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Experimental studies of control concepts for a parallel manipulator with flexible links
Publikationstyp
Journal Article
Date Issued
2015-07-11
Sprache
English
Author(s)
Institut
TORE-URI
Volume
29
Issue
7
Start Page
2685
End Page
2691
Citation
Journal of Mechanical Science and Technology 29 (7): 2685-2691 (2015-07-23)
Publisher DOI
Scopus ID
Publisher
Springer
Control of flexible multibody systems, such as flexible manipulators, is a challenging task. This is especially true if end-effector trajectory tracking is aspired. On the one hand, these systems require a large number of generalized coordinates to describe their dynamical behavior accurately. On the other hand, only a small subset of these values can be measured or reconstructed on-the-fly. Hence, it is difficult, if not nearly impossible, to use a state controller. In addition, flexible systems are underactuated, i.e. they possess less control inputs than generalized coordinates. In case of a non-collocated output controller, which is the case for end-effector trajectory tracking, the closed loop of the system might lose passivity and is non-minimum phase. In order to achieve end-effector trajectory tracking, exact and approximate feed-forward controls can be applied. In this work, two different versions of such concepts are compared experimentally. These model-based concepts are computed off-line and they supply, next to the required input values, a C<sup>1</sup>-continuous solution of the complete state vector which can be used for feedback control. If the system is non-minimum phase, a two-sided boundary value problem has to be solved and the solution includes a pre-actuation as well as a post-actuation phase. While the exact method incorporates all dynamical effects of the flexible multibody system, the approximate concepts neglect certain implications, for example the dynamical effects due to the flexibility. In addition to the presentation of the theoretical basics of the control approaches and the underlying models, this contribution addresses some of the crucial obstacles, which have to be overcome for the operation of the test bench, e.g., signal conditioning, state reconstruction and friction compensation. Since the installed sensors do not allow the direct measurement of the endeffector position, image tracking is used to judge the quality of the different control approaches.
Subjects
Experimental studies
Feed-forward control
Flexible multibody system
Servo constraints
DDC Class
600: Technik
Funding Organisations
More Funding Information
The authors would like to thank the German Research Foundation (DFG) for their financial support of the project within the Cluster of Excellence in Simulation Technology (EXC 310/2) at the University of Stuttgart and the project SE 1685/3-1.