Title page for ETD etd-164413049751491


Type of Document Dissertation
Author Matheu, Enrique E.
Author's Email Address matheu@vt.edu
URN etd-164413049751491
Title Active and Semi-Active Control of Civil structures Under Seismic Excitation
Degree PhD
Department Engineering Science and Mechanics
Advisory Committee
Advisor Name Title
Beattie, Christopher A.
Hajj, Muhammad R.
Hendricks, Scott L.
Singh, Mahendra P.
Thangjitham, Surot
Keywords
  • active control
  • semi-active control
  • sliding mode control
Date of Defense 1997-05-06
Availability unrestricted
Abstract
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.

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