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Aerospace
Volume 9
Issue 11
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Aerospace, Volume 9, Issue 11 (November 2022) – 107 articles

Cover Story (view full-size image): ArgoMoon is a 6U CubeSat, designed and assembled by the Italian company Argotec and funded by the Italian Space Agency, which will fly in a cis-lunar orbit, as a secondary payload of NASA’s Space Launch System on its maiden flight. The ArgoMoon mission aims to capture detailed pictures of the Interim Cryogenic Propulsion Stage and confirm the deployment of the other CubeSats. Afterwards, ArgoMoon will be guided in a highly elliptical Earth orbit, where the ground operations, including navigation, will be intensively tested as a technological demonstration. The navigation process will require a precise Orbit Determination and Flight Path Control to satisfy the requirements. This manuscript describes the design and performance characterization of the navigation of the ArgoMoon mission. View this paper
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20 pages, 4236 KiB  
Article
Numerical Comparison of Contact Force Models in the Discrete Element Method
by Ziwen Li, Xiangyuan Zeng, Tongge Wen and Yonglong Zhang
Aerospace 2022, 9(11), 737; https://doi.org/10.3390/aerospace9110737 - 21 Nov 2022
Cited by 8 | Viewed by 3152
Abstract
The discrete element method (DEM) is usually applied in analyzing the scientifical origin/evolution of the asteroids and the landing/sampling of the regolith. In order to manage the contact between the non-spherical granules, the Polygonal Contact Model (PCM) has been introduced into the DEM [...] Read more.
The discrete element method (DEM) is usually applied in analyzing the scientifical origin/evolution of the asteroids and the landing/sampling of the regolith. In order to manage the contact between the non-spherical granules, the Polygonal Contact Model (PCM) has been introduced into the DEM method. This paper applies four different contact force models in the newly-proposed DEM algorithm to analyze their difference and implication. The four contact force models include one linear model and three nonlinear models derived from the complete Mindlin–Deresiewicz equations. By considering the macroscopical results and calculation efficiency, the single-collision and multiple-collision cases are analyzed by comparing the four contact models. Specifically, the restitution coefficient, the angular velocity, the rebound angle, and the kinetic energy are applied as indicators for the single collision. The multiple-collision case is studied under the Brazil nut effect with ellipsoidal granules. Additionally, the softening feasibility is also discussed by decreasing the Young’s modulus of the material, mainly analyzing the outgoing results and the calculation efficiency. Full article
(This article belongs to the Special Issue Dynamics and Control Problems on Asteroid Explorations)
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35 pages, 5098 KiB  
Article
Individualisation of Inflight Catering Meals—An Automation Concept for Integrating Pre-Ordered Meals during the Flight for All Passengers
by Rafael Mortensen Ernits, Matthias Reiß, Michael Bauer, Axel Becker and Michael Freitag
Aerospace 2022, 9(11), 736; https://doi.org/10.3390/aerospace9110736 - 21 Nov 2022
Cited by 5 | Viewed by 6670
Abstract
Inflight catering services are crucial for air travel. Airlines provide food and beverages to the passengers during the flight with different options depending on, e.g., the flying class, distance, and type of service. Our contribution outlines previous efforts to optimise the inflight catering [...] Read more.
Inflight catering services are crucial for air travel. Airlines provide food and beverages to the passengers during the flight with different options depending on, e.g., the flying class, distance, and type of service. Our contribution outlines previous efforts to optimise the inflight catering processes and highlights the possibilities to individualise the current services. Individualisation is a growing trend and may challenge the processes that are possibly not wholly prepared to deliver a customised meal for each passenger onboard the aircraft. We present our passenger survey which confirms the demand for the individualisation of inflight meals; we explored which dimensions can be supported by incorporating automation. We performed an analysis of the current inflight catering process for developing automation concepts. Subsequently, an automation concept for the individualisation of inflight meals through pre-ordering is introduced, followed by an evaluation scenario. Within the evaluation, it was possible to consider the feasibility of the individualisation of inflight catering meals and to deliver requirements for the further development of automated services. Full article
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11 pages, 3394 KiB  
Article
Development of SMA Spring Linear Actuator for an Autonomous Lock and Release Mechanism: Application for the Gravity-Assisted Pointing System in Moon to Earth Alignment of Directional Devices
by Girolamo Costanza, Giovanni Ottavio Delle Monache, Maria Elisa Tata and Stefano Filosi
Aerospace 2022, 9(11), 735; https://doi.org/10.3390/aerospace9110735 - 21 Nov 2022
Cited by 2 | Viewed by 3049
Abstract
The next generation lunar reflector (NGLR) experiment is one of the experiments selected by NASA in the framework of the commercial lunar payload services (CLPS) initiative. The experiment, inspired by the lunar laser ranging (LLR) experiments of the Apollo era, is basically a [...] Read more.
The next generation lunar reflector (NGLR) experiment is one of the experiments selected by NASA in the framework of the commercial lunar payload services (CLPS) initiative. The experiment, inspired by the lunar laser ranging (LLR) experiments of the Apollo era, is basically a single cube corner reflector (CCR) capable of reflecting a beam coming from a laser station on Earth that must be deployed on the Moon and pointed toward the mean Earth direction. In this work, a prototype of an actuator for the lock and release system of the reflector package was conceived, built, and tested in laboratory conditions. Since the entire pointing system must be passive, the actuator is designed to be operated by an SMA spring actuated by the thermal radiation of the Sun and regolith on the Moon. In lab conditions, the prototype, activated by a heat gun, showed the capability of the SMA spring to operate a lock and release pin, whose diameter is 4 mm, subjected to a preload of F = 7 N exerted by the releasing spring. Full article
(This article belongs to the Section Astronautics & Space Science)
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15 pages, 4144 KiB  
Article
RCS Prediction Using Prony Method in High-Frequency Band for Military Aircraft Models
by Sungbae Ahn and Jinhwan Koh
Aerospace 2022, 9(11), 734; https://doi.org/10.3390/aerospace9110734 - 21 Nov 2022
Cited by 5 | Viewed by 2688
Abstract
Obtaining Radar Cross Section (RCS) data, one of the essential parameters for aircraft design, generally takes a lot of time and cost. Measurement time and accuracy of measurement results may be affected depending on the RCS measurement method and environment. When it comes [...] Read more.
