考虑算法的实船试航船速测量不确定度分析

实船试航中影响船速测量结果的因素很多,对其进行测量不确定度分析时应考虑的不确定度来源也有很多。采用“测量不确定度表示指南”规定的方法,将船速算法作为不确定度源,对其测量结果进行了不确定度分析。不确定度分析以某油船为例,分别考虑了实际航速平均法和逐点法两种算法,并对两种算法得到的结果作了讨论。

Uncertainty Analysis of Ship Velocity Measurement in Sea Trial Considering Ship Velocity Algorithm

There are many factors which affect the measurement result of ship velocity and many uncertainty sources when analyzing the uncertainty in ship velocity measurement.This article briefly introduces "Guide to the Expression of Uncertainty in Measurement"(GUM).Comparing with the uncertainty analysis method of ITTC,the GUM method is all-purpose and effective.Using the GUM method,ship velocity algorithm is taken as the uncertainty source,and the uncertainty in ship velocity measurement is analyzed.Setting up an example of a large oil tanker,two velocity computing methods that is "average of each actual speed"and "point by point",are used in this paper.These two methods need the data from DGPS,so the precision of the DGPS receiver,the quality of signal from GPS satelite and signal from difference station are carefully considered.As for "average of each actual speed " method,the measuring error of each actual speed given by DGPS is the uncertainty source.The standard uncertainty of each actual speed and its effective degrees of freedom are calculated.Assuming the confidence level is 95%,the combined standard uncertainty and the expanded uncertainty of ship velocity are computed.As for "step by step " method,the measuring errors of position and time given by DGPS are the uncertainty source.The standard uncertainty of position and time and their effective degrees of freedom are calculated.Assuming the confidence level is 95%,the combined standard uncertainty and the expanded uncertainty of ship velocity are also computed.The uncertainty evaluation results of the two methods are compared.