Transactions of Nanjing University of Aeronautics & Astronautics
Issue S2,2023 Table of Contents
2023(S2):1-8.
DOI: 10.16356/j.1005-1120.2023.S2.001
Abstract:
Aiming at the selection of structural parameters and layout of the launch method， which are concerned by technicians at the initial stage of designing a new unmanned aerial vehicle （UAV）， a dynamic model of catapult launch is established by taking a UAV as the research object. On this basis， the influence of the main parameters such as the length of the launch bar and the installation point of the launch bar on the fuselage on safety of the UAV catapult launch is analyzed， and the simulation results show that increasing the length of the launch bar， decreasing the horizontal distance and increasing the vertical distance between the installation point and the centroid of the UAV can increase the pitch angle of the UAV， reduce the axial load and slow down the oscillation of the nose landing gear during the process of catapult launch， which can effectively improve safety of catapult launch. When the length of the launch bar is increased to 800 mm， the horizontal distance is decreased to 289 mm or the vertical distance is increased to 365 mm， there is a risk that the nose landing gear will leave the track surface in advance. When the horizontal distance is increased to 589 mm or the vertical distance is decreased to 265 mm， the sudden-extension of the nose landing gear will appear.
Aiming at the selection of structural parameters and layout of the launch method， which are concerned by technicians at the initial stage of designing a new unmanned aerial vehicle （UAV）， a dynamic model of catapult launch is established by taking a UAV as the research object. On this basis， the influence of the main parameters such as the length of the launch bar and the installation point of the launch bar on the fuselage on safety of the UAV catapult launch is analyzed， and the simulation results show that increasing the length of the launch bar， decreasing the horizontal distance and increasing the vertical distance between the installation point and the centroid of the UAV can increase the pitch angle of the UAV， reduce the axial load and slow down the oscillation of the nose landing gear during the process of catapult launch， which can effectively improve safety of catapult launch. When the length of the launch bar is increased to 800 mm， the horizontal distance is decreased to 289 mm or the vertical distance is increased to 365 mm， there is a risk that the nose landing gear will leave the track surface in advance. When the horizontal distance is increased to 589 mm or the vertical distance is decreased to 265 mm， the sudden-extension of the nose landing gear will appear.
2023(S2):9-17.
DOI: 10.16356/j.1005-1120.2023.S2.002
Abstract:
The flying-wing layout， characterized by its distinctive aerodynamic fusion of the wing and fuselage， markedly augments the effective lift surface area of an aircraft. Both shape optimization and layout optimization play equally vital roles in enhancing the aerodynamic performance of this kind of configurations. In this paper， to address the aerodynamic shape optimization challenges pertaining to flying-wing unmanned aerial vehicle （UAV）， an efficient parametric modeling method is introduced. This method facilitates the parametric deformation control of complex shapes. It integrates gradient-based optimization algorithms， discrete adjoint methods， and computational fluid dynamics （CFD） techniques grounded in Reynolds average Navier-Stokes （RANS） equations to achieve aerodynamic shape optimization and reduce drag for flying-wing UAV， resulting in a notable 7.17% improvement in the lift-to-drag ratio. The optimization results indicate that， while adhering to constraint requirements， the aerodynamic optimization design method based on these methodologies exhibits robust adaptability to wing-fuselage blended configurations， effectively enhancing the aerodynamic performance of unmanned aerial vehicles.
The flying-wing layout， characterized by its distinctive aerodynamic fusion of the wing and fuselage， markedly augments the effective lift surface area of an aircraft. Both shape optimization and layout optimization play equally vital roles in enhancing the aerodynamic performance of this kind of configurations. In this paper， to address the aerodynamic shape optimization challenges pertaining to flying-wing unmanned aerial vehicle （UAV）， an efficient parametric modeling method is introduced. This method facilitates the parametric deformation control of complex shapes. It integrates gradient-based optimization algorithms， discrete adjoint methods， and computational fluid dynamics （CFD） techniques grounded in Reynolds average Navier-Stokes （RANS） equations to achieve aerodynamic shape optimization and reduce drag for flying-wing UAV， resulting in a notable 7.17% improvement in the lift-to-drag ratio. The optimization results indicate that， while adhering to constraint requirements， the aerodynamic optimization design method based on these methodologies exhibits robust adaptability to wing-fuselage blended configurations， effectively enhancing the aerodynamic performance of unmanned aerial vehicles.
