Abstract
The existing researches on singularity of parallel mechanism are mostly limited to the property and regularity of singularity locus and there is no further research into the geometric relationship between uncontrolled kinematic screw and parallel mechanism in singularity. A 3UPS-S parallel mechanism is presented which fulfils 3-DOF in rotation. The regularity of nutation angle singularity is analyzed based on the Jacobian matrix, and the singularity surface of 3UPS-S parallel mechanisms is obtained. By applying the concept of reciprocal product in screw theory, the singular kinematic screw is derived when 3UPS-S parallel mechanism is in singularity. The geometric relationship between singular kinematic screw and singular configuration of 3UPS-S parallel mechanism is investigated by using programs in MATLAB. It is revealed that there are two kinds of situation. Firstly, the three limbs of 3UPS-S parallel mechanism intersect the singular kinematic screw in space simultaneously; Secondly, two limbs cross the singular kinematic screw while the third limb parallels with that screw. It is concluded that the nutation angle singularity of 3UPS-S parallel mechanism belongs to the singular linear complexes. This paper sheds light into and clarifies the geometric relationship between singular kinematic screw and singular configuration of 3UPS-S parallel mechanism.
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This project is supported by Aeronautical Science Foundation of China (Grant No. 20081651025)
HAN Xianguo, born in 1970, is currently an associate professor at College of Mechanical Engineering and Automation, Beihang University, China. He obtained his PhD degree from Beihang University, China, in 2002 and his key areas of research are digital flexible assembly and parallel mechanism.
LIU Yanlong, born in 1988, is working for his master degree at College of Mechanical Engineering and Automation, Beihang University, China. He obtained his bachelor degree from Hu’nan University, China, in 2010. His research focuses on the design of parallel mechanism.
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Han, X., Liu, Y. Geometric condition of 3UPS-S parallel mechanism in singular configuration. Chin. J. Mech. Eng. 27, 130–137 (2014). https://doi.org/10.3901/CJME.2014.01.130
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DOI: https://doi.org/10.3901/CJME.2014.01.130