To address the poor surface quality and non-uniform polishing in internal micro-channels of additively manufactured components， where traditional finishing methods are inapplicable and unidirectional processing exhibits limitations， this study adopts a bidirectional finishing mode. Combining simulation and experimentation， it systematically investigates the effects of water-based silicon carbide （SiC） and alumina （Al₂O₃） abrasives on hole enlargement uniformity， surface roughness， and surface morphology under both unidirectional and bidirectional processing conditions. Results demonstrate that bidirectional processing significantly improves polishing uniformity compared with unidirectional processing. Specifically， the difference in hole enlargement between inlet and outlet is reduced from 51 μm to 27 μm using SiC abrasives， and from 40 μm to 20 μm using Al2O3 abrasives. Furthermore， bidirectional processing markedly reduces and homogenizes surface roughness across all regions： Roughness values in SiC-processed channels decrease to 3.726 （inlet）， 3.612 （outlet）， and 3.639 μm （middle）， while those in Al₂O₃-processed channels decrease to 4.127 （inlet）， 3.876 （outlet）， and 3.963 μm （middle）. Comparative analysis indicates SiC outperformes Al₂O₃， yielding channels with an average surface roughness approximately 0.3 μm lower under bidirectional processing （inlet： 0.4 μm lower， outlet： 0.26 μm lower， middle： 0.32 μm lower）.
Taking the Hexaglide‑type parallel mechanism as the research object， the unit wrench screw of each limb is obtained by analyzing the geometric characteristics of the mechanism， and the first‑order force influence coefficient matrix is derived based on the static equilibrium conditions. Using a zero‑column construction method， the determinant of this matrix is made singular， thereby identifying the geometric conditions under which the mechanism becomes singular. Furthermore， by constructing linear dependencies among rows and columns， the conditions under which the Hexaglide mechanism does not exhibit configuration singularity are derived. On this basis， three types of singularity conditions are unified into a parametric form， and a quantifiable geometric safety distance index is defined， which can be incorporated into an optimization model for singularity avoidance at the design stage. This work provides theoretical support and a methodological foundation for the design of such mechanisms.
Fahad M. Al-Qahtani, Mujahed Aldhaifallah, Sami El Ferik
et al.
This study addresses the problem of attitude and altitude tracking for a quadrotor system in the presence of parameter uncertainties. The goal is to develop a robust control strategy that can handle the nonlinear, strongly coupled dynamics of the quadrotor. To achieve this, we propose a fractional-order sliding mode control (FOSMC) scheme, which is specifically designed to improve system performance under uncertain parameters. The FOSMC approach is combined with additional adaptive laws to further enhance the robustness of the control system. We derive the necessary control laws and apply them to the quadrotor’s state-space representation, ensuring that the system remains stable and performs accurately in the presence of uncertainties. Numerical simulations are conducted to evaluate the effectiveness of the proposed control strategy. The results show that the FOSMC-based controller successfully achieves precise tracking of both attitude and altitude, demonstrating significant robustness against parameter variations and disturbances. In conclusion, the proposed FOSMC scheme provides a reliable solution for controlling quadrotor systems in uncertain environments, offering the potential for real-world applications in autonomous UAV operations.
To enhance the accuracy and efficiency of reliability analyses for an aero-engine vectoring exhaust nozzle (VEN), a dual-stochastic extreme response surface method based on the genetic algorithm (DSERSM-GA) is developed by integrating the genetic algorithm, the random extremum response surface method, and the dual response surface method in the paper. In the proposed method, a limited set of Monte Carlo samples is strategically utilized to construct and optimize a population-based response surface model, forming a robust mathematical framework for reliability prediction. The uncertainty sources considered include aerodynamic loads acting on the vector nozzle, material densities of the expansion plate and triangular link, as well as the elastic moduli of these components. Stress and deformation responses of both the expansion plate and triangular link are employed as the performance metrics. The proposed DSERSM-GA methodology is validated through dynamic reliability simulations applied to a vector nozzle system, yielding distributions and corresponding reliability indices of critical responses. Comparative analyses against traditional Monte Carlo Simulation (MCS) and conventional Extreme Response Surface Methods (ERSM) demonstrate that the DSERSM-GA significantly reduces computational costs while preserving high predictive accuracy.
Nutchanon Suvittawat, Christian Kurniawan, Jetanat Datephanyawat
et al.
