Theoretical study on response of two-dimensional compound pendulum to ground vibration

Active vibration isolation against low-frequency ground tilt is important for detection of gravitational wave, however until now few low-frequency ground tilt detection and vibration isolation systems with high precision have been reported. We reported a kind of active vibration isolation system called as two-dimensional compound pendulum, which is constructed by connecting a cylindrical simple pendulum with a U-shape inverse pendulum. The structure of the two-dimensional compound pendulum is designed and its response to the ground vibration is investigated by means of analytical mechanic. The simulations show that the compound pendulum system is not only sensitive to low-frequency tilt vibration but also suppresses effectively high frequency tilt vibration and low frequency horizontal vibration, which is consistent with the theoretical results, and we discuss the possibility of experimental investigation on the response to low-frequency tilt vibration. Therefore, the designed compound pendulum is feasible for detecting ground tilt vibration.