Parametric Vibration of Elevator.

Abstract

This paper deals with parametric vibration of an elevator caused by variable stiffness of the guide rail. The guide rail is lined with rail brackets which are arranged at equal intervals. The rail is stiff on the brackets, but soft between the brackets. That is to say, the elevator cab vibrates because the stiffness of the rail varies periodically. The elevator cab vibrates in the transverse and rotational directions. We calculated the stable and unstable regions of this two-dimensional vibration, and confirmed the results by experiment. The elevator cab vibrates with large amplitude when the frequency of stiffness variation of the rail is twice the natural frequency of the elevator cab. The softer the rail is, the more the cab vibrates. If the stiffness of the rail is at least three times as high as the stiffness of the guide roller, the elevator cab will hardly vibrate. We also examine the effect of damper. If there is a little damper, we can sufficiently prevent this parametric vibration. According to these results, we indicate a design method for prevention of the parametric vibration of an elevator.