自主式無人水面船隊觀測海灣流場之點量測與積分量測估測誤差比較研究

Comparison of Bay Current Estimations using Point and Integral Measurements Surveyed with a Fleet of Autonomous Surface Vehicles

張理源(Li-Yuan Zhang)

指導教授 ： 郭振華

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202000068

摘要

本研究利用多載具進行海灣內的流速量測，透過比較兩種感測器估算得到的模型誤差作為根據，進而探討自主水面載具編隊於望海巷灣的建圖成效。在本文中，流速的觀測手段，可藉由常見的船載式聲學都卜勒流速剖面儀（Acoustic Doppler Current Profilers , ADCP）對量測點進行精準的流速測量或者藉由海洋聲學層析成像（Ocean acoustic tomography , OAT）遙測海洋內部的大面積區域。藉由開放邊界模態分析可以建立僅具備幾何條件的流場模態，並以對流場模態係數的估算得以適當的內插與過濾流場。基於開放邊界模態分析作為觀測模型，透過卡爾曼濾波器將單點流速量測的模型與面域內部流速遙測的模型進行狀態更新，更新後的地圖可得到更低不確定性的地圖，藉由2017年於基隆望海巷海域，以一編組隊伍配備有一台ADCP與聲學層析儀所搜集之實驗數據進行分析，融合由該次資料估算的流場模型作為模擬所需的流場，在考量載具的耗能下設計載具的航行模擬，並以相同的條件比較望海巷灣內點量測與線量測之差別。由結果可以得到線量測具有比點量測更小的誤差。

關鍵字

開放邊界模態分析 ； 水聲層析法 ； 海流建圖 ； 狀態更新 ； 無人船舶 ； 誤差分析

並列摘要

This study investigates measurement of the current field in the bay using multi-vehicles in a formation. Observations of the current can be performed by the point measurement with the shipboard Acoustic Doppler Current Profilers (ADCP) or remote-sensing a velocity field by Ocean Acoustic Tomography (OAT). Open-boundary modal analysis (OMA) is employed to establish a set of modes constrained by geometric profiles of the bay, and the currents field can be interpolated and filtered by the estimated mode coefficients. Based on OMA as the observation matrix, an optimal state estimator is used to fuse the status of the ADCP and the OAT estimations. The updated map is a map with lower uncertainty. Based on the analysis of experimental data collected using an ADCP and OAT in WangHiXiang Bay in 2017, the current model estimated from the experimental data was used as a ground truth for the comparison of estimation error produced by the ADCP and OAT. Considering the energy consumption, and observation time, a fleet of autonomous surface vehicle (ASVs) that carries OAT will result in less estimation error in current measurements compared to the fleet that carries ADCP.

並列關鍵字

open-boundary modal analysis ； ocean acoustic tomography ； current mapping ； state update ； autonomous surface vehicle ； error analysis

參考文獻

W. Munk, and C. Wunsch. "Ocean acoustic tomography: A scheme for large scale monitoring." Deep Sea Research, vol. 26A, pp. 123-161, February 1979.

C.-F. Huang, Y.-W. Li, and N. Taniguchi, "Mapping of ocean currents in shallow water using moving ship acoustic tomography." The Journal of the Acoustical Society of America, vol. 145, pp. 858-868, February 2019.

B. L. Lipphardt, A. D. Kirwan, C. E. Grosch, J. K. Lewis and J. D. Paduan, "Blending HF radar and model velocities in Monterey Bay through normal mode analysis." Journal of Geophysical Research, vol. 105, No. C2, pp.3425-3450, February 2000.

F. Lekien, C. Coulliette, R. Bank and J. Marsden, "Open‐boundary modal analysis: Interpolation, extrapolation, and filtering." Journal of Geophysical Research, vol. 109, C12004, December 2004.

D. M. Kaplan and F. Lekien, "Spatial interpolation and filtering of surface current data based on open‐boundary modal analysis." Journal of Geophysical Research, vol. 112, No. 1, C12007, December 2007.