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With the development of inspection robot control technology, wheel-legged robots are increasingly used in complex underground space inspection. To address low stability during obstacle crossing in unstructured terrains, a motion control strategy integrating an improved CPG algorithm and a biological reflex mechanism is proposed. It introduces an adaptive coupling matrix, augmented with the Lyapunov function, and vestibular/stumbling reflex models for real-time motion feedback. Simulink–Adams virtual prototypes and single-wheeled leg experiments (on the left front leg) were used to verify the system. Results show that the robot’s turning oscillation was ≤±0.00593 m, the 10° tilt maintained a stable center of mass at 10.2° with roll angle fluctuations ≤±5°, gully-crossing fluctuations ≤±0.01 m, and pitch recovery ≤2 s. The experiments aligned with the simulations, proving that the strategy effectively suppresses vertical vibrations, ensuring stable and high-precision inspection. Full article

27 pages, 11483 KiB

Open AccessArticle

Vibration Characteristic Analysis and Dynamic Reliability Modeling of Multi-Rotor UAVs

by Keyi Zhou, Di Zhou, Xiru Wang, Yonglin Guo and Huimin Chen

Machines 2025, 13(8), 697; https://doi.org/10.3390/machines13080697 - 6 Aug 2025

Abstract

To address the unclear vibration failure mechanism and the lack of system-level reliability evaluation methods for multirotor transport UAVs under complex operating conditions, this paper proposes a comprehensive analysis method that combines fluid–structure interaction dynamics with dynamic reliability theory. First, the study analyzes rotor dynamics and vibration characteristics under bidirectional fluid–structure coupling and obtains vibration displacement data. Then, it builds a dynamic reliability model using the Second-Order Reliability Method (SORM) and the Laplace method. The model explores reliability evolution in a dynamic airflow coupling environment. Finally, it establishes a multi-rotor UAV system reliability evaluation method and analyzes the impact of rotor number and layout on system reliability. The results provide a theoretical basis for structural optimization, reliability assurance, and fault tolerance improvement of multi-rotor UAVs under complex conditions. Full article

(This article belongs to the Special Issue AI-Driven Intelligent Maintenance and Health Management for Complex Industrial Systems)

11 pages, 264 KiB

Open AccessArticle

Boundary Feedback Control of a Cascade System of Fractional PDE-ODEs

by Dong-Xing Fu, Yi-Ying Feng, Zhi-Wen Zhu, Mi-Mi Hou and Jia Wang

Fractal Fract. 2025, 9(8), 514; https://doi.org/10.3390/fractalfract9080514 - 6 Aug 2025

Abstract

The fractional PDE-ODE coupled system with Neumann boundary condition is considered in this paper. We design a boundary state feedback controller using the Backstepping method to stabilize the considered system. According to operator semigroup theory, we obtain a unique solution of the investigated [...] Read more.

(This article belongs to the Section Engineering)

23 pages, 12563 KiB

Open AccessArticle

Optimization of Grouser–Track Structural Parameters for Enhanced Tractive Performance in Unmanned Amphibious Tracked Vehicles

by Yaoyao Chen, Xiaojun Xu, Wenhao Wang, Xue Gao and Congnan Yang

Actuators 2025, 14(8), 390; https://doi.org/10.3390/act14080390 - 6 Aug 2025

Abstract

This study focuses on optimizing track and grouser structural parameters to enhance UATV drawbar pull, particularly under soft soil conditions. A numerical soil thrust model for single-track shoes was developed based on track–soil interaction mechanics, revealing distinct mechanistic roles: track structural parameters (length/width) govern pressure–sinkage relationships at the track base, while grouser structural parameters (height, spacing, V-shaped angle) dominate shear stress–displacement dynamics on grouser shear planes. A novel DEM-MBD coupling simulation framework was established through soil parameter calibration and multi-body dynamics modeling, demonstrating that soil thrust increases with grouser height and V-shaped angle, but decreases with spacing, with grouser height exhibiting the highest sensitivity. A soil bin test validated the numerical model’s accuracy and the coupling method’s efficacy. Parametric optimization via the Whale Optimization Algorithm (WOA) achieved a 55.86% increase in drawbar pull, 40.38% reduction in ground contact pressure and 57.33% improvement in maximum gradability. These advancements substantially improve the tractive performance of UATVs in soft beach terrains. The proposed methodology provides a systematic framework for amphibious vehicle design, integrating numerical modeling, high-fidelity simulation, and experimental validation. Full article

