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Volume 9
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Aerospace, Volume 9, Issue 10 (October 2022) – 103 articles

Cover Story (view full-size image): Propulsion systems based on storable bipropellants have relied on hydrazine/nitrogen tetroxide and other toxic variants for a long time. At present, a clear intent to find alternative “green” solutions has been established in both the scientific and industrial communities. "Green propulsion" is a wide concept, regarding both the environment and humans, and is related to the life cycle of a propulsion technology, extending to the awareness of the long-term effects caused by its use. This paper compares alternative storable propellant couples. The analysis presents a wide database, including physical properties, performance, and toxicity, and proposes a methodology to create a common rank. The paper underlines that a unique solution does not exist, but rather, each mission leads to dedicated optimal options. View this paper
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25 pages, 6767 KiB  
Article
Simulation of Forced Convection Frost Formation in Microtubule Bundles at Ultra-Low Temperature
by Youzhi Mi, Meng Liu, Hao Wu, Jun Wang and Ruikai Zhao
Aerospace 2022, 9(10), 630; https://doi.org/10.3390/aerospace9100630 - 21 Oct 2022
Viewed by 1889
Abstract
Hypersonic vehicles are an important area of research in the aerospace field today. One of the important issues is the power of the engine. In order to achieve large-span flight speeds, a more efficient approach is to use combined power systems. However, the [...] Read more.
Hypersonic vehicles are an important area of research in the aerospace field today. One of the important issues is the power of the engine. In order to achieve large-span flight speeds, a more efficient approach is to use combined power systems. However, the problem of pre-cooler icing can occur in combined engine applications. The flow in the pre-cooler is extremely complex. Outside the tube is the high-temperature wet air entering from the engine intake, and the tube cooling is the ultra-low temperature cooling medium. Icing not only increases the heat exchange resistance of the pre-cooler during operation and affects the heat exchange performance of the pre-cooler, but also causes a large total pressure loss, resulting in a degradation of the engine performance. There is a lack of research on the icing law of the pre-cooler under different parameters. Therefore, it is necessary to conduct a corresponding numerical calculation study on pre-cooler icing and explore the influence of various influencing factors on icing. In this paper, a mathematical model of icing (frost) is established for the frosting phenomenon that may occur during the operation of the pre-cooler. Additionally, the principle of heat and mass transfer in the icing process is described by the mathematical model, and the influence of different parameters on the frosting parameters is explored by using the computational fluid dynamics (CFD) method. The law of tube bundle icing under different parameters was calculated, and the variation laws of frost layer morphology and wet air pressure drop were obtained. The laws of tube bundle icing under different parameters were calculated, and the changes in frost layer pattern and wet air pressure drop when each parameter was changed, which can provide guidance for the design and application of pre-coolers in the future. Full article
(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)
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18 pages, 10406 KiB  
Article
Numerical Study on Improved Geometry of Outlet Pressure Ripple in Parallel 2D Piston Pumps
by Yu Huang, Qianqian Lu, Wei Shao, Li Liu, Chuan Ding and Jian Ruan
Aerospace 2022, 9(10), 629; https://doi.org/10.3390/aerospace9100629 - 21 Oct 2022
Cited by 1 | Viewed by 1551
Abstract
Because the axial piston pump is often used in the aerospace and aviation fields, it is necessary to pay attention to its outlet pressure and flow characteristics. The parallel 2D piston pump proposed, based on the axial piston pump, has no structural flow [...] Read more.
Because the axial piston pump is often used in the aerospace and aviation fields, it is necessary to pay attention to its outlet pressure and flow characteristics. The parallel 2D piston pump proposed, based on the axial piston pump, has no structural flow ripple because it has a rail with a uniform acceleration and deceleration. Now, the pump is used in the special working conditions of the aerospace field, and it is required to meet the rated flow of 50 L/min, the rated load of 8 MPa, and an extremely low-pressure ripple. Based on CFD technology, this paper studies the pump’s outlet flow and pressure ripples through numerical simulation. According to the causes of the outlet pressure ripple, an improved geometry is determined to further reduce the outlet pressure ripple. Using a high-frequency pressure sensor to measure the outlet pressure ripple of the optimized pump prototype, it was found that the outlet pressure ripple rate of the prototype was only 6%. The parallel 2D piston pump has been proved by the simulation and test that its outlet pressure ripple is extremely low. However, it is not effective to reduce the outlet flow ripple by increasing the pre-pressure and reducing the backflow. In parallel 2D piston pumps, it is still necessary to find a new method to further reduce outlet pressure and flow ripples. Full article
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16 pages, 6853 KiB  
Article
Stability Enhancement and Noise Reduction of an Axial Compressor with Foam Metal Casing Treatment
by Jia Li, Xu Dong, Dakun Sun, Yuqing Wang, Chunwang Geng and Xiaofeng Sun
Aerospace 2022, 9(10), 628; https://doi.org/10.3390/aerospace9100628 - 21 Oct 2022
Cited by 4 | Viewed by 1729
Abstract
Foam metal is a foam-like substance with a high porosity; it has been used in flow control, vibration abatement, and acoustic absorption, mainly based on its physical properties. The aim of the current paper is to investigate the effect of foam metal casing [...] Read more.
Foam metal is a foam-like substance with a high porosity; it has been used in flow control, vibration abatement, and acoustic absorption, mainly based on its physical properties. The aim of the current paper is to investigate the effect of foam metal casing treatments on the stability and acoustic level of a low-speed axial flow compressor. The experimental results show that the casing treatment improves the stall margin by 14.9%, without any efficiency loss. In terms of noise, the SPL of the tonal noise at the third order of BPF is reduced by 3.2 dB, while the SPL of the broadband noise is reduced up to 2.4 dB. The comparison in evolutions of the tip structure in a smooth casing condition and with a casing treatment indicates that the casing treatment affects the origination and the development of the tip leakage vortex. The working mechanism is also discussed. Full article
(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)
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12 pages, 4819 KiB  
Article
Influence of Gas-to-Wall Temperature Ratio on the Leakage Flow and Cooling Performance of a Turbine Squealer Tip
by Dongjie Yan, Hongmei Jiang, Jieling Li, Wenbo Xie, Zhaoguang Wang, Shaopeng Lu and Qiang Zhang
Aerospace 2022, 9(10), 627; https://doi.org/10.3390/aerospace9100627 - 20 Oct 2022
Cited by 3 | Viewed by 1540
Abstract
In high-pressure turbines, there is a large difference in temperature between the mainstream and the turbine blade surface. Most of the turbine blade tip heat transfer studies were conducted under the assumption that the Over-Tip-Leakage (OTL) flow field is independent of the wall [...] Read more.
