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Optimization of a redundantly actuated 5R symmetrical parallel mechanism based on structural stiffness

Published online by Cambridge University Press:  15 May 2014

Sangrok Jin ,
Jongwon Kim  and
TaeWon Seo
Sangrok Jin
Affiliation:
School of Mechanical and Aerospace Engineering, Seoul Nat'l University, Seoul 151-019, Republic of Korea
Jongwon Kim*
Affiliation:
School of Mechanical and Aerospace Engineering, Seoul Nat'l University, Seoul 151-019, Republic of Korea
TaeWon Seo*
Affiliation:
School of Mechanical Engineering, Yeungnam University, Gyeongsan 712-749, Republic of Korea
*
*Corresponding author. E-mail: jongkim@snu.ac.kr, taewon_seo@yu.ac.kr
*Corresponding author. E-mail: jongkim@snu.ac.kr, taewon_seo@yu.ac.kr
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Summary

A redundantly actuated parallel kinematic machine (PKM) can be used to avoid singularities, normalize manipulability, and increase the stiffness of anon-redundant mechanism. In this study, a redundantly actuated symmetrical PKM with five revolute (5R) joints is optimized for isotropic stiffness in the workspace. The stiffness of the 5R symmetrical PKM is calculated by the superposition of the actuator stiffness and the structural stiffness. We compared the stiffness of anon-redundant PKM and a redundant PKM. Compliance ellipses of the actuator stiffness and the structural stiffness of the non-redundant PKM resulted in the same configurations in the workspace, while those of the redundant PKM resulted in very different configurations. Optimization was performed by determining the optimal actuator torques that are needed to maximize the conditioning index. Optimal results considering structural stiffness can provide a more uniform directional stiffness than optimal results considering the index. When the strength of the linkages in a PKM is weak, the structural stiffness affects the actual stiffness considerably. We believe that the results of this study can be used to help design and control redundant PKMs.

Keywords

Parallel mechanismRedundant actuationOptimizationStiffness analysisStructural stiffness
Type
Articles
Information
Robotica , Volume 33 , Issue 9 , November 2015 , pp. 1973 - 1983
Copyright
Copyright © Cambridge University Press 2014 

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