Amplitude-Phase Inconsistency Extraction and In Situ Calibration Technique of Six-Degree-of-Freedom Capacitance Sensor for Space Gravitational Wave Detection

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The high precision multiple degree-of-freedom (DoF) capacitance sensor operating in milli-hertz band is critical for satellite platform inertial sensing of space gravitational wave (GW) detection mission, and the amplitude-phase characteristics inconsistency among the capacitive sensing channels may seriously deteriorate the displacement sensing performance. In this article, a novel architecture of 6-DoF capacitive sensing circuits (CSCs) with digital quadrature demodulation is proposed, and the impact of 6-channel displacement sensing front-ends (DSFs) parameters inconsistency on the output signals and displacement sensing performance is also analyzed. The amplitude-phase inconsistency extraction and in-orbit in situ calibration technique for the 6-channel capacitance sensor is proposed and verified by an invented ground-equivalent evaluation scheme. Finally, a 6-DoF CSCs prototype for the inertial sensors of “China TianQin Project” has been developed and tested. The results show the mean values and the standard deviations of the translational and rotational displacement detection errors are reduced from1.32~μm, 5.67 mdeg to 30.86 nm,86.92~μdeg, and from 18.22 nm,76.51~μdeg to 12.23 nm,32.97~μdeg, at the specific carrier frequency, respectively. The method may be utilized to periodically calibrate CSCs to significantly improve the prolonged in-orbit running performance of the inertial sensor.