In high-pressure turbines, there is a large difference in temperature between the mainstream and the turbine blade surface. Most of the turbine blade tip heat transfer studies were conducted under the assumption that the Over-Tip-Leakage (OTL) flow field is independent of the wall thermal condition. Recent numerical and experimental studies have revealed that the two-way coupling effect between aerodynamics and heat transfer should not be neglected. The heat transfer coefficient obtained by the conventional method is not able to match the realistic engine condition accurately. This study investigates the impact of the wall thermal boundary condition on the tip cooling performance of squealer turbine blades. The RANS CFD result was validated against experimental tip heat transfer data obtained from a high-speed test rig with the effect of high-speed relative casing motion. The aerothermal performance for both uncooled and cooled squealer tips was studied at two different gas-to-wall temperature ratios, 1.7 and 1.1; the reference temperature is 204 K. It was found that the location and strength of cavity vortices varied with different wall thermal boundary conditions, leading to different signatures in tip heat transfer and cooling performance. It is recommended that the experimental heat transfer data and film cooling effectiveness obtained at the near-adiabatic wall boundary condition should be corrected before their application to the tip cooling design process. It would be more reliable to match the wall-to-gas temperature ratio during the tip experimental study. Full article
(This article belongs to the Special Issue Cooling/Heat transfer (Volume II))
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21 pages, 7182 KiB  
Article
In-Flight Radome Slope Estimation for Homing Guidance Using Bearing-Only Measurement via Gaussian Process Regression
by Kelin Lu, Bingyu Jin and Ning Zhang
Aerospace 2022, 9(10), 626; https://doi.org/10.3390/aerospace9100626 - 20 Oct 2022
Cited by 2 | Viewed by 2123
Abstract
The radome refraction problem gives rise to guidance performance deterioration for homing missiles. Aiming to eliminate the effect of radome refraction on the radar seeker, a novel method is proposed for correcting the radome-induced measurement error by using the estimated guidance information. A [...] Read more.
The radome refraction problem gives rise to guidance performance deterioration for homing missiles. Aiming to eliminate the effect of radome refraction on the radar seeker, a novel method is proposed for correcting the radome-induced measurement error by using the estimated guidance information. A dynamic model for the estimation system is formulated and the guidance information is estimated online via a multiple-model filtering framework. A Gaussian process regression scheme is introduced to reconstruct the mapping model with respect to the radome error and look angle. Furthermore, an analytical expression for radome slope estimation is derived by calculating the derivative of the surrogate function, represented with Gaussian process models. The contaminated measurement is corrected based on the estimated guidance information and radome slope. Extensive simulation results illustrate that the proposed method is able to estimate the radome slope accurately and improve the guidance accuracy effectively. Full article
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15 pages, 3520 KiB  
Article
Lagrange Optimization of Shock Waves for Two-Dimensional Hypersonic Inlet with Geometric Constraints
by Yuling Li, Lianjie Yue, Chengming He, Wannan Wu and Hao Chen
Aerospace 2022, 9(10), 625; https://doi.org/10.3390/aerospace9100625 - 20 Oct 2022
Cited by 1 | Viewed by 1510
Abstract
The present paper focuses on the Lagrange optimization of shock waves for a two-dimensional hypersonic inlet by limiting the cowl internal angle and inlet length. The results indicate the significant influences of geometric constraints on the configuration of shock waves and performances of [...] Read more.
The present paper focuses on the Lagrange optimization of shock waves for a two-dimensional hypersonic inlet by limiting the cowl internal angle and inlet length. The results indicate the significant influences of geometric constraints on the configuration of shock waves and performances of an inlet. Specifically, the cowl internal angle mainly affects the internal compression section; the inlet length affects both the internal and external compression sections where the intensity of internal and external compression shock waves shows a deviation of equal. In addition, the performances of optimized inlets at off-design points are further numerically simulated. A prominent discovery is that a longer inlet favors a higher total pressure recovery at the positive AOA; conversely, a shorter inlet can increase the total pressure recovery at the negative AOA. Full article
(This article belongs to the Special Issue Aerodynamics Design)
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19 pages, 4661 KiB  
Article
Cluster-Based Aircraft Fuel Estimation Model for Effective and Efficient Fuel Budgeting on New Routes
by Jefry Yanto and Rhea P. Liem
Aerospace 2022, 9(10), 624; https://doi.org/10.3390/aerospace9100624 - 20 Oct 2022
Cited by 5 | Viewed by 1905
Abstract
Fuel burn accounts for up to 25% of an aircraft’s total operating cost and has become one of the most important decision factors in the airline industry. Hence, prudent fuel estimation is essential for airlines to ensure smooth operation in the upcoming [...] Read more.
Fuel burn accounts for up to 25% of an aircraft’s total operating cost and has become one of the most important decision factors in the airline industry. Hence, prudent fuel estimation is essential for airlines to ensure smooth operation in the upcoming financial year. Challenges arise when airlines need to estimate the total fuel consumption of new sectors where data are not available. This necessitates the derivation of a robust parametric model that can represent the characteristics of the new route even in the absence of relevant data. To address this issue, we propose a two-step approach to derive a model that can accurately estimate the aircraft fuel needed. The developed approach involves both unsupervised learning and a regression model. For the unsupervised learning step, hierarchical density-based spatial clustering of applications with noise (HDBSCAN) is used to cluster the principal component analysis (PCA)-reduced data. This step can automatically separate flight sectors based on their underlying characteristics, as revealed by their principal components, upon filtering the noise in the data. Afterward, multivariate linear regression (MLR) is used to derive the equations for each cluster. The PCA-based clustered model is shown to be superior to using a global model for a single aircraft type. This approach yields fuel estimation with less than 5% root mean square error for existing routes within each cluster. More importantly, the proposed method can accurately estimate the total fuel of a new route with less than 2% aggregate error, thereby addressing one of the current limitations in the airline fuel estimation study. Full article
(This article belongs to the Special Issue Application of Data Science to Aviation II)
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25 pages, 7146 KiB  
Article
A New Mapped WENO Method for Hyperbolic Problems
by U S Vevek, Bin Zang and T. H. New
Aerospace 2022, 9(10), 623; https://doi.org/10.3390/aerospace9100623 - 19 Oct 2022
Viewed by 1793
Abstract
In this study, a new family of rational mapping functions gRM(ω;k,m,s) is introduced for seventh-order WENO schemes. gRM is a more general family of mapping functions, which includes other mapping functions such [...] Read more.
