Design of sensing head for gravity gradient tensor based on superconductor

Based on superconducting Meissner effect and quantum interference principle, the design of sensing head for gravity gradient tensor is presented according to compliant parallel mechanism form. It contains six sensing mechanisms which simultaneously have freedoms of motion and rotation. Sensing mechanisms are mounted symmetrically on a cube, and symmetrical mechanism pairs rotate 90° relatively to be mutually perpendicular. Axial distance of mechanism pairs can be used to directly measure inline-component of gravity gradient, and perpendicular distribution can make the mechanism pairs measure both cross-component of gravity gradient and common-mode angular acceleration. The superconducting coil converts the proof mass displacement to inductance, and further into magnetic intensity change by superconducting circuit, which can be measured by superconducting quantum interference device. Sensing mechanism is compliant parallel mechanism with eight branches and space symmetric form, which realize symmetric mechanics properties, uniform deformation, minimal departure, and no stress concentration. The stiffness analysis results indicate that the stiffness of design motion is small, and the stiffness of parasitic motion large. Gravity gradient tensor can be deduced by conversion of coordinates, and the measurement precision of 1E is predicted to obtain.