NONLINEAR ACTIVE CONTROL OF DIRECT OUTPUT FEEDBACK SYSTEMS

• Main Authors: Hsu, Wen-Lien, 許文連
• Other Authors: Lin Chi-Chung
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/36482436008401185327

碩士 === 國立中興大學 === 土木工程學系 === 84 === ABSTRACTLinear quadratic regulator has been used extensively in many control systemsdesigned for structural control applications due to its stability androbustness.However, the results obtained from simulations, model experimentsand full-scale structural applications show that it is difficult to employquadratic performance criteria and linear feedback control lawsto produce a significant peak response reduction when the peak response occursduring the first few cycles of the time history,which is usually the caseunder seismic ground excitations. Since peak response is closely related tostructural safety,control algorithms which provide improved peak responsereduction are desirable. A class of nonlinear control law is presentedin this repor for this purpose. It is showen that nonlinear control lawcan significantly improve peak response reduction under the same constraintsimposed on the control resources as in the linear quadratic regulator case.In real active control systems, time is consumed in the acquisition of response and excitation data,data processing, on-line calculation, and control force execution.Most of previous studies neglected the time delay effect based on theaugument that flexible structures usually have a fairly long naturalperiod compared with the delay time, which makes the time delay effectnegligible. However,The delay time may be minimized by employing more advanced hardware andsoftware. But, time delay cannot be avoided and eliminated even withpresent-day technology. Small delay timenot only can render the control ineffective, but also may cause the systeminstability. Hence, time delay effect must be considered in control designbefore real implementation of active control can be put into action.For this purpose, in this study, the full-order mathematical model ofa structure is considered to develop the optimal time-delayed directoutput feedback control algorithm for discrete-time structural systems.Optimal output feedback gains are obtained through variational processsuch that certain prescribed quadratic performance index is minimized.They are calculated by solving three linear algebraic equationssimultaneously using Kronecker algebra. And then, discrete-time control forcesare obtained from the multiplication of output measurements by thesepre-calculated feedback gains.