直升机吊舱姿态变化对电磁场测量的影响规律及其校正方法研究

A study on the effect of bird′s attitude on helicopter EM data and the correction method

在直升机航空电磁法中,吊舱的姿态变化(如摆动、倾斜、偏航等)会使磁偶极子相对正常飞行时在方向和位置上发生变化,使得接收线圈处的电磁响应产生误差.传统的基于重叠偶极模型的姿态校正方法只考虑了磁偶极子方向上的变化,而忽略了磁偶极子位置上的变化,因此校正效果受到了一定的限制.本文分析了五种不同电性参数的均匀半空间模型中线圈系在姿态变化前后的电磁响应比,进而提出了一种新的姿态校正方法,该方法综合考虑了磁偶极子方向和位置变化对姿态变化前后的电磁响应比的影响,并推导出总姿态变化电磁响应比与方向和位置单独变化时电磁响应比的乘积近似成固定比例关系.为了验证本文提出的总姿态校正方法,本文分别使用本方案及基于重叠偶极模型的姿态校正方法对五组具有代表性的合成数据进行了校正.对比结果表明,本文的总姿态校正方法较之重叠偶极姿态校正方法能较大地提高校正精度.

The attitude changes of the bird can influence both the direction and position of the magnetic dipole which may introduce errors into helicopter electromagnetic （EM） data. The traditional attitude correction methods using a superposed dipole model only consider the change of direction but ignore the position variation, so limit correction effects. We employ five models with different electrical parameters and calculated the EM response ratios before and after attitude change. We further propose a new attitude correction method which takes both the changes of direction and position before and after attitude change into account. We deduce an approximately constant relationship between the EM response ratio of the total attitude effect and the product of the EM response ratios when the direction effect and position changes separately. In order to test the new total attitude correction method, this paper employ five sets of synthetic data for correction using the superposed dipole correction method and our scheme, respectively. Thecomparison indicates that the total attitude correction method suggested in this paper is able to generate a better correction result than the superposed dipole method.