Aerospace

13 pages, 4041 KiB

Open AccessArticle

An Efficient Analysis Method of Aluminum Alloy Helicopter Fuselage Projectile Damage Based on Projectile Breakdown Theory

by Xiaobing Xing, Jianfeng Tan, Yuxiao Yang, Tian Yong, Linjun Yu and Yun Zhou

Aerospace 2024, 11(6), 500; https://doi.org/10.3390/aerospace11060500 - 20 Jun 2024

Viewed by 358

Abstract

The shape and structure of helicopter fuselage are complex, and it is difficult for a finite element method (FEM) to investigate helicopter fuselage projectile damage in a multi-projectile environment. An efficient analysis method for helicopter fuselage projectile damage is then proposed by coupling [...] Read more.

The shape and structure of helicopter fuselage are complex, and it is difficult for a finite element method (FEM) to investigate helicopter fuselage projectile damage in a multi-projectile environment. An efficient analysis method for helicopter fuselage projectile damage is then proposed by coupling the projectile breakdown theory, which is derived from the existing empirical formula for penetrating ductile metals, and the model of projectile impact. Then, the characteristics of the helicopter fuselage impact coordinate, residual velocity, and fuselage damage area under a multi-projectile attack are investigated. The results show that the predicted residual velocities agree with the experiments. The maximum errors of the residual velocity and the fuselage damage area are 4.7% and 9.56%, respectively. Compared with the FEM, the computational time of the proposed method is reduced by 92.1%, and its efficiency is obviously improved. As the incidence angle increases, the residual velocity decreases, and the damage area increases. When the incidence angle of the projectile body is large, the projectile body cannot penetrate the surface of the fuselage, resulting in flume skid damage and a large area of damage. Full article

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32 pages, 32908 KiB

Open AccessArticle

An Analytical Reentry Solution Based Online Time-Coordinated A* Path Planning Method for Hypersonic Gliding Vehicles Considering No-Fly-Zone Constraint

by Zihan Xie, Changzhu Wei, Naigang Cui and Yingzi Guan

Aerospace 2024, 11(6), 499; https://doi.org/10.3390/aerospace11060499 - 20 Jun 2024

Viewed by 345

Abstract

To meet the time-coordinated requirement of hypersonic gliding vehicles to reach a single target simultaneously in the presence of no-fly-zone constraints, this paper proposes a time-coordinated A* path planning method considering multiple constraints. The path planning method is designed based on an analytical [...] Read more.

To meet the time-coordinated requirement of hypersonic gliding vehicles to reach a single target simultaneously in the presence of no-fly-zone constraints, this paper proposes a time-coordinated A* path planning method considering multiple constraints. The path planning method is designed based on an analytical steady gliding path model and the framework of the A* algorithm. Firstly, an analytical steady gliding path model is designed based on a quadratic function-type altitude-velocity profile. It can derive the control commands explicitly according to the desired terminal altitude and velocity, thus establishing a mapping between the terminal states and the control commands. Secondly, the node extension method of the A* algorithm is improved based on the mapping. Taking the terminal states as new design variables, a feasible path-node set is produced by a one-step integration using the control commands derived according to different terminal states. This node extension method ensures the feasibility of the path nodes while satisfying terminal constraints. Next, the path evaluation function of the A* algorithm is modified by introducing a heuristic switching term to select the most proper node as a waypoint, aiming to minimize the arrival time deviation. Meanwhile, introducing the penalty items into the path evaluation function satisfies the no-fly-zone constraints, process constraints, and control variable constraints. Finally, an online time-coordinated method is proposed to determine a commonly desired arrival time for several hypersonic gliding vehicles. It eliminates the need to specify the arrival time in advance and improves the capability to deal with sudden threats, increasing the path planning method’s online application capability. The proposed method can achieve online time-coordinated multi-constraint path planning for several hypersonic gliding vehicles, whose effectiveness and superiority are verified by simulations. Full article

(This article belongs to the Special Issue Dynamics, Guidance and Control of Aerospace Vehicles)

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18 pages, 2320 KiB

Open AccessArticle

Comprehensive Measurement of Position and Velocity in the Transverse Direction Using the Crab Pulsar

by Yuan Feng, Huanzi Zhang, Jianfeng Chen, Jin Liu and Xin Ma

Aerospace 2024, 11(6), 498; https://doi.org/10.3390/aerospace11060498 - 20 Jun 2024

Viewed by 316

Abstract

Traditional X-ray pulsar ranging and velocity measurement methods only estimate the radial position and velocity information of the pulsar. For non-linear orbits, errors in the transverse position and velocity of the pulsar lead to errors in the radial velocity of the pulsar, leading [...] Read more.

Traditional X-ray pulsar ranging and velocity measurement methods only estimate the radial position and velocity information of the pulsar. For non-linear orbits, errors in the transverse position and velocity of the pulsar lead to errors in the radial velocity of the pulsar, leading to distortion of the X-ray pulsar profile. Based on this, we propose using the distortion of the pulsar profile to infer the transverse position and velocity information of the pulsar. First, a model of the distortion of the pulsar profile due to errors in the transverse position and velocity is established, and the observable directions of the transverse position and velocity are given separately. Then, considering that the distortions in the pulsar profile caused by errors in the transverse position and velocity are indistinguishable, we establish a reactive motion state measure related to the observable directions for the transverse position and velocity errors as a new observable measure in X-ray pulsar navigation. The experimental results show that the precision of the reactive motion state measure reaches 0.57, equivalent to a position error of 284.50 m or a velocity error of 0.57 m/s. Full article

(This article belongs to the Special Issue Space Navigation and Control Technologies)

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29 pages, 2080 KiB

Open AccessArticle

Summary of Lunar Constellation Navigation and Orbit Determination Technology

by Xiao Zhang, Zhaowei Sun, Xiao Chen, Linxin Pan and Yubin Zhong

Aerospace 2024, 11(6), 497; https://doi.org/10.3390/aerospace11060497 - 20 Jun 2024

Viewed by 354

Abstract

The Moon is the closest celestial body to the Earth. Its rich unique resources are an important supplement to the Earth’s resources and have a profound impact on the sustainable development of human society. As large-scale exploration missions gradually progress, demands for communication, [...] Read more.

