Complex oscillations including chaotic motions have been identified in
off-shore and submerged mooring systems characterized by nonlinear fluid-structure
interactions and restoring forces. In this paper, a means of controlling
these nonlinear oscillations is addressed. When applied, the controller is able to
drive the system to periodic oscillations of arbitrary periodicity. The controller
applies a perturbation to the nonlinear system at prescribed time intervals to guide
a trajectory towards a stable, periodic oscillatory state. The controller utilizes the
pole placement method, a state feedback rule designed to render the system
asymptotically stable. An outline of the proposed method is presented and
applied to the fluid-structure interaction system and several examples of the
controlled system are given. The effects of random noise in the excitation force
are also investigated and the subsequent influence on the controller identified. A
means of extending the controller design is explored to provide adequate control
in the presence of moderate noise levels. Meanwhile, in the presence of over
powering noise or system measurements that are not well defined, certain filtering
and estimation techniques are investigated for their applicability. In particular,
the Iterated Kalman Filter is investigated as a nonlinear state estimator of the
nonlinear oscillations in these off-shore compliant structures. It is seen that
although the inclusion of the nonlinearities is theoretically problematic, in
practice, by applying the estimator in a judicious manner and then implementing
the linear controllers outlined above, the system is able to estimate and control the
nonlinear systems over a wide area of pseudo-stochastic regimes. / Graduation date: 2006
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29586 |
| Date | 08 March 2006 |
| Creators | King, Paul E. |
| Contributors | Yim, Solomon C. S. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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