Aircraft skin surface defect detection is critical for aviation safety but is currently mostly reliant on manual or visual inspections. Recent advancements in computer vision offer opportunities for automation. This paper reviews the current state of computer vision algorithms and their application in aircraft defect detection, synthesizing insights from academic research (21 publications) and industry projects (18 initiatives). Beyond a detailed review, we experimentally evaluate the accuracy and feasibility of existing low-cost, easily deployable hardware (drone) and software solutions (computer vision algorithms). Specifically, real-world data were collected from an abandoned aircraft with visible defects using a drone to capture video footage, which was then processed with state-of-the-art computer vision models—YOLOv9 and RT-DETR. Both models achieved mAP50 scores of 0.70–0.75, with YOLOv9 demonstrating slightly better accuracy and inference speed, while RT-DETR exhibited faster training convergence. Additionally, a comparison between YOLOv5 and YOLOv9 revealed a 10% improvement in mAP50, highlighting the rapid advancements in computer vision in recent years. Lastly, we identify and discuss various alternative hardware solutions for data collection—in addition to drones, these include robotic platforms, climbing robots, and smart hangars—and discuss key challenges for their deployment, such as regulatory constraints, human–robot integration, and weather resilience. The fundamental contribution of this paper is to underscore the potential of computer vision for aircraft skin defect detection while emphasizing that further research is still required to address existing limitations.
Due to the influence of slip flow and wake, the tail rotor of a helicopter may produce strong unsteady aerodynamic force in its main rotor interference flow field, which may affect the helicopter control and lead to structural failure. Although the unsteady flow field simulation method can capture the details of the flow field, the calculation amount is large. Therefore, this paper presents a fast method of tail rotor aerodynamic force prediction based on coupled momentum source and blade element theory. The momentum source model takes into account the disturbance of the flow field of a main rotor to that of a tail rotor. The induced velocity of the tail rotor is extracted from the flow field, and its quasi-steady aerodynamic force is solved iteratively with the blade element theory. In order to verify the accuracy of the method, this paper carries out the prediction of the tail rotor's aerodynamic characteristics under the main rotor's interference with different sideslip angles. In the range of 0° to 30° sideslip angles, the error of the tail rotor's average pull coefficient obtained with the fast prediction method is 2.31% to 4.50% compared with the wind tunnel experiment. Compared with the experiment, the error of the unsteady flow simulation method using the sliding grid is -4.50% to 1.20%, but the calculation amount of the experiment is only 9.61%. In the forward flight state of a small sideslip, regardless of whether the rotor slip sweeps the tail rotor, compared with the tail rotor's average pull predicted with the unsteady flow simulation method, the error of the fast prediction method is -6.19% to 6.15%. The average value of the unsteady pull coefficient of a single blade and the peak value of the first and second order blade passing frequency are close to those of the unsteady flow simulation method.
With the increasing demands of ultra-large space antennas, on-orbit assembly stands out as a promising solution. However, this achievement necessitates the reconfiguration design of the whole antenna structure to maintain structural integrity and stability. In light of this challenge, a novel rapid design method is proposed for the unit configuration of modular-assembled antennas in this paper. The method utilizes an inscribed regular hexagon, which is positioned within a horizontal topological circle. The hexagon is subsequently projected onto a spinning paraboloid, resulting in the creation of unit nodes that conform to the shape of the paraboloid. The configuration of the unit topology is then determined based on the arrangement of these nodes. By using the method, two units of space-assembled antennas are designed. The topology design of the cable network is carried out for the modular unit. The pretensions of the cables are calculated. The results of the case study reveal that the developed modular units fulfill the requirements of the on-orbit-assembly antenna structure and can solve the engineering application difficulties of this type of antenna.
