Research On Quality Control Technology For Strapdown Gravimeter Datum

The gravity field is one of the most basic physical characteristics of the earth.Continuous and rapid determination of gravity information is of great significance to science and engineering.Strapdown gravimeter is an important dynamic method to efficiently obtain accurate gravity field information.With the development of technology,strapdown gravimeter has been applied to the practice of gravity survey and datum construction in China.National University of Defense Technology has been studying strapdown gravimetry since 2002.Supported by the national high technology research and development program of China,the National University of Defense Technology has been broken through core technology of strapdown gravimetry.The SGA-WZ series strapdown gravity measurement system has been developed.In this paper,the method of data quality control for Strapdown gravimeter is studied.From three angles of theory,simulation and actual data,the theory and error characteristics of Strapdown gravimeter,the method of quality evaluation and improving measurement quality,and the new gravimetry method are studied.The main research results are summarized as follows:1.Based on the principle of Strapdown gravity measurement,it is pointed out that due to the error of inertial sensors,strapdown gravimeter has unavoidable errors in the low frequency part,in which the error factors are coupled with each other.The optimization method of strapdown gravimeter based on information fusion is used to correct the low-frequency error.The method fuses the high-frequency information obtained from strapdown gravimetry with the low frequency part from prior information to realize the whole gravimetry.2.In view of the shortcomings of the classical strapdown gravimetry evaluation method,a novel strapdown gravimetry quality evaluation method based on carrier dynamics is developed,which can approximately real-time evaluate the quality of strapdown gravimeter measurement data.The evaluation model of this method has considerable generality after it is established,which can evaluate the measurement of the same strapdown gravimeter under the same type of carrier.In addition,in order to evaluate the measurement quality of different carriers,another strapdown gravity measurement quality assessment method based on filtering convergence is also proposed,which is a supplement to the dynamic method.3.Aiming at the problem of error parameter drift in strapdown gravimeter and the decrease of accuracy when the dynamics is large,a strapdown gravimeter error estimation and correction method based on carrier maneuver is investigated.Taking scalar measurements as an example,the scale factor error and time delay error of accelerometer in strapdown gravimeter are estimated and corrected by the investigated method.The idea of this method can also be used in the measurement of horizontal components of gravity disturbance.4.A strapdown vector gravimetry smoothing algorithm based on forward and backward strapdown inertial navigation algorithm is proposed.The forward and backward smoothing algorithm not only improves the performance of the filter based on the use of observations,but also improves the accuracy of attitude measurement through the complementary characteristics of the forward and backward algorithms of SINS.The accuracy of horizontal component of gravity disturbance is better than that of 2mGal.5.A new strapdown gravimetry method based on turntable technology is investigated.The performance of strapdown gravimetry is improved by horizontal stabilized platform and single axis rotation mechanism.The stable platform improves the performance of strapdown gravimeter by isolating angular motion of carrier,the accuracy of which is at the same level of GT-2A gravimeter.Two modulation schemes,course tracking and continuous rotation modulation schemes,using a single-axis rotating mechanism are studied.The course tracking scheme decouples the coupling relationship between the measurement error and the direction of motion.The performance of course tracking scheme is verified by simulation experiments.The continuous rotation scheme modulates the error signal of gravity disturbance into a higher frequency signal by rotation,and then eliminates the error signal by low-pass filtering.Static turntable experiments show that the single axis continuous rotation modulation scheme can effectively suppress the linear error in strapdown gravimetry.In addition,although most of the data and experiments in this paper are derived from airborne applications,most of the methods proposed in this paper can not only be used in airborne strapdown gravity survey,but also be applied to ground vehicle or marine gravimetry after appropriate adjustment.