(This article belongs to the Special Issue Modeling, Dynamics, Intelligent Control, and Fault Diagnosis of Vehicle Systems—2nd Edition)

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15 pages, 1805 KiB

Open AccessArticle

Indoor Application of Coupled FLOCponics System with Caipira Lettuce (Lactuca sativa) Affects the Growth Performance and Water Characteristics of Far Eastern Catfish (Silurus asotus) and Tropical Eel (Anguilla bicolor)

by Jun Seong Park, Hae Seung Jeong, Jeong-ho Lee and Ju-ae Hwang

Animals 2025, 15(15), 2305; https://doi.org/10.3390/ani15152305 - 6 Aug 2025

Abstract

In this study, we sought to improve the productivity of Far Eastern catfish (Silurus asotus) and tropical eel (Anguilla bicolor), which are high-value fish species in the Republic of Korea, as well as that of associated crops by applying biofloc technology (BFT)-based aquaponics systems. The following three systems were used: the flow-through system (FTS), BFT, and BFT aquaponics system (BAPs). Caipira lettuce (Lactuca sativa) was utilized and hydroponics (HP) was implemented to compare crop productivity. After 42 days of treatment, the BAPs and BFT systems improved fish productivity, with weight gain rates of 134.47 ± 1.80% in BAPs-cat, 130.38 ± 0.95% in BFT, and 114.21 ± 6.62% in FTS for S. asotus, and 70.61 ± 3.26% in BAPs-eel, 62.37 ± 7.04% in BFT, and 47.83 ± 1.09% in FTS for A. bicolor. During the experiment, the total ammonia nitrogen and NO₂⁻-N concentrations were stable in all plots. In the case of NO₃⁻-N, BFT showed an increasing tendency while both BAPs showed a decrease compared with that of the BFT. BAPs-cat (total weight: 224.1 ± 6.37 g) and HP (220.3 ± 7.17 g) resulted in similar growth. However, in BAPs-eel was 187.7 ± 3.46 g due to root degradation. Water content analysis showed that BAPs-cat and BAPs-eel contained sufficient K, Ca, P, and S, which are important for crop growth. Overall, the effect of BAPs on fish growth was higher than that of FTS. This study reveals that integrating BFT with aquaponics improves productivity for high-value fish and associated crops while maintaining stable water quality. This method offers sustainable, efficient production, reduces environmental impact, and provides insights for future research in sustainable aquaculture practices. Full article

(This article belongs to the Special Issue Innovations in Aquaculture: New Technologies, Culture Systems and Integration of Emerging Species)

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28 pages, 2475 KiB

Open AccessArticle

Optimal Scheduling of a Hydropower–Wind–Solar Multi-Objective System Based on an Improved Strength Pareto Algorithm

by Haodong Huang, Qin Shen, Wan Liu, Ying Peng, Shuli Zhu, Rungang Bao and Li Mo

Sustainability 2025, 17(15), 7140; https://doi.org/10.3390/su17157140 - 6 Aug 2025

Abstract

Under the current context of the large-scale integration of wind and solar power, the coupling of hydropower with wind and solar energy brings significant impacts on grid stability. To fully leverage the regulatory capacity of hydropower, this paper develops a multi-objective optimization scheduling model for hydropower, wind, and solar that balances generation-side power generation benefit and grid-side peak-regulation requirements, with the latter quantified by the mean square error of the residual load. To efficiently solve this model, Latin hypercube initialization, hybrid distance framework, and adaptive mutation mechanism are introduced into the Strength Pareto Evolutionary Algorithm II (SPEAII), yielding an improved algorithm named LHS-Mutate Strength Pareto Evolutionary Algorithm II (LMSPEAII). Its efficiency is validated on benchmark test functions and a reservoir model. Typical extreme scenarios—months with strong wind and solar in the dry season and months with weak wind and solar in the flood season—are selected to derive scheduling strategies and to further verify the effectiveness of the proposed model and algorithm. Finally, K-medoids clustering is applied to the Pareto front solutions; from the perspective of representative solutions, this reveals the evolutionary trends of different objective trade-off schemes and overall distribution characteristics, providing deeper insight into the solution set’s distribution features. Full article

