| dc.description.abstract | Mechanical vibration is an important topic in the study and design of
exible structures.
This dissertation studies the active vibration control of a
exible structure
subjected to arbitrary, unmeasurable disturbance forces. The control objective is to
reduce the structure vibration globally. The concept of independent modal space
control is adopted. Here, discrete sensors and actuators are used. The modal lters
are chosen as the state estimator to obtain the modal coordinates and modal velocities
for the modal space control. Because of the existence of the disturbance forces,
the vibration control only with the state feedback control law can not suppress the
vibration well. The method of disturbance forces cancellation is then added in the
control loop. In order to implement the disturbance forces cancellation, the unknown
disturbance modal forces must be observed. Three di erent kinds of control
algorithms are developed, in the dissertation, for the active vibration control. All
of them involve the suitable disturbance force observers to observe the disturbance
modal forces. The observed disturbance modal forces then are included in the control
loops to cancel out the undesired excitation. The rst method employs the modal
space feedforward and feedback control loops to suppress the structure vibration. A
disturbance force observer, based on the inverse dynamics technique, is established.
The control gains are derived from the extended optimal control algorithm, where
the disturbance modal forces are treated as exogenous state variables. Second, the
author applies the H1 control to the structure vibration attenuation. The model
error compensator is employed to observe the unknown disturbance modal forces forthe direct cancellation. After the implementation of the disturbance modal forces
cancellation, there are still some residual disturbance modal forces which excite the
structure. The disturbance attenuation problem is concerned in the design of the
state feedback control law. For ensuring the in
uence of the residual disturbance
modal forces is reduced to an acceptable level, the robust static H1 state feedback
controller is designed here. In the last, the author studies the application of using
the discrete-time variable structure control method to reduce the vibration of the
exible structure. A discrete-time variable structure controller with a disturbance
force observer is adopted here due to its distinguished robustness property of insensitiveness
to parameters uncertainties and external disturbances. The included
disturbance force observer can observe the unknown disturbance modal forces, which
are used in the discrete-time variable structure control law to cancel out the excitations.
The upperbound limitations of the unknown disturbances in the variable
structure control, therefore, are no longer needed. The performances of estimating
the disturbance modal forces and the vibration reduction of the
exible structure of
the three control laws are discussed. | en_US |