The Moon is the closest celestial body to the Earth. Its rich unique resources are an important supplement to the Earth’s resources and have a profound impact on the sustainable development of human society. As large-scale exploration missions gradually progress, demands for communication, navigation, surveying and other services of lunar-space probes have significantly increased. Constellation navigation and orbit determination technology will become an indispensable part of future lunar exploration infrastructure. This article systematically analyzes the current status of lunar relay navigation satellite networks at home and abroad, summarizes the technical principles of single-satellite and constellation navigation and orbit determination, discusses the technical difficulties in lunar navigation constellation orbit determination and navigation, and analyzes possible solutions. Finally, the development trend of research on high-precision orbit determination and navigation methods for lunar navigation constellations is proposed. Full article

(This article belongs to the Special Issue Space Navigation and Control Technologies)

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18 pages, 5724 KiB

Open AccessArticle

Pixel-Wise and Class-Wise Semantic Cues for Few-Shot Segmentation in Astronaut Working Scenes

by Qingwei Sun, Jiangang Chao, Wanhong Lin, Dongyang Wang, Wei Chen, Zhenying Xu and Shaoli Xie

Aerospace 2024, 11(6), 496; https://doi.org/10.3390/aerospace11060496 - 20 Jun 2024

Viewed by 329

Abstract

Few-shot segmentation (FSS) is a cutting-edge technology that can meet requirements using a small workload. With the development of China Aerospace Engineering, FSS plays a fundamental role in astronaut working scene (AWS) intelligent parsing. Although mainstream FSS methods have made considerable breakthroughs in [...] Read more.

Few-shot segmentation (FSS) is a cutting-edge technology that can meet requirements using a small workload. With the development of China Aerospace Engineering, FSS plays a fundamental role in astronaut working scene (AWS) intelligent parsing. Although mainstream FSS methods have made considerable breakthroughs in natural data, they are not suitable for AWSs. AWSs are characterized by a similar foreground (FG) and background (BG), indistinguishable categories, and the strong influence of light, all of which place higher demands on FSS methods. We design a pixel-wise and class-wise network (PCNet) to match support and query features using pixel-wise and class-wise semantic cues. Specifically, PCNet extracts pixel-wise semantic information at each layer of the backbone using novel cross-attention. Dense prototypes are further utilized to extract class-wise semantic cues as a supplement. In addition, the deep prototype is distilled in reverse to the shallow layer to improve its quality. Furthermore, we customize a dataset for AWSs and conduct abundant experiments. The results indicate that PCNet outperforms the published best method by 4.34% and 5.15% in accuracy under one-shot and five-shot settings, respectively. Moreover, PCNet compares favorably with the traditional semantic segmentation model under the 13-shot setting. Full article

(This article belongs to the Section Astronautics & Space Science)

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9 pages, 188 KiB

Open AccessArticle

Air Traffic Controllers’ Rostering: Sleep Quality, Vigilance, Mental Workload, and Boredom: A Report of Two Case Studies

by Michela Terenzi, Giorgia Tempestini and Francesco Di Nocera

Aerospace 2024, 11(6), 495; https://doi.org/10.3390/aerospace11060495 - 20 Jun 2024

Viewed by 326

Abstract

Fatigue in air traffic management (ATM) is a well-recognized safety concern. International organizations like ICAO and EASA have responded by advocating for fatigue risk management systems (FRMSs). EU Regulation 2017/373, implemented in January 2020, mandates specific requirements for air traffic service providers (ANSPs) [...] Read more.

Fatigue in air traffic management (ATM) is a well-recognized safety concern. International organizations like ICAO and EASA have responded by advocating for fatigue risk management systems (FRMSs). EU Regulation 2017/373, implemented in January 2020, mandates specific requirements for air traffic service providers (ANSPs) regarding controller fatigue, stress, and rostering practices. These regulations are part of broader safety management protocols. Despite ongoing efforts to raise awareness about fatigue in ATC, standardized operational requirements remain elusive. To address this gap, Eurocontrol recently published “Guidelines on fatigue management in ATC rostering systems” (23 April 2024). This initiative aims to facilitate the adoption of common fatigue management standards across operations. However, neither EU Regulation 2017/373 nor existing documentation provides definitive rostering criteria. ANSPs typically derive these criteria from a combination of scientific research, best practices, historical data, and legal and operational constraints. Assessing and monitoring fatigue in the real-world ATC setting is complex. The multifaceted nature of fatigue makes it difficult to study, as it is influenced by many factors including sleep quality, circadian rhythms, psychosocial stressors, individual differences, and environmental conditions. Long-term studies are often required to fully understand these complex interactions. This paper presents two case studies that attempt to create an evidence-based protocol for fatigue risk monitoring in ATC operations. These studies utilize a non-invasive approach and collect multidimensional data. The cases involved en-route and tower (TWR) controllers from different ATC centers. The results highlight the importance of fatigue assessment in ATC and shed light on the challenges of implementing fatigue monitoring systems within operational environments. Full article

(This article belongs to the Special Issue Human Factors during Flight Operations)

23 pages, 4538 KiB

Open AccessReview

The U.S. Air Force Next-Generation Air-Refueling System: A Resurgence of the Blended Wing Body?

by Guilherme Fernandes and Victor Maldonado

Aerospace 2024, 11(6), 494; https://doi.org/10.3390/aerospace11060494 - 20 Jun 2024

Viewed by 468

Abstract

The interest in flying wings dates as far as the early years of the aviation age. Early investigations of the feasibility of the concept demonstrated increased aerodynamic efficiency and reduced fuel consumption. However, structural, engine integration, and stability and control issues prevented further [...] Read more.

The interest in flying wings dates as far as the early years of the aviation age. Early investigations of the feasibility of the concept demonstrated increased aerodynamic efficiency and reduced fuel consumption. However, structural, engine integration, and stability and control issues prevented further development. In the 1990s, a new concept, the blended wing body (BWB), was created to alleviate some of the concerns of flying wings while maintaining increased efficiency and adding further benefits, such as reduced pollutant and noise emissions. Despite the promise, technical hurdles once again proved to be a deal breaker and, as of 2024, the only successful flying wing is the B-2 Spirit, an extremely complex and expensive aircraft. Nowadays, with the world quickly transitioning towards cleaner energy, the interest in the BWB has been renewed. The latest technological advancements in the aerospace industry should make its development more plausible; however, passenger comfort issues remain. Surprisingly, the BWB development may come from an unexpected application, as a tanker aircraft. As the U.S. Air Force is seeking a replacement to hundreds of aging tankers, a startup company was recently funded to develop the concept and build a prototype. In this study, we explore the history of blended designs from its early days, highlighting its opportunities and challenges—and why the design is an intriguing fit for application as a tanker aircraft. Full article

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26 pages, 7019 KiB

Open AccessArticle

A Smart Wing Model: From Design to Testing in a Wind Tunnel with a Turbulence Generator

by Ioan Ursu, George Tecuceanu, Daniela Enciu, Adrian Toader, Ilinca Nastase, Minodor Arghir and Manuela Calcea

Aerospace 2024, 11(6), 493; https://doi.org/10.3390/aerospace11060493 - 19 Jun 2024

Viewed by 389

Abstract

The paper concerns the technology of the design, realization, and testing of a flexible smart wing in a wind tunnel equipped with a turbulence generator. The system of smart wing, described in detail, consists mainly of: a physical model of the wing with [...] Read more.