Obtaining Radar Cross Section (RCS) data, one of the essential parameters for aircraft design, generally takes a lot of time and cost. Measurement time and accuracy of measurement results may be affected depending on the RCS measurement method and environment. When it comes to the RCS measurement method, the direct approach, which measures RCS on a real item, is more accurate than the indirect approach, which is implemented through simulation. However, in consideration of balancing accuracy, time and cost, the indirect approach is more generally used due to its efficiency. In this paper, in order to find an optimized method for more improved prediction results of indirect approach in the high-frequency band, three prediction methods are proposed: the Prony method, the Matrix pencil method (MPM) and the Rational Function method. It is confirmed that the RCS prediction result utilizing the Prony method in the high-frequency band has the minimum error in the case of Prony and MPM Methods, which have not been utilized for RCS prediction in the high-frequency band, and the Rational function method with currently applicable cases are employed. The prediction methods are, respectively, applied to a model based on three military aircraft models such as Jet Plane, F-117 and Transport Plane, and its simulation is performed under identical conditions. The original data and the extrapolated data obtained from the methods are compared at a certain angle for each model, and the errors between the extrapolated data are also compared in order to verify the efficacy of the prediction methods. Full article
(This article belongs to the Section Aeronautics)
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18 pages, 2051 KiB  
Article
Venus Life Finder Habitability Mission: Motivation, Science Objectives, and Instrumentation
by Sara Seager, Janusz J. Petkowski, Christopher E. Carr, Sarag J. Saikia, Rachana Agrawal, Weston P. Buchanan, David H. Grinspoon, Monika U. Weber, Pete Klupar, Simon P. Worden, Iaroslav Iakubivskyi, Mihkel Pajusalu, Laila Kaasik and on behalf of the Venus Life Finder Mission Team
Aerospace 2022, 9(11), 733; https://doi.org/10.3390/aerospace9110733 - 21 Nov 2022
Cited by 6 | Viewed by 3178
Abstract
For over half a century, scientists have contemplated the potential existence of life within the clouds of Venus. Unknown chemistry leaves open the possibility that certain regions of the Venusian atmosphere are habitable. In situ atmospheric measurements with a suite of modern instruments [...] Read more.
For over half a century, scientists have contemplated the potential existence of life within the clouds of Venus. Unknown chemistry leaves open the possibility that certain regions of the Venusian atmosphere are habitable. In situ atmospheric measurements with a suite of modern instruments can determine whether the cloud decks possess the characteristics needed to support life as we know it. The key habitability factors are cloud particle droplet acidity and cloud-layer water content. We envision an instrument suite to measure not only the acidity and water content of the droplets (and their variability) but additionally to confirm the presence of metals and other non-volatile elements required for life’s metabolism, verify the existence of organic material, and search for biosignature gases as signs of life. We present an astrobiology-focused mission, science goals, and instruments that can be used on both a large atmospheric probe with a parachute lasting about one hour in the cloud layers (40 to 60 km) or a fixed-altitude balloon operating at about 52 km above the surface. The latter relies on four deployable mini probes to measure habitability conditions in the lower cloud region. The mission doubles as a preparation for sample return by determining whether a subset of cloud particles is non-liquid as well as characterizing the heterogeneity of the cloud particles, thereby informing sample collection and storage methods for a return journey to Earth. Full article
(This article belongs to the Special Issue The Search for Signs of Life on Venus: Science Objectives and Mission Designs)
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16 pages, 6645 KiB  
Article
Deep Muti-Modal Generic Representation Auxiliary Learning Networks for End-to-End Radar Emitter Classification
by Zhigang Zhu, Zhijian Yi, Shiyao Li and Lin Li
Aerospace 2022, 9(11), 732; https://doi.org/10.3390/aerospace9110732 - 20 Nov 2022
Cited by 5 | Viewed by 1917
Abstract
Radar data mining is the key module for signal analysis, where patterns hidden inside of signals are gradually available in the learning process and its superiority is significant for enhancing the security of the radar emitter classification (REC) system. Owing to the disadvantage [...] Read more.
Radar data mining is the key module for signal analysis, where patterns hidden inside of signals are gradually available in the learning process and its superiority is significant for enhancing the security of the radar emitter classification (REC) system. Owing to the disadvantage that radio frequency fingerprinting (RFF) caused by the imperfection of emitter’s hardware is difficult to forge, current deep-learning REC methods based on deep-learning techniques, e.g., convolutional neural network (CNN) and long short term memory (LSTM) are difficult to capture the stable RFF features. In this paper, an online and non-cooperative multi-modal generic representation auxiliary learning REC model, namely muti-modal generic representation auxiliary learning networks (MGRALN), is put forward. Multi-modal means that multi-domain transformations are unified to a generic representation. After this, the representation is employed to facilitate mining the implicit information inside of the signals and to perform the better model robustness, which is achieved by using the available generic genenation to guide the network training and learning. Online means the learning process of REC is only once and the REC is end-to-end. Non-cooperative denotes no demodulation techniques are used before the REC task. Experimental results on the measured civil aviation radar data demonstrate that the proposed method enables one to achieve superior performance. Full article
(This article belongs to the Section Aeronautics)
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18 pages, 7958 KiB  
Article
Range-Based Reactive Deployment of a Flying Robot for Target Coverage
by Mingyang Lyu, Yibo Zhao and Hailong Huang
Aerospace 2022, 9(11), 731; https://doi.org/10.3390/aerospace9110731 - 20 Nov 2022
Cited by 1 | Viewed by 2023
Abstract
Flying robots, also known as drones and unmanned aerial vehicles (UAVs), have found numerous applications in civilian domains thanks to their excellent mobility and reduced cost. In this paper, we focus on a scenario of a flying robot monitoring a set of targets, [...] Read more.
Flying robots, also known as drones and unmanned aerial vehicles (UAVs), have found numerous applications in civilian domains thanks to their excellent mobility and reduced cost. In this paper, we focus on a scenario of a flying robot monitoring a set of targets, which are assumed to be moving as a group, to which the sparse distribution of the targets is not applicable. In particular, the problem of finding the optimal position for the flying robot such that all the targets can be monitored by the on-board ground facing camera is considered. The studied problem can be formulated as the conventional smallest circle problem if all the targets’ locations are given. Because it may be difficult to obtain the locations in practice, such as in Global Navigation Satellite Systems (GNSS) dined environments, a range-based navigation algorithm based on the sliding mode control method is proposed. This algorithm navigates the flying robot toward the farthest target dynamically, using the estimated robot–target distances from the received signal strength, until the maximum robot–target distance cannot be further reduced. It is light computation and easily implementable, and both features help to improve the energy efficiency of the flying robot because no heavy computation is required and no special sensing device needs to be installed on the flying robot. The presented solution does not directly solve the smallest circle problem. Instead, our proposed method dynamically navigates the flying robot to the center of the group of targets using the extracted distance information only. Simulations in Matlab and Gazebo have been conducted for both stationery and mobile targets to verify the effectiveness of the proposed approach. Full article
(This article belongs to the Special Issue Energy Efficiency of Small-Scale UAVs)
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23 pages, 5135 KiB  
Article
Neural-Network-Based Terminal Sliding Mode Control of Space Robot Actuated by Control Moment Gyros
by Xinhui Xia, Yinghong Jia, Xinlong Wang and Jun Zhang
Aerospace 2022, 9(11), 730; https://doi.org/10.3390/aerospace9110730 - 19 Nov 2022
Cited by 5 | Viewed by 1887
Abstract
This paper studies the trajectory tracking control of a space robot system (SRS) in the presence of the lumped uncertainties with no prior knowledge of their upper bound. Although some related control methods have been proposed, most of them have either not been [...] Read more.