2023(S2):18-25.
DOI: 10.16356/j.1005-1120.2023.S2.003
Abstract:
First， a one-dimensional steady model of the scramjet is established. Particularly for the combustion with three modes， the one-dimensional gas dynamic governing equations are introduced to describe the axial distribution of the flow. Second， a one-dimensional dynamic model is derived by considering the volume effect based on the steady model. The model running results show that the results of the model are in good agreement with the experimental data. Further， a three-input-one-output proportional-integral （PI） controller is designed. The simulations show that the model can meet the requirements of scramjet control system design.
First， a one-dimensional steady model of the scramjet is established. Particularly for the combustion with three modes， the one-dimensional gas dynamic governing equations are introduced to describe the axial distribution of the flow. Second， a one-dimensional dynamic model is derived by considering the volume effect based on the steady model. The model running results show that the results of the model are in good agreement with the experimental data. Further， a three-input-one-output proportional-integral （PI） controller is designed. The simulations show that the model can meet the requirements of scramjet control system design.
2023(S2):26-31.
DOI: 10.16356/j.1005-1120.2023.S2.004
Abstract:
The vibration environment during satellite launch is very harsh， and the vibration excitation spectrum from all directions is extremely wide. The satellite is easily damaged， leading to the failure of launch mission. The whole-spacecraft vibration isolation is achieved by modifying the structure of the payload attach fitting （PAF）， or placing a vibration isolation device between the original adapter and the star-arrow connection surface. This paper improves the traditional PAF， and a semi-active vibration isolation system based on electromagnetic mechanics is designed. Maxwell software is used to simulate the static performance of the active vibration isolation module， and an experimental system is built to verify the simulation results. It is preliminarily confirmed that the designed device can meet the vibration isolation requirements.
The vibration environment during satellite launch is very harsh， and the vibration excitation spectrum from all directions is extremely wide. The satellite is easily damaged， leading to the failure of launch mission. The whole-spacecraft vibration isolation is achieved by modifying the structure of the payload attach fitting （PAF）， or placing a vibration isolation device between the original adapter and the star-arrow connection surface. This paper improves the traditional PAF， and a semi-active vibration isolation system based on electromagnetic mechanics is designed. Maxwell software is used to simulate the static performance of the active vibration isolation module， and an experimental system is built to verify the simulation results. It is preliminarily confirmed that the designed device can meet the vibration isolation requirements.
2023(S2):32-39.
DOI: 10.16356/j.1005-1120.2023.S2.005
Abstract:
The reentry trajectory optimization of a variable-configuration vehicle （VCV） is studied. A surrogate model is established for quick prediction of vehicle aerodynamics at different deformation and flight conditions. The time histories of deformation， angle of attack and bank angle are all taken as trajectory optimization variables， and the performance of the VCV in landing coverage area and the maneuverability to avoid obstacles are quantitatively studied. Simulation results show that compared with the fixed-configuration vehicle （FCV）， the VCV can achieve the optimal morphing in addition to the optimal control along the reentry glide trajectory， thus leading to better reentry trajectory performance.
The reentry trajectory optimization of a variable-configuration vehicle （VCV） is studied. A surrogate model is established for quick prediction of vehicle aerodynamics at different deformation and flight conditions. The time histories of deformation， angle of attack and bank angle are all taken as trajectory optimization variables， and the performance of the VCV in landing coverage area and the maneuverability to avoid obstacles are quantitatively studied. Simulation results show that compared with the fixed-configuration vehicle （FCV）， the VCV can achieve the optimal morphing in addition to the optimal control along the reentry glide trajectory， thus leading to better reentry trajectory performance.
