Improving static stiffness of the parallel manipulator using inverse singularities

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• 作者：Jokin Aginaga^a ; ^{jokin.aginaga@unavarra.es} ; Isidro Zabalza^a ; Oscar Altuzarra^b ; Jasiel Ná ; jera^a
• 关键词：Parallel manipulator ; Stiffness ; Singularities ; Inverse singularities
• 刊名：Robotics and Computer-Integrated Manufacturing
• 出版年：2012
• 期刊代码：107_07365845
• 类别：cp
• 出版时间：August, 2012
• 卷：28
• 期：4
• 页码：458-471
• 文件大小：2465 K

摘要

The accuracy of parallel manipulators is linked to their stiffness and this has been shown to be configuration dependent. Indeed, certain types of singular configurations are usually avoided because of the associated loss of stiffness. These undesirable singularities are direct singularities, in which actuators cannot balance external loads. By contrast, inverse singularities do not cause this loss of stiffness. With appropriate design, the manipulator can be operated in a workspace with no direct singularities but which does contain some inverse ones. In this paper, a methodology for calculating the stiffness matrix of parallel manipulators is presented. Applied to the manipulator, it is demonstrated that inverse singularities are much stiffer than non-singular configurations. In addition, an approach to motion planning is devised which makes use of inverse singularities to obtain stiffer trajectories. Results show a significant improvement in the stiffness along the trajectory.