The paper concerns the technology of the design, realization, and testing of a flexible smart wing in a wind tunnel equipped with a turbulence generator. The system of smart wing, described in detail, consists mainly of: a physical model of the wing with an aileron; an electric servomotor of broadband with a connecting rod-crank mechanism for converting the rectilinear motion of the servoactuator into the aileron deflection; two transducers: an encoder for measuring the deflection of the control aileron and an accelerometer mounted on the wing to measure its bending and torsional vibrations; a procedure for determining the mathematical model of the wing by experimental identification; a turbulence generator in the wind tunnel; implemented

ℋ_{\infty}

and LQG algorithms for active control of vibrations. The attenuation experimentally obtained for the aeroelastic vibrations of the wing, but also for those accentuated by the turbulence, reaches values of up to 50%. Full article

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22 pages, 1070 KiB

Open AccessArticle

Analytic Solutions for Volume, Mass, Center of Gravity, and Inertia of Wing Segments and Rotors of Constant Density

by Benjamin C. Moulton and Douglas F. Hunsaker

Aerospace 2024, 11(6), 492; https://doi.org/10.3390/aerospace11060492 - 19 Jun 2024

Viewed by 447

Abstract

In the preliminary design of aircraft lifting surfaces, accurate mass and inertia properties can be difficult to obtain. Typically, such methods as computer-aided design or statistical processes are used to determine these properties. These methods require significant time and effort to implement. The [...] Read more.

In the preliminary design of aircraft lifting surfaces, accurate mass and inertia properties can be difficult to obtain. Typically, such methods as computer-aided design or statistical processes are used to determine these properties. These methods require significant time and effort to implement. The present paper presents an exact analytic method for calculating the volume, mass, center of gravity, and inertia properties of wing segments and rotors of constant density. The influence of taper, spanwise thickness distribution, airfoil geometry, and sweep are included. The utility of the method is presented, and the accuracy is evaluated with various test cases via percent difference with a corresponding computer-aided design model. These case studies demonstrate the present method to be accurate to within about 1% for typical wing geometries and within about 1.3% for typical propeller geometries. Full article

(This article belongs to the Section Aeronautics)

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28 pages, 21291 KiB

Open AccessArticle

Electrostatic Signal Self-Adaptive Denoising Method Combined with CEEMDAN and Wavelet Threshold

by Yan Liu, Hongfu Zuo, Zhenzhen Liu, Yu Fu, James Jiusi Jia and Jaspreet S. Dhupia

Aerospace 2024, 11(6), 491; https://doi.org/10.3390/aerospace11060491 - 19 Jun 2024

Viewed by 384

Abstract

A novel low-pass filtering self-adaptive (LPFA) denoising method combining complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) and a wavelet threshold (WT) strategy is proposed to solve the problem of the aero-engine gas-path electrostatic signal noise, which challenges the gas-path component condition [...] Read more.

A novel low-pass filtering self-adaptive (LPFA) denoising method combining complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) and a wavelet threshold (WT) strategy is proposed to solve the problem of the aero-engine gas-path electrostatic signal noise, which challenges the gas-path component condition monitoring and feature extraction techniques. Firstly, the integration of CEEMDAN addresses modal aliasing and intermittent signal challenges, while the proposed low-pass filtering method autonomously selects valuable signal components. Additionally, the application of the WT in the unselected components enhances the extraction of useful information, presenting a unique and advanced approach to electrostatic signal denoising. Moreover, the proposed method is applied to simulated signals with different input signal-to-noise ratios and experimental fault electrostatic signals of a micro-turbojet engine. The comparison with several traditional approaches in a denoising test for the simulated signals and experimental signals reveals that the proposed method performs better in extracting the effective components of the signal and eliminating noise. Full article

(This article belongs to the Section Aeronautics)

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19 pages, 1217 KiB

Open AccessArticle

Optimal Guidance for Heliocentric Orbit Cranking with E-Sail-Propelled Spacecraft

by Alessandro A. Quarta

Aerospace 2024, 11(6), 490; https://doi.org/10.3390/aerospace11060490 - 19 Jun 2024

Viewed by 398

Abstract

In astrodynamics, orbit cranking is usually referred to as an interplanetary transfer strategy that exploits multiple gravity-assist maneuvers to change both the inclination and eccentricity of the spacecraft osculating orbit without changing the specific mechanical energy, that is, the semimajor axis. In the [...] Read more.

In astrodynamics, orbit cranking is usually referred to as an interplanetary transfer strategy that exploits multiple gravity-assist maneuvers to change both the inclination and eccentricity of the spacecraft osculating orbit without changing the specific mechanical energy, that is, the semimajor axis. In the context of a solar sail-based mission, however, the concept of orbit cranking is typically referred to as a suitable guidance law that is able to (optimally) change the orbital inclination of a circular orbit of an assigned radius in a general heliocentric three-dimensional scenario. In fact, varying the orbital inclination is a challenging maneuver from the point of view of the velocity change, so orbit cranking is an interesting mission application for a propellantless propulsion system. The aim of this paper is to analyze the performance of a spacecraft equipped with an Electric Solar Wind Sail in a cranking maneuver of a heliocentric circular orbit. The maneuver performance is calculated in an optimal framework considering spacecraft dynamics described by modified equinoctial orbital elements. In this context, the paper presents an analytical version of the three-dimensional optimal guidance laws obtained by using the classical Pontryagin’s maximum principle. The set of (analytical) optimal control laws is a new contribution to the Electric Solar Wind Sail-related literature. Full article

(This article belongs to the Special Issue Advances in CubeSat Sails and Tethers (2nd Edition))

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23 pages, 7915 KiB

Open AccessArticle

Aircraft Wake Evolution Prediction Based on Parallel Hybrid Neural Network Model

by Leilei Deng, Weijun Pan, Yuhao Wang, Tian Luan and Yuanfei Leng

Aerospace 2024, 11(6), 489; https://doi.org/10.3390/aerospace11060489 - 19 Jun 2024

Viewed by 427

Abstract

To overcome the time-consuming drawbacks of Computational Fluid Dynamics (CFD) numerical simulations, this paper proposes a hybrid model named PA-TLA (parallel architecture combining a TCN, LSTM, and an attention mechanism) based on the concept of intelligent aerodynamics and a parallel architecture. This model [...] Read more.

