Abstract
For full-maglev vertical superconducting gravity instruments, displacement control in the non-sensitive axis is a key technique to suppress cross-coupling noise in a dynamic environment. Motion decoupling of the test mass is crucial for the control design. In practice, when levitated, the test mass is always in tilt, and unknown parameters will be introduced to the scale factors of displacement detection, which makes motion decoupling work extremely difficult. This paper proposes a method for decoupling the translation and rotation of the test mass in the non-sensitive axis for full-maglev vertical superconducting gravity instruments. In the method, superconducting circuits at low temperature and adjustable gain amplifiers at room temperature are combined to measure the difference between the scale factors caused by the tilt of the test mass. With the measured difference of the scale factors, the translation and rotation are decoupled according to the theoretical model. This method was verified with a test of a home-made full-maglev vertical superconducting accelerometer in which the translation and rotation were decoupled.
Highlights
Full-maglev vertical superconducting gravity instruments (FM-VSGIs) possess numerous advantages compared with traditional instruments thanks to the lack of mechanical connection between the test mass and the base of the instrument
Adjustable gain amplifiers at room temperature combining with the superconducting quantum interference devices (SQUIDs) are utilized to determine the difference between the unknown parameters introduced by the tilt of the test mass
Adjustable gain amplifiers combined with superconducting circuits were used to determine the difference of the scale factors caused by the tilt of the test mass
Summary
Full-maglev vertical superconducting gravity instruments (FM-VSGIs) possess numerous advantages compared with traditional instruments thanks to the lack of mechanical connection between the test mass and the base of the instrument. In the FM-VSGI developed by the ARKEX Company in the United Kingdom [18], to suppress cross-coupling noise, the researchers designed superconducting circuits for adjusting the sensitive axis of the test mass This approach does not allow for the suppression of cross-coupling noise in a dynamic environment, because the displacement of the test mass must be first controlled, motion decoupling of the test mass is essential for control. Adjustable gain amplifiers at room temperature combining with the superconducting quantum interference devices (SQUIDs) are utilized to determine the difference between the unknown parameters introduced by the tilt of the test mass This difference is artificially compensated for the output of the SQUIDs and decoupling of translation and rotation are carried out by data processing according to a new motion model that takes account of the tilt of the test mass. The rest of the paper is organized as follows: In Section 2, a theoretical analysis of the decoupling method with a brief introduction of the FM-VSA is presented; In Section 3, the design and results of the experiment are provided and discussed; Section 4 features the conclusions
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