29 pages, 1496 KiB

Open AccessArticle

Advanced and Robust Numerical Framework for Transient Electrohydrodynamic Discharges in Gas Insulation Systems

by Philipp Huber, Julian Hanusrichter, Paul Freden and Frank Jenau

Eng 2025, 6(8), 194; https://doi.org/10.3390/eng6080194 - 6 Aug 2025

Abstract

For the precise description of gas physical processes in high-voltage direct current (HVDC) transmission, an advanced and robust numerical framework for the simulation of transient particle densities in the course of corona discharges is developed in this work. The aim is the scalable and consistent modeling of the space charge density under realistic conditions. The core component of the framework is a discontinuous Galerkin method that ensures the conservative properties of the underlying hyperbolic problem. The space charge density at the electrode surface is imposed as a dynamic boundary condition via Lagrange multipliers. To increase the numerical stability and convergence rate, a homotopy approach is also integrated. For the experimental validation, a measurement concept was realised that uses a subtraction method to specifically remove the displacement current component in the signal and thus enables an isolated recording of the transient ion current with superimposed voltage stresses. The experimental results on a small scale agree with the numerical predictions and prove the quality of the model. On this basis, the framework is transferred to hybrid HVDC overhead line systems with a bipolar design. In the event of a fault, significant transient space charge densities can be seen there, especially when superimposed with new types of voltage waveforms. The framework thus provides a reliable contribution to insulation coordination in complex HVDC systems and enables the realistic analysis of electrohydrodynamic coupling effects on an industrial scale. Full article

(This article belongs to the Section Electrical and Electronic Engineering)

16 pages, 2899 KiB

Open AccessArticle

The Coupling Mechanism of the Electricity–Gas System and Assessment of Attack Resistance Based on Interdependent Networks

by Qingyu Zou and Lin Yan

Eng 2025, 6(8), 193; https://doi.org/10.3390/eng6080193 - 6 Aug 2025

Abstract

Natural gas plays a critical role in integrated energy systems. In this context, the present study proposes an optimization model for the electricity–gas coupling system, grounded in the theory of interdependent networks. By integrating network topology parameters with real-time operational metrics, the model substantially enhances system robustness and adaptability. To quantify nodal vulnerability and importance, the study introduces two novel evaluation indicators: the Electric Potential–Closeness Fusion Indicator (EPFI) for power networks and the Pressure Difference–Closeness Comprehensive Indicator (PDCI) for natural gas systems. Leveraging these indicators, three coupling paradigms—assortative, disassortative, and random—are systematically constructed and analyzed. System resilience is assessed through simulation experiments incorporating three attack strategies: degree-based, betweenness centrality-based, and random node removal. Evaluation metrics include network efficiency and the variation in the size of the largest connected subgraph under different coupling configurations. The proposed framework is validated using a hybrid case study that combines the IEEE 118-node electricity network with a 20-node Belgian natural gas system, operating under a unidirectional gas-to-electricity energy flow model. Results confirm that the disassortative coupling configuration, based on EPFI and PDCI indicators, exhibits superior resistance to network perturbations, thereby affirming the effectiveness of the model in improving the robustness of integrated energy systems. Full article

(This article belongs to the Topic Advanced Strategies for Smart Grid Reliability and Energy Optimization)

21 pages, 8352 KiB

Open AccessArticle

Research on Vibration Characteristics of Electric Drive Systems Based on Open-Phase Self-Fault-Tolerant Control

by Wenyu Bai, Yun Kuang, Zhizhong Xu, Yawen Wang and Xia Hua

Appl. Sci. 2025, 15(15), 8707; https://doi.org/10.3390/app15158707 (registering DOI) - 6 Aug 2025