2023(S2):40-47.
DOI: 10.16356/j.1005-1120.2023.S2.006
Abstract:
Global navigation satellite system （GNSS） is an important navigation sensor for the required navigation performance （RNP） operation. The positioning accuracy of GNSS determines whether the civil aircraft can meet the RNP flight requirements. Due to the limited computing power of airborne receivers， the calculation delay may reduce the positioning accuracy. To meet the high precision requirements， this error caused by calculation delay can no longer be ignored. This paper proposes a two-step iterative optimization of satellite selection algorithm based on the position dilution of precision （PDOP） contribution. It can effectively reduce the calculation delay and improve the positioning accuracy under the RNP operation. The simulation shows that the method has better real-time performance than the traditional algorithm， which is of great significance for ensuring the flight safety of civil aircraft.
Global navigation satellite system （GNSS） is an important navigation sensor for the required navigation performance （RNP） operation. The positioning accuracy of GNSS determines whether the civil aircraft can meet the RNP flight requirements. Due to the limited computing power of airborne receivers， the calculation delay may reduce the positioning accuracy. To meet the high precision requirements， this error caused by calculation delay can no longer be ignored. This paper proposes a two-step iterative optimization of satellite selection algorithm based on the position dilution of precision （PDOP） contribution. It can effectively reduce the calculation delay and improve the positioning accuracy under the RNP operation. The simulation shows that the method has better real-time performance than the traditional algorithm， which is of great significance for ensuring the flight safety of civil aircraft.
2023(S2):48-53.
DOI: 10.16356/j.1005-1120.2023.S2.007
Abstract:
In order to achieve fast and high accuracy of strapdown initial alignment， a four-position initial alignment algorithm based on forward and reverse filtering is proposed. The proposed scheme divides the whole alignment process into three stages： Coarse alignment， backtracking alignment and fine alignment. In the first stage， coarse alignment is performed， and data are collected and stored. In the second stage， the unscented Kalman filter（KF） is used for backtracking alignment. In the third stage， the KF is used for fine alignment. Four-position data are sampled in the whole process. The proposed scheme is used for initial alignment， and high precision alignment is achieved on the basis of ensuring fast alignment. The simulation results show that the alignment scheme can quickly complete the initial alignment and achieve a high alignment accuracy， and the sky misalignment error is within 10″.
In order to achieve fast and high accuracy of strapdown initial alignment， a four-position initial alignment algorithm based on forward and reverse filtering is proposed. The proposed scheme divides the whole alignment process into three stages： Coarse alignment， backtracking alignment and fine alignment. In the first stage， coarse alignment is performed， and data are collected and stored. In the second stage， the unscented Kalman filter（KF） is used for backtracking alignment. In the third stage， the KF is used for fine alignment. Four-position data are sampled in the whole process. The proposed scheme is used for initial alignment， and high precision alignment is achieved on the basis of ensuring fast alignment. The simulation results show that the alignment scheme can quickly complete the initial alignment and achieve a high alignment accuracy， and the sky misalignment error is within 10″.
2023(S2):54-61.
DOI: 10.16356/j.1005-1120.2023.S2.008
Abstract:
In order to explore the aircraft noise prediction methods beyond the best practice model and scientific model， this paper uses multiple linear regression model and random forest regression model to predict the aircraft noise value of Seattle-Tacoma International Airport in the summer of 2020—2022. The experiment confirm the feasibility and advantages of the machine learning model in aircraft noise prediction tasks and find that the meanR 2 ![]()
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In order to explore the aircraft noise prediction methods beyond the best practice model and scientific model， this paper uses multiple linear regression model and random forest regression model to predict the aircraft noise value of Seattle-Tacoma International Airport in the summer of 2020—2022. The experiment confirm the feasibility and advantages of the machine learning model in aircraft noise prediction tasks and find that the mean
2023(S2):62-68.