Unmanned aerial vehicle (UAV) systems have recently become essential for mapping, surveying, and three-dimensional (3D) modeling applications. These systems are capable of providing highly accurate products through integrated advanced technologies, including a digital camera, inertial measurement unit (IMU), and Global Navigation Satellite System (GNSS). UAVs are a cost-effective alternative to traditional aerial photogrammetry, and recent advancements demonstrate their effectiveness in many applications. In UAV-based photogrammetry, ground control points (GCPs) are utilized for georeferencing to enhance positioning precision. The distribution, number, and location of GCPs in the study area play a crucial role in determining the accuracy of photogrammetric products. This research evaluates the accuracy of positioning techniques for image acquisition for photogrammetric production and the effect of GCP distribution models. The camera position was determined using real-time kinematic (RTK), post-processed kinematic (PPK), and precise point positioning-ambiguity resolution (PPP-AR) techniques. In the criteria for determining the GCPs, six models were established within the İstanbul Technical University, Ayazaga Campus. To assess the accuracy of the points in these models, the horizontal, vertical, and 3D root mean square error (RMSE) values were calculated, holding the test points stationary in place. In the study, 2.5 cm horizontal RMSE and 3.0 cm vertical RMSE were obtained with the model containing five homogeneous GCPs by the indirect georeferencing method. The highest RMSE values of all three components in RTK, PPK, and PPP-AR methods were obtained without GCPs. For all six models, all techniques have an error value of sub-decimeter. The PPP-AR technique yields error values that are comparable to those of the other techniques. The PPP-AR appears to be an alternative to RTK and PPK, which usually require infrastructure, labor, and higher costs.
Mario Carta, Shahrokh Shahpar, Tiziano Ghisu
et al.
As turbine entry temperatures of modern jet engines continue to increase, additional thermal stresses are introduced onto the high-pressure turbine rotors, which are already burdened by substantial levels of centrifugal and gas loads. Usually, for modern turbofan engines, the temperature distribution upstream of the high-pressure stator is characterized by a series of high-temperature regions, determined by the circumferential arrangement of the combustor burners. The position of these high-temperature regions, both radially and circumferentially in relation to the high-pressure stator arrangement, can have a strong impact on their subsequent migration through the high-pressure stage. Therefore, for a given amount of thermal power entering the turbine, a significant reduction in maximum rotor temperatures can be achieved by adjusting the inlet temperature distribution. This paper is aimed at mitigating the maximum surface temperatures on a high-pressure turbine rotor from a modern commercial turbofan engine by conducting a parametric analysis and optimization of the inlet temperature field. The parameters considered for this study are the circumferential position of the high-temperature spots, and the overall bias of the temperature distribution in the radial direction. High-fidelity unsteady (phase-lag) and conjugate heat transfer simulations are performed to evaluate the effects of inlet clocking and radial bias on rotor metal temperatures. The optimized inlet distribution achieved a 100 K reduction in peak high-pressure rotor temperatures and 7.5% lower peak temperatures on the high-pressure stator vanes. Furthermore, the optimized temperature distribution is also characterized by a significantly more uniform heat load allocation on the stator vanes, when compared to the baseline one.
Manuela Vieira, Gonçalo Galvão, Manuel A. Vieira
et al.
This study combines Visible Light Communication (VLC) and Artificial Intelligence (AI) to enhance traffic signal control, reduce congestion, and improve safety, through real-time monitoring and dynamic traffic management. Leveraging VLC technology, the system uses existing road infrastructure to transmit live data on vehicle and pedestrian positions, speeds, and queues. AI agents, employing Deep Reinforcement Learning (DRL), process this data to manage traffic flows dynamically, applying anti-bottleneck and rerouting techniques to balance pedestrian and vehicle waiting times. A centralized global agent coordinates the local agents controlling each intersection, enabling indirect communication and data sharing to train a unified DRL model. This model makes real-time adjustments to traffic light phases, utilizing a queue/request/response system for adaptive intersection management. Tested using simulations and real-world trials involving standard and rerouting scenarios, the approach demonstrates significantly better performance in regard to the rerouting configuration, reducing congestion and enhancing traffic flow and pedestrian safety. Scalable and adaptable to various intersection types, including four-way, T-intersections, and roundabouts, the system’s efficacy is validated using the SUMO urban mobility simulator, resulting in notable reductions to travel and waiting times for both vehicles and pedestrians.
Mechanical engineering and machinery, Machine design and drawing
In response to safety concerns pertaining to multi-UAV formation flights, a novel obstacle avoidance method based on an Improved Adaptive Artificial Potential field (IAAPF) is presented. This approach enhances UAV obstacle avoidance capabilities by utilizing segmented attraction potential fields refined with adaptive factors and augmented with virtual forces for inter-UAV collision avoidance. To further enhance the control and stability of multi-UAV formations, a Sliding Mode Control (SMC) method is integrated into the IAAPF-based obstacle avoidance framework. Renowned for its robustness and ability to handle system uncertainties and disturbances, the SMC method is combined with a feedback control system that utilizes inner and outer loops. The outer loop generates the desired path based on the leader’s state and control commands, while the inner loop tracks these trajectories and adjusts the follower UAVs’ motions. This design ensures that obstacle feedback is accounted for before the desired state information is received, enabling effective obstacle avoidance while maintaining formation integrity. Integrating leader-follower formation control techniques with SMC-based multi-UAV obstacle avoidance strategies ensures the effective convergence of the formation velocity and spacing to predetermined values, meeting the cooperative obstacle avoidance requirements of multi-UAV formations. Simulation results validate the efficacy of the proposed method in reaching otherwise unreachable destinations within obstacle-rich environments, while ensuring robust collision avoidance among UAVs.
