TIME DELAY CONSIDERATION ON A NEW ACTIVE CONTROL ALGORITHM

Computer-Aided Civil and Infrastructure Engineering, 2010

A simple integral type quadratic functional is proposed as the performance index so that the optimal control policy is derived based on the minimization of the proposed performance index between the successive control instants by using the method of calculus of variations. The resulting optimal control law is applied to seismically excited linear buildings modeled as lumped mass shear frame structures. Active tendon actuators are considered as control devices. The performance of the proposed control (PC) is investigated when the example structure is subjected to three different seismic inputs and compared to the uncontrolled case and the classical linear optimal control (CLOC), which requires the solution of nonlinear matrix Riccati equation. It is shown by numerical simulation results that the PC is capable of suppressing the uncontrolled seismic vibrations of the linear structures and performs better than the CLOC.

Journal of Structural Control , 1995

(The authors of this paper are Ahmet Süner, Abhijit Nagchaudhuri and Şenol Utku) This work studies the determination of controls to suppress the vibration of a building structure subjected to earthquake excitation. Also studied are the effect of time delay in controls on the response of the structure, determination of time delay limits, and time delay compensation. The control problem is nonautonomous due to the existence of external excitation during the application of controls. The control methods that are used in the autonomous system cannot be applied directly t o the nonautonomous problem. Therefore the methods that may be applicable t o the nonautonomous problem need to be investigated. In this study, the problem is formulated as a disturbance rejection problem. Determination of controls is discussed with the help of insight provided by classical control methods. A simple control method which is based on large feedback gains is implemented. Time delay effect and compensation are studied through the use of classical control methods.

Engineering Structures, 2019

The biggest challenge and criticism on active control systems in earthquake engineering applications point out the issues that could occur because of a possible power loss of the active controller system during an earthquake. The power supply of an active control system can be disabled during an earthquake. This study is written to introduce a simple structural model to overcome the challenges defined above, and to investigate the performance of this system. The integrated active and semi-active control system is named as "INASA." The proposed control method of the INASA system both minimizes integrated active and semi-active control energy, as well as the structural energies. A building with an active tendon controller system, with the integration of an MR damper, is considered as an example structure. For numerical validation of the INASA system, near-fault and farfault earthquakes are used. The electrical current need for operation of the MR damper as well as the time-delay effects of the active tendon controllers are also taken into account for more realistic dynamic simulations. The dynamic performance of the INASA system under different earthquakes is compared to the building equipped with the MR damper the conventional uncontrolled structure. The results showed that the INASA system could work without any stability problems under both earthquakes. Time-delays did not have a negative effect on the system. And a reasonable reduction in uncontrolled response is achieved with very small power requirement. In the possible case of a power loss, the deactivation of the active tendon control system did not lead to a discrepancy, because the MR damper continued to operate with a very small power requirement and showed a good performance.

Journal of Structural Control, 1995

This work studies the determination of controls t o suppress the vibration of a building structure subjected to earthquake excitation. Also studied are the effect of time delay in controls on the response of the structure, determination of time delay limits, and time delay compensation. T h e control problem is nonautonomous due to the existence of external excitation during the application of controls. The control methods that are used in the autonomous system cannot be applied directly t o the nonautonomous problem. Therefore the methods that may be applicable t o the nonautonomous problem need to be investigated. In this study, the problem is formulated as a disturbance rejection problem. Determination of controls is discussed with the help of insight provided by classical control methods. A simple control method which is based on large feedback gains is implemented. Time delay effect and compensation are studied through the use of classical control methods.

2018

A simple integral type quadratic functional is proposed as the performance index so that the optimal control policy is derived based on the minimization of the proposed performance index between the successive control instants by using the method of calculus of variations. The resulting optimal control law is applied to seismically excited linear buildings modeled as lumped mass shear frame structures. Active tendon actuators are considered as control devices. The performance of the proposed control (PC) is investigated when the example structure is subjected to three different seismic inputs and compared to the uncontrolled case and the classical linear optimal control (CLOC), which requires the solution of nonlinear matrix Riccati equation. It is shown by numerical simulation results that the PC is capable of suppressing the uncontrolled seismic vibrations of the linear structures and performs better than the CLOC.

