Tuning the Stiffness Balance Using Characteristic Frequencies as a Criterion for a Superconducting Gravity Gradiometer.

Xikai Liu,Dong Ma,Xiangdong Liu,Liang Chen

doi:10.3390/s18020517

Abstract

Tuning the stiffness balance is crucial to full-band common-mode rejection for a superconducting gravity gradiometer (SGG). A reliable method to do so has been proposed and experimentally tested. In the tuning scheme, the frequency response functions of the displacement of individual test mass upon common-mode accelerations were measured and thus determined a characteristic frequency for each test mass. A reduced difference in characteristic frequencies between the two test masses was utilized as the criterion for an effective tuning. Since the measurement of the characteristic frequencies does not depend on the scale factors of displacement detection, stiffness tuning can be done independently. We have tested this new method on a single-component SGG and obtained a reduction of two orders of magnitude in stiffness mismatch.

Highlights

Over the past few decades, the airborne rotating gravity gradiometer has been proven to be a powerful tool in geodetic surveys and mineral exploration [1,2,3,4]
It should be noted that we only considered the airborne superconducting gravity gradiometer (SGG) in the following
The tuning scheme was successfully applied to a single-component SGG, where the stiffness balance was improved by about two orders of magnitude

Summary

Introduction

Over the past few decades, the airborne rotating gravity gradiometer has been proven to be a powerful tool in geodetic surveys and mineral exploration [1,2,3,4]. The SGG adopts an off-line method to tune common-mode balance [8] This is to say, the instrument should be finely tuned to the optimum state before measurement. In [8], Moody and his colleagues proposed a wide-band stiffness-tuning method In this method, assuming the scale factors of displacement detection for two oscillators are identical, the supercurrents are finely adjusted to null the response to the applied common-mode acceleration. This method does not work if the scale factor of displacement-detecting is badly matched. The tuning scheme was successfully applied to a single-component SGG, where the stiffness balance was improved by about two orders of magnitude

Theoretical Analysis

When the stiffness parameters of the

Experimental Test

Experimental

Findings

Conclusions