DOI: 10.16356/j.1005-1120.2023.S2.009
Abstract:
Traditional structural health monitoring （SHM） software mainly runs on Windows operating systems， so it has large capacity and needs the support of operating environment. It is hard to transplant the existing SHM software to the embedded SHM system. A type of damage alarm software based on Gaussian mixture model （GMM） migration is designed in C language environment to make it convenient to integrate into the embedded SHM system. The proposed software is verified by the damage monitoring experiment on aircraft lug specimen under varying load， and the results demonstrate that the proposed software can realize effective and reliable structural damage alarm function.
Traditional structural health monitoring （SHM） software mainly runs on Windows operating systems， so it has large capacity and needs the support of operating environment. It is hard to transplant the existing SHM software to the embedded SHM system. A type of damage alarm software based on Gaussian mixture model （GMM） migration is designed in C language environment to make it convenient to integrate into the embedded SHM system. The proposed software is verified by the damage monitoring experiment on aircraft lug specimen under varying load， and the results demonstrate that the proposed software can realize effective and reliable structural damage alarm function.
2023(S2):69-76.
DOI: 10.16356/j.1005-1120.2023.S2.010
Abstract:
Aiming at the contact operation problem of aerial manipulator， a non-singular terminal sliding mode compliant control algorithm for aerial manipulator based on disturbance observer is designed. The algorithm introduces disturbance observer on the basis of nonsingular terminal sliding mode control. The disturbance is estimated to reduce the system estimation error， the disturbance of the manipulator and the influence of external disturbance on the rotorcraft. Finally， the simulation results show that the proposed controller has good robustness. Meanwhile， it can reduce the system estimation error， the disturbance of the manipulator and the external disturbance， and ensure the stability of the contact force under smooth movement.
Aiming at the contact operation problem of aerial manipulator， a non-singular terminal sliding mode compliant control algorithm for aerial manipulator based on disturbance observer is designed. The algorithm introduces disturbance observer on the basis of nonsingular terminal sliding mode control. The disturbance is estimated to reduce the system estimation error， the disturbance of the manipulator and the influence of external disturbance on the rotorcraft. Finally， the simulation results show that the proposed controller has good robustness. Meanwhile， it can reduce the system estimation error， the disturbance of the manipulator and the external disturbance， and ensure the stability of the contact force under smooth movement.
2023(S2):77-84.
DOI: 10.16356/j.1005-1120.2023.S2.011
Abstract:
Multi-camera pose monitoring system is a high precision digital measuring equipment which can be used to obtain the three-dimensional position information of the target in environment. We constructed a new agent system consisting of many Mecanum wheel mobile robots and multi-camera pose monitoring system， which can be divided into three parts： positioning subsystem， communication subsystem and control subsystem. First， the multi-camera system acts as a positioning system to locate the agent through the reflective target balls， then the communication subsystem sends large positioning information to the control subsystem in real time. The control subsystem identifies different agents， and converts the pose relationship under the camera coordinate system to the world coordinate system. Finally， according to the position relationship between different agents， the corresponding cooperative control algorithm is designed to solve the input parameters required by a single agent， and control the agent to reach the specified position precisely. The experiment results show that the agent positioning assisted by the multi-camera pose monitoring system has small positioning error， which can make the whole agent cluster have good cooperative control performance.
Multi-camera pose monitoring system is a high precision digital measuring equipment which can be used to obtain the three-dimensional position information of the target in environment. We constructed a new agent system consisting of many Mecanum wheel mobile robots and multi-camera pose monitoring system， which can be divided into three parts： positioning subsystem， communication subsystem and control subsystem. First， the multi-camera system acts as a positioning system to locate the agent through the reflective target balls， then the communication subsystem sends large positioning information to the control subsystem in real time. The control subsystem identifies different agents， and converts the pose relationship under the camera coordinate system to the world coordinate system. Finally， according to the position relationship between different agents， the corresponding cooperative control algorithm is designed to solve the input parameters required by a single agent， and control the agent to reach the specified position precisely. The experiment results show that the agent positioning assisted by the multi-camera pose monitoring system has small positioning error， which can make the whole agent cluster have good cooperative control performance.
