One of most primitive problems by unmanned underwater vehicle intelligent swarm (UIS) is coordination control, which has a great significance for realization of target hunting with great performance of efficiency and robustness. Existing studies concentrate on behavior-based centralized or distributed control approaches with the prior knowledge and mostly do not elaborately consider behavior conflicts and constraint differences. Therefore, a novel behavior-driven coordination control framework including topology architecture and swarm control which is inspired by immune mechanism, is investigated for target hunting of heterogeneous UIS under unknown and uncertain environment in this paper. For topology architecture, a hybrid non-central distributed topology is developed as a novel immune-inspired architecture to regulate agents with self-organizational and fault-tolerance features. For swarm control, a dual-layer switching control scheme composed by global control and local control, is proposed to drive behaviors via behavioral-intensity, the trigger of switching is when the target is detected. The global control approach is employed to search target, in which two constraints of energy consumption and healthy-state are considered to achieve good operational reliability. While the local control approach is developed to form the dynamic alliance of tracking and capturing, in which behavioral-intensity control strategy for behavior aggregation and decision-making control strategy for behavior selection are respectively designed to avoid behavior conflicts. Simulation results demonstrate that proposed framework can accomplish hunting under various situations such as hunter agent is random or fixed distribution, and the number of targets asynchronously appears. It is confirmed that our framework is capable of achieving the target hunting under unknown and uncertain environment with greater efficiency and robustness.

In the neuroimaging and brain mapping communities, researchers have proposed a variety of computational methods to map functional brain networks (FBNs). Recently, it has been proven that deep learning (DL) can be applied on functional magnetic resonance image (fMRI) data with superb representation power over the traditional machine learning methods. However, due to the lack of labeled data and the high dimension of fMRI volume images, DL suffers from overfitting in both supervised and unsupervised training processes. In this work, we proposed a novel generative model: deep variational autoencoder (DVAE) to tackle the challenge of insufficient data and incomplete supervision. The experimental results showed that the representations learned by DVAE are interpretable and meaningful compared to those learned from well-known sparse dictionary learning (SDL). Besides, the organization of some FBN patterns derived from different layers in DVAE was observed in a hierarchical fashion. Furthermore, we showed that DVAE has better performance on small dataset over autoencoder (AE). By using attention deficit hyperactivity disorder (ADHD)-200 dataset as our test bed, we constructed a DVAE-based modeling and classification pipeline in which all subjects’ functional connectivities estimated by FBNs were taken as input features to train a classifier. Finally, the results achieved by our pipeline reached state-of-the-art classification accuracies on three ADHD-200 sites compared with other fMRI-based methods.

Extracting useful features from ship-radiated noise can improve the performance of passive sonar. The entropy feature is an important supplement to existing technologies for ship classification. However, the existing entropy feature extraction methods for ship-radiated noise are less reliable under noisy conditions because they lack noise reduction procedures or are single-scale based. In order to simultaneously solve these problems, a new feature extraction method is proposed based on improved complementary ensemble empirical mode decomposition with adaptive noise (ICEEMDAN), normalized mutual information (norMI), and multiscale improved permutation entropy (MIPE). Firstly, the ICEEMDAN is utilized to obtain a group of intrinsic mode functions (IMFs) from ship-radiated noise. The noise reduction process is then conducted by identifying and eliminating the noise IMFs. Next, the norMI and MIPE of the signal-dominant IMFs are calculated, respectively; and the norMI is used to weigh the corresponding MIPE result. The multi-scale entropy feature is finally defined as the sum of the weighted MIPE results. Experimental results show that the recognition rate of the proposed method achieves 90.67% and 83%, respectively, under noise free and 5 dB conditions, which is much higher than existing entropy feature extraction algorithms. Hence, the proposed method is more reliable and suitable for feature extraction of ship-radiated noise in practice.

This article is concerned with the trajectory tracking control problem for small unmanned underwater vehicles (UUVs) with dynamic uncertainty, external disturbance, input saturation, and even unmeasured velocities. To guarantee transient and steady-state prescribed performance, a finite-time prescribed performance control (PPC) method is designed for the boundness and convergence of tracking errors, where the desired settling time can be chosen in advance to obtain a fast convergence, instead of existing exponential-time and asymptotic-time convergence. To attenuate the adverse effects of saturation constraints, an energy-efficient smoothing auxiliary system governed by implementing switching functions is formulated to automatically achieve the dynamic compensation, wherein a discontinuous singularity can be completely avoided. Then, both full-state and output-feedback control schemes are developed by incorporating neural networks and first-order filtering into backstepping procedures, and particularly a high-gain observer is employed to recover unmeasured velocities. The closed-loop system is proven to be uniformly ultimately bounded (UUB). Finally, simulation and experimental results validate the effectiveness of the proposed methods.

Although a software defined network (SDN) realizes the flexible configuration and centralized control of network resources, there are potential security risks and challenges. Network security situation awareness (NSSA) technology associates and integrates multi-source heterogeneous information to analyze the impact of the information on the whole network, and network security situation assessment can grasp the network security situation information in real time. However, the existing situation assessment methods have low assessment accuracy, and most of the studies focus on traditional networks, while there are few situation assessment studies in the SDN environment. In this paper, by summarizing the important index parameters of SDN, a network security situation assessment model based on the improved back propagation (BP) neural network (based on the cuckoo search algorithm) is proposed, and the step factor of the cuckoo search algorithm (CS) was improved to improve the search accuracy. The model maps the situation elements to the layers of the neural network, and optimizes the weights and thresholds of the BP neural network through the cuckoo search algorithm to obtain the global optimal solution; it finally realizes the purpose of situation assessment and the comprehensive rating of the SDN environment. In this paper, the evaluation model was verified on the network set up in Mininet. The experimental results show that the situation assessment curve of this model is closer to the real situation value, and the accuracy rate is 97.61%, with good situation assessment results.

This article investigates the singularity-free practical fixed-time fault-tolerant control problem for unmanned underwater vehicles (UUVs) with input and output constraints. Firstly, with the aid of fuzzy logic system (FLS) and fixed-time stability, a fixed-time disturbance observer (FTDO) is developed to compensate for the lumped disturbance including uncertain dynamics, external disturbances, actuator faults, and input saturation. Moreover, to guarantee the optimal tracking accuracy of output errors and reduce consumption of control inputs, an appointed-time prescribed performance control (APPC) scheme is devised by integrating both the appointed-time performance function and unlimited-domain transformation function. Additionally, based on a novel prescribed sliding mode manifold that utilizes the precise estimation and prescribed performance, an adaptive non-singular fast terminal sliding mode controller (ANFTSMC) is proposed to stabilize tracking errors with fixed-time convergence while avoiding singularity constraints. Within this framework, an adaptive term is introduced to compensate for the unknown and time-varying input gains. Finally, Lyapunov stability analysis proves that all signals in the closed-loop system can achieve practical fixed-time stability, with all tracking errors confined strictly within prescribed regions. Numerical simulations further validate the effectiveness of the proposed scheme.