Task-Based Comparison of Parallel Translational Kinematic Structures

• Aufgabenbasierter Vergleich von translatorischen, parallelkinematischen Strukturen

Prause, Isabel; Corves, Burkhard (Thesis advisor); Herder, Just (Thesis advisor)

Aachen (2016, 2017)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2016

Abstract

Well known is Clavel’s DELTA robot, but there are other parallel kinematic structures (PKS) with three translational degrees of freedom. They differ in the assembly and the limb structure. A broad range of PKS based on different joint and limb arrangements has been synthesized in the past years, but only a small number has been further investigated in research.Therefore, in this thesis, a structure catalog comprising different PKS with their respective characteristics is created. The selection is based on lists of previously synthesized PKS. Furthermore, different frame configurations are investigated. For in total 25 different PKS the structure catalog is expanded by mathematical descriptions. In a first step, the kinematic dimensions are optimized with respect to two load cases: 1) rectangular workspace with low external forces and 2) cylindrical workspace with higher external forces. The results show that not all selected PKS possess good transmission qualities. Hence, some PKS are excluded from further analysis.Then, a general research study of the selected structures is performed. Different dimensions of the PKS are considered and analyzed to identify the influence of selected parameter configurations on the overall performance. To do so, various criteria are applied within a prescribed workspace. This analysis and the comparison afterwards result in further reduction of the PKS for the final task-adapted dimensional synthesis. Three tasks and trajectories respectively are considered: pick & place, positioning and guidance task.The optimization of the kinematic dimensions is based on a flexible objective function that allows adjusting the function value by including different criteria with adaptable weights. To select appropriate criteria, a compilation of criteria to measure, analyze and compare the performance of PKS is presented. Finally, the performance of the PKS along the trajectories or within the prescribed workspace is analyzed. The optimization and analysis results show that some of the selected PKS can fulfill the described tasks and that no "best" PKS can be found.

Institutions

• Chair and Institute of Mechanism Theory, Machine Dynamics and Robotics [411910]