Pendulum motion in airborne HEM systems
Pendulum motion in airborne HEM systems
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DOI：
10.1071/eg06355
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发表时间：
2006-12
影响因子：
0.9
通讯作者：
A. Davis;J. Macnae;T. Robb
中科院分区：
文献类型：
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作者：
A. Davis;J. Macnae;T. Robb
直升机电磁系统通常在拖曳的鸟中具有发射器-接收器线圈对，其在飞行中表现为复杂的复摆。被拖曳的鸟的摆运动不仅在测量信号中产生几何和感应效应，而且它们还可能导致高度误差。可以从视频记录和GPS位置观察到拖鸟摆的振荡，最有用的是将其分为两种模式：一种是沿行进方向（直线），另一种是垂直于行进方向（交叉线）。我们分析了电磁和高度数据的一个RESOLVE调查的Chowilla洪泛平原，伦马克附近，南澳。拖曳鸟的顺线和跨线运动具有不同的振荡频率。引起被拖鸟俯仰的直线运动和产生横摇的交叉线运动在数据中产生系统误差，在无量纲同相除以归纳极限（R/G）域中很容易看出。我们表明，由于这两种模式的钟摆运动的鸟摆动是负责高度误差，和滤波器设计使用所观察到的振荡周期可以在很大程度上纠正的R/G域数据。滤波过程不需要比通常从典型电磁勘测提供的测量更多的测量。
Helicopter electromagnetic systems typically have a transmitter-receiver coil pair in a towed bird that, in flight, behaves as a complex compound pendulum. Pendulum motions of the towed bird create not only a geometric and inductive effect in the measured signal, but they may also contribute to altitude error. The oscillation of the towed-bird pendulum can be observed from both video recordings and GPS positions and is most usefully broken down into two modes: one in the direction of travel (in-line) and one perpendicular to the direction of travel (cross-line). We analyse the electromagnetic and altitude data for a RESOLVE survey on the Chowilla flood plain, near Renmark, South Australia. The in-line and cross-line motions of the towed bird are shown to have different frequencies of oscillation. In-line motions, which cause pitching of the towed bird, and cross-line motions, which generate roll, create a systematic error in data easily evident in the dimensionless in-phase divided by inductive limit (R/G) domain. We show that the bird swing due to both modes of pendulum motion is responsible for altitude error, and that a filter designed to use the observed period of oscillation can largely correct the R/G domain data. The filtering process does not require any more measurements than are usually provided from a typical electromagnetic survey.