To overcome the time-consuming drawbacks of Computational Fluid Dynamics (CFD) numerical simulations, this paper proposes a hybrid model named PA-TLA (parallel architecture combining a TCN, LSTM, and an attention mechanism) based on the concept of intelligent aerodynamics and a parallel architecture. This model utilizes CFD data to drive efficient predictions of aircraft wake evolution at different initial altitudes during the approach phase. Initially, CFD simulations of continuous initial altitudes during the approach phase are used to generate aircraft wake evolution data, which are then validated against real-world LIDAR data to verify their reliability. The PA-TLA model is designed based on a parallel architecture, combining Long Short-Term Memory (LSTM) networks, Temporal Convolutional Networks (TCNs), and a tensor concatenation module based on the attention mechanism, which ensures computational efficiency while fully leveraging the advantages of each component in a parallel processing framework. The study results show that the PA-TLA model outperforms both the LSTM and TCN models in predicting the three characteristic parameters of aircraft wake: vorticity, circulation, and Q-criterion. Compared to the serially structured TCN-LSTM, PA-TLA achieves an average reduction in mean squared error (MSE) of 6.80%, in mean absolute error (MAE) of 7.70%, and in root mean square error (RMSE) of 4.47%, with an average increase in the coefficient of determination (R²) of 0.36% and a 35% improvement in prediction efficiency. Lastly, this study combines numerical simulations and the PA-TLA deep learning architecture to analyze the near-ground wake vortex evolution. The results indicate that the ground effect increases air resistance and turbulence as vortices approach the ground, thereby slowing the decay rate of the wake vortex strength at lower altitudes. The ground effect also accelerates the dissipation and movement of vortex centers, causing more pronounced changes in vortex spacing at lower altitudes. Additionally, the vortex center height at lower altitudes initially decreases and then increases, unlike the continuous decrease observed at higher altitudes. Full article

(This article belongs to the Section Aeronautics)

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21 pages, 5940 KiB

Open AccessArticle

Improved YOLOv5 Network for Aviation Plug Defect Detection

by Li Ji and Chaohang Huang

Aerospace 2024, 11(6), 488; https://doi.org/10.3390/aerospace11060488 - 19 Jun 2024

Viewed by 393

Abstract

Ensuring the integrity of aviation plug components is crucial for maintaining the safety and functionality of the aerospace industry. Traditional methods for detecting surface defects often show low detection probabilities, highlighting the need for more advanced automated detection systems. This paper enhances the [...] Read more.

Ensuring the integrity of aviation plug components is crucial for maintaining the safety and functionality of the aerospace industry. Traditional methods for detecting surface defects often show low detection probabilities, highlighting the need for more advanced automated detection systems. This paper enhances the YOLOv5 model by integrating the Generalized Efficient Layer Aggregation Network (GELAN), which optimizes feature aggregation and boosts model robustness, replacing the conventional Convolutional Block Attention Module (CBAM). The upgraded YOLOv5 architecture, incorporating GELAN, effectively aggregates multi-scale and multi-layer features, thus preserving essential information across the network’s depth. This capability is vital for maintaining high-fidelity feature representations, critical for detecting minute and complex defects. Additionally, the Focal EIOU loss function effectively tackles class imbalance and concentrates the model’s attention on difficult detection areas, thus significantly improving its sensitivity and overall accuracy in identifying defects. Replacing the traditional coupled head with a lightweight decoupled head improves the separation of localization and classification tasks, enhancing both accuracy and convergence speed. The lightweight decoupled head also reduces computational load without compromising detection efficiency. Experimental results demonstrate that the enhanced YOLOv5 architecture significantly improves detection probability, achieving a detection rate of 78.5%. This improvement occurs with only a minor increase in inference time per image, underscoring the efficiency of the proposed model. The optimized YOLOv5 model with GELAN proves highly effective, offering significant benefits for the precision and reliability required in aviation component inspections. Full article

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22 pages, 11923 KiB

Open AccessArticle

Numerical Study on the Cooling Method of Phase Change Heat Exchange Unit with Layered Porous Media

by Ruo-Ji Zhang, Jing-Yang Zhang and Jing-Zhou Zhang

Aerospace 2024, 11(6), 487; https://doi.org/10.3390/aerospace11060487 - 19 Jun 2024

Viewed by 325

Abstract

The implementation of heat sinks in high-power pulse electronic devices within hypersonic aircraft cabins has been facilitated by the emergence of innovative phase change materials (PCMs) characterized by excellent thermal conductivity and high latent heat. In this study, a representative material, layered porous [...] Read more.

The implementation of heat sinks in high-power pulse electronic devices within hypersonic aircraft cabins has been facilitated by the emergence of innovative phase change materials (PCMs) characterized by excellent thermal conductivity and high latent heat. In this study, a representative material, layered porous media filled with paraffin wax, was utilized, and a three-dimensional numerical model based on the enthalpy-porosity approach was employed. A thermal response research was conducted on the Phase Change Heat Exchange Unit with Layered Porous Media (PCHEU-LPM) with different cooling methods. The results indicate that water cooling proved to be suitable for the PCHEU-LPM with a heat flux of 50,000 W/m². Additionally, parametric studies were performed to determine the optimal cooling conditions, considering the inlet temperature and velocity of the cooling flow. The results revealed that the most suitable conditions were strongly influenced by the coolant inlet parameters, along with the position of the PCM interface. Finally, the identification of the parameter combination that minimizes temperature fluctuations was achieved through the Response Surface Analysis method (RSA). Subsequent verification through simulation further reinforced the reliability of the proposed optimal parameters. Full article

(This article belongs to the Section Aeronautics)

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15 pages, 1059 KiB

Open AccessArticle

Coaxial Helicopter Attitude Control System Design by Advanced Model Predictive Control under Disturbance

by Zhi Chen, Xiangyu Lin and Wanyue Jiang

Aerospace 2024, 11(6), 486; https://doi.org/10.3390/aerospace11060486 - 19 Jun 2024

Viewed by 415

Abstract

This paper proposes an advanced model predictive control (MPC) scheme for the attitude tracking of coaxial drones under wind disturbances. Unlike most existing MPC setups, this scheme embeds steady-input, steady-output, and steady-state conditions into the optimization problem as decision variables. Consequently, the coaxial [...] Read more.

