Research Papers

Workspace Analysis of a Three DOF Cable-Driven Mechanism

[+] Author and Article Information
Alireza Alikhani, S. Ali Sadough Vanini

Department of Mechanical Engineering, AmirKabir University of Technology, Tehran, Iran

Saeed Behzadipour

Department of Mechanical Engineering, University of Alberta, Edmonton, AB, T6G 2G8, Canada

Aria Alasty

Department of Mechanical Engineering, Center of Excellence in Design, Robotics and Automation (CEDRA), Sharif University of Technology, Tehran, Iran

J. Mechanisms Robotics 1(4), 041005 (Sep 17, 2009) (7 pages) doi:10.1115/1.3204255 History: Received October 28, 2008; Revised May 25, 2009; Published September 17, 2009

A cable-driven mechanism based on the idea of BetaBot (2005, “A New Cable-Based Parallel Robot With Three Degrees of Freedom,” Multibody Syst. Dyn., 13, pp. 371–383) is analyzed and geometrical description of its workspace boundary is found. In this mechanism, the cable arrangement eliminates the rotational motions leaving the moving platform with three translational motions. The mechanism has potentials for large scale manipulation and robotics in harsh environments. A detailed analysis of the tensionable workspace of the mechanism is presented. The mechanism, in a tensionable position, can develop tensile forces in all cables to maintain its rigidity under arbitrary external loading. A set of conditions on the geometry of the mechanism is proposed for which the tensionable workspace becomes a well defined convex polyhedron. The geometrical shape of the workspace is then described and the tensionability of the mechanism inside the workspace is proved. The proof is quite general and based on a geometrical approach.

Copyright © 2009 by American Society of Mechanical Engineers
Topics: Cables , Mechanisms , Force
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Figure 1

The general structure of LCDR

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Figure 2

Parallelogram abcd formed by a pair of parallel cable

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Figure 3

LCDR geometry that represents conditions (1 and 2)

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Figure 4

The three upper planes formed by parallel upper cables meet at a point called R and three lower planes formed by the lower cables meet a point called R′

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Figure 5

(a) The polyhedron formed by the upper cables, (b) the cone formed by upper cable force directions, (c) the cone formed by the lower cables, and (d) the polyhedron formed by the fixed end of all cables

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Figure 6

The forces diagram of the moving platform




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