Transactions of Nanjing University of Aeronautics & Astronautics
Volume 0,Issue 1,2024 Table of Contents
2024(1):1-34.
DOI: 10.16356/j.1005-1120.2024.01.001
Abstract:
Multicomponent and multilevel 3D printing materials （McMl3DPMs） are an emerging class of advanced materials stemming from the convergence of cellular materials， composites， and additive manufacturing. Since their additive manufacturing-derived 3D architectures span a wide range of composition and structural levels， McMl3DPMs are conferred with outstanding mechanical properties that are often considered to be mutually exclusive （e.g.， high strength and high toughness）. The scientific challenges that have to be addressed to realize high-performance McMl3DPMs for structural applications are highlighted， and examples of recent research efforts to tackle them are presented. These are reviewed from three aspects： Structural design， manufacturing process modeling， and defect characterization and property evaluation. Finally， we point out the shortcomings of the current research and identify the future development of McMl3DPMs， including discussing several possible directions to further advance the development of the emerging field.
Multicomponent and multilevel 3D printing materials （McMl3DPMs） are an emerging class of advanced materials stemming from the convergence of cellular materials， composites， and additive manufacturing. Since their additive manufacturing-derived 3D architectures span a wide range of composition and structural levels， McMl3DPMs are conferred with outstanding mechanical properties that are often considered to be mutually exclusive （e.g.， high strength and high toughness）. The scientific challenges that have to be addressed to realize high-performance McMl3DPMs for structural applications are highlighted， and examples of recent research efforts to tackle them are presented. These are reviewed from three aspects： Structural design， manufacturing process modeling， and defect characterization and property evaluation. Finally， we point out the shortcomings of the current research and identify the future development of McMl3DPMs， including discussing several possible directions to further advance the development of the emerging field.
2024(1):35-42.
DOI: 10.16356/j.1005-1120.2024.01.002
Abstract:
This paper developed a synthesis process based on the aerodynamic theories of rotorcraft and fixed-wing aircraft to estimate the performance of electric vertical takeoff and landing （eVTOL） aircraft， which commonly adopt multiple rotors for vertical flight， and propeller and wing for forward flight. Momentum theory analysis and blade element analysis have been well used to analyze flight performance of rotor and propeller. Using the synthesis theory， this study investigated flight performance of 12 eVTOL aircraft including multicopter， lift & cruise， and vectored thrust categories. Flight profiles of driving motor， rotor， and airframe at hovering， climb and descent， and forward flight were estimated. It was also indicated that specifications of the electric propulsion system were defined to match the propeller or rotor to satisfy the flight mission.
This paper developed a synthesis process based on the aerodynamic theories of rotorcraft and fixed-wing aircraft to estimate the performance of electric vertical takeoff and landing （eVTOL） aircraft， which commonly adopt multiple rotors for vertical flight， and propeller and wing for forward flight. Momentum theory analysis and blade element analysis have been well used to analyze flight performance of rotor and propeller. Using the synthesis theory， this study investigated flight performance of 12 eVTOL aircraft including multicopter， lift & cruise， and vectored thrust categories. Flight profiles of driving motor， rotor， and airframe at hovering， climb and descent， and forward flight were estimated. It was also indicated that specifications of the electric propulsion system were defined to match the propeller or rotor to satisfy the flight mission.
2024(1):43-52.
DOI: 10.16356/j.1005-1120.2024.01.003
Abstract:
A multidisciplinary analysis toolchain specifically for rotorcraft has been developed at JAXA. HeliDesign provides the sizing of a conventional or a compound helicopter to meet the specified mission requirement based on preliminary semi-empirical relations. rFlight delivers the trim analysis and performance of a rotorcraft together with the linearized flight dynamics models based on analytical formulations of the rotor aerodynamics from blade-element theory. rBET/RMT is a low fidelity tool based on blade-element theory. For high-fidelity aeroelastic analysis of a rotating blade， rFlow3D is constructed based on high-resolution CFD and loosely coupled with computational structural dynamics （CSD） to obtain the elastic deformations of a rotor blade， while the natural frequencies and modes are obtained using rMode. rGrid tools support the automatic grid generations around a rotor blade to be computed in rFlow3D. Acoustic signature from a rotorcraft can be predicted using rNoise based on the FW-H equations using the output from rFlow3D. These tools have been applied for new rotorcraft developments and the high-fidelity toolchain has been validated with reliable test data with satisfactory accuracy.