This paper proposes an advanced model predictive control (MPC) scheme for the attitude tracking of coaxial drones under wind disturbances. Unlike most existing MPC setups, this scheme embeds steady-input, steady-output, and steady-state conditions into the optimization problem as decision variables. Consequently, the coaxial drone’s attitude can slide along the state manifold composed of a series of steady states. This allows it to move toward the optimal reachable equilibrium. To address disturbances that are difficult to accurately measure, an extended state observer is employed to estimate the disturbances in the prediction model. This design ensures that the algorithm maintains recursive stability even in the presence of disturbances. Finally, numerical simulations and flight tests are provided to confirm the effectiveness of the proposed method through comparison with other control algorithms. Full article

(This article belongs to the Section Aeronautics)

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16 pages, 5387 KiB

Open AccessArticle

Investigation on Accelerated Initiation of Oblique Detonation Wave Induced by Laser-Heating Hot-Spot

by Yirong Xin, Jiahao Shang, Gaoxiang Xiang and Qiu Wang

Aerospace 2024, 11(6), 485; https://doi.org/10.3390/aerospace11060485 - 19 Jun 2024

Viewed by 532

Abstract

A reliable initiation of oblique detonation is critical in oblique detonation engines, especially for oblique detonation engines under extreme conditions such as a high altitude and low Mach number, which may lead to excessive length of the induction zone and even the phenomenon [...] Read more.

A reliable initiation of oblique detonation is critical in oblique detonation engines, especially for oblique detonation engines under extreme conditions such as a high altitude and low Mach number, which may lead to excessive length of the induction zone and even the phenomenon of extinction. In this paper, surface ignition was applied to the initiation of oblique detonation, and a high-temperature region was set on the wedge to simulate the presence of a hot-spot induced by the laser heating. The two-dimensional multi-component Navier–Stokes equations considering a detailed H₂ combustion mechanism are solved, and the oblique detonation wave accelerated by a hot-spot is studied. In this paper, hot-spots in the induction zone on the wedge, are introduced to explore the possibility of hot-spot initiation, providing a potential method for initiation control. Results show that these methods can effectively promote the accelerated initiation of the oblique detonation. Furthermore, the hot-spot temperature, size and position are varied to analyze their effects on the initiation position. Increasing the temperature and size of the hot-spot both can accelerate initiation, but from the perspective of energy consumption, a small hot-spot at a high temperature is preferable for accelerating ODW initiation than a large hot-spot at a low temperature. The initiated position of the oblique detonation is sensitive to the position of the hot-spots; if a 2000 K hotspot is at the beginning of the wedge, then the ODW’s initiation distance will be reduced to about 30% of that without hotspot acceleration. Full article

(This article belongs to the Special Issue Advances in Detonative Propulsion)

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21 pages, 8115 KiB

Open AccessArticle

Evaluation of Sonic Boom Shock Wave Generation with CFD Methods

by Samuele Graziani, Francesco Petrosino, Jacob Jäschke, Antimo Glorioso, Roberta Fusaro and Nicole Viola

Aerospace 2024, 11(6), 484; https://doi.org/10.3390/aerospace11060484 - 19 Jun 2024

Viewed by 662

Abstract

Over the past two decades, there has been a renewed interest in the development of a new generation of supersonic aircraft for civil purposes that could potentially succeed Concorde. However, the noise annoyance is still considered one of the hampering factors to meet [...] Read more.

Over the past two decades, there has been a renewed interest in the development of a new generation of supersonic aircraft for civil purposes that could potentially succeed Concorde. However, the noise annoyance is still considered one of the hampering factors to meet public consensus. This paper aims at revealing the potential of numerical simulations to predict sonic boom signature in Near Field at early design stages. In particular, the paper further demonstrates the applicability of the numerical approach proposed by NASA and other partners during the Sonic Boom Prediction Workshops held between 2014 and 2021, to compute the pressure signature of aircraft in the zone close to it. The results highlight the suitability of the approach (1) to capture the impact of aircraft flight condition variations on the sonic boom signature, (2) to enable the characterization of novel aircraft layout, including Mach 5 waverider configuration, (3) to provide near-field shock wave noise predictions that can be used to evaluate shock propagation, on-ground signature analyses, and annoyance assessment. Full article

(This article belongs to the Special Issue Sustainable Civil Supersonic and Hypersonic Aircraft: Main Challenges and Latest Developments)

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15 pages, 58652 KiB

Open AccessArticle

Research on the Heat Dissipation in Aviation-Integrated Communication Equipment Based on Graphene Films

by Jingyi Qian, Min Liu, Quan Zhao, Shimiao Luo, Feng Xia and Yunfeng Bai

Aerospace 2024, 11(6), 483; https://doi.org/10.3390/aerospace11060483 - 18 Jun 2024

Viewed by 431

Abstract

Aviation-integrated communication equipment is integral to modern aircraft to ensure its performance and safety. The heat dissipation problems of equipment have become increasingly prominent for the high electronic integration and system power consumption. To solve the above problem, the heat dissipation performance of [...] Read more.

Aviation-integrated communication equipment is integral to modern aircraft to ensure its performance and safety. The heat dissipation problems of equipment have become increasingly prominent for the high electronic integration and system power consumption. To solve the above problem, the heat dissipation performance of aviation-integrated communication equipment based on graphene films is deeply studied. This paper establishes a three-dimensional model of aviation-integrated communication equipment to simulate the distribution of temperature fields. The influence between aluminum alloy and graphene films on the surface of magnesium alloy on the heat dissipation performance of aviation-integrated communication equipment is studied. The simulation results show that the heat balance time of the equipment using graphene films on the surface of magnesium alloy is reduced from 3600 s to 800 s, representing an approximately 77.78% improvement; the measured equipment exhibited a reduction in its overall thermal equilibrium temperature, decreasing from 68.1 °C to 66.3 °C, representing an improvement of approximately 2.64%. Full article

(This article belongs to the Special Issue Design and Analysis of Advanced Composites and Structures in Aerospace)

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23 pages, 8853 KiB

Open AccessArticle

Fluid–Structure Interactions between Oblique Shock Trains and Thin-Walled Structures in Isolators

by Xianzong Meng, Ruoshuai Zhao, Qiaochu Wang, Zebin Zhang and Junlei Wang

Aerospace 2024, 11(6), 482; https://doi.org/10.3390/aerospace11060482 - 18 Jun 2024

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Abstract

Understanding aeroelastic issues related to isolators is pivotal for the structural design and flow control of scramjets. However, research on fluid–structure interactions (FSIs) between thin-walled structures and the isolator flow remains limited. This study delves into the FSIs between thin-walled panels and the [...] Read more.

