表层海水中声纳定位的声速问题

Sound Velocity Problem of Undersea Positioning in Up Ocean

海水温盐跃层和深度方向上的梯度变化,导致海水声速的跃层和梯度变化,这种变化既有系统性,又有随机性,声速的不确定性导致水下定位系统的不稳定性问题。本文针对浅水水下定位系统中声速大小和声线弯曲问题进行研究,提出了用于几何法定位的平均海水声速线估计定位法。另外,基于射线声线理论构成的距离观测方程和时间观测方程都是不可导的非线性方程,该方程组的最小二乘问题是一类特殊的非线性最小二乘问题。本文提出了先分组迭代、后统计分析的"两步法"实现对这类特殊非线性最小二乘问题的求解。

Thermocline and halocline of sea water and its varying gradient cause isocline and varying gradient of sound velocity,which have both systematic and random variations.The random variation of sound velocity,which can not be expressed by an analytic function,is the most significant reason that leads the stability problem of underwater positioning system.For most geometry positioning systems,a method that takes the mean sound velocity as a parameter of system is suggested,which can greatly improve the performance,especially in the shallow water.Based on acoustic ray theory,both the distance equation and the time equation are not differentiable nonlinear equations.The adjustment of this kind of equations is so called Special Nonlinear Least Square problem（SNLS）.By Dividing all equations into sub groups,iterating in sub group,and analyzing the results,the resolution of SNLS problem can be figured out by suggested ＂two-step＂ approach.