A multidisciplinary analysis toolchain specifically for rotorcraft has been developed at JAXA. HeliDesign provides the sizing of a conventional or a compound helicopter to meet the specified mission requirement based on preliminary semi-empirical relations. rFlight delivers the trim analysis and performance of a rotorcraft together with the linearized flight dynamics models based on analytical formulations of the rotor aerodynamics from blade-element theory. rBET/RMT is a low fidelity tool based on blade-element theory. For high-fidelity aeroelastic analysis of a rotating blade， rFlow3D is constructed based on high-resolution CFD and loosely coupled with computational structural dynamics （CSD） to obtain the elastic deformations of a rotor blade， while the natural frequencies and modes are obtained using rMode. rGrid tools support the automatic grid generations around a rotor blade to be computed in rFlow3D. Acoustic signature from a rotorcraft can be predicted using rNoise based on the FW-H equations using the output from rFlow3D. These tools have been applied for new rotorcraft developments and the high-fidelity toolchain has been validated with reliable test data with satisfactory accuracy.
2024(1):53-65.
DOI: 10.16356/j.1005-1120.2024.01.004
Abstract:
When the helicopter flies forward， the aerodynamic environment will lead to the instantaneous asymmetry of aerodynamic load on the blades with different angles， which will form a large range of low-frequency vibration on the fuselage through the transmission of the infrastructure. To eliminate the vibration force with multi-directional amplitude variation， using the active control principle of structural response， an active vibration elimination electric actuator system based on the x-LMS algorithm is designed， and the vibration reduction experiment is carried out. Firstly， the scheme of two motors rotating in the same direction in a single actuator is established by comparison. Through the combination of actuators， the mathematical model of output force is deduced. Secondly， the system control block diagram of load phase difference cross-coupling is designed. For the phase outer loop with coupling， the parameter range that meets the requirements of the system stability margin is determined by the method of characteristic value of the feedback matrix， and then the optimal solution is found in the obtained parameter stability region according to the sensitivity function and input tracking performance. Then， a helicopter active vibration control system based on the x-LMS algorithm is proposed， and the damping effect of the system is verified by simulation. Finally， the experimental prototype is developed， the dynamic experiment and steady-state experiment are carried out， and the actual damping effect of the system is verified by the vibration elimination experiment.
When the helicopter flies forward， the aerodynamic environment will lead to the instantaneous asymmetry of aerodynamic load on the blades with different angles， which will form a large range of low-frequency vibration on the fuselage through the transmission of the infrastructure. To eliminate the vibration force with multi-directional amplitude variation， using the active control principle of structural response， an active vibration elimination electric actuator system based on the x-LMS algorithm is designed， and the vibration reduction experiment is carried out. Firstly， the scheme of two motors rotating in the same direction in a single actuator is established by comparison. Through the combination of actuators， the mathematical model of output force is deduced. Secondly， the system control block diagram of load phase difference cross-coupling is designed. For the phase outer loop with coupling， the parameter range that meets the requirements of the system stability margin is determined by the method of characteristic value of the feedback matrix， and then the optimal solution is found in the obtained parameter stability region according to the sensitivity function and input tracking performance. Then， a helicopter active vibration control system based on the x-LMS algorithm is proposed， and the damping effect of the system is verified by simulation. Finally， the experimental prototype is developed， the dynamic experiment and steady-state experiment are carried out， and the actual damping effect of the system is verified by the vibration elimination experiment.
2024(1):66-75.
DOI: 10.16356/j.1005-1120.2024.01.005
Abstract:
The main rotor is the lift surface and control surface of a helicopter， and its normal health is crucial for the safety of the helicopter. The rotor fault diagnosis technology is still a weak link in the field of helicopter health and usage monitoring system （HUMS）， and the development of rotor fault diagnosis technology is of great value. Based on information fusion technology， the mechanism of rotor failure is analyzed， the rotor failure model is established， and the fault feature information of blades， hub and airframe under different faults are obtained by fluid structure coupled simulation， thus generating data sets for network training and verification. Then genetic algorithm-backpropagation （GA-BP） neural network is used to diagnose three types of helicopter rotor faults， namely， misadjusted trim-tab， misadjusted pitch control rod and imbalanced mass. Three cascaded levels of networks are used to identify fault classification， location and severity， respectively. Finally， the rotor faults are diagnosed and analyzed by the weighted Dempster-Shafer （D-S） evidence theory. The results demonstrate that the rotor blade fault diagnosis method based on the improved D-S evidence theory can be successfully applied to rotor blade fault diagnosis with good identification results.