Understanding aeroelastic issues related to isolators is pivotal for the structural design and flow control of scramjets. However, research on fluid–structure interactions (FSIs) between thin-walled structures and the isolator flow remains limited. This study delves into the FSIs between thin-walled panels and the isolator flow, as characterized by an oblique shock train, by quantitatively analyzing 11 flow parameters assessing the structural response, separation zones, shock structures, flow symmetry, and performance. The results reveal that an FSI triggers panel flutter under oblique shock train conditions, with the panel shapes exhibiting a combination of first- and second-mode responses, peaking at 0.75 of the panel length. Compared to rigid wall conditions, isolators with a flexible panel at the bottom wall experience downstream movement of the separation zones and shock structures, reduced flow symmetry, and minor changes in performance. Transient fluctuations occur due to the panel flutter. Two flexible panels at the top and bottom walls have a comparatively lesser influence on the averaged parameters but exhibit more violent transient fluctuations. Furthermore, the FSI effects under oblique shock train conditions are contrasted with those under normal shock train conditions. The flutter response under normal shock train conditions is more pronounced, with a larger amplitude and higher frequency, driven by the heightened participation of the first-mode response. The effects of FSIs under normal shock train conditions on the averaged parameters are the opposite (with a larger influence) to those under oblique shock train conditions, with significantly more drastic transient fluctuations. Overall, this study sheds light on the complex and substantial influence of FSIs on the isolator flow, emphasizing the necessity of considering FSIs in future isolator design and development endeavors. Full article

(This article belongs to the Special Issue Aeroelasticity, Volume IV)

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26 pages, 28425 KiB

Open AccessArticle

The Electrostatic Induction Characteristics of SiC/SiC Particles in Aero-Engine Exhaust Gases: A Simulated Experiment and Analysis

by Yan Liu, Zhenzhen Liu, Fang Bai, Hongfu Zuo, Zezhong Guo and Xin Li

Aerospace 2024, 11(6), 481; https://doi.org/10.3390/aerospace11060481 - 17 Jun 2024

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Abstract

This study investigates the electrostatic induction characteristics of silicon carbide-fiber-reinforced silicon carbide (SiC/SiC) particles within aero-engine exhaust gases using a dedicated J20 turbojet engine experimental platform. Our comprehensive experiments explored the electrostatic properties of SiC/SiC particles under varying engine operational states—specifically focusing on [...] Read more.

This study investigates the electrostatic induction characteristics of silicon carbide-fiber-reinforced silicon carbide (SiC/SiC) particles within aero-engine exhaust gases using a dedicated J20 turbojet engine experimental platform. Our comprehensive experiments explored the electrostatic properties of SiC/SiC particles under varying engine operational states—specifically focusing on different thermal conditions, particle mass concentrations, particle sizes, and exhaust gas velocities compared to those of common engine exhaust constituents like carbon (C) and iron (Fe) particles. The results demonstrate that SiC/SiC particles consistently maintain a stable positive charge across varied temperatures, significantly diverging from the behaviors of carbon (C) and iron (Fe) particles. Additionally, our findings reveal that higher mass concentrations of SiC/SiC particles, smaller particle sizes within a certain range, and greater exhaust gas velocities of the aero-engine all lead to increased particle charge and more pronounced electrostatic induction characteristics. This study highlights the potential of electrostatic sensors for the early detection and diagnosis of failures in aero-engines, offering crucial insights into the development of more resilient real-time aero-engine health monitoring systems. Full article

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13 pages, 3843 KiB

Open AccessArticle

Decomposing Carbon Intensity Trends in China’s Civil Aviation: A Comprehensive Analysis from 1998 to 2019

by Jinglei Yu, Mengyuan Lu, Kaifeng Wang, Jinmei Ge, Zan Tao, Zheng Xu and Longfei Chen

Aerospace 2024, 11(6), 480; https://doi.org/10.3390/aerospace11060480 - 17 Jun 2024

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Abstract

Carbon emission intensity is an important index reflecting an entity’s low-carbon competitiveness. This paper presents an extended logarithmic mean divisia index (LMDI) model to dissect carbon intensity within China’s civil aviation from 1998 to 2019, revealing a significant reduction in CO₂ emissions [...] Read more.

Carbon emission intensity is an important index reflecting an entity’s low-carbon competitiveness. This paper presents an extended logarithmic mean divisia index (LMDI) model to dissect carbon intensity within China’s civil aviation from 1998 to 2019, revealing a significant reduction in CO₂ emissions per air transport revenue. It attributes this decrease to technological advancements, optimized fleet structures, and improved operational efficiencies, highlighting the impact of larger, more efficient aircraft and enhanced load factors. The study also explores economic factors influencing carbon efficiency, suggesting a comprehensive approach encompassing technological innovation and strategic operational improvements for sustainable aviation development. Full article

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15 pages, 5067 KiB

Open AccessArticle

High-Temperature DIC Deformation Measurement under High-Intensity Blackbody Radiation

by Seng Min Han and Nam Seo Goo

Aerospace 2024, 11(6), 479; https://doi.org/10.3390/aerospace11060479 - 17 Jun 2024

Viewed by 386

Abstract

During the high-speed flight of a vehicle in the atmosphere, surface friction with the air generates aerodynamic heating. The aerodynamic heating phenomenon can create extremely high temperatures near the surface. These high temperatures impact material properties and the structure of the aircraft, so [...] Read more.

During the high-speed flight of a vehicle in the atmosphere, surface friction with the air generates aerodynamic heating. The aerodynamic heating phenomenon can create extremely high temperatures near the surface. These high temperatures impact material properties and the structure of the aircraft, so thermal deformation measurement is essential in aerospace engineering. This paper revisits high-temperature deformation measurement using the digital image correlation (DIC) technique under high-intensity blackbody radiation with a precise speckle pattern fabrication and a heat haze reduction method. The effects of the speckle pattern on the DIC measurement have been thoroughly studied at room temperature, but high-temperature measurement studies have not reported such effects so far. We found that the commonly used methods to reduce the heat haze effect could produce incorrect results. Hence, we propose a new method to mitigate heat haze effects. An infrared radiation heater was employed to make an experimental setup that could heat a specimen up to 950 °C. First, we mitigated image saturation using a short-wavelength bandpass filter with blue light illumination, a standard procedure for high-temperature DIC deformation measurement. Second, we studied how to determine the proper size of the speckle pattern in a high-temperature environment. Third, we devised a reduction method for the heat haze effect. As proof of the effectiveness of our developed experimental method, we successfully measured the deformation of stainless steel 304 specimens from 25 °C to 800 °C. The results confirmed that this method can be applied to the research and development of thermal protection systems in the aerospace field. Full article

(This article belongs to the Special Issue Current Trend of High Temperature and Pressure Materials in Hypersonic Vehicles)

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14 pages, 2634 KiB

Open AccessArticle

Research on the Movement Speed of Situational Map Symbols Based on User Dynamic Preference Perception

by Mu Tong, Shanguang Chen, Xinyue Wang and Chengqi Xue

Aerospace 2024, 11(6), 478; https://doi.org/10.3390/aerospace11060478 - 17 Jun 2024

Viewed by 367

Abstract

When designing situational maps, selecting distinct and visually comfortable movement speeds for dynamic elements is an ongoing challenge for designers. This study addresses this issue by conducting two experiments to measure the human eye’s ability to discern moving speeds on a screen and [...] Read more.