This paper studies the trajectory tracking control of a space robot system (SRS) in the presence of the lumped uncertainties with no prior knowledge of their upper bound. Although some related control methods have been proposed, most of them have either not been applied to SRSs or lack rigorous stability proof. Therefore, it is still a challenge to achieve high accuracy and rigorous theoretical proof for tracking control of SRSs. This paper proposes a new integrated neural network- based control scheme for the trajectory tracking of a SRS actuated by control moment gyros (CMGs). A new adaptive non-singular terminal sliding mode (ANTSM) control method is developed based on an improved radial basis function neural network (RBFNN). In the control method, a new weight update law is proposed to learn the upper bound of the lumped uncertainties. With the advantages of RBFNN and ANTSM, the controller has high control accuracy, fast learning speed and finite-time convergence. Different from most on-ground robotic manipulator controllers, a kinematic controller with position and attitude control laws is also designed for the satellite platform to remain stable. The stability of the closed-loop system is proved by the Lyapunov method with a high mathematical standard. Comparative simulation results demonstrate the effectiveness of the proposed control scheme with preferable performance and robustness. 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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13 pages, 4207 KiB  
Article
Influence of Nose Landing Gear Torsional Damping on the Stability of Aircraft Taxiing Direction
by Yiyao Jiang, Guang Feng, Panglun Liu, Li Yuan, Jianbin Ding and Bingyan Jiang
Aerospace 2022, 9(11), 729; https://doi.org/10.3390/aerospace9110729 - 19 Nov 2022
Cited by 9 | Viewed by 4281
Abstract
The design of the nose landing gear (NLG) torsional damping is very important to avoid the taxiing vibration of the aircraft. On the one hand, increasing the torsional damping can suppress the nose wheel shimmy. On the other hand, if the design value [...] Read more.
The design of the nose landing gear (NLG) torsional damping is very important to avoid the taxiing vibration of the aircraft. On the one hand, increasing the torsional damping can suppress the nose wheel shimmy. On the other hand, if the design value is too large, it will cause unstable vibration of the aircraft direction, and the latter will often be ignored, which will bring potential risks to the taxiing safety of the aircraft. In this paper, by establishing a multibody dynamics model (MBD) of aircraft taxiing, including NLG, main landing gear (MLG), airframe, related force elements and kinematic pairs, the effect of the torsional damping of NLG on aircraft directional stability is studied, and the key taxiing parameters of aircraft taxiing in an unstable direction are obtained. In order to propose the damping design specification for the nose landing gear anti-shimmy system, the critical value of torsional damping for stable taxiing in the direction of the aircraft is calculated. It is found that nose wheel shimmy and the unstable vibration of the aircraft direction will occur simultaneously, but the vibration frequencies are different. Therefore, in addition to the anti-shimmy design, the influence of the aircraft’s directional unstable vibration must also be considered in the engineering application. Full article
(This article belongs to the Special Issue Structural Dynamics and Control)
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31 pages, 1466 KiB  
Article
Prescribed Performance Adaptive Balance Control for Reaction Wheel-Based Inverted Pendulum-Type Cubli Rovers in Asteroid
by He Huang, Zejian Li, Zongyi Guo, Jianguo Guo, Le Suo and Haoliang Wang
Aerospace 2022, 9(11), 728; https://doi.org/10.3390/aerospace9110728 - 18 Nov 2022
Cited by 3 | Viewed by 1948
Abstract
This paper investigates the issue of balance control for reaction-wheeled inverted pendulum-type Cubli Rovers on asteroids, and an adaptive control scheme is proposed via the prescribed performance control technique. The main feature lies in the fact that the transient behavior is satisfied which [...] Read more.
This paper investigates the issue of balance control for reaction-wheeled inverted pendulum-type Cubli Rovers on asteroids, and an adaptive control scheme is proposed via the prescribed performance control technique. The main feature lies in the fact that the transient behavior is satisfied which is required critically in the environment of asteroids. The attitude model of reaction-wheeled inverted pendulum-type Cubli Rovers is first constructed by virtue of the momentum moment theorem and Eulerian kinematics. Based on that, the gravitational field in the asteroid is described and the avoiding jumping condition is analyzed. Then, an adaptive prescribed performance control (APPC) method is proposed to obtain the fine tracking performance of the equilibrium error such that the inverted pendulum-type Cubli Rovers achieve the self-balancing motion. The proposed method is capable of ensuring the tracking errors inside the preset boundary functions, and the asymptotic stability of all states in the closed-loop system is guaranteed via the Lyapunov stability theory. The simulation and comparison results on the environment of asteroids verify the effectiveness and superiority of the presented control law. Full article
(This article belongs to the Special Issue Dynamics and Control Problems on Asteroid Explorations)
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15 pages, 4437 KiB  
Article
Dynamic Numerical Simulation of Hybrid Rocket Motor with HTPB-Based Fuel with 58% Aluminum Additives
by Hui Tian, Xiangyu Meng, Hao Zhu, Chengen Li, Lingfei He and Guobiao Cai
Aerospace 2022, 9(11), 727; https://doi.org/10.3390/aerospace9110727 - 18 Nov 2022
Cited by 6 | Viewed by 2183
Abstract
The addition of aluminum (Al) to the fuel is an effective way to increase the regression rate of hybrid rocket motors (HRMs). Due to its high regression rate, the impact of the regression of combustion surface on the performance of HRMs cannot be [...] Read more.
The addition of aluminum (Al) to the fuel is an effective way to increase the regression rate of hybrid rocket motors (HRMs). Due to its high regression rate, the impact of the regression of combustion surface on the performance of HRMs cannot be ignored. Therefore, it is significant to establish a dynamic numerical simulation model to predict the performance of HRMs. In this study, the dynamic simulation model was established based on dynamic mesh technology and was verified by a firing test. The results show that the simulation results agree well with the experimental results, and the errors of the average thrust and combustion chamber pressure are 3.4% and 1.4%, respectively. The dynamic simulation shows that with the regression of the combustion surface, the vortex of the pre-combustion chamber is divided into two vortices. The vortex near the front of the grain will increase the regression rate downstream. The results show that the addition of Al can obviously improve the regression rate of HRMs. The fuel containing 58% Al can improve the regression rate by 88.8% compared with the fuel with pure hydroxyl-terminated polybutadiene (HTPB). Moreover, due to the higher combustion temperature and the scouring of metal particles, the ablation rate of the nozzle with carbon ceramic materials reaches 0.16 mm/s. This investigation provides a valuable reference for HRMs design and simulation. Full article
(This article belongs to the Section Astronautics & Space Science)
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18 pages, 7436 KiB  
Article
An Observer-Based Stiffness Estimation for Space Target Capture by Space Robot with Controllable Damping Mechanism
by Rui Chang, Qingxuan Jia, Ming Chu and Xiaodong Zhang
Aerospace 2022, 9(11), 726; https://doi.org/10.3390/aerospace9110726 - 18 Nov 2022
Viewed by 2021
Abstract
The space target capturing task using the spacecraft-manipulator system (SMS) has special significance in on-orbit servicing due to its theoretical challenges and practical value. The contact force between the end effector (gripper) and the target exerted by the tumbling motion of the space [...] Read more.