In this study, a new family of rational mapping functions gRM(ω;k,m,s) is introduced for seventh-order WENO schemes. gRM is a more general family of mapping functions, which includes other mapping functions such as gM and gIM as special cases. The mapped WENO scheme WENO-IM(2,0.1), which uses gIM, performs excellently at fifth order but rather poorly at seventh order. The reason for this loss of accuracy was found to be the over-amplification of very small weights by the mapping process, which can be traced back to the large slope of gIM at ω = 0. For m > 1, gRM can be designed to have a unit slope at ω = 0, which will preserve small weights with little to no amplification. It has been demonstrated through several one-dimensional linear advection test cases that the mapped WENO scheme WENO-RM(6,3,2 × 103), which uses the mapping function gRM(ω;6,3,2 × 103), outperforms both WENO-M and WENO-IM(2,0.1) at seventh order. The proposed scheme also performs better at a number of one-dimensional inviscid gas flow problems compared to other popular WENO schemes such as the WENO-Z scheme. Full article
(This article belongs to the Special Issue Advances in Aerospace Sciences and Technology III)
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25 pages, 11151 KiB  
Article
Research on Trajectory Prediction of a High-Altitude Zero-Pressure Balloon System to Assist Rapid Recovery
by Jiwei Tang, Shumin Pu, Peixi Yu, Weicheng Xie, Yunfei Li and Binxing Hu
Aerospace 2022, 9(10), 622; https://doi.org/10.3390/aerospace9100622 - 19 Oct 2022
Cited by 7 | Viewed by 3256
Abstract
A comprehensive simulation model is established to predict the trajectory of a high-altitude zero-pressure balloon flight system with no parachute that is required to carry the load floating at the designated altitude for several hours or less. A series of mathematical models, including [...] Read more.
A comprehensive simulation model is established to predict the trajectory of a high-altitude zero-pressure balloon flight system with no parachute that is required to carry the load floating at the designated altitude for several hours or less. A series of mathematical models, including thermal dynamic, atmospheric, earth, wind, geometry, and exhaust models, are developed to predict the trajectory of the balloon flight system. Based on these models, the uncertainties of the launch parameters and the corresponding flight performance are simulated. Combined with the control strategy, the entire flight trajectory is simulated and discussed in detail, including the ascending, floating, and descending phases. The results show that the vertical velocity takes on a W shape during the ascent process. Furthermore, the balloon begins to gradually descend with weakening solar radiation after noon. Moreover, the landing vertical speed of the balloon flight system can approach zero with the control strategy applied, whereas the lateral drift range is more limited relative to the uncontrolled flight mode. The results and conclusions presented herein contribute to the design and operation of a zero-pressure balloon flight system within limited airspace to improve the rapid recovery ability of the flight system. Full article
(This article belongs to the Special Issue Mission Analysis and Design of Lighter-than-Air Flying Vehicles)
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13 pages, 1948 KiB  
Article
Flight/Propulsion Integrated Control of Over-Under TBCC Engine Based on GA-LQR Method
by Huafeng Yu, Yingqing Guo, Xinghui Yan and Jiamei Wang
Aerospace 2022, 9(10), 621; https://doi.org/10.3390/aerospace9100621 - 19 Oct 2022
Cited by 4 | Viewed by 2245
Abstract
Turbine-based combined cycle (TBCC) engines are one of the ideal powers for reusable air-breathing supersonic aircraft, but the flight/propulsion integrated control and mode transition restricts its use. This paper takes the Mach 4 over-under TBCC engine as the research object. The inlet is [...] Read more.
Turbine-based combined cycle (TBCC) engines are one of the ideal powers for reusable air-breathing supersonic aircraft, but the flight/propulsion integrated control and mode transition restricts its use. This paper takes the Mach 4 over-under TBCC engine as the research object. The inlet is established by the quasi-one-dimensional calculation theory, which can reflect the shock wave position. An iterative method is proposed, which points out that the flow rate in the mode transition depends on the flow capacity. By connecting the input and output that affect each other, the simulation of the coupling characteristics of the aircraft and engine are realized. A GA-LQR-based controller design method is proposed and verified through the aircraft’s climb and mode transition conditions. The simulation shows that the integrated control system can ensure the stability of the aircraft and the safe operation of the engine in the above two situations. During the mode transition process, the aircraft altitude and Mach number fluctuate less than 1%, and the normal shock wave of inlet is in a safe position. Full article
(This article belongs to the Special Issue Advances in Hypersonic Aircraft Propulsion Technology)
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16 pages, 13229 KiB  
Article
Formation Mechanism and Modeling Method of Wrinkling Defects in Variable Angle Tow Steering Fiber Placement
by Minghui Yi, Fei Liu, Wuxiang Zhang and Xilun Ding
Aerospace 2022, 9(10), 620; https://doi.org/10.3390/aerospace9100620 - 19 Oct 2022
Cited by 2 | Viewed by 2016
Abstract
Variable angle tow steering technology is capable of manufacturing complex aviation parts with a trajectory of intricate curvature planned based on stress or profile characteristics, which greatly improves the forming efficiency, design flexibility and mechanical properties of composite structures. In view of the [...] Read more.
Variable angle tow steering technology is capable of manufacturing complex aviation parts with a trajectory of intricate curvature planned based on stress or profile characteristics, which greatly improves the forming efficiency, design flexibility and mechanical properties of composite structures. In view of the forming defects such as buckling and wrinkles caused by the lateral bending of fiber prepreg tow, a theoretical buckling model based on the Rayleigh Ritz method, the principle of minimum potential energy and the viscoelastic foundation is established, in which the adhesion coefficient is characterized by the degree of intimate contact to introduce process parameters. On the basis of the contact mechanics analysis, the distribution of the compaction pressure and bending stress is studied to improve the theoretical model, and the critical buckling load and the minimum radius of the tow under the normal and tangential contact conditions are determined precisely. Finally, the finite element models of compaction and variable angle steering placement are proposed, and the theoretical model and simulation model are verified by corresponding trials. It is demonstrated that defects can be effectively suppressed through optimizing process parameters. Full article
(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)
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29 pages, 17259 KiB  
Article
Numerical Investigation on Unsteady Shock Wave/Vortex/Turbulent Boundary Layer Interactions of a Hypersonic Vehicle during Its Shroud Separation
by Pengcheng Cui, Hongyin Jia, Jiangtao Chen, Guiyu Zhou, Xiaojun Wu, Mingsheng Ma, Huan Li and Jing Tang
Aerospace 2022, 9(10), 619; https://doi.org/10.3390/aerospace9100619 - 19 Oct 2022
Cited by 3 | Viewed by 2800
Abstract
Hypersonic vehicles are drawing more and more attention now and for the near future, especially in the low-altitudes near space, from 20 km to 45 km. The reliable separation of the protecting shroud from the hypersonic vehicle is a prerequisite and critical issue [...] Read more.