When designing situational maps, selecting distinct and visually comfortable movement speeds for dynamic elements is an ongoing challenge for designers. This study addresses this issue by conducting two experiments to measure the human eye’s ability to discern moving speeds on a screen and examines how symbol movement speeds within situational maps affect users’ subjective experiences, task performance, and visual comfort. The first experiment measured participants’ speed discrimination capabilities for Landolt Ring of varying sizes moving at 0–256°/s, yielding speed discrimination thresholds of 7–23% and a sensitive velocity range of 1–64°/s. The second experiment evaluated observers’ visual perceptions of moving elements within a cognitive task across the same range of 1–64°/s, identifying three significant benchmarks—8°/s, 16°/s, and 32°/s. These can be utilized to categorize slow-, moderate-, and fast-moving symbols in situational maps. The findings can aid in designing human–machine interface environments with improved viewer experience and visual comfort for both Air Traffic Control interfaces and situational maps. Full article

(This article belongs to the Topic Uncertainty Quantification in Design, Manufacturing and Maintenance of Complex Systems)

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25 pages, 4683 KiB

Open AccessArticle

Concept Evaluation of Radical Short–Medium-Range Aircraft with Turbo-Electric Propulsion

by W. J. Vankan, W. F. Lammen, E. Scheers, P. J. Dewitte and Sebastien Defoort

Aerospace 2024, 11(6), 477; https://doi.org/10.3390/aerospace11060477 - 17 Jun 2024

Viewed by 520

Abstract

Ambitious targets for the coming decades have been set for further reductions in aviation greenhouse gas emissions. Hybrid electric propulsion (HEP) concepts offer potential for the mitigation of these aviation emissions. To investigate this potential in an adequate level of detail, the European [...] Read more.

Ambitious targets for the coming decades have been set for further reductions in aviation greenhouse gas emissions. Hybrid electric propulsion (HEP) concepts offer potential for the mitigation of these aviation emissions. To investigate this potential in an adequate level of detail, the European research project IMOTHEP (Investigation and Maturation of Technologies for Hybrid Electric Propulsion) explores key technologies for HEP in close relation with developments of aircraft missions and configuration. This paper presents conceptual-level design investigations on radical HEP aircraft configurations for short–medium-range (SMR) missions. In particular, a blended-wing-body (BWB) configuration with a turbo-electric powertrain and distributed electric propulsion is investigated using NLR’s aircraft evaluation tool MASS. For the aircraft and powertrain design, representative top-level aircraft requirements have been defined in IMOTHEP, and the reference aircraft for the assessment of potential benefits is based on the Airbus A320neo aircraft. The models and data developed in IMOTHEP and presented in this paper show that the turbo-electric BWB configuration has potential for reduced fuel consumption in comparison to the reference aircraft. But in comparison to advanced turbofan-powered BWB configurations, which have the same benefits of the BWB airframe and advanced technology assumptions, this potential is limited. Full article

(This article belongs to the Special Issue Multidisciplinary Design Optimization for Climate-Neutral Transport Aviation)

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15 pages, 4614 KiB

Open AccessArticle

Wind Shear Response of Aircraft with C* and C*U Controller during Approach

by Yufei Yan and Lei Song

Aerospace 2024, 11(6), 476; https://doi.org/10.3390/aerospace11060476 - 17 Jun 2024

Viewed by 403

Abstract

This study investigates the impact of wind shear on the flight dynamics of commercial aircraft where C* and C*U control laws are employed during the approach phase. Given the high incidence of flight accidents during takeoff and landing attributed to wind shear, this [...] Read more.

This study investigates the impact of wind shear on the flight dynamics of commercial aircraft where C* and C*U control laws are employed during the approach phase. Given the high incidence of flight accidents during takeoff and landing attributed to wind shear, this research aims to enhance aviation safety by analyzing control law behavior under varying wind shear conditions. A nonlinear flight simulation model was developed, utilizing aerodynamic and engine data from a B737, to explore the aircraft’s response to different wind shear intensities. The simulation analysis was used to compare the response of the aircraft with C* and C*U controllers, respectively, under different wind shear, and to evaluate the effectiveness of its stability enhancement in wind shear. It was found that in most cases, the controller can achieve a good stabilization effect, but in some cases of wind fields, the aircraft suffered more significant oscillation. Full article

(This article belongs to the Special Issue Advanced Aircraft Technology)

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16 pages, 16714 KiB

Open AccessArticle

Water Recuperation from Regolith at Martian, Lunar & Micro-Gravity during Parabolic Flight

by Dario Farina, Hatim Machrafi, Patrick Queeckers, Christophe Minetti and Carlo Saverio Iorio

Aerospace 2024, 11(6), 475; https://doi.org/10.3390/aerospace11060475 - 16 Jun 2024

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Abstract

Recent discoveries of potential ice particles and ice-cemented regolith on extraterrestrial bodies like the Moon and Mars have opened new opportunities for developing technologies to extract water, facilitating future space missions and activities on these extraterrestrial body surfaces. This study explores the potential [...] Read more.

Recent discoveries of potential ice particles and ice-cemented regolith on extraterrestrial bodies like the Moon and Mars have opened new opportunities for developing technologies to extract water, facilitating future space missions and activities on these extraterrestrial body surfaces. This study explores the potential for water extraction from regolith through an experiment designed to test water recuperation from regolith simulant under varying gravitational conditions. The resultant water vapor extracted from the regolith is re-condensed on a substrate surface and collected in liquid form. Three types of substrates, hydrophobic, hydrophilic, and grooved, are explored. The system’s functionality was assessed during a parabolic flight campaign simulating three distinct gravity levels: microgravity, lunar gravity, and Martian gravity. Our findings reveal that the hydrophobic surface demonstrates the highest efficiency due to drop-wise condensation, and lower gravity levels result in increased water condensation on the substrates. The experiments aimed to understand the performance of specific substrates under lunar, Martian, and microgravity conditions, providing an approach for in-situ water recovery, which is crucial for establishing economically sustainable water supplies for future missions. To enhance clarity and readability, in this paper, “H₂O” will be referred to as “water”. Full article

(This article belongs to the Special Issue The (Near) Future of Space Resources)

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19 pages, 10263 KiB

Open AccessArticle

Study on the Active Control of the Dynamic Stall of Rotor Airfoils Based on Plasma Excitation

by Weihong Kong, Keyi Guo and You Li

Aerospace 2024, 11(6), 474; https://doi.org/10.3390/aerospace11060474 - 15 Jun 2024

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Abstract

This paper studies a rotor dynamic stall control method using an alternating current dielectric barrier discharge (AC DBD) plasma actuator through numerical simulation methods. The flow field evolution during a dynamic stalling process under the excitation of AC DBD plasma discharge is analyzed [...] Read more.