The space target capturing task using the spacecraft-manipulator system (SMS) has special significance in on-orbit servicing due to its theoretical challenges and practical value. The contact force between the end effector (gripper) and the target exerted by the tumbling motion of the space target destabilizes the spacecraft base. A full-dimensional controllable damping mechanism (FDCDM) with a cross-axis structure was designed to buffer the transient impact force on the end joint. The introduction of a damping mechanism gives the space robot a variable stiffness and damping system, and a stiffness estimation algorithm is proposed to calibrate the system stiffness, as stiffness cannot be measured directly. The full-dimensional controllable damping mechanism (FDCDM) with a cross-axis structure is equivalent to a four-DOF tandem joint, and the whole-body dynamic model of the SMS endowed with a full-dimensional controllable damping mechanism (FDCDM) was established using the Kane equation. Then, an unknown input observer (UIO)-based identification theory is proposed to precisely estimate the internal flexibility torque and the corresponding joint stiffness. A model-based neural learning algorithm is proposed to update the variable parameter matrix of the observer. The simulation experiment results demonstrate that the flexibility torque and joint stiffness could be accurately estimated within the expected error, illustrating the feasibility and effectiveness of the proposed method. Full article
(This article belongs to the Special Issue Artificial Intelligence and Space Robotics: Perception, Autonomy, and Intelligence)
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23 pages, 13347 KiB  
Article
Body Force Model Implementation of Transonic Rotor for Fan/Airframe Simulations
by Andrea Magrini
Aerospace 2022, 9(11), 725; https://doi.org/10.3390/aerospace9110725 - 18 Nov 2022
Cited by 3 | Viewed by 2339
Abstract
Three-dimensional throughflow models represent a turbomachinery cascade via a force distribution without the need for detailed geometric modelling in the numerical solution, saving consistent computational resources. In this paper, we present the application of a body force method on an axial transonic fan [...] Read more.
Three-dimensional throughflow models represent a turbomachinery cascade via a force distribution without the need for detailed geometric modelling in the numerical solution, saving consistent computational resources. In this paper, we present the application of a body force method on an axial transonic fan implemented into an in-house tool for axisymmetric throughflow simulations. By a systematic comparison of local and integral quantities with a validated numerical solution, the capabilities and limitations of the model are discussed for different operating regimes. The implementation is first validated at the peak efficiency calibration point, providing a good duplication of blade flow variables and radial profiles. The design total pressure is matched with a 0.6% absolute difference and a slightly higher slope of the characteristic towards the stall. The isentropic efficiency curve is penalised after the choking mass flow rate calibration, presenting an absolute difference close to 2%, although with a consistent off-design trend. In general, the model provides a satisfactory representation of the flow field and the outflow spanwise distributions, with locally larger discrepancies near the endwalls. Finally, the method is applied to simulate the fan and outlet guide vanes installed into an isolated turbofan nacelle. The onset of intake stall at a high angle of attack is compared between the body force and a boundary conditions-based approaches, highlighting the importance of adopting fully coupled solution methods to study fan/airframe interaction problems. Full article
(This article belongs to the Section Aeronautics)
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16 pages, 4413 KiB  
Article
A Fuzzy Backstepping Attitude Control Based on an Extended State Observer for a Tilt-Rotor UAV
by Suiyuan Shen, Jinfa Xu and Qingyuan Xia
Aerospace 2022, 9(11), 724; https://doi.org/10.3390/aerospace9110724 - 17 Nov 2022
Cited by 5 | Viewed by 1885
Abstract
In order to overcome the influence of internal and external disturbances caused by rotor tilt motion and gust disturbance on the full flight mode control of a tilt-rotor unmanned aerial vehicle (UAV), a design method using fuzzy backstepping control based on an extended-state [...] Read more.
In order to overcome the influence of internal and external disturbances caused by rotor tilt motion and gust disturbance on the full flight mode control of a tilt-rotor unmanned aerial vehicle (UAV), a design method using fuzzy backstepping control based on an extended-state observer (FBS-ESO) is proposed. In this paper, fuzzy control is used to tune the parameters of the backstepping control law online, and the extended-state observer estimates the total disturbance of the controlled system to improve the controller’s robustness and anti-disturbance capability. This paper designs the attitude control system of a tilt-rotor UAV based on an FBS-ESO controller. The control performance of the FBS-ESO controller is tested in a hardware-in-loop simulation of the attitude control system. The simulation results show that changing the rotor tilt angle will destroy the stability of the traditional backstepping controller and active disturbance rejection controller (ADRC). In contrast, the FBS-ESO controller maintains good control performance. In addition, the performance of the FBS-ESO controller is not be significantly affected by adding external gust disturbance or changing the UAV parameters in the simulation. These disturbances significantly impact the traditional backstepping controller and ADRC. Therefore, the FBS-ESO controller has better anti-disturbance capabilities and robustness, as well as higher attitude control accuracy. Full article
(This article belongs to the Section Aeronautics)
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16 pages, 10006 KiB  
Article
Characterization and Testing of the Passive Magnetic Attitude Control System for the 3U AstroBio CubeSat
by Stefano Carletta, Augusto Nascetti, Sagar S. Gosikere Matadha, Lorenzo Iannascoli, Thiago Baratto de Albuquerque, Nithin Maipan Davis, Luigi Schirone, Gabriele Impresario, Simone Pirrotta and John R. Brucato
Aerospace 2022, 9(11), 723; https://doi.org/10.3390/aerospace9110723 - 17 Nov 2022
Cited by 4 | Viewed by 2552
Abstract
AstroBio CubeSat is a mission funded by the Italian Space Agency aimed at validating novel lab-on-chip technology, that would enable the use of micro- and nanosatellites as autonomous orbiting laboratories for research in astrobiology. This 3U CubeSat is equipped with a passive magnetic [...] Read more.
