Fuzzy-based variable gain approach for controlling cable-stayed bridges

S. Y. Ok, K. S. Park, C. Chung, H. M. Koh

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

Due to the vulnerability of cable-stayed bridges to dynamic loads such as earthquakes and strong winds, study on vibration control system for the cable-stayed bridges has been of great interest for the past few decades (Dyke 2003). The dynamic response control of the cable-stayed bridges provokes mutually conflicting response control problem. In particular, the strongly coupled model behavior and the complex cable-deck-tower connection configuration further increase the complexities of the response control problem. Viable control strategy for the cable-stayed bridges should thus account for the trade-offs existing between their dynamically induced responses. As one of the gain scheduling scheme (Parlos et al. 2001), variable gain feedback control approach is presented in this paper. The problems with the conventional gain scheduling scheme is: (a) it is difficult to select a set of discrete control gains and determine the proper switching condition among the gains for complex structure such as cable-stayed bridge; (b) degradation of control performance sometimes occurs due to control chattering caused by frequent discontinuous switching. In order to overcome these shortcomings, we present fuzzy-based variable gain approach, which is easy to select a set of discrete control gains, unnecessary to determine the switching condition among the gains, and able to modulate the continuously varying dynamic gain. The proposed technique is a hybrid method with a two-layer topology in which a lower layer consists of several conventional controllers, and a second supervisory layer possesses a fuzzy inference mechanism for endowing the controller with intelligence. Several controllers in the sub-layer are separately responsible for the individual response selected among the multiple target responses of the cable-stayed bridge to be controlled. Thus, each sub-controller is independently designed to efficiently reduce the selected response only. Then, a fuzzy supervisor determines the contribution level of each sub-controller through fuzzy inference mechanism to intelligently manage the overall enhanced control performance of the control system. To investigate the effectiveness of the proposed approach, two kinds of vibration control problems have been dealt with: the seismic response control of cable-stayed bridge and the wind-induced vibration control of cable-stayed bridge under construction. Example designs and numerical simulations of conventional linear quadratic Gaussian (LQG) control system and new fuzzy-based variable gain control system have been performed for the sake of comparison of control performance. The results of the robust performance between the LQG control system and two FSC systems under uncertainties in the bridge model and seismic excitations are compared. In numerical simulations, three historically recorded ground motions are used as input excitations, i.e., El Centro earthquake, Mexico City, and Gebze earthquakes. The peak accelerations of the earthquake records are 3.4170, 1.0432 and 2.5978 m/s2, respectively. From the simulated results, the two FSC systems successfully maintain an overall robust performance under the presence of uncertainties in bridge stiffness as well as the magnitude of the seismic (Graph Presented) event, while stiffness perturbation in the bridge model leads to a significant amplification in the seismic responses of the cable-stayed bridge for the LQG system. In particular, the outstanding robust performance of the FSC2 system demonstrate that the tuning process of the fuzzy rule is able to further enhance the seismic performance of the fuzzy-based variable gain approach for a cable-stayed bridge subject to earthquake excitations. Therefore, the FSC system clearly guarantees excellent robust performance against the uncertainties in the bridge model as well as seismic events, especially through the fine-tuning process of the fuzzy rules. Table 1 represents the simulated results of both systems when the cable-stayed bridge is subject to the self-excited wind loadings and a set of 100 randomly generated wind loadings. All the values in the table are the ratio of the maximum controlled responses to the maximum uncontrolled responses. Therefore, the control system exhibits better performance as the values of the performance ratio increase. Even though the performance of FSC system is a little inferior to that of LQG system for a few cases of the maximum vertical accelerations of the deck, the FSC system shows better control performance for the rest of the wind-induced responses than LQG system. Furthermore, the maxim level of total power required by FSC system is 0.768 kW, while LQG system requires 0.783 kW. Hence, the presented approach guarantees the overall enhanced control performance for the wind-induced cable-stayed bridge under construction. The comparative results show that the fuzzy-based variable control approach can efficiently reduce the dynamic responses of cable-stayed bridges while maintaining lower level of control efforts, and clearly guarantee the robust performance against the uncertainties of bridge model and seismic events involved. Therefore, it is concluded that the proposed technique is an effective control strategy for the vibration control of cable-stayed bridges.

Original languageEnglish
Title of host publicationProceedings of the 3rd International Conference on Bridge Maintenance, Safety and Management - Bridge Maintenance, Safety, Management, Life-Cycle Performane and Cost
Pages889-891
Number of pages3
StatePublished - 2006
Event3rd International Conference on Bridge Maintenance, Safety and Management - Bridge Maintenance, Safety, Management, Life-Cycle Performance and Cost - Porto, Portugal
Duration: 16 Jul 200619 Jul 2006

Publication series

NameProceedings of the 3rd International Conference on Bridge Maintenance, Safety and Management - Bridge Maintenance, Safety, Management, Life-Cycle Performance and Cost

Conference

Conference3rd International Conference on Bridge Maintenance, Safety and Management - Bridge Maintenance, Safety, Management, Life-Cycle Performance and Cost
Country/TerritoryPortugal
CityPorto
Period16/07/0619/07/06

Fingerprint

Dive into the research topics of 'Fuzzy-based variable gain approach for controlling cable-stayed bridges'. Together they form a unique fingerprint.

Cite this