A Novel Attitude Measurement While Drilling System Based on Single-Axis Fiber Optic Gyroscope

Aiming at the inability to achieve high-precision real-time magnetic heading angle estimation under single degree of freedom rotation, a novel attitude measurement while drilling (MWD) system is designed, which consists of a single-axis fiber optic gyroscope (FOG), a tri-axial micro-electromechanical system (MEMS) accelerometer, and a tri-axial magnetometer. The magnetometer bias calibration model based on uniform rotation is established and verification experiments are carried out. The uniform rotation experiment shows that six calibration results fluctuate within 5% of the mean. A real-time estimation model of the magnetic heading angle under random rotation is established, of which the theoretical error is less than 0.38°. Three real-time estimation experiments of magnetic heading angle are carried out, and the overall estimation error did not exceed 0.35°, and the average estimation error did not exceed 0.3°. Under continuous rotation of large angle, the bias estimation of the
$X$
-axis and
$Y$
-axis magnetometers can be achieved. The results show that the estimated value of the bias of the magnetometer under dynamic conditions can provide a reference for the initial magnetic heading angle measurement under static conditions. The experimental results prove the effectiveness of the proposed method, which provides a reference for the further improvement of the attitude MWD system.