AstroBio CubeSat is a mission funded by the Italian Space Agency aimed at validating novel lab-on-chip technology, that would enable the use of micro- and nanosatellites as autonomous orbiting laboratories for research in astrobiology. This 3U CubeSat is equipped with a passive magnetic attitude control system (PMACS), including permanent magnets and hysteresis strips, which allows for stabilizing the spacecraft with the longitudinal axis in the direction of the geomagnetic field vector. This work presents the process followed for the experimental characterization of the system, performed on the engineering unit of the satellite by using a Helmholtz cage facility and a spherical air-bearing to recreate environmental conditions similar to the ones experienced during the orbital motion. The hysteresis strips are characterized starting from the determination of the hysteresis loop, from which the energy dissipation per cycle and the apparent magnetic permeability are extracted. Tests performed by using the Helmholtz cage and the air-bearing facility allows for further investigating the damping torque produced by the PMACS and validating the abovementioned parameters. Numerical analysis is then used to select the number of permanent magnets which allows for achieving a pointing accuracy within an error of 10∘ within 24 h from the deployment. The analysis of the flight data supports the results obtained from the experimental test campaigns, confirming the effectiveness of the proposed methods and of the PMACS design. Full article
(This article belongs to the Special Issue Spacecraft Attitude Control Using Magnetic Actuators)
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16 pages, 3667 KiB  
Article
AI-Based Exhaust Gas Temperature Prediction for Trustworthy Safety-Critical Applications
by Asteris Apostolidis, Nicolas Bouriquet and Konstantinos P. Stamoulis
Aerospace 2022, 9(11), 722; https://doi.org/10.3390/aerospace9110722 - 17 Nov 2022
Cited by 6 | Viewed by 3883
Abstract
Data-driven condition-based maintenance (CBM) and predictive maintenance (PdM) strategies have emerged over recent years and aim at minimizing the aviation maintenance costs and environmental impact by the diagnosis and prognosis of aircraft systems. As the use of data and relevant algorithms is essential [...] Read more.
Data-driven condition-based maintenance (CBM) and predictive maintenance (PdM) strategies have emerged over recent years and aim at minimizing the aviation maintenance costs and environmental impact by the diagnosis and prognosis of aircraft systems. As the use of data and relevant algorithms is essential to AI-based gas turbine diagnostics, there are different technical, operational, and regulatory challenges that need to be tackled in order for the aeronautical industry to be able to exploit their full potential. In this work, the machine learning (ML) method of the generalised additive model (GAM) is used in order to predict the evolution of an aero engine’s exhaust gas temperature (EGT). Three different continuous synthetic data sets developed by NASA are employed, known as New Commercial Modular Aero-Propulsion System Simulation (N-CMAPSS), with increasing complexity in engine deterioration. The results show that the GAM can be predict the evolution of the EGT with high accuracy when using several input features that resemble the types of physical sensors installed in aero gas turbines currently in operation. As the GAM offers good interpretability, this case study is used to discuss the different data attributes a data set needs to have in order to build trust and move towards certifiable models in the future. Full article
(This article belongs to the Special Issue Selected Papers from the 1st International Conference for CBM in Aerospace)
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17 pages, 1393 KiB  
Article
Assessing an Image-to-Image Approach to Global Path Planning for a Planetary Exploration
by Guglielmo Daddi, Nicolaus Notaristefano, Fabrizio Stesina and Sabrina Corpino
Aerospace 2022, 9(11), 721; https://doi.org/10.3390/aerospace9110721 - 16 Nov 2022
Cited by 2 | Viewed by 1745
Abstract
This work considers global path planning enabled by generative adversarial networks (GANs) on a 2D grid world. These networks can learn statistical relationships between obstacles, goals, states, and paths. Given a previously unseen combination of obstacles, goals, and an initial state, they can [...] Read more.
This work considers global path planning enabled by generative adversarial networks (GANs) on a 2D grid world. These networks can learn statistical relationships between obstacles, goals, states, and paths. Given a previously unseen combination of obstacles, goals, and an initial state, they can be asked to guess what a new path would look like. We performed experiments on a 64 × 64 pixel grid that generated a training set by using randomly positioned obstacles and goals. The heuristic search algorithm A* was used to create training paths due to its significant presence in the literature and ease of implementation. We experimented with architectural elements and hyperparameters, converging to a pix2pix-based architecture in which the generator was trained to generate plausible paths given obstacles and two points. A discriminator tried to determine whether these maps were real or fake. Additionally, we defined a qualitative path-generation “success rate” metric derived from the Fréchet inception distance (FID) and optimized our architecture’s parameters, ultimately reaching a 74% success rate on the validation set. Furthermore, we discuss the applicability of this approach to safety-critical settings, concluding that this architecture’s performance and reliability are insufficient to offset the downsides of a black-box approach to path generation. Full article
(This article belongs to the Section Astronautics & Space Science)
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23 pages, 16997 KiB  
Article
Trajectory Optimization with Complex Obstacle Avoidance Constraints via Homotopy Network Sequential Convex Programming
by Wenbo Li, Wentao Li, Lin Cheng and Shengping Gong
Aerospace 2022, 9(11), 720; https://doi.org/10.3390/aerospace9110720 - 16 Nov 2022
Cited by 10 | Viewed by 2587
Abstract
Space vehicles’ real-time trajectory optimization is the key to future automatic guidance. Still, the current sequential convex programming (SCP) method suffers from a low convergence rate and poor real-time performance when dealing with complex obstacle avoidance constraints (OACs). Given the above challenges, this [...] Read more.
Space vehicles’ real-time trajectory optimization is the key to future automatic guidance. Still, the current sequential convex programming (SCP) method suffers from a low convergence rate and poor real-time performance when dealing with complex obstacle avoidance constraints (OACs). Given the above challenges, this work combines homotopy and neural network techniques with SCP to propose an innovative algorithm. Firstly, a neural network was used to fit the minimum signed distance field at obstacles’ different “growth” states to represent the OACs. Then, the network was embedded with the SCP framework, thus smoothly transforming the OACs from simple to complex. Numerical simulations showed that the proposed algorithm can efficiently deal with trajectory optimization under complex OACs such as a “maze”, and the algorithm has a high convergence rate and flexible extensibility. Full article
(This article belongs to the Special Issue Advances in Aerospace Sciences and Technology III)
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19 pages, 5400 KiB  
Article
Stability of a Flexible Asteroid Lander with Landing Control
by Weifeng Yan, Ruoyu Feng and Hexi Baoyin
Aerospace 2022, 9(11), 719; https://doi.org/10.3390/aerospace9110719 - 16 Nov 2022
Cited by 11 | Viewed by 1957
Abstract
Stable landing on asteroids is of considerable scientific and economic value but accompanied by huge difficulties. This paper proposes a novel flexible lander suitable for asteroids with microgravity and rugged surface. The gravity model with the artificial neural network and the surface model [...] Read more.
