robots.

Copyright © 2017 by ASME
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References

Figures

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Fig. 1

(a) Traditional design of 2DOF planar cable-robot with triangular workspace and (b) adaptive 2DOF planar cable-driven robot with pulley blocks that move along the sides of an equilateral triangle

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Fig. 2

(a) Dexterity index, (b) elastic stiffness index, and (c) normalized magnitude plot for the 2DOF traditional design with triangular workspace

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Fig. 3

(a) Elastic stiffness index, (b) normalized maximum, and (c) minimum magnitude plot for the three-cable, 2DOF design in ideal dexterity condition

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Fig. 4

Stiffness index as a function of r/b

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Fig. 5

Adaptive 2DOF planar cable robot with pulley blocks moving on linear guides

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Fig. 6

(a) The best feasible elastic stiffness index for a three-cable, 2DOF design. (b) Magnitude and (c) dexterity index for the condition of the best feasible elastic stiffness in three-cable system.

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Fig. 7

(a) A sample end-effector trajectory and the corresponding (b) cable configurations, (c) elastic stiffness, magnitude, and (d) the dexterity

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Fig. 8

Stiffness and dexterity change as a function of the parameter (r/b)

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Fig. 9

Adaptive 2DOF planar cable robot with pulley blocks moving on a circle

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Fig. 10

(a) Elastic stiffness index, (b) normalized stiffness magnitude for a 2DOF circular cable-driven parallel robot under ideal dexterity condition

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Fig. 11

The best feasible elastic stiffness and magnitude of the adaptive 2DOF planar cable robot with pulleys moving on a circle under the ideal dexterity condition

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Fig. 12

(a) Changing in value of α and (b) the dexterity index and the normalized stiffness magnitude from the center to the circumference under the isotropic elastic stiffness

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Fig. 13

Adaptive 3DOF planar cable robot with pulleys moving on a circumference

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Fig. 14

(a) Translational elastic stiffness index and (b) stiffness magnitude for a 3DOF circular cable-driven robot under ideal dexterity condition

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Fig. 15

Normalized translational stiffness magnitude change for a 3DOF planar adaptive system

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