International Journal of Engineering and Technology

This paper is written to present the state of the art of the new active and semi active approaches during the last decade. This is achieved by reviewing the active control approaches and semi-active control policies that have been proposed and validated analytically or numerically in the last ten years. All the papers reviewed in this study are within the scope of earthquake engineering. Brief information about these active control approaches and some of the resulting control policies are presented. To be able to show the effectiveness of the proposed approaches, the numerical examples of these papers are presented in this study. Because of the latest technological and computational advances, some of the most effective and complex algorithms have been studied and numerically validated during the last decade in earthquake engineering. This is the reason that this review considers the period of 2008-2018. The authors also include some of the new semi-active control policies that have been proposed numerically during the last decade. It has been concluded that, although there is an impressive research on numerically and/or analytically validating new active control approaches and new semi-active control policies of the years 2008-2018, there is not any real-building / real structure implementation of these active control approaches. Additionally there is a need of experimental validation of these active control methods that have been presented during the last decade.

Journal of Engineering Mechanics, 2006

In this paper we present and propose a design methodology that uses intentional time delays for the active control of structures. We use here positive velocity-feedback, time-delayed control and show that its performance is, in general, superior to the previously developed methodology of using time delayed, negative velocity-feedback control. A detailed study carried out in this paper of the nonsystem poles and their interaction with the system poles reveals the reasons for this. Analytical results related to performance and stability of the new method are presented. We apply the time delayed positive velocity feedback active control methodology to a multidegree-of-freedom system subjected to the S00E component of ground acceleration recorded during the El Centro 1940 earthquake. The excellent behavior in terms of stability, performance, and control efficiency that is demonstrated by our time-delayed control design as well as its facile implementation makes it attractive for earthquake hazard mitigation in a practical sense.

Smart Structures and Systems, 2011

During the last thirty years many structural control concepts have been proposed for the reduction of the structural response caused by earthquake excitations. Their research and implementation in practice have shown that seismic control of structures has a lot of potential but also many limitations. In this paper the importance of two practical issues, time delay and saturation effect, on the performance of controlled structures, is discussed. Their influence, both separately and in interaction, on the response of structures controlled by a modified pole placement algorithm is investigated. Characteristic buildings controlled by this algorithm and subjected to dynamic loads, such as harmonic signals and actual seismic events, are analyzed for a range of levels of time delay and saturation capacity of the control devices. The response reduction surfaces for the combined influence of time delay and force saturation of the controlled buildings are obtained. Conclusions regarding the choice of the control system and the desired properties of the control devices are drawn.

Structural Control and Health Monitoring, 2007

In this paper we develop the principles of time-delayed control design for the active control of structures in which the presence of large time delays in the control loop may make it difficult for their effects to be easily eliminated and/or compensated. A control design strategy is proposed that is different from what has been generally accepted hereto; it calls for taking advantage of these large, inherent time delays in the control design. The presence of large time delays in the control loop requires that we understand the infinite dimensionality of the system and so we introduce the concept of non-system poles. This is first done within the framework of an SDOF system with time-delayed velocity feedback control. Several new results are presented dealing with stability and performance issues. These results include and extend those available to date. Having developed control design principles with an SDOF system as the underlying basis, these principles are then developed for multi-actuator, multiple time-delay control of MDOF systems. A numerical example of a building structure modeled as an MDOF system that is subjected to strong earthquake ground shaking is presented. The control design based on the underlying principles shows good stability characteristics and effective performance behavior. We demonstrate its application to a structure subjected to strong earthquake ground shaking, thereby showing its usefulness in hazard mitigation.

2010

For many years bridge structures have been designed or constructed as passive structures that rely on their mass and solidity to resist external forces, while being incapable of adapting to the dynamics of an ever-changing environment. When the rigidity assumption is not met in particular for high-rise structures like bridge towers, a proper dynamic model should be established and conclusions made on the differential vibration of the tower when it is investigated out of the bridge system. The present work outlines a vibration control method by tendons on the tower of cable supported structures considering time delay effects, based on the discrete-time Linearization of the Feedback Gain Matrix. The efficiency of this vibration control method first proposed on the design process of a local bridge in Cameroon, is more compatible to the control of civil structures and is of great interest in accordance with simulation results.