A New Type of Inerter with Easily Adjustable Inertance and Superior Adaptability: Crank Train Inerter

A new type of inerter, called a crank train inerter (CTI), is investigated for structural vibration isolation. The CTI consists of a crank, a linking rod, a gear-pinion box, and a flywheel that generates inertance. It has advantages of quick adjustment of inertance and strong adaptability to other disturbances. First, the inertial force provided by the CTI is linearized and expressed in a simple format; the minimum length of linking rod and crank are obtained for a CTI operating linearly under various deformed configurations. Then, the motion equation of the coupled structure-CTI system is formulated, and transmissibility is analyzed. Laboratory experiments are next carried out to verify the CTI’s mechanical property and vibration isolation performance. It is shown that the inertance of the CTI obtained in the tests agrees well with the analytical result. CTIs can significantly decrease the amplitude-frequency responses at the fundamental frequency but cannot achieve vibration isolation in a full frequency range. Finally, the seismic control effect of base-isolated buildings with and without CTI is numerically studied. An optimal design method of the CTI is proposed, and the story drift ratio and deformation of the isolation layer can be reduced simultaneously with the optimal inertance. The installation methods of CTIs for buildings are also presented.

A crank train inerter is a kind of vibration isolator with simple structure and low cost. Compared with the traditional rack-and-pinion inerters and ball screw inerters, crank train inerters have the advantages of adjustable inertance and strong adaptability to other disturbances. In this paper, the inertance and linear condition (crank train inerters can be treated as linear inerters) of crank train inerters are obtained through theoretical derivation, and a series of experimental studies are carried out. The experimental results verify the easily adjustable inertance of crank train inerters and their strong adaptability to other disturbances, and also verify the reliability and practicality of its application in vibration isolation system. Crank train inerters can be used as a new implementation of inerter for vibration isolation of building structures, bridge structures, ships, machinery, or vehicles. In addition, crank train inerters can also be combined with a spring and dashpot to form tuned inerter dampers or tuned viscous mass dampers as vibration isolators or shock absorbers. The geometric nonlinearity of crank train inerters for large deformation and the vibration control effect of the integrated device with both a crank train inerter and other elements need further research.