The Need for Passive Damping In Feedback Controlled Flexible Structures
Report Number: WL-TR-91-3078 Volume II, pages GBB-1 to GBB-12
Author(s): von Flotow, A. H., Vos, D. W.
Corporate Author(s): Massachusetts Institute of Technology
Laboratory: Wright Laboratory
Date of Publication: 1991-08
Pages: 12
DoD Project: 2401
DoD Task: 240104
Identifier: This paper is part of a conference proceedings. See ADA241312
Abstract:
It is well established that an undamped infinite dimensional mathematical model of a flexible structure cannot be stabilized with finite bandwidth control; the required gain stabilization beyond the bandwidth is negated by the infinite structural gain at each resonance. Thus, even a mathematical model with no modeling uncertainty will show that passive damping is critical to enabling active control. What is less well known. are the benefits of passive damping for the robust control of real structures. There has been a tendency, in the research literature, to define the research problem to consist of developing control approaches for the broadband control (many modes in the control bandwidth) of poorly modeled, lightly damped, modally dense structures. There is ample reason to believe that such control is practically unachievable and that the attribute "lightly damped" is one of the most easily and readily remedied characteristics of such a problem structure. This paper reports upon the enabling effect of passive damping in the control of uncertain flexible structures, particularly with non-collocated actuators and sensors. Quantitative results are all single-input single-output and the benefits of passive damping are then understandable in terms of classical ideas of gain and phase stabilization. The paper derives approximate expressions for the minimum acceptable level of passive damping in terms of modeling uncertainty and desired bandwidth. These relationships can then be interpreted as specifying either a minimum level of passive damping or a minimum level of modeling fidelity. If the requirement is not met, robust control with the bandwidth including uncertain flexible dynamics is not possible with linear time invariant (LTI) compensation.
Provenance: University of Colorado Colorado Springs, Kraemer Family Library
Author(s): von Flotow, A. H., Vos, D. W.
Corporate Author(s): Massachusetts Institute of Technology
Laboratory: Wright Laboratory
Date of Publication: 1991-08
Pages: 12
DoD Project: 2401
DoD Task: 240104
Identifier: This paper is part of a conference proceedings. See ADA241312
Abstract:
It is well established that an undamped infinite dimensional mathematical model of a flexible structure cannot be stabilized with finite bandwidth control; the required gain stabilization beyond the bandwidth is negated by the infinite structural gain at each resonance. Thus, even a mathematical model with no modeling uncertainty will show that passive damping is critical to enabling active control. What is less well known. are the benefits of passive damping for the robust control of real structures. There has been a tendency, in the research literature, to define the research problem to consist of developing control approaches for the broadband control (many modes in the control bandwidth) of poorly modeled, lightly damped, modally dense structures. There is ample reason to believe that such control is practically unachievable and that the attribute "lightly damped" is one of the most easily and readily remedied characteristics of such a problem structure. This paper reports upon the enabling effect of passive damping in the control of uncertain flexible structures, particularly with non-collocated actuators and sensors. Quantitative results are all single-input single-output and the benefits of passive damping are then understandable in terms of classical ideas of gain and phase stabilization. The paper derives approximate expressions for the minimum acceptable level of passive damping in terms of modeling uncertainty and desired bandwidth. These relationships can then be interpreted as specifying either a minimum level of passive damping or a minimum level of modeling fidelity. If the requirement is not met, robust control with the bandwidth including uncertain flexible dynamics is not possible with linear time invariant (LTI) compensation.
Provenance: University of Colorado Colorado Springs, Kraemer Family Library
Other options for obtaining this report:
Via the Defense Technical Information Center (DTIC): Identifier: This paper is part of a conference proceedings. Access a record for the conference proceedings, and possibly a pdf download of the report, at DTIC Via National Technical Report Library: This report may be available for download from NTRL. Use the Title from this record to locate the item in DTIC Online Indications of Public Availability No digital image of an index entry indicating public availability is currently available There has been no verification of an indication of public availability from an inside cover statementRelated report(s)
This report is part of the following conference:
-
Proceedings of Damping '91: 13-15 February 1991 San Diego, California (EAA-1 through GBC-16)
WL-TR-91-3078 Volume II