Abstract

This paper presents an electromechanical coupling model integrating an equivalent magnetic network (EMN) model of a dual three-phase permanent magnet synchronous motor (DTP-PMSM) with the dynamic model of a helical planetary gear transmission system. Using this model, this study analyzes the dynamic characteristics of an electric drive system, specifically motor phase current, electromagnetic torque, and gear meshing force, under self-fault-tolerant control strategies. Simulation and experimental results demonstrate that the self-fault-tolerant control strategy enables rapid fault tolerance during open-phase faults, significantly reducing system fault recovery time. Meanwhile, compared to the open-phase faults conditions, the self-fault-tolerant control effectively suppresses most harmonic components within the system; only the second harmonic amplitude of the electromagnetic torque exhibited an increase. This harmonic disturbance propagates to the gear system through electromechanical coupling, synchronously amplifying the second harmonic amplitude in the gear system’s vibration response. This study demonstrates that self-fault-tolerant control strategies significantly enhance the dynamic response performance of the electric drive system under open-phase faults conditions. Furthermore, this study also investigates the electromechanical coupling mechanism through which harmonics generated by this strategy affect the gear system’s dynamic response, providing theoretical support for co-optimization electromechanical coupling design and fault-tolerant control in high-reliability electric drive transmission systems. Full article

(This article belongs to the Section Mechanical Engineering)

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18 pages, 1113 KiB

Open AccessArticle

Effects of Culture Period and Plant Growth Regulators on In Vitro Biomass Production and Phenolic Compounds in Seven Species of Hypericum

by Doina Clapa, Monica Hârţa, Ana Maria Radomir, Adrian George Peticilă, Loredana Leopold, Floricuţa Ranga and Dorin Ioan Sumedrea

Plants 2025, 14(15), 2437; https://doi.org/10.3390/plants14152437 - 6 Aug 2025

Abstract

This study evaluated biomass accumulation and phenolic compound production in seven Hypericum species (H. androsaemum, H. calycinum, H. hirsutum, H. kalmianum, H. olympicum, H. perforatum, and H. triquetrifolium) cultivated in vitro under varying growth regulator treatments and culture periods. Shoots were grown on Murashige and Skoog (MS) medium supplemented with benzyladenine (BA) or meta-topoline (mT) and analyzed after 40 and 60 days. MS medium supplemented with 0.2 mg/L BA was the most effective condition for promoting biomass across all species, with shoot fresh weight increasing significantly at 60 days, particularly in H. olympicum, H. perforatum, and H. triquetrifolium. High-performance liquid chromatography coupled with diode array detection and electrospray ionization mass spectrometry (HPLC-DAD-ESI-MS) identified 13 phenolic compounds, including flavonols, hydroxycinnamic acids, anthocyanins, phloroglucinols, and naphthodianthrones. Phenolic profiles were species-specific and influenced by culture period. H. kalmianum accumulated the highest total phenolic content (37.6 mg/g DW), while H. olympicum was the top producer of hypericin and pseudohypericin. These results highlight the crucial role of culture conditions in regulating both biomass and phytochemical production and provide a promising approach for producing bioactive metabolites in Hypericum species through in vitro systems. Full article

(This article belongs to the Special Issue Plant Tissue Culture V)

20 pages, 3036 KiB

Open AccessArticle

Chemometric Approach for Discriminating the Volatile Profile of Cooked Glutinous and Normal-Amylose Rice Cultivars from Representative Japanese Production Areas Using GC × GC-TOFMS

by Takayoshi Tanaka, Junhan Zhang, Shuntaro Isoya, Tatsuro Maeda, Kazuya Hasegawa and Tetsuya Araki

