Research On Field Calibration Method Of Gravity Sensors

In the field calibration process,the turntable used in the laboratory has high accuracy and large volume.In the actual gravity measurement process,it is difficult to provide such a high-precision three-axis turntable.However,the accelerometer component has poor parameter stability,and there is a problem of parameter drift and non-repetitive errors of successive starts,so the accelerometer component needs to be calibrated on site.Therefore,in order to reduce the dependence of calibration methods on high-precision turntables,this paper studies various accelerometer field calibration techniques,and in order to ensure the observability of accelerometer parameters,this paper selects a two-axis turntable with relatively low precision to provide sufficient observation position for calibration.The main work of this paper is as follows:1.The static multi-position mode observation calibration method is studied.Through the observability analysis of the method,the accelerometer scale factor and the sufficient condition of the zero offset are derived.At the same time,combined with the characteristics of the limited index two-axis turntable,the layout scheme is improved.The experimental results show that the accuracy of the estimation method of the accelerometer scale factor is basically the same as that of the traditional calibration method.2.The calibration method of parameter estimation iterative estimation is studied.The quartz flexible accelerometer component pulse output model of the linear measurement error and considering only the quadratic square term error are established.The Lagrangian multiplier method and Newton iteration method are used to solve the calculation problem of the tilt vector,and the initial value of the tilt vector is obtained by normalizing the pulse output of the accelerometer component.By maximizing the gravity value to each model parameter sensitivity function,the observability conditions of each parameter are derived,and the optimal calibration scheme is given.Experiments show that the calibration accuracy is comparable to the traditional method accuracy.3.The system level calibration filtering method is studied.Based on the strapdown inertial system error model,a filter model of system-level filtering method with accelerometer and gyro bias is established,considering the situation of the presence or absence of the lever arm in combination with the actual situation.The method is applied to a type of strapdown gravimeter.The experimental results show that the calibration accuracy is equivalent to the traditional calibration method based on high-precision three-axis turntable.