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Orientation workspace analysis of a special class of the Stewart–Gough parallel manipulators

Published online by Cambridge University Press:  15 January 2010

Yi Cao*
Affiliation:
School of Mechanical Engineering, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu 214122, P.R. China
Zhen Huang
Affiliation:
Robotics Research Center, Yanshan University, Qinghuangdao, Hebei 066004, P.R. China.
Hui Zhou
Affiliation:
School of Mechanical Engineering, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu 214122, P.R. China
Weixi Ji
Affiliation:
School of Mechanical Engineering, Jiangnan University, 1800 Lihu Avenue, Wuxi, Jiangsu 214122, P.R. China
*
*Corresponding author. E-mails: caoyi@jiangnan.edu.cn, caoyi@ysu.edu.cn

Summary

The workspace of a robotic manipulator is a very important issue and design criteria in the context of optimum design of robots, especially for parallel manipulators. Though, considerable research has been paid to the investigations of the three-dimensional (3D) constant orientation workspace or position workspace of parallel manipulators, very few works exist on the topic of the 3D orientation workspace, especially the nonsingular orientation workspace and practical orientation workspace. This paper addresses the orientation workspace analysis of a special class of the Stewart–Gough parallel manipulators in which the moving and base platforms are two similar semisymmetrical hexagons. Based on the half-angle transformation, a polynomial expression of 13 degree that represents the orientation singularity locus of this special class of the Stewart–Gough parallel manipulators at a fixed position is derived and graphical representations of the orientation singularity locus of this special class of the Stewart–Gough manipulators are illustrated with examples to demonstrate the result. Exploiting this half-angle transformation and the inverse kinematics solution of this special class of the Stewart–Gough parallel manipulators, a discretization method is proposed for computing the orientation workspace of this special class of the Stewart–Gough parallel manipulators taking limitations of active and passive joints and the link interference all into consideration. Based on this algorithm, this paper also presents a new discretization method for computing the nonsingular orientation workspace of this class of the manipulators, which not only can satisfy all the kinematics demand of this class of the manipulators but also can guarantee the manipulator is nonsingular in the whole orientation workspace, and the practical orientation workspace of this class of the manipulators, which not only can guarantee the manipulator is nonsingular and will never encounter any kinematic interference but also can satisfy the demand of the orientation workspace with a regular shape in practical application, respectively. Examples of a 6/6-SPS Stewart–Gough parallel manipulator of this special class are given to demonstrate these theoretical results.

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Type
Article
Copyright
Copyright © Cambridge University Press 2010

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