Non-sensitive axis feedback control of test mass in full-maglev vertical superconducting gravity instruments

Abstract Non-sensitive axis feedback control is crucial for cross-coupling noise suppression in the application of full-maglev vertical superconducting gravity instruments. This study proposes the non-sensitive axis feedback control of a test mass in a custom-made full-maglev vertical superconducting accelerometer. In the feedback system, special superconducting circuits are designed to decouple and detect multiple degree-of-freedom motions of the test mass. The decoupled motion signals are then passed through a PID controller and fed back to the side-wall coils to control the test mass. The displacement of the test mass is controlled within ± 2 nm and is reduced by approximately one order of magnitude in a laboratory environment. Accordingly, the noise level of the vertical superconducting accelerometer in the sensitive axis is reduced by a factor of 4–6 @ 0.03–0.1 Hz.