В машиностроении одними из наиболее перспективных являются аддитивные технологии (АТ) выращивания изделий из металлов и сплавов. Они находят все более широкое применение в производстве изделий в различных отраслях машиностроения. Термин «выращивание» связан с постепенным послойным характером изготовления сложного изделия на основе его компьютерной 3D-модели. Проволочные АТ экономически более выгодные в связи с более высокой производительности процесса и, на порядок более низкой стоимости проволоки по сравнению с порошками для популярных технологий SLM и LMD. Кроме того, современной промышленностью освоен выпуск проволоки из широкой номенклатуры материалов, среди которых: алюминий, низколегированные стали, нержавеющие стали, титановые, никелевые сплавы. Недостатком проволочных АТ является более грубая поверхность выращенных изделий. В статье приведены результаты проектирования и применения многофункционального оборудования для совместного использования аддитивных и субтрактивных технологий.
Engineering machinery, tools, and implements, Motor vehicles. Aeronautics. Astronautics
A remotely piloted aircraft system (RPAS) survey of an area containing the eastern extremity of King George Island, including Cape Melville and an extensive part of Destruction Bay, as well as small offshore islands, was undertaken in December 2022. Using RPAS, an inventory of the Destruction Bay area was performed. Chinstrap penguin and Antarctic shag nests were found on Cape Melville and on Trowbridge Island, Middle Island, and an unnamed area located between the Ørnen Rocks formation and Trowbridge Island. During the survey, 507 Antarctic shag nests and over 9000 chinstrap penguin nests were mapped in the investigated area; 458 Antarctic shag nests and 4960 ± 19 chinstrap penguin nests aggregated together on an 8.61 ha land section of Cape Melville were identified. The quantity of Antarctic shag nests found allows for the classification of the area of Cape Melville as an IBA. Among the 175 currently known colonies of Antarctic shags in Antarctica, this is the fifth largest. In this paper, we present the results of the survey, including orthophotos with mapped nest locations. We propose the following recommendations to policy makers and the scientific community: (1) the area of Cape Melville should be classified as an Antarctic Important Bird and Biodiversity Area; (2) based on the RPAS flight, a new boundary of the Cape Melville IBA is proposed; (3) the threshold value (based on >1% of species) to establish an IBA for Antarctic shags should be changed to 122 to reflect the increased estimate of the global population of Antarctic shags; and (4) an inventory of all areas, including previous IBAs that can be qualified as “major colonies of breeding native birds”, should be recommended at the Antarctic Treaty Consultative Meeting (ATCM). In logistically inaccessible bird breeding sites, such as the one presented here, RPASs should be used to carry out regular monitoring of Antarctic Important Bird and Biodiversity Areas.
The health of the landing gear retraction/extension(R/E) hydraulic system may be assessed using fuzzy comprehensive evaluation (FCE), however the traditional FCE method depends solely on human assessment by specialists, which is excessively subjective. To address the issue of excessive human subjective variables in the assessment, an improved FCE model based on enhanced risk coefficient is provided, which includes four consideration indexes: failure probability, failure severity, failure detection difficulty, and failure repair difficulty. To reduce subjective human judgment errors entirely due to expert experience, the improved FCE takes into account the likelihood of failure using a statistical method, the severity of failure using a fault simulation analysis based on the LMS Imagine.Lab AMESim simulation platform, and the difficulty of fault detection and repair using the aircraft manufacturer’s professional maintenance information. As part of the evaluation model, the range of health assessment values and accompanying treatment methods are included, making it easier to implement on a daily basis in aircraft maintenance. As a final step, the simulation is evaluated, and the simulated faults are calculated.