This paper studies a rotor dynamic stall control method using an alternating current dielectric barrier discharge (AC DBD) plasma actuator through numerical simulation methods. The flow field evolution during a dynamic stalling process under the excitation of AC DBD plasma discharge is analyzed using the two-dimensional Reynolds time-averaged (RANS) method. The impact of the AC DBD plasma discharge on the flow field is then simulated using the phenomenological method. The influence of the position and intensity of the plasma excitation on the static stall characteristics of the NACA0012 airfoil is also studied. Deformed mesh and dynamic mesh techniques are used to simulate an aerodynamic environment with variable incoming flow and variable angles of attraction on a rotor airfoil. The application of AC DBD plasma excitation for controlling mild and deep dynamic stalls of rotor blades is investigated. The obtained results show that the AC DBD plasma excitation accelerated the evolution and shedding of dynamic stall vortices and facilitated the reattachment of airflow. The application of plasma excitation allowed for significantly increasing the static stall angle of the airfoil and improving the lift coefficient. In addition, the intensity of the plasma excitation is a key factor affecting the control. Moreover, the application of AC DBD plasma excitation for rotor dynamic stalls allowed for reducing the size of the dynamic stall vortex, which helped mitigate the aerodynamic hysteresis effect caused by the dynamic stall and accelerated the recovery from aerodynamic forces. Full article

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24 pages, 30756 KiB

Open AccessArticle

Computational Investigations for the Feasibility of Passive Flow Control Devices for Enhanced Aerodynamics of Small-Scale UAVs

by Ali Arshad and Vadims Kovaļčuks

Aerospace 2024, 11(6), 473; https://doi.org/10.3390/aerospace11060473 - 13 Jun 2024

Viewed by 516

Abstract

The 4R-UAV project aims to develop aerodynamically efficient and environmentally friendly UAVs based on the 4R Circular Economy principle. In this study, the feasibility of the application of PFCDs (Passive Flow Control Devices) was investigated for the small-scale low-speed 4R-UAV wing. The application [...] Read more.

The 4R-UAV project aims to develop aerodynamically efficient and environmentally friendly UAVs based on the 4R Circular Economy principle. In this study, the feasibility of the application of PFCDs (Passive Flow Control Devices) was investigated for the small-scale low-speed 4R-UAV wing. The application of PFCDs for small-scale UAV wings is relatively unexplored. Two PFCD types, i.e., MVGs (Micro Vortex Generators) and winglets, were considered for the investigations. In the stepwise investigations, the aerodynamic performance of the MVGs and the winglets was analyzed for the short-span 4R-UAV wing, which was developed from the aerodynamically optimized airfoil SG6043mod. MVGs enhanced the wings near stall properties (especially maximum lift coefficient) and contributed to the delayed wing stall of up to 2°. MVGs manifested the main aerodynamic advantage, which was achieved at the higher angles of attack. Winglets, on the other hand, were found to be extremely effective in cruise conditions with improved pre-stall characteristics. Extensive investigations on winglets were carried out by designing six winglet configurations for the 4R-UAV wing. Blended-type winglets performed well and enhanced pre-stall properties by decreasing the drag (up to 10%) of the wing. The main performance improvement was found in the early angles of attack. In the final step, the combined effect of the integrated PFCDs was analyzed. The final wing (integrated MVGs and winglets) also exhibited enhanced performance with nearly 6% increased lift-to-drag ratio in cruise conditions. The limited aerodynamic advantage achieved from the PFCDs in small-scale UAV applications can be useful in specific (civil or military) missions. Further verifications are planned in the future by means of experimental and flight testing. Full article

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14 pages, 2769 KiB

Open AccessArticle

A Joint Surface Contact Stiffness Model Considering Micro-Asperity Interaction

by Tian Xia, Jie Qu and Yong Liu

Aerospace 2024, 11(6), 472; https://doi.org/10.3390/aerospace11060472 - 12 Jun 2024

Viewed by 402

Abstract

Mechanical joint interfaces are widely found in mechanical equipment, and their contact stiffness directly affects the overall performance of the mechanical system. Based on the fractal and elastoplastic contact mechanics theories, the K-E elastoplastic contact model is introduced to establish the contact stiffness [...] Read more.

Mechanical joint interfaces are widely found in mechanical equipment, and their contact stiffness directly affects the overall performance of the mechanical system. Based on the fractal and elastoplastic contact mechanics theories, the K-E elastoplastic contact model is introduced to establish the contact stiffness model for mechanical joint interfaces. This model considers the interaction effects between micro-asperities in the fully deformed state, including elasticity, first elastoplasticity, second elastoplasticity, and complete plastic deformation state. Based on this model, the effects of fractal parameters on normal contact stiffness and contact load are analyzed. It can be found that the larger fractal dimension D or smaller characteristic scale coefficient G will weaken the interaction between micro-asperities. The smoother processing surfaces lead to higher contact stiffness in mechanical joint interfaces. The applicability and effectiveness of the proposed model are verified by comparing it with the traditional contact model calculation results. Under the same load, the interaction between micro-rough surfaces leads to an increase in both overall deformation and contact stiffness. The accuracy of the predicted contact stiffness model is also validated by comparing it with experimental results. Full article

(This article belongs to the Special Issue State Monitoring and Health Management of Complex Equipment (2nd Edition))

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27 pages, 849 KiB

Open AccessReview

A Critical Review of Information Provision for U-Space Traffic Autonomous Guidance

by Ivan Panov and Asim Ul Haq

Aerospace 2024, 11(6), 471; https://doi.org/10.3390/aerospace11060471 - 12 Jun 2024

Viewed by 589

Abstract

This paper identifies and classifies the essential constraints that must be addressed to allow U-space traffic autonomous guidance. Based on an extensive analysis of the state of the art in robotic guidance, physics of flight, flight safety, communication and navigation, uncrewed aircraft missions, [...] Read more.

This paper identifies and classifies the essential constraints that must be addressed to allow U-space traffic autonomous guidance. Based on an extensive analysis of the state of the art in robotic guidance, physics of flight, flight safety, communication and navigation, uncrewed aircraft missions, artificial intelligence (AI), social expectations in Europe on drones, etc., we analyzed the existing constraints and the information needs that are of essential importance to address the identified constraints. We compared the identified information needs with the last edition of the U-space Concept of Operations and identified critical gaps between the needs and proposed services. A high-level methodology to identify, measure, and close the gaps is proposed. Full article

(This article belongs to the Topic Civil and Public Domain Applications of Unmanned Aviation)

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Aerospace, Volume 11, Issue 6 (June 2024) – 86 articles

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