Hypersonic vehicles are drawing more and more attention now and for the near future, especially in the low-altitudes near space, from 20 km to 45 km. The reliable separation of the protecting shroud from the hypersonic vehicle is a prerequisite and critical issue for the success of the entire flight mission. The unsteady multi-body separation characteristics and flow characteristics of hypersonic shroud separation at Mach 7.0 are investigated based on numerical simulation in this paper. The improved delayed detached eddy simulation (IDDES) method, dynamic hybrid overset mesh method, and HLLE++ numerical scheme are used to ensure numerical accuracy. Numerical results show that there are four types of vortexes and three types of shock waves inside the shrouds during the separation process, which generate complex shock wave/vortex/boundary layer interactions. Further, an unsteady process of the expansion-transfer-dissipation of an A-type vortex is found, which is the result of strong shock/vortex/boundary layer interactions. The adverse pressure gradient is the root cause driving the generation and transfer of the A-type vortex during the shroud separation. Furthermore, the transfer process of the A-type vortex only lasts for 5.52 ms but causes a large disturbance to the aerodynamic force of the shroud. The results of this paper could provide a reference for the design of near-space hypersonic vehicles. Full article
(This article belongs to the Section Astronautics & Space Science)
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18 pages, 4916 KiB  
Article
A New Method for Analyzing the Aero-Optical Effects of Hypersonic Vehicles Based on a Microscopic Mechanism
by Bo Yang, He Yu, Chaofan Liu, Xiang Wei, Zichen Fan and Jun Miao
Aerospace 2022, 9(10), 618; https://doi.org/10.3390/aerospace9100618 - 18 Oct 2022
Cited by 3 | Viewed by 2174
Abstract
Aero-optical effects are the key factors that restrict the accuracy of the optical sensors of hypersonic vehicles, and the numerical simulation of aero-optical effects is a powerful tool with which to analyze aero-optical distortion. Most existing research focuses on the simulation analysis of [...] Read more.
Aero-optical effects are the key factors that restrict the accuracy of the optical sensors of hypersonic vehicles, and the numerical simulation of aero-optical effects is a powerful tool with which to analyze aero-optical distortion. Most existing research focuses on the simulation analysis of refraction distortion based on the density field at the macro level via the ray-tracing method. In this paper, a method for analyzing aero-optical effects based on the interaction between photons and gas molecules is proposed and can explain the optical distortion and energy dissipation caused by aero-optical effects at the micro level. By establishing a transmission model of photons in turbulence, a simulation method of aero-optical effects based on a microscopic mechanism is designed and breaks through the limitations of a traditional macro method in energy analyses. The optical distortion parameters based on photonics are compared with the physical quantities of traditional aero-optical effects, which verifies the effectiveness of the micro analysis on the macro scale and provides a new idea for studying the microscopic mechanism of aero-optical effects. Full article
(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)
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22 pages, 5410 KiB  
Article
Simplified Model for Forward-Flight Transitions of a Bio-Inspired Unmanned Aerial Vehicle
by Ernesto Sanchez-Laulhe, Ramon Fernandez-Feria and Anibal Ollero
Aerospace 2022, 9(10), 617; https://doi.org/10.3390/aerospace9100617 - 18 Oct 2022
Cited by 7 | Viewed by 2176
Abstract
A new forward-flight model for bird-like ornithopters is presented. The flight dynamics model uses results from potential, unsteady aerodynamics to characterize the forces generated by the flapping wings, including the effects of the dynamic variables on the aerodynamic formulation. Numerical results of the [...] Read more.
A new forward-flight model for bird-like ornithopters is presented. The flight dynamics model uses results from potential, unsteady aerodynamics to characterize the forces generated by the flapping wings, including the effects of the dynamic variables on the aerodynamic formulation. Numerical results of the model, which are validated with flapping flight experimental data of an ornithopter prototype, show that state variables such as the pitch angle and the angle of attack oscillate with the flapping frequency, while their mean values converge towards steady-state values. The theoretical analysis of the system shows a clear separation of timescales between flapping oscillations and transient convergence towards the final forward-flight state, which is used to substantially simplify both the interpretation and the solution of the dynamic equations. Particularly, the asymptotic separation into three timescales allows for dividing the problem into a much simpler set of linear equations. The theoretical approximation, which fits the numerical results, provides a direct look into the influence of the design and control parameters using fewer computational resources. Therefore, this model provides a useful tool for the design, navigation and trajectory planning and control of flapping wing UAVs. Full article
(This article belongs to the Special Issue Aerodynamics Design)
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27 pages, 7268 KiB  
Article
Fractional-Order Sliding Mode Control Method for a Class of Integer-Order Nonlinear Systems
by Wenjie Qing, Binfeng Pan, Yueyang Hou, Shan Lu and Wenjing Zhang
Aerospace 2022, 9(10), 616; https://doi.org/10.3390/aerospace9100616 - 17 Oct 2022
Cited by 6 | Viewed by 2215
Abstract
In this study, the problem of the stabilisation of a class of nonautonomous nonlinear systems was studied. First, a fractional stability theorem based on a fractional-order Lyapunov inequality was formulated. Then, a novel fractional-order sliding surface, which was a generalisation of integral, first-order, [...] Read more.
In this study, the problem of the stabilisation of a class of nonautonomous nonlinear systems was studied. First, a fractional stability theorem based on a fractional-order Lyapunov inequality was formulated. Then, a novel fractional-order sliding surface, which was a generalisation of integral, first-order, and second-order sliding surfaces with varying fractional orders, was proposed. Finally, a fractional-order sliding mode-based control for a class of nonlinear systems was designed. The stability property of the system with the proposed method was easily proven as a fractional Lyapunov direct method by the fractional stability theorem. As an illustration, the method was used as a fractional guidance law with an impact angle constraint for a manoeuvring target. Simulation results demonstrated the applicability and efficiency of the proposed method. Full article
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27 pages, 3739 KiB  
Article
Visual Navigation Algorithm for Night Landing of Fixed-Wing Unmanned Aerial Vehicle
by Zhaoyang Wang, Dan Zhao and Yunfeng Cao
Aerospace 2022, 9(10), 615; https://doi.org/10.3390/aerospace9100615 - 17 Oct 2022
Cited by 7 | Viewed by 2401
Abstract
In the recent years, visual navigation has been considered an effective mechanism for achieving an autonomous landing of Unmanned Aerial Vehicles (UAVs). Nevertheless, with the limitations of visual cameras, the effectiveness of visual algorithms is significantly limited by lighting conditions. Therefore, a novel [...] Read more.
