Research On Rotary In-drilling Alignment Of Underground North-seeking Based On Triaxial MEMS Gyroscope

Gyro north seeker is a kind of instrument that uses inertia principle of gyroscope to seek north independently. It can realize all-weather, omni-directional, autonomous, rapid the direction measure, and also embrace the advantages of high precision, long time continuous work. Compared with traditional inertial sensors, MEMS(micro company mechanical systems, MEMS) gyroscope has many strong points like small volume, strong shock vibration, low cost, and high reliability. Therefore, the research of underground north-seeking system based on MEMS gyroscope is becoming a potential and long time of development direction. In view of the limitations of low measurement precision of the uniaxial MEMS gyroscope, complex subsurface environment, inapplicable of common north-seeking methods, the scheme of rotary in-drilling alignment was put forward to realize the underground north-seeking based on triaxial MEMS gyroscope. The main works are as follows:1. Expound the research background and significance of underground north-seeking based on triaxial MEMS gyroscope, and summarise the research status of north-seeking technology, including research status of compass north seeker, strapdown gyroscope north seeker and MEMS gyro north technology. The thesis elucidates the north-seeking technology and the principle of MEMS gyro, and respectively introduces the schemes of two-position north seeking, four-position north seeking, multi-position north seeking and continuous dynamics north seeking. Building on these, the research of rotary in-drilling alignment of underground north-seeking based on triaxial MEMS gyroscope is carried out, which has advantages of smaller drift, and low cost.2. Analyze the noise sources of triaxial MEMS gyroscope and collect about 1 hour static output data of triaxial MEMS gyroscope. Then the collected data are analyzed by Allan variance analysis method and the error coefficient of various noise sources are obtained, from which we know that quantization noise is the main noise source. With the help of dealing with the raw data of MEMS gyroscope by kalman filter, quantization noise coefficient and angle random walk coefficient are lowered by 1 ~ 2 orders of magnitude and other noise coefficients are slightly decreased. In consideration of the phenomenon that the triaxial MEMS gyroscope influenced by installation error, the improved calibration algorithm is put forward. By means of the improved calibration algorithm, measuring accuracy of MEMS gyroscope increases by about two orders of magnitude. For triaxial MEMS gyroscope zero drift influenced by temperature, the improved grey prediction model and least square method are carried out, and the mean absolute error of zero drift reduces to 0.4806 mV.3. Use triaxial MEMS gyroscope data to update attitude angle in real time by four-element method, and realize inversion control by the rotation control system, and compute the results of north-seeking, to implement the goal of ?in-drilling alignment?. Four experiments of rotary in-drilling alignment of underground north-seeking based on triaxial MEMS gyroscope are designed from different conditions. Through the comparison and analysis of experimental results, the maximum root mean square error and mean absolute error of north-seeking are 0.9067° and 0.9100° respectively. It has been verified that rotary in-drilling alignment of underground north-seeking based on triaxial MEMS gyroscope is feasible, which has high accuracy and good repeatability.