Structural Active Control For Suppressing Earthquake-Induced Vibrations Of Building Based On The Compensation Of Equivalent-Input-Disturbance

An earthquake is a harmful natural disaster. It causes the vibration of building structures and may damage them. In recent years, collapses of building structures due to large seismic waves have resulted in high mortality and a huge loss of property. Human being suffers a great loss from this kind of disasters. So, antiseismic building structures are one of the most important aspect need to be considered in the structural design. Structural vibration control is widely recognized as an effective way of mitigating catastrophic damage of structures induced by earthquakes. In addition to reinforcing the stiffness and intension of structures, isolation and control of vibration are important measures of antiseismic design. Passive, semiactive, active and/or hybrid vibration control for antiseismatic structures has been attracting considerable attention. In particular, active control for reducing the effects of earthquakes on building and other civil engineering structures has been receiving increasing attention. A lot of control algorithms have been applied in designing a structural vibration control system in civil engineering. However, it is still an unfinished subject to devise a control method that is simple, easy to implement, and can further suppress the structural vibration.This dissertation investigates a structural active control method by employing the method of equivalent input disturbance (EID). The presented method has ability of suppressing earthquake-induced vibrations of buildings effectively. The main achievements and contributions of this dissertation are as follows:(1) We analyze the control system configuration, which is based on the compensation of EID. It reveals that the vibration control performance is guaranteed by the control structure, in which an equivalent vibration signal on the control input channel is estimated and directly incorporated into the control input. From the standpoint of control, it is more reasonable to estimate a disturbance on the control input channel than to estimate the disturbance itself because we have to use the control input to improve the disturbance rejection performance. Even though the control system does not contain an internal model of a disturbance, the influence of an unknown disturbance is almost completely rejected in both the transient and steady-state responses. This method does not require the differentiation of measured outputs, or prior information on a disturbance; and it does not use the inverse dynamics of the plant, thereby avoiding the cancellation of unstable poles/zeros. The method only needs the input and output of the plant to produce an equivalent input disturbance, and does not require the state of the plant. This enlarges its range of application.(2) We study the design method of the EID-based structural active controller, and present a design method of the structural active control system. In order to suppress earthquake-induced vibrations of a building, we extend the control method based on the compensation of the EID to a multi-input multi-output structural control system for aseismatic design of structures. The control system configuration can be separated into two parts by using the separation theorem. Both of these two parts can be designed independently. We present a design method for the part of state observer and low-pass filter by employing the concept of perfect regulation.(3) We analyze the mechanism of disturbance rejection in the EID-based structural active control system. Analysis of the control system configuration shows that the control system has two degrees of freedom. The feedback controller consists of the state feedback; and the feedforward controller consists of the state observer and the low-pass filter. The addition of an EID estimator to a servo system improves the disturbance rejection performance through an integration in the feedforward path. The explanation makes it clear that the characteristics of the filter in the system strongly affect the disturbance rejection performance. Guidelines for the selection of the low-pass filter are given, based on an examination of simulation results. Regarding the choice of low-pass filter, we can conclude that:a first-order low-pass filter is the best. The cut-off angular frequency of the low-pass filter should be chosen to be five times higher than the highest angular frequency of the disturbance to be rejected.(4) We carry out the control system design through numerical examples and simulations to prove the validity of the proposed control method for reducing the seismic responses of the building structure. In the numerical simulations, historically recorded ground accelerations, i.e. the El-Centro, Kobe, Mexico and Northridge earthquakes are employed as external disturbances. The simulation results verify that the vibration control of this method is effective in reducing the seismic responses of structure. The maximum inter-story drift and maximum acceleration response of each floor can be considerably reduced when the proposed method is used. The root mean square of the inter-story drift of each floor also shows a similar tendency. As a result, the presented control method improves the seismic performance of a structural control system. The simulation results are also compared to those of the LQR, fuzzy supervisory control, and eigenstructure assignment control methods. The analysis of the simulation results show that the presented active strategy has better performance in reducing the seismic response of building and minimize the damages in the building structures caused by earthquake over those methods.(5) In order to prevent saturation phenomenon occurred in the structural control, we present the method of EID-based structural active control under actuator saturation. A three-story building structure under seismic loads is used to illustrate the feasibility of the presented method in reducing the structural vibration. The simulation results revealed that this method is effective to suppress the structural vibration. When the actuator capacity is small, the effect of structural control is also small. However, when the actuator capacity is increased, the relative benefits become more apparent.