Switching control based on the mode of vibration for dynamic absorber

A dynamic absorber is not effective except specific frequency. Therefore, it is generally necessary to use several dynamic absorbers to suppress two or more modes of vibration. In this paper, it aims at suppression of the primary and secondary modes with one semi-active dynamic absorber which consists of the air damper and spring installed on the top of the two-degree-of-freedom structure. The air damper can change not only the damping but also stiffness by the slit of the valve. The proposed semi-active control improves the suppression of two vibration modes by changing the slit of the air damper with an electromagnetic valve according to the size of the secondary mode of the structure.