Time-delay effect and its solution for optimal output feedback control of structures

C. C. Lin, J. F. Sheu, S. Y. Chu, L. L. Chung

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


This paper investigates the stability of MDOF optimal direct output feedback control systems through analysis of system modal properties after the application of time-delayed control force. Explicit formula and numerical solution are obtained to determine the maximum delay time and critical delay time which cause system instability and control ineffectiveness, respectively. The results indicate that direct velocity feedback has longer maximum and critical delay times than state feedback. The feedback of non-collocated measurements will reduce maximum delay time. The ratios of maximum and critical delay times to structural natural period decrease as the active damping increases. For a given damped structure, a critical control weighting factor exists. When a larger control weighting factor is used, the control system will remain stable even with longer delay time. A formula is also developed to determine the critical control weighting factor so as to make the stability of MDOF control systems dominated by lower modes. Hence, the maximum delay time and critical delay time can be significantly lengthened by selecting an appropriate control weighting factor and/or adding higher modal dampings.

Original languageEnglish
Pages (from-to)547-559
Number of pages13
JournalEarthquake Engineering and Structural Dynamics
Issue number6
Publication statusPublished - 1996 Jun

All Science Journal Classification (ASJC) codes

  • Geotechnical Engineering and Engineering Geology
  • Earth and Planetary Sciences (miscellaneous)


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