The main rotor is the lift surface and control surface of a helicopter， and its normal health is crucial for the safety of the helicopter. The rotor fault diagnosis technology is still a weak link in the field of helicopter health and usage monitoring system （HUMS）， and the development of rotor fault diagnosis technology is of great value. Based on information fusion technology， the mechanism of rotor failure is analyzed， the rotor failure model is established， and the fault feature information of blades， hub and airframe under different faults are obtained by fluid structure coupled simulation， thus generating data sets for network training and verification. Then genetic algorithm-backpropagation （GA-BP） neural network is used to diagnose three types of helicopter rotor faults， namely， misadjusted trim-tab， misadjusted pitch control rod and imbalanced mass. Three cascaded levels of networks are used to identify fault classification， location and severity， respectively. Finally， the rotor faults are diagnosed and analyzed by the weighted Dempster-Shafer （D-S） evidence theory. The results demonstrate that the rotor blade fault diagnosis method based on the improved D-S evidence theory can be successfully applied to rotor blade fault diagnosis with good identification results.
2024(1):76-87.
DOI: 10.16356/j.1005-1120.2024.01.006
Abstract:
To meet the urgent need for the lightweight design of gears under complex conditions in helicopter transmission systems， a design optimization method is proposed for a tilting prop bevel gear spoke plate structure with a high power density. Based on the variable density method considering stress constraints， topology optimization and reconstruction of the bevel gear spoke plate structure are performed， which yield a novel tilting prop bevel gear spoke plate structure with a high power density， differing from the traditional configuration. Introducing an evolution factor and the Markov chain based on the traditional particle swarm optimization （PSO） algorithm， an intelligent and advanced switching delayed PSO （SDPSO） algorithm is developed. The SDPSO algorithm can adaptively select switching strategies and delay information， and it is employed for the size optimization of a tilting prop bevel gear spoke plate structure. After optimization， the mass of the bevel gear spoke plate is reduced by 19.24%， and the maximum von Mises stress of all the operating conditions is reduced by 7.27%. Additionally， the stress distribution of each operating condition becomes more uniform， which demonstrates the structural advantages of the designed bevel gear spoke plate and the superiority of the proposed optimization method.
To meet the urgent need for the lightweight design of gears under complex conditions in helicopter transmission systems， a design optimization method is proposed for a tilting prop bevel gear spoke plate structure with a high power density. Based on the variable density method considering stress constraints， topology optimization and reconstruction of the bevel gear spoke plate structure are performed， which yield a novel tilting prop bevel gear spoke plate structure with a high power density， differing from the traditional configuration. Introducing an evolution factor and the Markov chain based on the traditional particle swarm optimization （PSO） algorithm， an intelligent and advanced switching delayed PSO （SDPSO） algorithm is developed. The SDPSO algorithm can adaptively select switching strategies and delay information， and it is employed for the size optimization of a tilting prop bevel gear spoke plate structure. After optimization， the mass of the bevel gear spoke plate is reduced by 19.24%， and the maximum von Mises stress of all the operating conditions is reduced by 7.27%. Additionally， the stress distribution of each operating condition becomes more uniform， which demonstrates the structural advantages of the designed bevel gear spoke plate and the superiority of the proposed optimization method.
2024(1):88-96.
DOI: 10.16356/j.1005-1120.2024.01.007
Abstract:
The influence of the length， diameter and fingertip angle of the finger lock on the unlocking force is studied， the theoretical calculation formula of the unlocking force is obtained， and the sensitivity of parameters to the unlocking force is analyzed. Firstly， the change law of the unlocking force is obtained by theoretical calculation. Then， the validity of the model is verified by experiments. Finally， the sensitivity of each parameter to the unlocking force is analyzed by orthogonal experiment. The result shows that the theoretical calculation formula is effective and reliable， the length， diameter 1 and diameter 2 of the finger lock are negatively correlated with the unlocking force， while the fingertip angle is positively correlated with the unlocking force； and the sensitivity of parameters affecting the unlocking force from high to low is finger lock length， diameter 1， fingertip angle and diameter 2.