In the recent years, visual navigation has been considered an effective mechanism for achieving an autonomous landing of Unmanned Aerial Vehicles (UAVs). Nevertheless, with the limitations of visual cameras, the effectiveness of visual algorithms is significantly limited by lighting conditions. Therefore, a novel vision-based autonomous landing navigation scheme is proposed for night-time autonomous landing of fixed-wing UAV. Firstly, due to the difficulty of detecting the runway caused by the low-light image, a strategy of visible and infrared image fusion is adopted. The objective functions of the fused and visible image, and the fused and infrared image, are established. Then, the fusion problem is transformed into the optimal situation of the objective function, and the optimal solution is realized by gradient descent schemes to obtain the fused image. Secondly, to improve the performance of detecting the runway from the enhanced image, a runway detection algorithm based on an improved Faster region-based convolutional neural network (Faster R-CNN) is proposed. The runway ground-truth box of the dataset is statistically analyzed, and the size and number of anchors in line with the runway detection background are redesigned based on the analysis results. Finally, a relative attitude and position estimation method for the UAV with respect to the landing runway is proposed. New coordinate reference systems are established, six landing parameters, such as three attitude and three positions, are further calculated by Orthogonal Iteration (OI). Simulation results reveal that the proposed algorithm can achieve 1.85% improvement of AP on runway detection, and the reprojection error of rotation and translation for pose estimation are 0.675∘ and 0.581%, respectively. Full article
(This article belongs to the Special Issue Vision-Based UAV Navigation)
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17 pages, 4661 KiB  
Article
Parameter Identification Method for a Periodic Time-Varying System Using a Block-Pulse Function
by Zhi Wang, Jun Wang, Jing Tian and Yu Liu
Aerospace 2022, 9(10), 614; https://doi.org/10.3390/aerospace9100614 - 17 Oct 2022
Viewed by 1575
Abstract
For periodic time-varying systems, a method of parameter identification based on the block-pulse function is presented. Firstly, the state-space equation of the system was expanded using the block-pulse function, then the recursion formula of the parameter identification of a time-varying system was obtained, [...] Read more.
For periodic time-varying systems, a method of parameter identification based on the block-pulse function is presented. Firstly, the state-space equation of the system was expanded using the block-pulse function, then the recursion formula of the parameter identification of a time-varying system was obtained, according to the irrespective and orthogonal characteristics of the block-pulse function. This study provides a wide range of applications by saving time in calculation with a highly accurate method. The parameter identification was carried out by including the numerical simulation model of a three-degree freedom system and the vibration experiment results of an asymmetrical rotor system. The state space wavelet method and EMD method were compared cross-sectionally with the proposed method; this shows that the proposed method is accurate and effective, which makes it valuable in numerous applications. It also has a certain application value for several related projects. Full article
(This article belongs to the Special Issue State Monitoring and Health Management of Complex Equipment)
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27 pages, 4159 KiB  
Article
From Single Aircraft to Communities: A Neutral Interpretation of Air Traffic Complexity Dynamics
by Ralvi Isufaj, Marsel Omeri, Miquel Angel Piera, Jaume Saez Valls and Christian Eduardo Verdonk Gallego
Aerospace 2022, 9(10), 613; https://doi.org/10.3390/aerospace9100613 - 17 Oct 2022
Cited by 5 | Viewed by 1587
Abstract
At present, decision-making in ATM is fragmented between different stakeholders who have different objectives. This fragmentation, in unison with competing KPAs, leads to complex interdependencies between performance indicators, which results in an imbalance, with some of these indicators being penalized to the apparent [...] Read more.
At present, decision-making in ATM is fragmented between different stakeholders who have different objectives. This fragmentation, in unison with competing KPAs, leads to complex interdependencies between performance indicators, which results in an imbalance, with some of these indicators being penalized to the apparent benefit of others. Therefore, it is necessary to support ATM stakeholders in systematically uncovering hidden trade-offs between KPAs. Existing literature confirms this claim, but how to solve it has not been fully addressed. In this paper, we envision air traffic complexity to be the framework through which a common understanding among stakeholders is enhanced. We introduce the concept of single aircraft complexity to determine the contribution of each aircraft to the overall complexity of air traffic. Furthermore, we describe a methodology extending this concept to define complex communities, which are groups of interdependent aircraft that contribute the majority of the complexity in a certain airspace. Through use-cases based on synthetic and real historical traffic, we first show that the algorithm can serve to formalize and improve decision-making. Further, we illustrates how the provided information can be used to increase transparency of the decision makers towards different airspace users. In order to showcase the methodology, we develop a tool that visualizes different outputs of the algorithm. Lastly, we conduct sensitivity analysis in order to systematically analyse how each input affects the methodology. Full article
(This article belongs to the Section Air Traffic and Transportation)
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21 pages, 4670 KiB  
Article
Metric for Structural Complexity Assessment of Space Systems Modeled Using the System Modeling Language
by Victor Emmanuel Pierre Lopez and Lawrence Dale Thomas
Aerospace 2022, 9(10), 612; https://doi.org/10.3390/aerospace9100612 - 17 Oct 2022
Viewed by 1914
Abstract
A complexity metric is proposed for the quantification of system complexity using information about the composition of a system and its interactions depicted in a System Modelling Language (SysML) model. The proposed metric is adapted from the complexity metric developed for design structure [...] Read more.
A complexity metric is proposed for the quantification of system complexity using information about the composition of a system and its interactions depicted in a System Modelling Language (SysML) model. The proposed metric is adapted from the complexity metric developed for design structure matrix (DSM) applications and was modified to allow the metric to be applied at different decomposition levels and to accommodate the inclusion of external interactions. The metric was applied to three case studies: a Mars lander, a CubeSat and a spacecraft thermal control system. The proposed metric attributed a higher amount of complexity due to the interactions compared to the DSM metric. This variance resulted in instances where the results differed for the two metrics. Despite these differences, both metrics behaved similarly to changes in component or interaction complexity. Full article
(This article belongs to the Special Issue Space System Engineering)
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23 pages, 10483 KiB  
Article
Dynamic Modeling and Analysis of Thrust Reverser Mechanism Considering Clearance Joints and Flexible Component
by Jingchao Zhao, Xiaoyu Wang, Chao Meng, Huitao Song, Zhong Luo and Qingkai Han
Aerospace 2022, 9(10), 611; https://doi.org/10.3390/aerospace9100611 - 17 Oct 2022
Cited by 4 | Viewed by 2821
Abstract
As a high-precision motion mechanism, the kinematics and dynamics of cascade thrust reverser are sensitive to the changes of nonlinear factors which are rarely considered in traditional dynamic modeling and optimization. In order to study the effect of nonlinear factors on the dynamics [...] Read more.
