固定翼航空电磁系统的线圈姿态及吊舱摆动影响研究与校正

固定翼时间域航空电磁探测系统在实际飞行测量过程中,发射线圈、接收线圈姿态和吊舱摆动状态不断变化,在测量数据中引入如发射磁矩方向、接收分量方向以及系统收发距等参数的误差,影响数据反演成像效果.本文基于固定翼时间域航空电磁正演理论,利用姿态变换,引入发射线圈、接收线圈双旋转矩阵;根据发射、接收线圈相对位置的几何关系,求得摆动格林张量;推导了任意姿态角度以及任意摆动角度情况下的固定翼航空电磁响应三分量计算表达式.通过层状大地模型的仿真计算,分别研究了发射、接收线圈各姿态以及吊舱摆动状态对航空电磁响应的影响,得出发射线圈、接收线圈俯仰旋转和吊舱同向摆动对系统电磁响应影响最强;仿真分析了实际测量中,三种角度同时存在情况下,航空电磁响应的定量变化规律.在此基础上,讨论了响应系数与大地电导率的关系,同时给出基于响应系数的固定翼航空电磁系统线圈姿态和摆动状态校正方法,准二维层状大地模型反演结果表明,校正后数据的反演精度提高了33.1%.

Study on influence and correction of coil attitude and bird swing for the fixed-wing time-domain electromagnetic system

During surveys of the fixed-wing time-domain electromagnetic system, the changing transmitter and receiver coil attitude and bird swing can introduce the system parameter errors into the survey data including the direction of transmitter magnetic moment, the component and position of receiver coils, as well as the horizontal distances between transmitter loop and the receiver coils, consequently affecting the inversion results. Based on the forward modeling of the fixed-wing time-domain electromagnetic, this paper suggests the rotation matrix of the transmitter and receiver coil according to the attitude variation algorithm, and obtains the swing Green's tensor by using the relative position between transmitter loop and receiver coils. Then the expression of three-component electromagnetic response with arbitrary attitude and swing angle is derived. The electromagnetic response in respect to the bird rotation and swing is studied. The simulation results indicate that the pitch of the transmitter and receiver coil and the in-line swing have the greatest influence on the electromagnetic response. Therefore, the variation of the electromagnetic response when the in-line swing angle and the pitch of the transmitter and receiver coil coexist is analyzed. On this basis, the relationship between the response coefficient and earth conductivity is discussed. Meanwhile, the correction of attitude and bird swing of the fixed-wing airborne electromagnetic system is conducted. The inversion results of a quasi-two-dimensional layered earth model show that the accuracy after correction is enhanced by 33.1%.