Type of Document Dissertation Author Lam, Margaretha Johanna Author's Email Address mjlam@cooper.edu URN etd-93197-1508 Title Hybrid Active/Passive Models with Frequency Dependent Damping Degree Doctor of Philosophy Department Mechanical Engineering Advisory Committee
Advisor Name Title Drs. Daniel Inman and William Saunders Committee Chair Al Wicks Committee Member Daniel J. Inman Committee Member Harley H. Cudney Committee Member Harry H. Robertshaw Committee Member William R. Saunders Committee Member Keywords
- active
- passive
- hybrid
- frequency dependent damping
- model reduction
- feedback
Date of Defense 1997-10-27 Availability unrestricted Abstract To add damping to structures, viscoelastic materials (VEM)are added to structures. In order to enhance the damping
effect of the VEM, a constraining layer is attached,
creating a passive constrained layer damping treatment
(PCLD). When this constraining layer is an active element,
the treatment is called active constrained layer damping
(ACLD). Recently, the investigation of ACLD treatments has
shown it to be an effective method of vibration suppression.
In this work, two new hybrid configurations are introduced
by separating the passive and active elements. In the first
variation, the active and passive element are constrained
to the same side of the beam. The other variation allows
one of the treatments to be placed on the opposite side of
the beam. A comparison will be made with pure active, PCLD,
ACLD and a variation which places the active element
underneath PCLD. Energy methods and Lagrange’s equation
are used to obtain equations of motion, which are
discretized using assumed modes method. The frequency
dependent damping is modeled using the Golla-Hughes-McTavish
(GHM) method and the system is analyzed in the time domain.
GHM increases the size of the original system by adding
fictitious dissipation coordinates that account for the
frequency dependent damping. An internally balanced model
reduction method is used to reduce the equations of motion
to their original size. A linear quadratic regulator and
output feedback are used to actively control vibration. The
length and placement of treatment is optimized using
different criteria. It is shown that placing the active
element on the opposite side of the passive element is
capable of vibration suppression with lower control effort
and more inherent damping. If the opposite surface is not
available for treatment, a suitable alternative places the
PZT underneath the PCLD. LQR provides the best control,
since it assumes all states are available for feedback.
Usually only select states are available and output
feedback is used. It is shown that output feedback, while
not as effective as full state feedback, is still able to
damp vibration.
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