An Ultralow-Frequency Vertical Isolation System Based on Composite Feedforward and Feedback Control

The atom gravimeter is a novel type of gravimeter that offers notable advantages, including high sensitivity and long-term stability. However, the accuracy and reliability of measurements obtained from atom gravity measurement systems are significantly influenced by vibrations. To address this issue, this article presents the design and development of an active and passive vibration isolation system aimed at reducing vibrations affecting the Raman mirror during dynamic measurements in atom gravimeters. The system is based on the passive vibration isolation platform. To meet the vertical vibration isolation requirements of the atom gravimeter and to be applicable in dynamic measurement applications, linear bearings are utilized to restrict the horizontal movement of the vibration isolation platform while allowing linear movement in the${z}$-axis direction. This effectively enhances the vibration isolation performance in the vertical direction. Additionally, three voice coil motors are evenly distributed on the vibration isolation platform at 120° intervals to prevent system instability and inclination caused by uneven force. Furthermore, a control strategy that combines adaptive feedforward control and proportional–integral–derivative (PID) feedback control is implemented to further improve the vibration isolation performance of the system. Experimental results demonstrate that the maximum vibration in the vertical direction can be suppressed by 98.34% in the frequency band below 10 Hz, which is particularly sensitive to the atom interferometer. The impact of vibration on the sensitivity of the cold atom gravimeter is two orders of magnitude lower than that experienced on the ground, significantly enhancing the accuracy of the atom gravimeter. These findings have substantial practical value and can be applied in scientific research and industrial applications within the field of atomic gravity measurement. They provide positive implications for the development of advanced dynamic measurement techniques for atom gravimeters.