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The new way of offshore operation and maintenance based on unmanned ships has outstanding advantages. Aiming at the problem of lack of overall understanding of the complex environment above and under the water surface during the operation and maintenance of unmanned ships, a stitching and fusion technology of overwater and underwater visual images for unmanned ships is proposed. The software and hardware framework of the overwater and underwater visual image fusion system is constructed, the image processing methods in different environments are defined, and the accurate acquisition of obstacle information is realized. In the two experimental scenarios, the stitching accuracy of the obstacle model based on an extended neighborhood method can reach more than 85% within the obstacle distance of 8m and more than 80% within the obstacle distance of 14m. An image-driven Frustum-PointNets detection algorithm is proposed to obtain comprehensive obstacle avoidance information. In addition, the average accuracy of the three-dimensional detection of the algorithm is up to 91.40%. These results are significant and have a good reference value, as it demonstrates that the stitching and fusion method can effectively obtain the comprehensive information of overwater and underwater objects for unmanned ship.

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The safety of unmanned ship berthing is of paramount importance. In order to explore the influence of wind and wave coupling, a berthing computational fluid dynamics (CFD) model was established, and the characteristics of speed field, pressure field, and vortex have been obtained under different speed, wind direction, and the quay wall distances. The results show that the total resistance of the hull against the current can be about 1.60 times higher compared to the downstream resistance, water flow resistance is the dominant factor, accounting for more than 80% of the total resistance. When changing the distance between ship and shore at fixed speed, the results found that the torque is small, but the growth rate is very large when driving below 2 m/s, and the torque growth rate is stable above 2 m/s. Based on the established coupling model, a multi-factor berthing safety study is carried out on an actual unmanned ship. The results show that when the speed increases from 4 m/s to 12 m/s, the curve slope is small, the resistance increases from 3666 N to 18,056 N, and the rear slope increases. The pressure increases with the speed, and when the speed is 24 m/s, the maximum pressure is up to 238,869 Pa. When the wind speed is fixed, the vertical force of the unmanned ship increases first and then decreases to zero and then reverses the same law change, and the maximum resistance is about 425 N at the wind angle of about 45 degrees; At 90 degrees, the maximum lateral force on an unmanned boat is about 638 N. The above results can provide control strategy for unmanned ship berthing safety, and provide theoretical basis for unmanned ship route planning and obstacle avoidance, safety design, etc.

According to the deficiencies of remote calibration mode based on material object reference, a new model of a remote calibration system for frequency based on in-place benchmark is introduced, which is made of a calibration subsystem on the spot and a remote management subsystem. The key technology of some key problems for the remote calibration system is particularly discussed, including the time and frequency benchmark receiving module based on global positioning system (GPS), frequency comparison based on a phase method, frequency division based on dual high-frequency phase locked loop (PLL), and remote calibration based on the web. The results show that the system possesses some characteristics, such as high precision, good versatility, and no limitation of time and place.