An active ultra-low frequency vertical vibration isolator

Abstract

An active ultra-low frequency vertical vibration isolator is presented in this paper, which could isolate the vibration from the earth. It could create an inertial reference point for precision physics research and experiments such as high precision absolute gravity measurement. This system is based on a structure with two-stage vertical suspension springs. For the second-stage spring, the suspension point is forced to track the suspended mass through closed loop control, and the length of the spring is almost constant and the restoring force of the mass is closed to zero. Consequently, a system with an ultra-low frequency is realized. With precision mechanical design, high resolution photoelectric detection method, and analog circuit feedback control, a vertical vibration isolation system has been constructed with a period of up to about 40s. This vibration isolator meets the demand of high precision absolute gravity measurement and is promisingly applied to the homemade T-1 absolute gravimeter.