A low frequency tunable miniature inertial pendulum energy harvester for underwater mooring platforms is proposed. This apparatus is a horizontal rotational energy harvester with a rolling pendulum. Accordingly, it can harvest energy from the rotational base excitation associated with low frequency over the range of 0.1 Hz to 0.4 Hz, even with large amplitude. Moreover, the natural frequency can be adjusted by geometrical tenability, manipulating the angular orientation of the layout of the harvester, for enhancing energy harvesting. The energy harvesting performance of the device is investigated through numerical simulations and experimental measurements. The harvester proposed in this work can be utilized on miniature ocean platforms over a broad low-frequency range of 0.1 Hz–0.4 Hz.

Aiming at the typical problems of deploying sonar buoys in appointed sea area, this paper summarizes two problems existing in previous studies and puts forward a quick deployment method for sonar buoys detection under the overview situation of underwater cluster targets. Firstly, considering the influence of an underwater target course on target strength, the overlapping coefficient "buoy group" mode is introduced to deploy the array. And combining with the random distribution law of underwater targets in the exploration area, the mathematical optimization model for sonar buoys detection under the overview situation of underwater cluster targets is established. Then, the fitness function corresponding to the buoy deployment optimization model is defined, and the adaptive fireworks algorithm is used to solve the optimization problem for obtaining the sonar buoys deployment scheme. Finally, through the comparison and analysis of results for the seven group simulation experiments, the conclusions that are beneficial to improve the detection efficiency of the sonar buoy deployment are obtained. The proposed method can provide useful support for underwater cluster multi-target detection and the problem of counterattack underwater cluster multi-platform.

Aiming at the problem of using fixed-wing UAVs (clusters) for rapid coverage search of submarines in large-scale sea areas, the Strategy of using a single UAV for Coverage Searching in form of Dubins Curve(SCSDC) and the Strategy of using fixed-wing UAVs cluster for cooperative Coverage Searching in form of Parallel Intervals(SCSPI) were proposed after selective removal of concave points in complex irregular concave polygonal areas. Firstly, the cost mathematical model of cooperative search for multiple UAVs was established. At the same time, considering the limitation of turning radius of UAVs, a Dubins curve coverage search strategy was proposed to avoid search blind areas. Secondly, the judgment conditions of “edge length threshold” and “angle threshold” were introduced, and the method of selective removal of concave points was proposed to transform the irregular concave polygon area into a regular convex polygonal area. Then, in order to reduce the searching cost of UAV’s “Ω” turning type and improve the timeliness of its submarine search, a strategy of UAV cluster cooperative coverage search in the form of parallel interval was proposed. Finally, a comparative verification experiment was designed for the strategy of SCSDC and SCSPI in a complex irregular polygon search area. The simulation results show that selection of the two different area coverage search strategies needs to be determined according to actual combat requirements. The experimental results well verify the effectiveness and application scope of the two area coverage search strategies, and provide information support for subsequent anti-submarine action.

This study investigates the effectiveness of UUV formations during navigation to designated target areas. The research focuses on propeller-equipped UUVs and employs a computational fluid dynamics (CFD) methodology to analyze the hydrodynamic interactions among multiple UUV formations while en route to their targeted exploration areas. Utilizing the relative drag coefficients ($r_l \mathrm{a}\mathrm{n}\mathrm{d} r_f$) and static thrust ($R_{fleets}$) as analytical parameters, this paper defines the relative distances ($a$ and $b$) between UUVs within a formation and conducts a comparative analysis of the hydrodynamic performance between individual UUVs and formation configurations. The study establishes correlations between relative distances and the hydrodynamic performance of formations. The findings reveal the following: 1. For both the lead UUV and the following UUV within the formation, the $r_l \mathrm{a}\mathrm{n}\mathrm{d} r_f$ heatmaps exhibit two distinct regions: a thrust region and a drag region. Notably, these regions significantly overlap. The maximum $r_l$ is 31.23%, while the minimum $r_f$ is −20.9%, corresponding to relative distances of $a$ = 0.12 and $b$ = 1.5. Conversely, the minimum $r_l$ is −12.2%, while the maximum $r_f$ is 22.03%, with relative distances of $a$ = 1.1 and $b$ = 0.2; 2. An analysis of formation static thrust $R_{fleets}$ reveals that it can be up to 7% greater than the drag experienced by self-propelled UUVs when relative distances $a$ and $b$ are set to 1.1 and 1, respectively. This highlights the enhanced performance achievable through formation navigation. The results presented in this paper offer valuable theoretical insights into the optimal design of relative distances within UUV formations, contributing to the advancement of UUV formation navigation strategies.

This study evaluates the power harnessing performance of a two-directional inertial pendulum energy harvester for miniature underwater mooring platforms (UMPs). This novel harvester can achieve a dominant rotational motion under different parametrical excitations. The two-directional energy harvesting performance is investigated through vibration platform experiments over roll-pitch coupling excitations. The frequency ratio between the pitch and roll motion is about 2 to 1, the roll excitation frequency is over the range of 0.2–0.3 Hz, and the pitch amplitude is much lower than the roll amplitude. Experimental results indicate that the inclination configuration of the harvester can improve two-directional energy harvesting performance significantly with low-frequency vibration. Geometrical tunability through adjusting inclination configuration for the harvester can enhance the two-directional energy harvesting apparently. Four prominent phenomena of the two-directional energy harvesting performance are observed with the increasing load resistance. The motion state transformation of the inertial pendulum can result in dramatical jumps or drops in two-directional energy harvesting.

In order to extend the working time of underwater mooring platforms (UMPs) deployed in the East China Sea and explore the feasibility of energy harvesting from ocean, a laboratory experimental investigation on the energy extraction of a direct-driven Sealed Ocean Kinetic Energy Harvester (SOKEH) for UMPs was carried out. The present research investigates the influence of parameters including damping, inertia modification (ballasting), and coupled excitation motions on the performance of the SOKEH. Results indicate that this type of ocean kinetic energy harvester has two good performance resonant frequencies, 1 Hz (large amplitude) and 1.1 Hz (small amplitude). It is also demonstrated that the damping, inertia modification (ballasting), and coupled excitation motions significantly affect the energy extrication of the device. It is also shown that these parameters can be adjusted in response to the excitation motions to optimize the energy extrication. This work provides a preliminary step towards the development of a sealed ocean kinetic energy harvester for UMPs.