Path Optimization of Underwater Glider Based on Depth-averaged Current Prediction Model
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摘要: 随着水下滑翔机在海洋调查及声学探测领域的广泛运用, 精准、高效控制其路径对精细化海洋观测至关重要。针对水下滑翔机受海流影响产生较大偏航差问题, 采用最小二乘支持向量机法(LSSVM)预测深平均流, 以单剖面偏航差最小为目标函数, 以实际航向与计划航向夹角不超过一定值为约束条件, 构建非线性约束极值模型, 确定预设剖面最优目标航向及出水点坐标, 从而实现路径优化目的。采用“海燕-II”型水下滑翔机历史数据进行验证, 结果表明: 1) LSSVM法预测深平均流准确性较高, 但当局部流向有明显变化时预测效果不佳, 取前3个剖面数据作为训练样本时预测效果更好; 2) 采用文中方法优化后, 水下滑翔机路径更稳定, 各剖面偏航差平均为281.1 m。Abstract: With the wide application of underwater gliders in the field of ocean surveying and underwater acoustic detection, accurate and efficient control of their path is important for refined ocean observation. In view of the problem that the underwater glider has a large path deviation due to the influence of current, the least-squares support vector machine (LSSVM) method is used to predict the depth-averaged current. The minimum path deviation of a single profile is taken as the objective function, with the constraint condition that the difference between the actual and planned heading does not exceed a certain value. A nonlinear constraint extremum model is constructed, and the optimal target heading and outlet point coordinate are calculated, to realize the goal of path optimization. The historical data of the Petrel-II glider are used for verification, and the following results are obtained. 1) The LSSVM method has high accuracy in predicting the depth-averaged current, however, its prediction accuracy is poor when the local current direction changes significantly. The prediction accuracy is higher when the first three historical profile data are used as training samples. 2) Following path optimization with the proposed method, the path of the glider is more stable, and the average path deviation is 281.1 m.
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表 1 水下滑翔机剖面信息统计表
Table 1. Profile information statistics of underwater glider
统计要素 最小值 最大值 平均值 标准差 运行时间/min 143.00 163.00 151.90 8.70 静水航速/(m/s) 0.41 0.69 0.54 0.05 实际航速/(m/s) 0.13 0.95 0.47 0.16 深平均流/(m/s) 0.01 0.53 0.28 0.12 表 2 深平均流预测误差统计
Table 2. Error statistics of predicted depth-averaged current
深平
均流剖面数 均方根误差 系数 最小
误差最大误差 误差均值 流速
/(m/s)3 0.016 0.992 −0.046 0.077 0.000 8 4 0.018 0.988 −0.056 0.057 0.001 1 5 0.020 0.986 −0.059 0.059 0.001 0 6 0.022 0.983 −0.068 0.068 0.001 2 流向
/(°)3 8.200 0.990 −41.500 51.600 0.200 0 4 10.200 0.988 −44.100 75.100 0.500 0 5 10.100 0.986 −40.300 70.400 0.500 0 6 13.000 0.976 −66.700 75.900 0.300 0 -
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