As a high-precision motion mechanism, the kinematics and dynamics of cascade thrust reverser are sensitive to the changes of nonlinear factors which are rarely considered in traditional dynamic modeling and optimization. In order to study the effect of nonlinear factors on the dynamics behavior of cascade thrust reverser mechanism, the dynamic model considering joint clearance and flexible component is established. Lankarani–Nikravesh and modified-Coulomb model are used to establish the contact force at the clearance, and the flexible component in the mechanism is modeled by the absolute node coordinate method. The effects of joint clearance value, clearance position, flexible component, and driving speed on the dynamic response of the mechanism are studied. Specifically, the nonlinear characteristics of the mechanism increase with the clearance value, and the joint clearance near the mobile fairing has greater influence on the kinematics and dynamics of blocker door. For the mechanical system with clearances, the flexible component can partially reduce the vibration of the system. The analysis of the motion synchronization of the thrust reverser actuators indicates that the asynchronous movement of actuators may increase the driving forces of actuators especially for the middle actuator. Full article
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26 pages, 14108 KiB  
Article
Aerodynamic Data-Driven Surrogate-Assisted Teaching-Learning-Based Optimization (TLBO) Framework for Constrained Transonic Airfoil and Wing Shape Designs
by Xiaojing Wu, Zijun Zuo and Long Ma
Aerospace 2022, 9(10), 610; https://doi.org/10.3390/aerospace9100610 - 17 Oct 2022
Cited by 6 | Viewed by 1996
Abstract
The surrogate-assisted optimization (SAO) process can utilize the knowledge contained in the surrogate model to accelerate the aerodynamic optimization process. The use of this knowledge can be regarded as the primary form of intelligent optimization design. However, there are still some difficulties in [...] Read more.
The surrogate-assisted optimization (SAO) process can utilize the knowledge contained in the surrogate model to accelerate the aerodynamic optimization process. The use of this knowledge can be regarded as the primary form of intelligent optimization design. However, there are still some difficulties in improving intelligent design levels, such as the insufficient utilization of optimization process data and optimization parameters’ adjustment that depends on the designer’s intervention and experience. To solve the above problems, a novel aerodynamic data-driven surrogate-assisted teaching-learning-based optimization (TLBO) framework is proposed for constrained aerodynamic shape optimization (ASO). The main contribution of the study is that ASO is promoted using historically aerodynamic process data generated during the gradient free optimization process. Meanwhile, nonparametric adjustment of the TLBO algorithm can help relieve manual design experience for actual engineering applications. Based on the structure of the TLBO algorithm, a model optimal prediction method is proposed as the new surrogate-assisted support strategy to accelerate the ASO process. The proposed method is applied to airfoil and wing shape designs to verify the optimization effect and efficiency. A benchmark aerodynamic design optimization is employed for the drag minimization of the RAE2822 airfoil. The optimized results indicate that the proposed method has advantages of high efficiency, strong optimization ability, and nonparametric characteristics for ASO. Moreover, the results of the wing shape optimization verify the advantages of the proposed methods over the surrogate-based optimization and direct optimization frameworks. Full article
(This article belongs to the Special Issue Aerodynamic Shape Optimization)
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22 pages, 3873 KiB  
Article
Remaining Useful Life Prediction for Aero-Engines Based on Time-Series Decomposition Modeling and Similarity Comparisons
by Mingxian Wang, Hongyan Wang, Langfu Cui, Gang Xiang, Xiaoxuan Han, Qingzhen Zhang and Juan Chen
Aerospace 2022, 9(10), 609; https://doi.org/10.3390/aerospace9100609 - 16 Oct 2022
Cited by 7 | Viewed by 2633
Abstract
The aero-engine is the heart of an aircraft; its performance deteriorates rapidly due to the high temperature and high-pressure environment during flights. It is necessary to predict the remaining useful life (RUL) to improve the reliability of aero-engines and provide security for reliable [...] Read more.
The aero-engine is the heart of an aircraft; its performance deteriorates rapidly due to the high temperature and high-pressure environment during flights. It is necessary to predict the remaining useful life (RUL) to improve the reliability of aero-engines and provide security for reliable flights. In previous flights, the sensors collected a lot of performance parameter data and formed a database regarding the aero-engine degradation process. These performance parameters cannot reflect the degradation process directly. In this paper, fuzzy clustering is applied to divide the degradation stages of the aero-engine, construct the health indicator, and describe the degradation process. Time-series decomposition modeling is applied to predict the degradation process of the health indicator. Based on the idea of similarity comparison, the RUL is predicted by comparing the similarity of time series through example learning. The method is verified and analyzed on the dataset published by National Aeronautics and Space Administration (NASA), and the mean square error (MSE) is 528. The result is better than the comparative method. Full article
(This article belongs to the Section Aeronautics)
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24 pages, 6153 KiB  
Article
Heat Conduction and Microconvection in Nanofluids: Comparison between Theoretical Models and Experimental Results
by Gianluigi Bovesecchi, Sandra Corasaniti, Girolamo Costanza, Fabio Piccotti, Michele Potenza and Maria Elisa Tata
Aerospace 2022, 9(10), 608; https://doi.org/10.3390/aerospace9100608 - 15 Oct 2022
Cited by 2 | Viewed by 1873
Abstract
A nanofluid is a suspension consisting of a uniform distribution of nanoparticles in a base fluid, generally a liquid. Nanofluid can be used as a working fluid in heat exchangers to dissipate heat in the automotive, solar, aviation, aerospace industries. There are numerous [...] Read more.
