Adaptive extraction of gravity information for drilling tool with magnetic and inertial integrated system

In order to solve the problem of the serious distortion of the attitude parameters about drilling tool caused by the strong vibration of the bottom drilling tool in the process of rotary steering drilling,a magnetic / inertial-based meth- od is proposed to extract the gravity information of the drilling tool. Firstly,a federal extraction framework for the gravi- ty information of drilling tool is designed with gyro data-based gravity recursive model selected as the main filter,and also the accelerometer data-based and magnetometer data-based gravity observation model are used as sub filter re- spectively. Secondly the robust estimation and fusion of the state and observation model about sub filters are carried out respectively,and the fusion weight between state and observation model is adaptively adjusted by the adaptive factor and the equivalent weight matrix,then the local robust estimation of gravity information is obtained. Thirdly the com- prehensive estimation of gravity information about drilling tool is further improved by means of federal filter. Coal mine drilling experiments indicate that the proposed method could effectively extract the dynamic gravity information of drill- ing tools,with the corresponding average error of inclination within 2. 5 degrees.