Oxidation tests of direct-sintered SiC were conducted in tube furnace in static air at 1200 ℃, 1300 ℃ and 1400 ℃ for 1 h, 5 h, 12 h and in Thermogravimetric Analyzer (TGA) at the same temperature for 24 h to obtain continuous mass change curves. Grazing incidence X-ray diffraction (GIXRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS) were used to characterize the oxidation products and to reveal the underlying mechanisms. And the ReaxFF Reactive Molecular Dynamics (ReaxFF MD) simulation was conducted in open-source LAMMPS code to study the oxidation behaviors of 6H-SiC. The results of Oxidation tests show that the oxidation of direct-sintered SiC obeys parabolic law, indicating the oxidation process is controlled by the diffusion of O2. Besides, it takes on a 3-stages oxidation kinetics. Morphology of oxide layer initially shows a transition from amorphous SiO2 to spherulitic features accompanied by a decreasing oxidation rate. After a long-time oxidation, spherulitic features are transformed to fine grain structure along with an increasing oxidation rate. The transition of SiO2 structure and the variation in oxidation rate are probably associated with the specific diffusion mode of O2 in the oxide layer. In combination with ReaxFF MD simulation, the oxidation mechanism of 6H-SiC is obtained. It reveals that O2 diffusion inwards controls the oxidation reaction of 6H-SiC along with the formation of C element, followed by oxidation into CO and CO2 and escapes in the form of bubbles.
Aleksander Suti, Gianpietro Di Rito, Roberto Galatolo
This paper deals with the development of a novel fault-tolerant control technique aiming at the diagnosis and accommodation of inter-turn short circuit faults in permanent magnet synchronous motors for lightweight UAV propulsion. The reference motor is driven by a four-leg converter, which can be reconfigured in case of a phase fault by enabling the control of the central point of the motor Y-connection. A crucial design point entails the development of fault detection and isolation (FDI) algorithms capable of minimizing the failure transients and avoiding the short circuit extension. The proposed fault-tolerant control is composed of two sections: the first one applies a novel FDI algorithm for short circuit faults based on the trajectory tracking of the motor current phasor in the Clarke plane; the second one implements the fault accommodation, by applying a reference frame transformation technique to the post-fault commands. The control effectiveness is assessed via nonlinear simulations by characterizing the FDI latency and the post-fault performances. The proposed technique demonstrates excellent potentialities: the FDI algorithm simultaneously detects and isolates the considered faults, even with very limited extensions, during both stationary and unsteady operating conditions. In addition, the proposed accommodation technique is very effective in minimizing the post-fault torque ripples.
Aerospace actuators can be found throughout modern commercial and experimental aircraft, as well as in military and space exploration. The aerospace industry is not only growing, but also rapidly changing and the demand for aerospace actuators is permanently increasing. Linear actuator is able to push, pull, and hold objects in a way that our bodies cannot. Additionally, electrically powered technology provides more sophisticated control options. Linear actuator drive many different functions that are essential to safe and efficient aircraft operation. Manufacturers and hobbyists alike are always on the hunt for new ways to automate functions while keeping development costs low. Providing cost-effective linear solutions for aerospace application is one of the biggest challenge. This research will provide a cost-effective actuator conceptual design for variable span morphing wing UAV. The cost-effective design will be presented along with the application-based selection of linear actuators for morphing wing UAV.
Antonio Cassiano Julio Filho, Auro Tikami, Elaine de Souza Ferreira de Paula
et al.
Annually, severe weather phenomena are responsible for tens of thousands of deaths and tens of billions of dollars of damage around the world. In Brazil, unlike other hydrometeorological events, severe atmospheric events are random and, therefore, do not have a sociospatial pattern. Because of that, there is a significant motivation to improve the prediction techniques for this kind of events, using high resolution numerical models. A large amount of high-quality observational data is required,
including lightning data in a very short-range. In addition, the detection of lightning flashes produced by storms is important for a wide variety of applications and in some areas of scientific research, which include the understanding of the human action on the climate and how the climate change can affect the behavior of storms in long range. One method to monitor
the lightning flashes is the implementation of sensors in satellites to obtain data. In this sense, the objective of the RaioSat project is to develop national technology for detecting lightning flashes from the space, in order to complement the existing data from the ground detection network, BrasilDAT. The main objective of this article is to present a methodology for the development of the RaioSat mission including some parts of the preliminary design and operational modes. Additionally, the article describes the expected results and the continuity of the project and a preliminary analysis of a constellation for
future projects.
Technology, Motor vehicles. Aeronautics. Astronautics