Decentralized Adaptive Fuzzy Control Theory And Experiments For Nonlinear Uncertain Structures

In recent years, several sizeable earthquakes have caused severe loss of livesand significant economic cost. The heavy damage or collapse to civil structures hasbeen considered as one of the most important reason. Therefore, it is so necessaryto investigate the theory and method on preventing the heavy damage to civilstructures and improving the seismic performance. A Lot of researches to data haveindicated that structural control is an effective methodology in increasing safety andperformance against the seismic excitations. Plenty of researches focused on thecontrol theory, methodology, technique and system subjected to linear structureshave been conducted in the world. However, few literatures can be found about thenonlinear structural control. Due to the severity of earthquakes, the dynamicbehavior of civil structures will unavoidably be nonlinear or inelastic. Earthquakereconnaissance has indicated that even civil structures equipped with vibrationcontrol devices may enter the plastic domain. Hence, it is imperative andinformative to bring out the critical aspects with respect to investigate the theoryand methodology on the nonlinear structural control.Due to the property of civil structures, such as structural complexity, highdimensionality, strong nonlinear hysteresis, multiphase coupling nonlinearity anduncertainty, this research effort studies the nonlinear decentralized control strategy,and reveals the principle of cumulative damage evolution, energy distribution andcontrol mechanism. The main research works are outlined as following:First, a nonlinear robust control approach is proposed to address the vibrationcontrol problem of civil structures using the subsystem property, in view of theinfluence of the key parts or vulnerable parts in nonlinear structures on the seismicperformance. Fuzzy logic system is employed to treat the nonlinear problem anduncertainty. The auxiliary control compensation is employed to attenuate the fuzzyestimated errors and external excitations. The Lyapunov’s Direct Methods areemployed to design the adaptive law and auxiliary control compensation. The input-to-state stability of the entire system can be guaranteed by the proposed controlmethod. Furthermore, H-infinity performance is achieved through a subsystem with the proposed controller. Numerical examples are presented to demonstrate theeffectiveness and robustness of the proposed controller.Second, shaking table tests of a reinforced concrete (RC) frame are performedto investigate the proposed decentralized adaptive fuzzy control algorithm. Theeffectiveness and robustness of the proposed controller in suppressing vibrations ofthe test structure with nonlinear hysteresis are demonstrated. The principle ofcumulative damage evolution is investigated for the controlled/uncontrolledstructure. The characteristic of energy distribution and damping mechanism arerevealed.Third, shaking table tests of soil-structure system are performed to furtherinvestigate the proposed decentralized adaptive fuzzy control algorithm. Thereinforced concrete (RC) frame resting in a laminar soil container is employed asthe test specimen. The effectiveness and robustness of the proposed controller insuppressing vibrations of the soil-structure system with strong nonlinear hysteresisand uncertainty are demonstrated. The principle of cumulative damage evolutionand characteristic of energy distribution in soil-structure system are investigated.The characteristic and mechanism of nonlinear vibrations in soil-structure systemare revealed.Finally, the proposed nonlinear robust controller is developed and integratedinto the OpenSees platform. The validity and feasibility of this programmer isconducted by comparing with the results in shaking table tests. The characteristicsof vibration control for the fixed-base model and soil-structure system are furtherinvestigated subjected to seismic excitations.