Foods 2025, 14(15), 2751; https://doi.org/10.3390/foods14152751 - 6 Aug 2025

Abstract

Cooked-rice aroma strongly affects consumer choice, yet the chemical traits distinguishing glutinous rice from normal-amylose japonica rice remain underexplored because earlier studies targeted only a few dozen volatiles using one-dimensional gas chromatography–mass spectrometry (GC-MS). In this study, four glutinous and seven normal Japanese cultivars were cooked under identical conditions, their headspace volatiles trapped with MonoTrap and qualitatively profiled by comprehensive GC × GC-TOFMS. The two-dimensional platform resolved 1924 peaks—about ten-fold previous coverage—and, together with hierarchical clustering, PCA, heatmap visualization and volcano plots, cleanly separated the starch classes (78.3% cumulative PCA variance; Euclidean distance >140). Volcano plots highlighted 277 compounds enriched in the glutinous cultivars and 295 in Koshihikari, including 270 compounds that were not previously documented in rice. Normal cultivars were dominated by ethers, aldehydes, amines and other nitrogenous volatiles associated with grainy, grassy and toasty notes. Glutinous cultivars showed abundant ketones, furans, carboxylic acids, thiols, steroids, nitro compounds, pyrroles and diverse hydrocarbons and aromatics, yielding sweeter, fruitier and floral accents. These results expand the volatile library for japonica rice, provide molecular markers for flavor-oriented breeding and demonstrate the power of GC × GC-TOFMS coupled with chemometrics for grain aroma research. Full article

(This article belongs to the Special Issue Advances in Volatile Flavor Analysis on Food Quality: Application by Volatilomics and Recent Analytical Technologies)

26 pages, 7095 KiB

Open AccessArticle

Collision Avoidance of Driving Robotic Vehicles Based on Model Predictive Control with Improved APF

by Lei Zhao, Hongda Liu and Wentie Niu

Machines 2025, 13(8), 696; https://doi.org/10.3390/machines13080696 - 6 Aug 2025

Abstract

To enhance road-testing safety for autonomous driving robotic vehicles (ADRVs), collision avoidance with sudden obstacles is essential during testing processes. This paper proposes an upper-level collision avoidance strategy integrating model predictive control (MPC) and improved artificial potential field (APF). The kinematic model of the driving robot is established, and a vehicle dynamics model considering road curvature is used as the foundation for vehicle control. The improved APF constraints are constructed. The boundary constraint uses a three-circle vehicle shape suitable for roads with arbitrary curvatures. A unified obstacle potential field constraint is designed for static/dynamic obstacles to generate collision-free trajectories. An auxiliary attractive potential field is designed to ensure stable trajectory recovery after obstacle avoidance completion. A multi-objective MPC framework coupled with artificial potential fields is designed to achieve obstacle avoidance and trajectory tracking while ensuring accuracy, comfort, and environmental constraints. Results from Carsim-Simulink and semi-physical experiments validate that the proposed strategy effectively avoids various obstacles under different road conditions while maintaining reference trajectory tracking. Full article

(This article belongs to the Special Issue Optimization-Based Motion Planning & Control for Autonomous Driving in Dynamic Environments)

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29 pages, 2766 KiB

Open AccessArticle

(H-DIR)²: A Scalable Entropy-Based Framework for Anomaly Detection and Cybersecurity in Cloud IoT Data Centers

by Davide Tosi and Roberto Pazzi

Sensors 2025, 25(15), 4841; https://doi.org/10.3390/s25154841 - 6 Aug 2025

Abstract

Modern cloud-based Internet of Things (IoT) infrastructures face increasingly sophisticated and diverse cyber threats that challenge traditional detection systems in terms of scalability, adaptability, and explainability. In this paper, we present (H-DIR)², a hybrid entropy-based framework designed to detect and mitigate anomalies in large-scale heterogeneous networks. The framework combines Shannon entropy analysis with Associated Random Neural Networks (ARNNs) and integrates semantic reasoning through RDF/SPARQL, all embedded within a distributed Apache Spark 3.5.0 pipeline. We validate (H-DIR)² across three critical attack scenarios—SYN Flood (TCP), DAO-DIO (RPL), and NTP amplification (UDP)—using real-world datasets. The system achieves a mean detection latency of 247 ms and an AUC of 0.978 for SYN floods. For DAO-DIO manipulations, it increases the packet delivery ratio from 81.2% to 96.4% (p < 0.01), and for NTP amplification, it reduces the peak load by 88%. The framework achieves vertical scalability across millions of endpoints and horizontal scalability on datasets exceeding 10 TB. All code, datasets, and Docker images are provided to ensure full reproducibility. By coupling adaptive neural inference with semantic explainability, (H-DIR)² offers a transparent and scalable solution for cloud–IoT cybersecurity, establishing a robust baseline for future developments in edge-aware and zero-day threat detection. Full article