Stable landing on asteroids is of considerable scientific and economic value but accompanied by huge difficulties. This paper proposes a novel flexible lander suitable for asteroids with microgravity and rugged surface. The gravity model with the artificial neural network and the surface model with the spherical harmonic method are introduced to establish the target asteroid’s dynamical environment. The flexible dynamics with the discrete shell model, the collision with the spring-damping model and viscous sliding friction, and the rigid coupling with the constraint violation stabilization method are elaborated for the lander. Combining the asteroid’s model with the lander’s dynamics, one successful landing scenario of the lander is presented. The lander’s landing stability of the final uncontrolled touching phase is studied through massive simulations. It is found that reasonable touching conditions can largely enhance the landing stability, and the lander can achieve a stable landing on the asteroid under a particular touching condition without control. The flexible lander’s comparison to the rigid lander is also discussed. It is concluded that the flexible lander does have higher adaptability and lower risk in asteroid landing. What is more, the attitude controller and position controller for the lander’s descent phase are also proposed and tested. Full article
(This article belongs to the Special Issue Dynamics and Control Problems on Asteroid Explorations)
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16 pages, 6386 KiB  
Article
Structural Efficiency Analysis of a Piston for Aviation Engines
by Zhongjian Pan, Qinghua He and Xiaobing Pang
Aerospace 2022, 9(11), 718; https://doi.org/10.3390/aerospace9110718 - 15 Nov 2022
Cited by 3 | Viewed by 2661
Abstract
The high-performance piston has a great impact on the performance parameters of the engine. The rapid design of a high-performance piston can shorten the research and development cycle and lower the experimental cost. At present, the piston design is mostly considered from a [...] Read more.
The high-performance piston has a great impact on the performance parameters of the engine. The rapid design of a high-performance piston can shorten the research and development cycle and lower the experimental cost. At present, the piston design is mostly considered from a single factor, but it has not been comprehensively designed from multiple factors. Starting from the concept of structural efficiency, this paper defines the restrictive factors affecting engine performance parameters in piston design, puts forward an evaluation method of quantifying the benefit of piston design on engine performance parameters, and deduces the calculation model. The piston is designed and iterated many times to obtain the best two schemes. The two schemes are quantitatively compared through the above calculation model and verified by experiments. The results show that the structural efficiency of the piston in scheme 2 is 4.6% higher than that in scheme 1. The calculation method is applicable to the design of key engine components, which can shorten the research and development cycle, save the test costs, and greatly improve the R&D efficiency. Full article
(This article belongs to the Section Aeronautics)
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11 pages, 6812 KiB  
Article
Optimal Earth Gravity-Assist Maneuvers with an Electric Solar Wind Sail
by Lorenzo Niccolai, Marco Bassetto, Alessandro A. Quarta and Giovanni Mengali
Aerospace 2022, 9(11), 717; https://doi.org/10.3390/aerospace9110717 - 14 Nov 2022
Cited by 1 | Viewed by 2387
Abstract
Propellantless propulsive systems such as Electric Solar Wind Sails are capable of accelerating a deep-space probe, only requiring a small amount of propellant for attitude and spin-rate control. However, the generated thrust magnitude is usually small when compared with the local Sun’s gravitational [...] Read more.
Propellantless propulsive systems such as Electric Solar Wind Sails are capable of accelerating a deep-space probe, only requiring a small amount of propellant for attitude and spin-rate control. However, the generated thrust magnitude is usually small when compared with the local Sun’s gravitational attraction. Therefore, the total velocity change necessary for the mission is often obtained at the expense of long flight times. A possible strategy to overcome this issue is offered by an Earth gravity-assist maneuver, in which a spacecraft departs from the Earth’s sphere of influence, moves in the interplanetary space, and then re-encounters the Earth with an increased hyperbolic excess velocity with respect to the starting planet. An Electric Solar Wind Sail could effectively drive the spacecraft in the interplanetary space to perform such a particular maneuver, taking advantage of an augmented thrust magnitude in the vicinity of the Sun due to the increased solar wind ion density. This work analyzes Earth gravity-assist maneuvers performed with an Electric Solar Wind Sail based probe within an optimal framework, in which the final hyperbolic excess velocity with respect to the Earth is maximized for a given interplanetary flight time. Numerical simulations highlight the effectiveness of this maneuver in obtaining a final heliocentric orbit with high energy. Full article
(This article belongs to the Special Issue Advances in CubeSat Sails and Tethers)
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22 pages, 14708 KiB  
Article
Effects of Aeroelastic Walls on the Aeroacoustics in Transonic Cavity Flow
by Stefan Nilsson, Hua-Dong Yao, Anders Karlsson and Sebastian Arvidson
Aerospace 2022, 9(11), 716; https://doi.org/10.3390/aerospace9110716 - 14 Nov 2022
Cited by 4 | Viewed by 2777
Abstract
The effects of elastic cavity walls on noise generation at transonic speed are investigated for the generic M219 cavity. The flow is simulated with the Spalart–Allmaras (SA) improved delayed detached-eddy simulation (IDDES) turbulence model in combination with a wall function. The structural analysis [...] Read more.
The effects of elastic cavity walls on noise generation at transonic speed are investigated for the generic M219 cavity. The flow is simulated with the Spalart–Allmaras (SA) improved delayed detached-eddy simulation (IDDES) turbulence model in combination with a wall function. The structural analysis software uses a modal formulation. The first 50 structural normal mode shapes are included in the simulation, spanning frequencies of 468–2280 Hz. Results are compared with those from a reference simulation with rigid cavity walls. A spectral analysis of pressure fluctuations from a microphone array above the cavity evinces a distinct tone at 816 Hz, which is absent in the reference simulation. Furthermore, the power of the 4th Rossiter mode at 852 Hz is depleted, implying a significant energy transfer from the fluid to the structure. Spectral proper orthogonal decomposition (SPOD) is employed for analyses of cavity wall pressure fluctuations and wall displacements. The SPOD mode energy spectra show results consistent with the spectra of the microphone array with respect to the tone at 816 Hz and the depletion of the energy at the 4th Rossiter mode. Furthermore, the SPOD mode energy spectra show energy spikes at additional frequencies, which coincide with structural eigenfrequencies. Full article
(This article belongs to the Special Issue Aeroacoustics and Noise Mitigation)
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14 pages, 1672 KiB  
Article
Validation for Aerodynamic Performance on Over-Expanded State of Single Expansion Ramp Nozzle Configuration
by Ye Chen, Zhongxi Hou, Bingjie Zhu, Zheng Guo and Boting Xu
Aerospace 2022, 9(11), 715; https://doi.org/10.3390/aerospace9110715 - 14 Nov 2022
Cited by 2 | Viewed by 2519
Abstract
The performance of a single expansion ramp nozzle (SERN) drastically declines on over-expanded conditions. A numerical code can accurately predict nozzle performance in the over-expanded state, which is crucial for the SERN configuration design. A Reynolds-averaged Navier–Stokes (RANS) simulation of the SERN jet [...] Read more.