2023(S2):85-93.
DOI: 10.16356/j.1005-1120.2023.S2.012
Abstract:
In order to optimize airspace resources and reduce operational costs， this paper investigates the air route network planning problem considering the avoidance of prohibited， restricted， and danger zones （PRDs）. Firstly， the airspace is discretized using the grid method， and the airspace information is binarized to enable the avoidance of these three zones. Then， a mathematical model is established with the objective of minimizing the total route length， considering factors such as nonlinear coefficient and flow constraints. The pathfinding process incorporates distance priority coefficients and collision risk coefficients， and the cellular automata algorithm is employed to solve the problem. Additionally， the results are further smoothed to obtain the shortest path. Finally， a case study is conducted using the air route network planning of Guangzhou FIR for verification. The results demonstrate that， compared to the current routes， the proposed approach effectively reduces the route length， decreases the number of waypoints， and lowers the nonlinear coefficient of the routes. These findings highlight the effectiveness of the improved cellular automata algorithm， which has important implications for real-world air route network planning.
In order to optimize airspace resources and reduce operational costs， this paper investigates the air route network planning problem considering the avoidance of prohibited， restricted， and danger zones （PRDs）. Firstly， the airspace is discretized using the grid method， and the airspace information is binarized to enable the avoidance of these three zones. Then， a mathematical model is established with the objective of minimizing the total route length， considering factors such as nonlinear coefficient and flow constraints. The pathfinding process incorporates distance priority coefficients and collision risk coefficients， and the cellular automata algorithm is employed to solve the problem. Additionally， the results are further smoothed to obtain the shortest path. Finally， a case study is conducted using the air route network planning of Guangzhou FIR for verification. The results demonstrate that， compared to the current routes， the proposed approach effectively reduces the route length， decreases the number of waypoints， and lowers the nonlinear coefficient of the routes. These findings highlight the effectiveness of the improved cellular automata algorithm， which has important implications for real-world air route network planning.
2023(S2):94-102.
DOI: 10.16356/j.1005-1120.2023.S2.013
Abstract:
The flow field characteristics in the reforming channel and the temperature distribution characteristics of the catalytic bed under the hot air heating condition are first investigated in a double-jacketed methanol steam reforming （MSR） reactor. It is shown that the temperature of the catalytic bed decreases rapidly along the flow direction， with the minimum temperature region at 15 mm to 20 mm from the catalytic bed inlet. And the temperature increases gradually with the flow direction to approach the heating temperature. In addition， the temperature gradually increases along the radius from the center to the wall， and heat transfer resistance makes the temperature in the middle of the catalyst bed lower than the temperature around. Based on this reaction characteristic， a variable cross-sectional reforming reactor is proposed in this paper to completely utilize the heat supply energy and improve the reaction efficiency. The response surface methodology （RSM） is then used to optimize the structural parameters of the variable cross-section reactor. It is shown that the methanol conversion is significantly increased at the same boundary conditions for the outer radius R1=49.94 mm at the reforming inlet of the heating channel， the radius R2=39.99 mm at the minimum cross-section and the distance D=98.44 mm from the minimum cross-section to the catalytic bed inlet.
