Attitude Algorithm And Error Analyse In Measure While Drilling (MWD) System Based On Fiber Optical Gyroscope (FOG)

The main function of the inclinometer is to measure the angle of inclination,azimuth and tool face angle. Currently the sensors used for drilling are accelerometers and magnetometers, because the magnetometer is vulnerable to electromagnetic interference caused by various factors, so must to install expensive non-magnetic collars to improve the accuracy. Optical fiber gyroscope (FOG) is considered as the alternatives of magnetometers when measured underground, which can significantly improve the measurement accuracy. And the method used inertial navigation to calculate the attitude and speed,. The system can achieve the real-time measurement which the magnetic sensor can not achieve.The paper firstly introduce the basic principle of measurement while drilling(MWD) ,inertial navigation system(INS).At the same time, I compare three methods: Euler Angle method, Orientation cosine method and quaternion method. At last , I choose the quaternion method .At the selection of the sensor, by introduce the quartz flexible accelerometer and optical fiber gyroscope and the inclinometer principle based on three-axis quartz accelerometer and three-axis optic fiber gyroscope by adopting inertial navigation method. We give the reason how to choose the sensor. Then give a detail formula contains the rough initial ,the accurate initial and calculations of the attitude by quaternion method based on inertial navigation method. Then we get the inclination angle,azimuth and tool face angle. Then analysis and compensation the systematic error and sensor error . Last completed the software which used to achieve the solution method and a number of peripheral functions, at the same time completed the system debugging. Both the theoretical analysis and the debug results show that the algorithm is properly designed, meet the requirements.