More credible communication reliability and more economical resource consumption are technological trends for multiple leaderless unmanned surface vehicles (USVs), while the realistic marine environment severely threatens system communication quality. Within this context, this paper investigates the leaderless formation control problem of USVs experiencing inter-vehicle communication interruptions. Concretely, by establishing the formation error system, the concerned leaderless formation control problem is tactfully transformed into the formation error consensus problem. Taking communication interruptions into account, a distributed controller is developed to achieve formation error consensus with intermittent inter-vehicle communications. Simultaneously, to endow the leaderless formation system with high economy, a novel intermittent dynamic interleaved periodic event-triggered mechanism (IDIPETM) is integrated into the controller synthesis, leaving the USVs to interact with each other only at preset periodic event-detecting instants. By assigning exclusive interleave bias to each vehicle, the proposed IDIPETM naturally eliminates the possibility that multiple USVs simultaneously broadcast information, thereby eradicating the communication congestion phenomenon inherent in the existing periodic event-triggered mechanisms. Finally, the theoretical analysis and simulation results are provided to evaluate the effectiveness and superiority of the proposed control scheme.

Growing demands for marine missions are driving the trend of maneuvering the large-scale fleet of electric marine surface vehicles (LSF-EMSVs) through obstacle-laden environments. Against this backdrop, this article investigates the collision-free distributed flocking control problem for LSF-EMSVs under the fully intermittent communication scenario. Existing collision-free works considering intermittent communication would like to assume that the transmission of relative position is continuous. In contrast, we discuss the case where the transmissions of all states are interrupted and use the term fully intermittent to distinguish it. To address this challenge, a weight-based adjacency matrix is developed to assess the communication connectivity and collision risk simultaneously. Accordingly, the collision avoidance analysis can be isolated from the dynamic layer, simplifying the control design. Then, a switching estimator based on intermittent relative positions is introduced for collision avoidance and communication maintaining, even on the period of communication interruption. Based on these designs, a completely distributed flocking control scheme is proposed for LSF-EMSVs, which is solely rely on the relative position and self course and velocities. Effectiveness of the proposed control schemes is demonstrated by theoretical analysis and semi-physical simulation results.

Underwater image stitching is a technique employed to seamlessly merge images with overlapping regions, creating a coherent underwater panorama. In recent years, extensive research efforts have been devoted to advancing image stitching methodologies for both terrestrial and underwater applications. However, existing image stitching methods, which do not utilize detector information, heavily rely on matching feature pairs and tend to underperform in situations where underwater images contain regions with blurred feature textures. To address this challenge, we present an improved scale-invariant feature transform (SIFT) underwater image stitching method. This method enables the stitching of underwater images with arbitrarily acquired images featuring blurred feature contours and that do not require any detector information. Specifically, we perform a coarse feature extraction between the reference and training images, and then we acquire the target image and perform an accurate feature extraction between the reference and target images. In the final stage, we propose an improved fade-in and fade-out fusion method to obtain a panoramic underwater image. The experimental results show that our proposed method demonstrates enhanced robustness, particularly in scenarios where detecting feature points is challenging, when compared to traditional SIFT methods. Additionally, our method achieves higher matching accuracy and produces higher-quality results in the stitching of underwater images.

The development of unmanned surface vehicles (USVs) technologies considerably promote the application of Internet of Things (IoT) in marine activities. However, frequently changed geometrical configurations and potential network congestion severely threaten system performance. Regarding this, this article proposes an anti-competition communication mechanism-based affine formation maneuver control (AFMC) scheme for the Internet of USVs. First, an auxiliary system is introduced to construct two-layer-based formation maneuver structure, i.e., localization layer and tracking layer. In the localization layer, an intermittent interleaved period event-triggered mechanism (IIPETM) is proposed such that each individual could enjoy interleaved communication periods. Then, by establishing a backstepping-based controller in the tracking layer, formation members will sail along a trajectory generated by the localization layer, thus forming the desired geometrical configuration. The proposed method can significantly reduce network throughput and improve communication efficiency even under intermittent network connectivity. Finally, theoretical analysis and simulations are performed to validate the feasibility of the proposed method.

Network’s communication mechanism and reliability are main factors that affect the maneuverability and robustness of networked unmanned surface vehicles (NUSVs). This article investigates event-driven affine formation maneuver control (AFMC) of NUSVs. Two synchronously occurring configuration maneuvers, i.e., position formation and attitude consensus, can be achieved under the event-driven AFMC in manner of discrete neighboring communication. Nevertheless, the communication channel will be simultaneously occupied by multiple packets when different nodes trigger their events at the same time. Worse still, the broadcasted packets may lose when inter-vehicle Euclidean distances are maneuvered beyond the allowable communication range, failing to achieve the pre-specified maneuvering requirement. Regarding this, by introducing a reference system for each vehicle, a novel dynamic interleaved periodic event-triggered mechanism (DIPETM) is subsequently explored to prevent NUSVs from communication competition. Based on this framework, an inner-dynamic variable determined by the conditional-prescribed event detecting period is firstly constructed, which is not only designed to optimize the triggering frequency, but also responsible for evaluating the secondary damage caused by random packet losses. Numerical simulations are conducted to illustrate the efficacy of this work. Note to Practitioners —The swarm of NUSVs often needs to operate for extended periods in complex environments, which may challenge its maneuverability and robustness. One expectation is the ability to maneuver the entire formation in a distributed manner, performing arbitrary configuration transformation. However, limited communication resources problems are not ignorable, especially when confronting unreliable network connectivity during frequent formation maneuver processes. The reasons lie in three aspects. Firstly, physical hardware prefers the data to be detected and transmitted in manner of discrete form. Secondly, the available communication channel is always limited, leading to only a few nodes being permitted to broadcast packets at the same time. Thirdly, random packet losses phenomenon may cover the significant broadcasted packets, resulting in system instability. Within this context, we design a novel DIPETM based AFMC scheme to solve the aforementioned problems while satisfying the formation maneuver expectation.

In this paper, a robust path-following control strategy is proposed to deal with the path-following problem of the underactuated autonomous underwater vehicle (AUV) with multiple uncertainties and input saturation, and the effectiveness of the proposed control strategy is verified by semi-physical simulation experiments. Firstly, the control laws are constructed based on the traditional backstepping method; the multiple uncertainties are treated as lumped uncertainties, which can be estimated and eliminated by the employed extended state observers (ESOs). In addition, the influence of input saturation can be compensated by the designed auxiliary dynamic compensators. Secondly, to simplify controller design and address the “complexity explosion”, two command filters are used to obtain the estimated value of the unknown sideslip angular velocity and the desired yaw angular acceleration, respectively. Finally, the superiority and robustness of the proposed control strategy are verified through computer simulation. A semi-physical simulation experiment platform is built based on the NI Compact cRIO-9068 and PLC S7-1200 to further demonstrate the effectiveness of the proposed control strategy.