The performance of a single expansion ramp nozzle (SERN) drastically declines on over-expanded conditions. A numerical code can accurately predict nozzle performance in the over-expanded state, which is crucial for the SERN configuration design. A Reynolds-averaged Navier–Stokes (RANS) simulation of the SERN jet in an over-expanded state was performed to verify the numerical performance of the well-established commercial CFD solver (ANSYS FluentTM v202) and rhoCentralFoam solver in OpenFOAM. The wall pressure distributions and flow field characteristics including the shock structures and the width of the jet were studied in detail with an inlet nozzle pressure ratio (NPR) of 1.5, 3, 4, and 8. The SERN aerodynamic performance with an inlet NPR ranging from 1.5 to 9 was then calculated. The results showed that the Fluent 3D simulation could qualitatively predict the characteristics of the internal and external flow of the nozzle, because it overestimated the wall pressure and shock wave position. Two-dimensional (2D) simulations made it difficult to capture the external flow structure due to the 3D effects. The simulation results of rhoCentralFoam for over-expanded SERN flow were not ideal. The Fluent can produce physical solutions, and it achieved limited success. The existing errors were mainly caused by the inlet boundary setting. Full article
(This article belongs to the Special Issue Fluid Flow Mechanics (2nd Edition))
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19 pages, 5606 KiB  
Article
Bio-Inspired Self-Organized Fission–Fusion Control Algorithm for UAV Swarm
by Xiaorong Zhang, Wenrui Ding, Yufeng Wang, Yizhe Luo, Zehao Zhang and Jing Xiao
Aerospace 2022, 9(11), 714; https://doi.org/10.3390/aerospace9110714 - 12 Nov 2022
Cited by 4 | Viewed by 2046
Abstract
Swarm control has become a challenging topic for the current unmanned aerial vehicle (UAV) swarm due to its conflicting individual behaviors and high external interference. However, in contrast to static obstacles, limited attention has been paid to the fission–fusion behavior of the swarm [...] Read more.
Swarm control has become a challenging topic for the current unmanned aerial vehicle (UAV) swarm due to its conflicting individual behaviors and high external interference. However, in contrast to static obstacles, limited attention has been paid to the fission–fusion behavior of the swarm against dynamic obstacles. In this paper, inspired by the interaction mechanism and fission–fusion motion of starlings, we propose a Bio-inspired Self-organized Fission–fusion Control (BiSoFC) algorithm for the UAV swarm, where the number of UAVs in the sub-swarm is controllable. It solves the problem of swarm control under dynamic obstacle interference with the tracking function. Firstly, we establish the kinematic equations of the individual UAV and swarm controllers and introduce a fission–fusion control framework to achieve the fission–fusion movement of the UAV swarm with a lower communication load. Afterward, a sub-swarm selection algorithm is built upon the topological interaction structure. When a swarm is faced with different tasks, the swarm that can control the number of agents in a sub-swarm can accomplish the corresponding task with a more reasonable number of agents. Finally, we design a sub-swarm trapping algorithm with a tracking function for the dynamic obstacles. The simulation results show that the UAV swarm can self-organize fission sub-swarms to cope with dynamic obstacles under different disturbance situations, and successfully achieve the goal of protecting the parent swarm from dynamic obstacles. The experimental results prove the feasibility and effectiveness of our proposed control algorithm. 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, 7281 KiB  
Article
The Influence of Steady Air Jet on the Trailing-Edge Shock Loss in a Supersonic Compressor Cascade
by Yinxin Zhu, Zhenbing Luo, Wenqiang Peng, Qiang Liu, Yan Zhou, Wei Xie, Pan Cheng, Zhengxue Ma and Xuzhen Xie
Aerospace 2022, 9(11), 713; https://doi.org/10.3390/aerospace9110713 - 12 Nov 2022
Cited by 1 | Viewed by 1715
Abstract
To effectively reduce shock wave loss at the trailing edge of a supersonic cascade under high back-pressure, a shock wave control method based on air jets is proposed. The air jet was arranged on the pressure side of the blade in the upstream [...] Read more.
To effectively reduce shock wave loss at the trailing edge of a supersonic cascade under high back-pressure, a shock wave control method based on air jets is proposed. The air jet was arranged on the pressure side of the blade in the upstream of the trailing-edge shock. The flow control mechanism and effects of parameters were analyzed by computational methods. The results show that the air jet formed an oblique shock wave in the cascade passage which decelerated and pressurized the airflow. The resulting expansion wave downstream of the jet slot weakened the strength of the trailing-edge shock. This could effectively change the normal shock into oblique shock and thus weaken the shock loss. Optimal control effect was achieved when the mass flow rate ratio of the jet to the passage airflow remained 0.35–1.11% and the distance from the jet slot to the shock foot of the trailing-edge shock was about five times the thickness of the boundary layer. The proposed method can reduce the total pressure loss of a supersonic cascade, with the maximum improvement effect reaching 7.29% compared to the no-control state. Full article
(This article belongs to the Special Issue Flow Control and Drag Reduction)
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20 pages, 6225 KiB  
Article
Aerodynamic and Structural Aspects of a Distributed Propulsion System for Commuter Airplane
by Pavel Hospodář, Jan Klesa, Daniel Demovič and Nikola Žižkovský
Aerospace 2022, 9(11), 712; https://doi.org/10.3390/aerospace9110712 - 12 Nov 2022
Cited by 4 | Viewed by 3629
Abstract
In this paper, an aerodynamic and structural computation framework was produced to develop a more efficient aircraft configuration considering a wing with a distributed electric propulsion and its use in different flight missions. For that reason, a model of a regional airplane was [...] Read more.
In this paper, an aerodynamic and structural computation framework was produced to develop a more efficient aircraft configuration considering a wing with a distributed electric propulsion and its use in different flight missions. For that reason, a model of a regional airplane was used as a case study. The considered model was a nine-seat light airplane with a cruise speed of 500 km/h at an altitude 9000 m. The design of the distributed system is introduced, then the aerodynamic and structural aspects of the new wing with distributed electric propulsion system are calculated, and finally flight performances are calculated for the purpose of analysis of the DEP effect. The design of the DEP system aimed at meeting the required landing conditions and the masses of its components, such as the electric motors, the control units and the power source of the DEP system were estimated. Aerodynamic calculations included computations of different wing aspect ratios. These calculations take into account the drag of the existing airplane parts such as fuselage and tail surfaces. A modified lifting-line theory was used as a computational tool for the preliminary study. It was used to calculate the wing drag in cruise regime and to determine the distribution of aerodynamic forces and moments. Next, based on aerodynamic calculations and flight envelope, the basic skeletal parts of the wing were designed and the weight of the wing was calculated. Finally, fuel consumption calculations for different wing sizes were made and compared with the original design. The results show that a wing with a 35% reduction in area can reduce fuel consumption by more than 6% while keeping the same overall weight of the aircraft. Full article
(This article belongs to the Special Issue Turboprop Aircraft Design and Optimization)
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21 pages, 2754 KiB  
Article
A Hybrid Model Integrating HFACS and BN for Analyzing Human Factors in CFIT Accidents
by Bin Meng and Na Lu
Aerospace 2022, 9(11), 711; https://doi.org/10.3390/aerospace9110711 - 12 Nov 2022
Cited by 4 | Viewed by 2911
Abstract
Controlled flight into terrain (CFIT) is considered a typical accident category of “low-probability-high consequence”. Human factors play an important role in CFIT accidents in such a complex and high-risk system. This study aims to explore the causal relationship and inherent correlation of CFIT [...] Read more.
