基于椭球拟合的矿用钻孔测斜仪罗差快速校准方法

Magnetic deviation fast calibration method of borehole inclinometer for coal mine based on ellipsoid fitting

工作面地质透明化是煤矿井下工作面智能开采的关键技术之一,透明化工作面所需地质信息的采集依赖矿井地球物理勘探、矿井钻探、随采监测及回采揭露.煤矿井下各种钻孔的轨迹数据是建立精准地质模型的基础数据,采用矿用钻孔测斜技术可以获得钻孔轨迹数据.目前矿用钻孔测斜仪均采用基于地磁场和重力场测量的测斜技术,即采用三轴磁强计和三轴加速度计组成硬件系统,采用泊松模型建模加速度计和磁强计的误差源,利用无磁转台多位置标定法求解误差系数进行误差补偿,通常可以保证令人满意的测量精度.然而,矿用钻孔测斜仪在煤矿井下复杂的硬磁和软磁环境中长期使用,会导致磁强计的罗差发生变化从而测量精度下降,考虑到经济和时间等成本,矿用钻孔测斜仪的快速校准变得必要而迫切.由于加速度计误差系数不受磁影响,无需二次校准,矿用钻孔测斜仪校准问题就变成三轴磁强计的罗差校准问题.为实现三轴磁强计的罗差校准,从描述硬磁和软磁干扰的泊松模型出发,分析了含有误差的测量值Hbm与真实磁场向量Hb之间的关系,推导了利用椭球拟合实现磁强计误差补偿的具体算法,开发了矿用测斜仪地面快速校准装置,并进行了数值模拟和实验验证.数值模拟表明该算法准确、可信,实验结果表明借助于该校准装置和误差补偿算法无需依赖专用的无磁转台就可以方便、快捷地实现测斜仪的自动校准.采用该方法校准后测斜仪的误差从2.8°降低到0.9°以内,即使在大倾角情况下也能保持较好的精度,可靠地保障了煤矿井下钻孔轨迹测量的准确性.

The geological transparentizing of mining work face is one of the key technologies for intelligent mining of fully-mechanized coal mining face in coal mine. The collection of geological information required by the transparentizing mining work face depends on geophysical exploration, mine drilling, monitoring while coal mining and mining reveal. The track data of various boreholes in coal mine is the basic data for establishing accurate geological model. Borehole trajectory data can be obtained by means of mining borehole inclination measurement technique. Current mine borehole inclinometer are made based on the survey of geomagnetic field and gravity field measurement technology, which use three axis magnetometer and three-axis accelerometer as hardware system, and use the Poisson model modeling error of accelerometer and magnetometer source, and use the method of multi position calibration relied on nonmagnetic turntable to solve error coefficient of error compensation, it can ensure satisfactory measurement accuracy. However, the mine borehole inclinometer has been used for a long time in the complex hard magnetic and soft magnetic environment in coal mine, which will lead to variation of magnetometer compass deviation and thus decrease measurement accuracy. Considering the cost of economy and time, the fast calibration of the mine borehole inclinometer becomes necessary and urgent. Because the error coefficient of the accelerometer is not affected by magnetic field and no secondary calibration is needed, the calibration problem of the borehole inclinometer for mining becomes the calibration problem of compass deviation of triaxial magnetometer. To realize three-axis magnetometer compass deviation calibration, Poisson model for describing the hard magnetic and soft magnetic interference is studied, and the relationship between the measured value with errors H^b_m and the real magnetic field vector H^b_m is analyzed. Then an algorithm for error compensation of magnetometer by ellipsoid fitting is derived, and a ground fast calibration device for mining inclinometer is developed. Finally, a numerical simulation and experimental verification was carried out. The numerical simulation shows that the algorithm is accurate and reliable, and the experimental results show that the automatic calibration of the inclinometer can be realized conveniently and quickly by means of the alignment device and error compensation algorithm without relying on the special nonmagnetic turntable. With this fast calibration method, error of the inclinometer is reduced from 2.8° to less than 0.9°, which can maintain good accuracy even under the condition of large inclination. This method effectively ensures the accuracy of borehole track measurement in underground coal mine.