底混响空间相关函数方法估计载体姿态

Method for vessel attitude estimation by spatial correlation function for bottom reverberation

在海底是起伏不大的非均匀薄层的假设条件下,建立了底混响空间相关函数模型。当混噪比较高时,模型中空间相关函数相位等于基元间垂向矢量与波数的乘积。对于平面阵而言,基元间垂向矢量是由于基阵载体姿态引起的。因此,可以给出底混响空间相关函数相位与载体横摇角和纵摇角之间的关系式。如果接收阵存在3个接收基元,它们对应平行四边形面积与对角线之比不小于半波长,那么可以通过解方程组的方法得到横摇角和纵摇角的确定解或优化解。由于相位模糊的存在, 解的范围是有限的。通过Fisher信息矩阵得到了这种方法姿态估计的Cramer-Rao下限。仿真实验和海试结果表明这种方法是可行的。

Under the assumption that the sea bottom is an almost-flat and randomly rough thin layer, a spatial correlation model for bottom reverberation was constructed. At high reverberation noise ratio, the phase of the spatial correlation function is the product of sound-wave number and the vertical vector between two hydrophones. In a nominally horizontal plane, roll and pitch bring on the vertical vector between the hydrophones. Then an equation including roll, pitch and the phase of the spatial correlation function was found. If a parallelogram can be constructed by 3 hydrophones and the ratios of its acreage to diagonals are not smaller than half of wavelength, roll and pitch could be obtained analytically or by optimal method. However, the ranges of roll and pitch are restricted because of the phase ambiguity. Using Fisher information matrix, the Cramer-Rao lower bound is obtained. Results from computer simulation and sea test prove the feasibility of the method.