Research on Ultra-Low Frequency Vibration Isolation Systems and Active Control for Large Precision Instruments

In this paper, an ultra-low frequency active vibration isolation unit is designed using a parallel structure of gas-magnetic combination. This structural design endows the isolation system with high static stiffness and low dynamic stiffness characteristics. These characteristics effectively address the load-bearing issues of vibration isolation systems for large precision instruments, resulting in a shallow natural frequency. The vibration isolation system is controlled using a discrete-time LQG controller based on a state-space model. Simulation studies and experimental results indicate that the designed ultra-low frequency vibration isolation system has a natural frequency of 0.6 Hz, with vibration attenuation reaching 40 dB at 10 Hz. Vibrations at the natural frequency of the system are effectively suppressed by active control. Compared with passive vibration isolation, active control reduces the maximum velocity amplitude of the vibration isolation platform to about 21%. The ultra-low frequency active vibration isolation system designed in this paper demonstrates excellent isolation against floor disturbances over a wide frequency range, meeting the micro-vibration isolation requirements of various large precision instruments.