Development of ultralow frequency active vertical vibration isolation system based on geometric anti-spring structure
Absolute gravimeters have emerged as essential instruments for geophysics,metrology,and geological exploration.A significant constraint on their measurement accuracy is environmental vibration.This study introduces an ultralow frequency active vertical vibration isolator,specifically designed to improve measurement precision.This isolator employs geometric anti-springs instead of the traditional cylindrical spiral springs used in classical absolute gravimeters to support the proof mass.The geometric anti-spring structure offers high static stiffness and low dynamic stiffness,making it an optimal choice.The isolator is implemented with precision displacement detection and feedback control to achieve an extended period.This paper presents both the equivalent and control models,and derives the transfer function of the vibration isolator.Experimental results demonstrate that the system period surpasses 20 seconds,and the custom-built isolator fulfills the requirements for microgal level high precision absolute gravimetrical measurement.Furthermore,the isolator can maintain stable operation in a standard laboratory environment for several weeks.Considering that the load can be positioned at the top of the vibration structure,the isolator is applicable for both classical and atom absolute gravimeters.
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