Path planning is a prerequisite for autonomous underwater vehicles to perform tasks autonomously. Many shortest distance algorithms are applied, and ocean currents are ignored to plan a short path in distance, which is usually time and energy consuming. In fact, the favourable currents can be exploited while avoiding the opposite ocean flows. Based on the bioinspired neural network architecture, this paper proposes a novel dynamic neural network model to plan the time-saving path in ocean current environments. After that, the path is smoothed by the B-spline algorithm. Analysis of the model shows that it can find out the minimum time path. Many simulations have also been introduced to test the effectiveness of the proposed model, showing good results. The dynamic neural network model has no learning procedure and can run in parallel. It has the advantages of loose parameter restrictions and wide spreading of neural activities. In addition, it has also been proven to be suitable for strong ocean currents.

Task assignment is an important research topic in multiple AUV (Autonomous Underwater Vehicle) cooperative working system. However, many studies concentrate on minimizing total distance of AUVs serving targets at different locations, and mostly do not pay attention to workload balance among inhomogeneous AUVs. What is more, most of them do not think of the effect of ocean current while distributing tasks. To solve these problems, a novel dual competition strategy based on SOM (self-organizing map) neural network is put forward. An AUV makes use of surplus sailing distance to a target when it competes with others for engaging the target. In order to fulfill a balanced task assignment among AUVs, a task balance coefficient is also proposed. Meanwhile, a hybrid path planning approach is applied to guide AUVs to reach their targets safely. The good performance of the proposed algorithm for distributing tasks among AUVs is demonstrated through simulation studies. From the comparison study of SOM algorithm, Hungarian algorithm, k-means algorithm and the proposed dual competition strategy, it can be found that the task assignment with the proposed strategy is more rational and fair.

Encircling and capturing foreign unmanned underwater vehicles (UUVs) by multiple defensive UUVs has recently attracted increasing attention. Previous studies using a self-organized map neural network for target allocation suffer from team imbalance and heavy communication burden problems. In addition, the cooperation of defensive UUVs in a team is insufficient. Aiming at these problems, this article forms balanced encircling teams with the estimated travel time acquired in local communication through distributed auction. The quantum particle swarm optimization algorithm is used to optimize the initial encircling circle for fast encirclement, and then dynamically shrink the encircling circle to improve cooperation. Finally, the encirclement control of the defensive UUV is achieved by a fast marching model predictive velocity planner and a proportional–integral controller. In real multi-island waters, this article adopts the proposed algorithm to simulate the encircling of foreign UUVs, which have the same speed as that of defensive UUVs. The simulation results show that the algorithm has advantages in shortening the chasing distance and improving the encircling efficiency. A pool validation experiment is also conducted to verify the effectiveness of the algorithm.

The call for green shipping is increasing, and the reduction of greenhouse gas emissions from ships becomes more and more important. Traditional ship energy efficiency monitoring is based on the noon reports, which are susceptible to human error and have a time delay. Many ship energy efficiency monitoring systems have been designed and developed, but they usually cannot send data to the shore in time. In order to identify abnormal fuel consumption in time, this paper realizes a big data collection system for ship energy efficiency monitoring based on the BeiDou System. The system installed on two sister container ships has already collected a lot of data. Big data analysis methods, such as principal component analysis (PCA) and correlation analysis, are applied in the system to realize data visualization and analysis. Using PCA, it turns out that the shaft power of the main engine is related to a certain ship speed, which is also affected by load and weather conditions, and is the biggest factor in determining fuel consumption. To realize the assessment of hull fouling and the optimization of ship trim, a useful physics-based analysis is proposed. The analysis shows that the fouling of ship body greatly increases its resistance. Our analysis method can also find the best trim under specific loading condition. All these points are important for reducing fuel consumption and improving ship efficiency.

Path planning for autonomous underwater vehicles (AUVs) is a key research focus in the marine domain, requiring consideration of the underwater environment’s complexity and the efficiency of the planning algorithms. Firstly, this paper uses the grid method to construct a realistic ocean terrain for the underwater environment and incorporates obstacles and ocean currents. Also, the AUV’s movement strategy and posture are illustrated and constrained by a visual search strategy. Secondly, an improved artificial jellyfish search (IJS) algorithm is to overcome the drawbacks of low convergence accuracy and adaptability of the basic algorithm. The IJS algorithm determines the optimal path point by optimizing the objective function. This objective function not only takes into account factors such as path navigation time and path safety but also designs an ocean current disturbance model, which facilitates the AUV to successfully reach the target point while avoiding obstacles and strong side currents. Finally, the optimal smoothed path is output using a cubic spline midpoint interpolation method. Multiple simulation experiments are carried out on the constructed environment model. The comparison results show that the IJS algorithm with a short running time has the optimal time cost and ocean current penalty cost for the planned path. In addition, the IJS algorithm is also shown to be adaptable in the field of multi-AUV movements.