MR dampers in smart structures with nonlinear non-affine dynamics improvising intelligent control
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The increasing complexity of high-rise buildings, cable-stayed long-span bridges, deep-sea offshore structures or suspension systems demands effective tools for control and health monitoring. These infrastructure systems are usually integrated with actuation, sensing, computation resources and information networks, taking advantage of the synergy of civil engineering and mechatronics in an emerging area called civiltronics. Towards the achievement of high performance smart structures, semi-active vibration control in complex civil structures has been very promising, particularly in the mitigation of external excitations and dynamic loadings owing to its meritorious features of low cost, strong robustness and high reliability against various loading sources. Structural behavior and energy efficiency can be improved via directly controlling the input of the smart devices. For example, semi-active controlled dampers, from the dissipation point of view by using suitable control schemes for parameterized relationships describing the system dynamics of the structure integrated with the smart devices with respect to the applied electrical signal. This research is concerned with the problem of controlling the nonlinear, non-affine dynamics of smart structures with magneto-rheological (MR) dampers. A laboratorial set-up of a one-storey steel frame and a benchmark five-storey building model integrated with MR dampers are used in this research. These smart structures are subject to scaled earthquake vibrations excited by a shake table. A static hysteresis model is adopted for the MR damper, in which current-dependent nonlinear functions are used to represent the damper force-velocity characteristics. Here the semi-active control problem of the smart structure system is formulated in current-input non-affine nonlinear state space equations. The complications in the design are tackled by using intelligent control, whereby adaptive fuzzy logic control is proposed to deal with nonlinearity of the control dynamics and non-affinity in the control input, assuming the availability of the displacement and velocity information of the last floor. Here, self-organising adaptive fuzzy logic control is developed to prevent cases that the resulting fuzzy inference system may be unnecessarily large or too small to adequately represent the complex dynamics of the smart structure under control. The main objectives of this research are thus to model the overall smart structure system and to develop self-organising adaptive fuzzy logic schemes for the continuous-time multiple-input multiple-output uncertain nonlinear dynamics of the structure. The proposed control algorithms are implemented in MATLAB and SIMULINK. To illustrate their effectiveness in seismic vibration suppression of civil structures due to earthquake excitations, simulation results are presented together with discussions on performance evaluation and further remarks on the implementation aspects.
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