Active and Semi-Active Control of Civil Structures under Seismic Excitation
The main focus of this study is on the active and semi-active control of civil engineering structures subjected to seismic excitations. Among different candidate control strategies, the sliding mode control approach emerges as a convenient alternative, because of its superb robustness under par...
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| Format: | Others |
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Virginia Tech
2014
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| Online Access: | http://hdl.handle.net/10919/30310 http://scholar.lib.vt.edu/theses/available/etd-164413049751491/ |
| Summary: | The main focus of this study is on the active and
semi-active control of civil engineering structures subjected
to seismic excitations. Among different candidate control
strategies, the sliding mode control approach emerges as a
convenient alternative, because of its superb robustness
under parametric and input uncertainties. The analytical
developments and numerical results presented in this
dissertation are directed to investigate the feasibility of
application of the sliding mode control approach to civil
structures. In the first part of this study, a unified treatment
of active and semi-active sliding mode controllers for civil
structures is presented. A systematic procedure, based on
a special state transformation, is also presented to obtain
the regular form of the state equations which facilitates the
design of the control system. The conditions under which
this can be achieved in the general case of control
redundancy are also defined. The importance of the
regular form resides in the fact that it allows to separate
the design process in two basic steps: (a) selection of a
target sliding surface and (b) determination of the
corresponding control actions. Several controllers are
proposed and extensive numerical results are presented to
investigate the performance of both active and semi-active
schemes, examining in particular the feasibility of
application to real size civil structures. These numerical
studies show that the selection of the sliding surface
constitutes a crucial step in the implementation of an
efficient control design. To improve this design process, a
generalized sliding surface definition is used which is based
on the incorporation of two auxiliary dynamical systems.
Numerical simulations show that this definition renders a
controller design which is more flexible, facilitating its
tuning to meet different performance specifications. This
study also considers the situation in which not all the state
information is available for control purposes. In practical
situations, only a subset of the physical variables, such as
displacements and velocities, can be directly measured. A
general approach is formulated to eliminate the explicit
effect of the unmeasured states on the design of the sliding
surface and the associated controller. This approach,
based on a modified regular form transformation, permits
the utilization of arbitrary combinations of measured and
unmeasured states. The resulting sliding surface design
problem is discussed within the framework of the classical
optimal output feedback theory, and an efficient algorithm
is proposed to solve the corresponding matrix nonlinear
equations. A continuous active controller is proposed
based only on bounding values of the unmeasured states
and the input ground motion. Both active and semi-active
schemes are evaluated by numerical simulations, which
show the applicability and performance of the proposed
approach. === Ph. D. |
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