Safety and reliability are vital for robotic fish, which can be improved through fault diagnosis. In this study, a method for diagnosing sensor faults is proposed, which involves using Gramian angular field fusion with particle swarm optimization and lightweight AlexNet. Initially, one-dimensional time series sensor signals are converted into two-dimensional images using the Gramian angular field method with sliding window augmentation. Next, weighted fusion methods are employed to combine Gramian angular summation field images and Gramian angular difference field images, allowing for the full utilization of image information. Subsequently, a lightweight AlexNet is developed to extract features and classify fused images for fault diagnosis with fewer parameters and a shorter running time. To improve diagnosis accuracy, the particle swarm optimization algorithm is used to optimize the weighted fusion coefficient. The results indicate that the proposed method achieves a fault diagnosis accuracy of 99.72% when the weighted fusion coefficient is 0.276. These findings demonstrate the effectiveness of the proposed method for diagnosing depth sensor faults in robotic fish.

This article presents a rigorous investigation of the global dissipativity (GD) and quasi-synchronization (QS) of fractional-order complex-valued neural networks (FOCVNNs) with mixed delays and external disturbances. The considered mixed delays consist of both time-varying delays (TVDs) and infinite distributed delays (IDDs), which significantly complicate the dynamical analysis of fractional-order systems. To address this challenge, the fractional comparison principle is first extended to accommodate IDD. Based on this extension, a generalized fractional Halanay inequality is established, providing an effective analytical tool for fractional-order systems with mixed delays. By employing the proposed inequality, two sufficient conditions are derived to guarantee GD and QS of FOCVNNs with mixed delays and external disturbances under designed feedback control. Finally, the effectiveness and applicability of the theoretical analysis are demonstrated through two illustrative examples, including a standard numerical simulation and a secure communication scheme constructed from a fractional-order chaotic system with mixed delays.