Optimization of external tilt-control setpoints for a superconducting gravimeter based on internal displacement voltage response

The external tilt control state is one of the important factors affecting the long-term stable observation of superconducting gravimeters. Influenced by factors such as mechanical assembly errors of the instrument and relative position deviations between internal and external structures, the horizontal zero position of the external tilt control system is not necessarily equivalent to the optimal response state of the internal superconducting magnetic levitation sensing system. To address this issue, this paper proposes an optimization method for the external tilt setpoint based on the internal displacement voltage response, establishing a local response model among external tilt, magnetic levitation force balance, and displacement voltage under small tilt angle and locally quasi-static conditions. A local quadratic relationship is established using the mean tilt angle and mean displacement voltage within the plateau segment, and verified through the original local scanning and supplementary experiments adopting a fixed tilt step size and a unified recording duration. The supplementary experiments yield average extreme positions of -4309.75 μrad and -3997.92 μrad for the X-axis and Y-axis, respectively, with inter-test sample standard deviations of 6.89 μrad and 7.16 μrad, respectively. The average extreme positions of the two axes differ from the original experimental results by 2.04 μrad and 2.05 μrad, respectively. Under the local geometric approximation, the equivalent gravity projection corresponding to the inter-test variation in the extreme position is approximately 0.048 μGal. This method can provide a reference for the optimization of the external tilt setpoint during the installation and commissioning of superconducting gravimeters.