A nanofluid is a suspension consisting of a uniform distribution of nanoparticles in a base fluid, generally a liquid. Nanofluid can be used as a working fluid in heat exchangers to dissipate heat in the automotive, solar, aviation, aerospace industries. There are numerous physical phenomena that affect heat conduction in nanofluids: clusters, the formation of adsorbate nanolayers, scattering of phonons at the solid–liquid interface, Brownian motion of the base fluid and thermophoresis in the nanofluids. The predominance of one physical phenomenon over another depends on various parameters, such as temperature, size and volume fraction of the nanoparticles. Therefore, it is very difficult to develop a theoretical model for estimating the effective thermal conductivity of nanofluids that considers all these phenomena and is accurate for each value of the influencing parameters. The aim of this study is to promote a way to find the conditions (temperature, volume fraction) under which certain phenomena prevail over others in order to obtain a quantitative tool for the selection of the theoretical model to be used. For this purpose, two sets (SET-I, SET-II) of experimental data were analyzed; one was obtained from the literature, and the other was obtained through experimental tests. Different theoretical models, each considering some physical phenomena and neglecting others, were used to explain the experimental results. The results of the paper show that clusters, the formation of the adsorbate nanolayer and the scattering of phonons at the solid–liquid interface are the main phenomena to be considered when φ = 1 ÷ 3%. Instead, at a temperature of 50 °C and in the volume fraction range (0.04–0.22%), microconvection prevails over other phenomena. Full article
(This article belongs to the Special Issue Thermophysics and Heat Transfer for Aerospace Applications)
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18 pages, 6529 KiB  
Article
Advanced Control of an Electric Fuel-Oil Pump for Small Turbojet Engines
by Ladislav Főző and Rudolf Andoga
Aerospace 2022, 9(10), 607; https://doi.org/10.3390/aerospace9100607 - 15 Oct 2022
Cited by 5 | Viewed by 2723
Abstract
One way to efficiently control the fuel flow of small turbojet engines is to use direct control of the speed of a suitable electric fuel pump, as opposed to using relief valves. Brushless drive electric (BLDC) motors are suitable for this application, especially [...] Read more.
One way to efficiently control the fuel flow of small turbojet engines is to use direct control of the speed of a suitable electric fuel pump, as opposed to using relief valves. Brushless drive electric (BLDC) motors are suitable for this application, especially for small turbojet engines. This, however, comes with certain problems, which are caused by the backpressure of the engine on the fuel system, delays in data acquisition, sensor noise and so on. This paper presents a comprehensive approach in the methodological design of a dynamic model of a fuel system with a BLDC fuel/oil pump and control algorithms, which can overcome the mentioned problems. Three approaches are evaluated to obtain a stable and precise fuel metering of the engine. This article describes the design of an inverse control model, a standard PID controller and an adaptive fuzzy controller for fuel-flow control during engine operation. The main scientific contribution of the presented study is a simple, yet robust, fuzzy adaptive controller with a lean and comprehensive rule base that can precisely and efficiently meter fuel for small turbojet engines, validated in laboratory conditions using the iSTC-21v turbojet engine. Full article
(This article belongs to the Section Aeronautics)
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21 pages, 4885 KiB  
Article
Earthwork Volume Calculation, 3D Model Generation, and Comparative Evaluation Using Vertical and High-Oblique Images Acquired by Unmanned Aerial Vehicles
by Kirim Lee and Won Hee Lee
Aerospace 2022, 9(10), 606; https://doi.org/10.3390/aerospace9100606 - 15 Oct 2022
Cited by 11 | Viewed by 4454
Abstract
In civil engineering and building construction, the earthwork volume calculation is one of the most important factors in the design and construction stages; therefore, an accurate calculation is necessary. Moreover, because managing earthworks is highly important, in this study, a three-dimensional (3D) model [...] Read more.
In civil engineering and building construction, the earthwork volume calculation is one of the most important factors in the design and construction stages; therefore, an accurate calculation is necessary. Moreover, because managing earthworks is highly important, in this study, a three-dimensional (3D) model for earthwork calculation and management was performed using an unmanned aerial vehicle (UAV) and an RGB camera. Vertical and high-oblique images (45°, 60°, and 75°) were acquired at 50 and 100 m heights for accurate earthwork calculations and a 3D model, and data were generated by dividing the images into eight cases. Cases 1–4 were images acquired from a height of 50 m, and cases 5–8 were images acquired from a height of 100 m. (case 1: 90°, case 2: 90° + 45°, case 3: 90° + 60°, case 4: 90° + 75°, case 5: 90°, case 6: 90° + 45°, case 7: 90° + 60°, case 8: 90° + 75°). Three evaluations were performed on the data. First, the accuracy was evaluated through checkpoints for the orthophoto; second, the earthwork volumes calculated via a global positioning system and UAV were compared; finally, the 3D model was evaluated. Case 2, which showed the lowest root mean square error in the orthophoto accuracy evaluation, was the most accurate. Case 2 was the most accurate in the earthwork volume evaluation and 3D model compared to other cases. Through this study, the best results were obtained when using a vertical image and a high-oblique image of 40 to 50° when generating a 3D model for earthwork volume calculation and management. In addition, if the UAV is not affected by obstacles, it is better to shoot at about 50 m or less than to shoot the UAV height too high. Full article
(This article belongs to the Special Issue Applications of Drones)
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18 pages, 6577 KiB  
Article
Aerodynamic Characteristics of Bristled Wings in Flapping Flight
by Tong Shen, Zhan Tu, Daochun Li, Zi Kan and Jinwu Xiang
Aerospace 2022, 9(10), 605; https://doi.org/10.3390/aerospace9100605 - 15 Oct 2022
Cited by 1 | Viewed by 1809
Abstract
This study focuses on the aerodynamics of the smallest flying insects’ bristled wings. We measured and analyzed wing morphological data from 38 specimens of Mymaridae. Bristled wing flight was numerically simulated at Reynolds numbers from 1 to 80. The aerodynamic force, power, and [...] Read more.
This study focuses on the aerodynamics of the smallest flying insects’ bristled wings. We measured and analyzed wing morphological data from 38 specimens of Mymaridae. Bristled wing flight was numerically simulated at Reynolds numbers from 1 to 80. The aerodynamic force, power, and efficiency of bristled wings using lift-based stroke, drag-based stroke, and clap-and-fling mechanism were evaluated. An unusual clap-and-fling pattern considering bristle crossing was first proposed. Our study shows that with a reduction in the wingspan of Mymaridae, the proportion of the wingtip bristled area increases. A lift-based stroke is superior to a drag-based stroke in terms of vertical force production and aerodynamic efficiency at 5 ≤ Re ≤ 20. Bristled wings employing the clap-and-fling mechanism achieve both vertical force and efficiency augmentation, while bristle crossing incurs a substantial horizontal force and contributes little to vertical force augmentation. Full article
(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)
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28 pages, 3217 KiB  
Article
Manned Mars Mission Analysis Using Mission Architecture Matrix Method
by Diyang Shen, Yuxian Yue and Xiaohui Wang
Aerospace 2022, 9(10), 604; https://doi.org/10.3390/aerospace9100604 - 14 Oct 2022
Cited by 4 | Viewed by 2543
Abstract
With the development of deep space exploration technology, manned missions to Mars are expected to be realized in the near future. However, the journey to Mars requires more supplies and fuel than near-Earth missions, including moon landings. Using the traditional Apollo-style mission method [...] Read more.