The flow field characteristics in the reforming channel and the temperature distribution characteristics of the catalytic bed under the hot air heating condition are first investigated in a double-jacketed methanol steam reforming （MSR） reactor. It is shown that the temperature of the catalytic bed decreases rapidly along the flow direction， with the minimum temperature region at 15 mm to 20 mm from the catalytic bed inlet. And the temperature increases gradually with the flow direction to approach the heating temperature. In addition， the temperature gradually increases along the radius from the center to the wall， and heat transfer resistance makes the temperature in the middle of the catalyst bed lower than the temperature around. Based on this reaction characteristic， a variable cross-sectional reforming reactor is proposed in this paper to completely utilize the heat supply energy and improve the reaction efficiency. The response surface methodology （RSM） is then used to optimize the structural parameters of the variable cross-section reactor. It is shown that the methanol conversion is significantly increased at the same boundary conditions for the outer radius R1=49.94 mm at the reforming inlet of the heating channel， the radius R2=39.99 mm at the minimum cross-section and the distance D=98.44 mm from the minimum cross-section to the catalytic bed inlet.
2023(S2):103-109.
DOI: 10.16356/j.1005-1120.2023.S2.014
Abstract:
The power distribution characteristic of a parallel hybrid excitation generator （PHEG） is studied and optimized. The PHEG consists of a permanent magnet machine part （PMMP）， a flux modulation machine part （FMMP）， and a rectifier. The winding coupling relationship and inductance characteristic of PMMP and FMMP are illustrated. By introducing the controllable devices， the internal power factor angle of the PHEG can be adjusted， which provides the possibility to optimize the power distribution between PMMP and FMMP. Based on the analysis of the phasor diagrams， it is found that the output capacity of PMMP in PHEG with an active rectifier is improved. Therefore， PHEG can output constant power and voltage over a wider speed with the lower loss， which verifies that PHEG with an active rectifier is a promising candidate in the aircraft DC power generation system.
The power distribution characteristic of a parallel hybrid excitation generator （PHEG） is studied and optimized. The PHEG consists of a permanent magnet machine part （PMMP）， a flux modulation machine part （FMMP）， and a rectifier. The winding coupling relationship and inductance characteristic of PMMP and FMMP are illustrated. By introducing the controllable devices， the internal power factor angle of the PHEG can be adjusted， which provides the possibility to optimize the power distribution between PMMP and FMMP. Based on the analysis of the phasor diagrams， it is found that the output capacity of PMMP in PHEG with an active rectifier is improved. Therefore， PHEG can output constant power and voltage over a wider speed with the lower loss， which verifies that PHEG with an active rectifier is a promising candidate in the aircraft DC power generation system.
2023(S2):110-120.
DOI: 10.16356/j.1005-1120.2023.S2.015
Abstract:
The paper investigates the effect of main parameters on particle distribution in centrifugally cast magnesium matrix composites using theoretical and experimental studies. The study aims to depict solidification impacts on particle movement， along with other main forces. The findings demonstrate that the rotation speed， solidification interval， and density differential between the matrix and particles affect the thickness of the particle-segregated zone caused centrifugal force. Additionally， the comparison of SiCp distribution in the AZ91 matrix composite between the theoretical model and experiments shows that the proposed analysis is acceptable at 10%（in weight） at the middle zone. The difference between the experimental and theoretical results is 5.83%， 10.20%， and 4.86% in the outer region and 2.64%， 1.58%， and 2.36% in the middle region for each of 5%， 10%， and 15%（in weight） composites， respectively.
The paper investigates the effect of main parameters on particle distribution in centrifugally cast magnesium matrix composites using theoretical and experimental studies. The study aims to depict solidification impacts on particle movement， along with other main forces. The findings demonstrate that the rotation speed， solidification interval， and density differential between the matrix and particles affect the thickness of the particle-segregated zone caused centrifugal force. Additionally， the comparison of SiCp distribution in the AZ91 matrix composite between the theoretical model and experiments shows that the proposed analysis is acceptable at 10%（in weight） at the middle zone. The difference between the experimental and theoretical results is 5.83%， 10.20%， and 4.86% in the outer region and 2.64%， 1.58%， and 2.36% in the middle region for each of 5%， 10%， and 15%（in weight） composites， respectively.
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