Theoretical Analysis Of Matching The Consistency Of Accelerometers For Rotating Gravity Gradiometer

Gravity gradient measurements have obtained a wide range of applications in geodesy, resources exploration, inertial navigation, military security and other fields. There has been a continuously growing interest in developing different gravity gradiometers. The rotating accelerometer gravity gradiometer is unique one in that it can work near the terrestrial space and on different kinds of moving platforms.The rotating accelerometer gravity gradiometer employs a set of four or eight accelerometers to measure weak gravity gradient signal. They are equi-placed on the periphery of a low speed rotating disc with their sensitive axis tangential to the circumsference of the disc. Hence, the gradient information is modulated onto the double frequency of the rotation and thus lowers the noise from the rotation. By consistently matching every pair of accelerometers oppositely placed relative to the spin circle center and then all the pairs, the translation and rotational acceleration in rotating gravity gradiometers can be greatly suppressed and the gravity gradient signal can be enhanced by four times. Therefore, the principle and method to match accelerometer is one of the key techniques to implement such gradiometers.In this thesis, we have studied how to match accelerometers in the rotating accelerometer gravity gradiometer. Aiming at the ultimate resolution of 1E/?Hz, we have analyzed accelerometers' coefficients matching requirements for two opposite accelerometers and two pairs of such accelerometers; and then, we have analyzed the matching of scale factors and concluded that the matching of scale factors can be achieved between the opposite accelerometers and accelerometers pairs by using the orthogonal demodulation method; finally based on the afore-mentioned matching principle of accelerometers, we have built a matching simulation model and theoretically verified the feasibility of the matching method; by investigating the phase demodulation signal during the scale factor matching experiment, we have realized the adjustment of the first order coefficient KO, and the experiment results have demonstrated the validity of the adjusting method.With scale factor consistency achieved, the effects of the second order coefficients K_2I, K_5I and K_6I on the gravity gradient signal have been analyzed in details. By introducing two feedback loops, the second order coefficients K_2I, K_5I and K_6I are modulated to a higher frequency at first and then their overall undesired influences are eliminated. Based on this theoretical analysis, the matching simulation has been conducted and the feasibility of the matching method has been verified. The work provides the theoretical knowledge for subsequent experiments related to second order coefficients matching.