(This article belongs to the Special Issue Privacy and Cybersecurity in IoT-Based Applications)

16 pages, 6256 KiB

Open AccessArticle

Influence of Alpha/Gamma-Stabilizing Elements on the Hot Deformation Behaviour of Ferritic Stainless Steel

by Andrés Núñez, Irene Collado, Marta Muratori, Andrés Ruiz, Juan F. Almagro and David L. Sales

J. Manuf. Mater. Process. 2025, 9(8), 265; https://doi.org/10.3390/jmmp9080265 - 6 Aug 2025

Abstract

This study investigates the hot deformation behaviour and microstructural evolution of two AISI 430 ferritic stainless steel variants: 0A (basic) and 1C (modified). These variants primarily differ in chemical composition, with 0A containing higher austenite-stabilizing elements (C, N) compared to 1C, which features lower interstitial content and slightly higher Si and Cr. This research aimed to optimize hot rolling conditions for enhanced forming properties. Uniaxial hot compression tests were conducted using a Gleeble thermo-mechanical system between 850 and 990

^{\circ}

C at a strain rate of 3.3 s

^{- 1}

, simulating industrial finishing mill conditions. Analysis of flow curves, coupled with detailed microstructural characterization using electron backscatter diffraction, revealed distinct dynamic restoration mechanisms influencing each material’s response. Thermodynamic simulations confirmed significant austenite formation in both materials within the tested temperature range, notably affecting their deformation behaviour despite their initial ferritic state. Material 0A consistently exhibited a strong tendency towards dynamic recrystallization (DRX) across a wider temperature range, particularly at 850

^{\circ}

C. DRX led to a microstructure with a high concentration of low-angle grain boundaries and sharp deformation textures, actively reorienting grains towards energetically favourable configurations. However, under this condition, DRX did not fully complete the recrystallization process. In contrast, material 1C showed greater activity of both dynamic recovery and DRX, leading to a much more advanced state of grain refinement and recrystallization compared to 0A. This indicates that the composition of 1C helps mitigate the strong influence of the deformation temperature on the crystallographic texture, leading to a weaker texture overall than 0A. Full article

30 pages, 2504 KiB

Open AccessArticle

Battery Energy Storage Systems: Energy Market Review, Challenges, and Opportunities in Frequency Control Ancillary Services

by Gian Garttan, Sanath Alahakoon, Kianoush Emami and Shantha Gamini Jayasinghe

Energies 2025, 18(15), 4174; https://doi.org/10.3390/en18154174 - 6 Aug 2025

Abstract

Battery energy storage systems (BESS) are considered a good energy source to maintain supply and demand, mitigate intermittency, and ensure grid stability. The primary contribution of this paper is to provide a comprehensive overview of global energy markets and a critical analysis of BESS’ participation in frequency control ancillary service (FCAS) markets. This review synthesises the current state of knowledge on the evolution of the energy market and the role of battery energy storage systems in providing grid stability, particularly frequency control services, with a focus on their integration into evolving high-renewable-energy-source (RES) market structures. Specifically, solar PV and wind energy are emerging as the main drivers of RES expansion, accounting for approximately 61% of the global market share. A BESS offers greater flexibility in storage capacity, scalability and rapid response capabilities, making it an effective solution to address emerging security risks of the system. Moreover, a BESS is able to provide active power support through power smoothing when coupled with solar photovoltaic (PV) and wind generation. In this paper, we provide an overview of the current status of energy markets, the contribution of battery storage systems to grid stability and flexibility, as well as the challenges that BESS face in evolving electricity markets. Full article

(This article belongs to the Special Issue Innovations and Recent Trends in Power Systems: Smart Grids, Energy Storage Systems and Electric Vehicle Integrations)

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