Controlled flight into terrain (CFIT) is considered a typical accident category of “low-probability-high consequence”. Human factors play an important role in CFIT accidents in such a complex and high-risk system. This study aims to explore the causal relationship and inherent correlation of CFIT accidents by the Human Factors Analysis and Classification System (HFACS) and Bayesian network (BN). A total of 74 global CFIT accident investigation reports from 2001 to 2020 were collected, and the main contributing factors were classified and analyzed based on the Human Factors Analysis and Classification System. Then, the model was transformed into a Bayesian network topology structure. To ensure accuracy, the prior probability of each root node was computed by the fuzzy number theory. Afterward, using the bidirectional reasoning ability of the Bayesian network under uncertainty, this study performed a systematic quantitative analysis of the controlled flight into terrain accidents, including causal reasoning analysis, diagnostic analysis, sensitivity analysis, most probable explanation, and scenario analysis. The results demonstrate that the precondition for unsafe acts (30.5%) has the greatest impact on the controlled flight into terrain accidents among the four levels of contributing factors. Inadequate supervision, intentional noncompliance with SOPs/cross-check, GPWS not installed or failure, adverse meteorological environment, and ground-based navigation aid malfunction or not being available are recognized as the top significant contributing factors. The contributing factors of the high sensitivity and most likely failure are identified, and the coupling effect between the different contributing factors is verified. This study can provide guidance for CFIT accident analysis and prevention. Full article
(This article belongs to the Section Air Traffic and Transportation)
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26 pages, 5476 KiB  
Article
Optimal Cooperative Guidance Strategies for Aircraft Defense with Impact Angle Constraints
by Quancheng Li, Tian Yan, Mengjing Gao, Yonghua Fan and Jie Yan
Aerospace 2022, 9(11), 710; https://doi.org/10.3390/aerospace9110710 - 12 Nov 2022
Cited by 3 | Viewed by 1931
Abstract
Given the limitations of escape maneuvers and decoy deployment of combat aircraft under missile attacks; active defense dramatically improves the survival chances by launching active defense missiles to intercept incoming missiles. Different from previous work, this paper implemented impact angle constraints on the [...] Read more.
Given the limitations of escape maneuvers and decoy deployment of combat aircraft under missile attacks; active defense dramatically improves the survival chances by launching active defense missiles to intercept incoming missiles. Different from previous work, this paper implemented impact angle constraints on the defense missile to achieve a better defense effect. The low-cost active defense missile with limited maneuverability is considered to cooperate with the aircraft through three mechanisms, namely two-way cooperation without any predetermined strategy, one-way cooperation with the defense missile employing a linear guidance strategy, and one-way cooperation with independent evasion maneuver for the target. Three optimal cooperative guidance strategies with impact angle constraints were investigated. Finally, a nonlinear two-dimensional model for agents with first-order autopilot dynamics was simulated to verify the performance of the proposed strategies. The simulation results indicated that the cooperative mechanism directly affects the available range of impact angles, and the constraints of a big impact angle can be realized by introducing the nonlinear model parameters and considering the angle variation between the velocity vector and the initial line-of-sight. Furthermore, the two-way cooperative mechanism achieves the best performance and more flexible solutions to accommodate different vehicle maximum overload limits. Full article
(This article belongs to the Section Aeronautics)
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18 pages, 1006 KiB  
Article
Mechanical Characteristics of Lunar Regolith Drilling and Coring and Its Crawling Phenomenon: Analysis and Validation
by Junyue Tang, Tian Yang, Xiren Chen, Zhiheng Zhang, Ye Tian, Weiwei Zhang and Shengyuan Jiang
Aerospace 2022, 9(11), 709; https://doi.org/10.3390/aerospace9110709 - 12 Nov 2022
Cited by 5 | Viewed by 2462
Abstract
The collection of lunar regolith with complete stratigraphic information is the key to analyzing the evolution and composition of the moon. To keep each sample’s stratification for further analysis, a sampling method called flexible-tube coring has been adopted for Chinses lunar explorations. Given [...] Read more.
The collection of lunar regolith with complete stratigraphic information is the key to analyzing the evolution and composition of the moon. To keep each sample’s stratification for further analysis, a sampling method called flexible-tube coring has been adopted for Chinses lunar explorations. Given the uncertain physical properties of lunar regolith, drilling force and core lift force should be adjusted immediately in piercing process. Otherwise, only a small amount of core could be sampled, and overload drilling faults could occur correspondingly. Due to the fact that the cored regolith is inevitably connected to the flexible tube, coring characteristics may have a great influence on both lifting force and sampling quantity. To comprehend the regolith coring characteristics, a flexible-tube coring motion mechanics model was established and verified to acquire the lifting force results accurately. Herein, the judgment conditions for the flexible tube crawling phenomenon are proposed. Finally, the accuracy of the model is verified by comparing it with the Chang’e V telemetry data. This article provides theoretical support for the design and regulation improvement of Chang’e VI drilling and coring in the future. Full article
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15 pages, 1250 KiB  
Article
Mixed-Sensitivity Control for Drag-Free Spacecraft Based on State Space
by Yuan Liu and Changwu Jiang
Aerospace 2022, 9(11), 708; https://doi.org/10.3390/aerospace9110708 - 12 Nov 2022
Cited by 1 | Viewed by 1598
Abstract
This paper investigates a mixed-sensitivity control method for a class of drag-free spacecraft-needed frequency-separation control, which overcomes the coupled problem of a multiple-in multiple-out (MIMO) system with multiple sensitive-axes and disturbances of actuators. Firstly, the relative dynamics equation is established based on the [...] Read more.
This paper investigates a mixed-sensitivity control method for a class of drag-free spacecraft-needed frequency-separation control, which overcomes the coupled problem of a multiple-in multiple-out (MIMO) system with multiple sensitive-axes and disturbances of actuators. Firstly, the relative dynamics equation is established based on the character of displacement error, which is separated by that test-mass (TMs) tracking ideal orbit with high-frequency displacement and cavity of spacecraft tracking TMs with low-frequency displacement. Secondly, the feedback gain matrix is obtained by the LMI/SDP, which is devised by a general system containing a weight function. Finally, the simulation results demonstrate the performance of the proposed method. Full article
(This article belongs to the Special Issue Emerging Space Missions and Technologies)
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