| Summary: | 碩士 === 逢甲大學 === 自動控制工程學系 === 88 === A structural damper is one kind of passive control to dissipate energy. In recent years, it has been successfully applied to the design of high buildings to reduce the swing during the gust. Although it is proved to be an effective energy-dissipater, the researches are confined to its elastic limit, and the nonlinear characteristics are still unknown.
In this thesis, the describing function method is used to study the hysteresis of the structural damper. The relations with the structure''s elongation among elastic coefficient, resonant frequency, period ratio and damping ratio are derived while the deformation is entering the nonlinear range from describing function, the equivalent viscous damper is used to study the vibration of structure.
On the other hand, the circuit of passive filter with inductor is simple to design. It doesn''t need any active switch to reduce the input current harmonic of the distortion and increases the power factor. Usually, the inductance of the inductor is assumed to be constant when designing a passive filter. It is all right when the current through the inductor is small, but it is not true when the current is large. The large current will cause the inductor exhibit significant magnetic hysteretic behavior. It will reduce the inductance of inductor and degrade effect of the filter. It is not clear how the inductance changes when the inductor undergoing a large current. In this thesis, we use the describing function and Stemmetz formula to analyze the behavior of magnetic hysteresis. The results are used to derive the relations between inductance and current, and provide as a useful tool when designing a passive filter with inductors undergoing a large current.
Besides, we derive the algebraic method to get the damping ratio of the system when structural damper enters the deformation region, and derive the algebraic method to get the steady current across the inductor as an inductor happens magnetic hysteresis owing to large current by describing function method.
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