With the development of deep space exploration technology, manned missions to Mars are expected to be realized in the near future. However, the journey to Mars requires more supplies and fuel than near-Earth missions, including moon landings. Using the traditional Apollo-style mission method will result in the spacecraft reaching the LEO mass of 2000 tons, which is not easy to achieve. The use of the modular design method and multiple launches will significantly reduce the mass of a single launch. In addition, the use of nuclear power engines (Nuclear Thermal Propulsion, NTP, and Nuclear Electric Propulsion, NEP) can greatly improve propulsion efficiency, reducing the mass of the propellant. This paper uses the Mission Architecture Matrix (MAM) method to concisely and precisely analyze a series of mission architectures in the case of impulse maneuver transfer and low-thrust transfer. The results show that when only chemical propulsion (specific impulse is 440 s) is used, the maximum LEO launch mass in the optimal mission architecture is 325 tons, and the total LEO mass of the system is 1142 tons. With the usage of NTP (specific impulse is 900 s) and NEP (the specific impulse is 6000 s) technology, the maximum LEO launch mass in the optimal mission architecture is only 85 tons, and the total LEO mass of the system is only about 400 tons. Considering the current rocket technology, the total cost is about USD 1149 million US. Full article
(This article belongs to the Section Astronautics & Space Science)
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16 pages, 3662 KiB  
Article
Physics-Informed MTA-UNet: Prediction of Thermal Stress and Thermal Deformation of Satellites
by Zeyu Cao, Wen Yao, Wei Peng, Xiaoya Zhang and Kairui Bao
Aerospace 2022, 9(10), 603; https://doi.org/10.3390/aerospace9100603 - 14 Oct 2022
Cited by 4 | Viewed by 2039
Abstract
The rapid analysis of thermal stress and deformation plays a pivotal role in the thermal control measures and optimization of the structural design of satellites. For achieving real-time thermal stress and thermal deformation analysis of satellite motherboards, this paper proposes a novel Multi-Task [...] Read more.
The rapid analysis of thermal stress and deformation plays a pivotal role in the thermal control measures and optimization of the structural design of satellites. For achieving real-time thermal stress and thermal deformation analysis of satellite motherboards, this paper proposes a novel Multi-Task Attention UNet (MTA-UNet) neural network which combines the advantages of both Multi-Task Learning (MTL) and U-Net with an attention mechanism. Furthermore, a physics-informed strategy is used in the training process, where partial differential equations (PDEs) are integrated into the loss functions as residual terms. Finally, an uncertainty-based loss balancing approach is applied to weight different loss functions of multiple training tasks. Experimental results show that the proposed MTA-UNet effectively improves the prediction accuracy of multiple physics tasks compared with Single-Task Learning (STL) models. In addition, the physics-informed method brings less error in the prediction of each task, especially on small data sets. Full article
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16 pages, 1850 KiB  
Article
Dynamics, Deployment and Retrieval Strategy for Satellite-Sail Transverse Formation with Model Inaccuracy
by Yini Zhong and Rui Zhong
Aerospace 2022, 9(10), 602; https://doi.org/10.3390/aerospace9100602 - 14 Oct 2022
Cited by 2 | Viewed by 1559
Abstract
One of the important applications of the space tethered system is formation flying. To satisfy the requirement for interferometry of ground targets by remote-sensing satellites, a new type of tethered solar sail spacecraft has been proposed in recent research. The replacement of subsatellites [...] Read more.
One of the important applications of the space tethered system is formation flying. To satisfy the requirement for interferometry of ground targets by remote-sensing satellites, a new type of tethered solar sail spacecraft has been proposed in recent research. The replacement of subsatellites of conventional tethered satellite systems with solar sail spacecraft allows for a special formation configuration in which the main satellite is in sun-synchronous orbit and the subsolar sail is in displaced orbit. If the solar sail is at the appropriate attitude, the main satellite and the solar sail spacecraft connected by metal tethers could move side by side, hence this formation system is called transverse formation. The relative baseline of this transverse formation system is perpendicular to the ground trajectory of the satellite, effectively solving the problem that the relative baseline of conventional orbital formations varies in a trigonometric cycle. Researchers on the past ignored the mass and elasticity of the tether, and considered the tether just a constraint in the model system. Since the solar sail is generally quite light compared to the other components of the system, the model inaccuracy caused by ignoring the mass of the tether on the dynamic model and control is extremely obvious. This paper investigates the relative dynamics and control of a proposed system during the deployment process with the mass of the tether. Two precise models of satellite-sail systems are established. One is based on the dumbbell model with the mass tether for the tethered satellite system, and the other is on the basis of the beads model of a tethered satellite system. The rigid one is for control design and the flexible one is for dynamic simulation. It is concluded that the length of the tether and attitude angle of the transverse formation configuration can be decoupled and controlled separately. On the basis of the models, a length rate and LQR control law is developed and the control of the deployment and retrieval process of the tethered solar sail system is investigated. Numerical simulations are performed to verify the accuracy of the conclusions. Full article
(This article belongs to the Special Issue Latest Advancements in Aeronautics and Astronautics: Celebrating the 70th Anniversary of Beihang University)
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34 pages, 2765 KiB  
Article
Development and Evaluation of Single Pilot Operations with the Human-Centered Design Approach
by Min Li, Miao Wang, Dongjin Ding and Guoqing Wang
Aerospace 2022, 9(10), 601; https://doi.org/10.3390/aerospace9100601 - 14 Oct 2022
Cited by 2 | Viewed by 3168
Abstract
The high costs of pilot training and remuneration have placed a heavy financial burden on airlines, prompting people to actively study Single Pilot Operations (SPO). Achieving SPO undoubtedly requires the development of the new conceptual framework, and how to reallocate system functions among [...] Read more.
The high costs of pilot training and remuneration have placed a heavy financial burden on airlines, prompting people to actively study Single Pilot Operations (SPO). Achieving SPO undoubtedly requires the development of the new conceptual framework, and how to reallocate system functions among new agents to obtain optimal system design has become the primary problem in the early stages of the system lifecycle. To solve this problem, this paper applied the Human-centered Design (HCD) approach for the first time to the development and evaluation of SPO in the typical approach and landing scenario. Firstly, the combination of Hierarchical Task Analysis (HTA) and Abstraction Hierarchy (AH) was used to identify five function requirements and six function assumptions for the transition from the current Two-crew Operations (TCO) to the future SPO to develop the SPO model. Subsequently, the TCO and SPO models were transformed into two network models to evaluate the result of system function reallocation from the network level and node level using Social Network Analysis (SNA). The network parameters of both levels show that the future SPO developed in this paper has the advantages of better stability, less pilot workload and higher safety than the current TCO. Full article
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