The influence of the length， diameter and fingertip angle of the finger lock on the unlocking force is studied， the theoretical calculation formula of the unlocking force is obtained， and the sensitivity of parameters to the unlocking force is analyzed. Firstly， the change law of the unlocking force is obtained by theoretical calculation. Then， the validity of the model is verified by experiments. Finally， the sensitivity of each parameter to the unlocking force is analyzed by orthogonal experiment. The result shows that the theoretical calculation formula is effective and reliable， the length， diameter 1 and diameter 2 of the finger lock are negatively correlated with the unlocking force， while the fingertip angle is positively correlated with the unlocking force； and the sensitivity of parameters affecting the unlocking force from high to low is finger lock length， diameter 1， fingertip angle and diameter 2.
2024(1):97-106.
DOI: 10.16356/j.1005-1120.2024.01.008
Abstract:
The flapping-wing robot （FWR） is a kind of high-biomimetic aerial vehicle that can perform military reconnaissance and civil monitoring missions. When performing these missions， obstacle avoidance is a necessary function to ensure safety of FWRs. In this paper， an autonomous monocular-vision-based obstacle avoidance system is designed for FWRs， where all the image processing computations are implemented by using an on-board computer. In this system， the weight of the on-board computer is reduced to 48 g so that the FWR could fly properly. The workflow of the system can be divided into the following steps. First， the image acquisition module captures videos of the surrounding environment. Second， the on-board computer calculates the rudder angle and turning direction by processing the optical flow information from the first-person view. Finally， the flight control board receives the calculated results and controls the FWR to avoid obstacles. A ground station performs real-time monitoring of the FWR flight process， and experimental results demonstrate the effectiveness of the obstacle avoidance system designed in this paper.
The flapping-wing robot （FWR） is a kind of high-biomimetic aerial vehicle that can perform military reconnaissance and civil monitoring missions. When performing these missions， obstacle avoidance is a necessary function to ensure safety of FWRs. In this paper， an autonomous monocular-vision-based obstacle avoidance system is designed for FWRs， where all the image processing computations are implemented by using an on-board computer. In this system， the weight of the on-board computer is reduced to 48 g so that the FWR could fly properly. The workflow of the system can be divided into the following steps. First， the image acquisition module captures videos of the surrounding environment. Second， the on-board computer calculates the rudder angle and turning direction by processing the optical flow information from the first-person view. Finally， the flight control board receives the calculated results and controls the FWR to avoid obstacles. A ground station performs real-time monitoring of the FWR flight process， and experimental results demonstrate the effectiveness of the obstacle avoidance system designed in this paper.
2024(1):107-121.
DOI: 10.16356/j.1005-1120.2024.01.009
Abstract:
In view of the problem that the extravehicular fixed handrail is difficult to meet astronaut’s complex extravehicular activity （EVA） needs， we propose a new design of movable handrail to benefit the EVA of astronauts. Specifically， we fully consider the hand force characteristics of astronauts in the pressurized spacesuit and design the parameters for geometric dimension and spring stiffness of each operating component in the movable handrail. In addition， in order to meet the needs of astronauts to operate the movable handrail with one hand during EVA， each operating component can be self-lock. Dynamics simulation analysis of each operating component is performed with ADAMS software. Simulation results show that operating components can be locked under appropriate operating force. We develop an engineering prototype of the extravehicular movable handrail based on the design and analysis result. Experimental verifications are carried out in terms of function， environment and ergonomics， which show that the proposed prototype can not only realize the clamping of the extravehicular fixed handrail but also freely adjust its own length and angle. In addition， the measured operating force is basically consistent with the theoretical value， and there is little change in the operating force before and after the force and thermal environment tests. All these experiments show that the proposed movable handrail has good adaptability to low-orbit environment of the space station.
In view of the problem that the extravehicular fixed handrail is difficult to meet astronaut’s complex extravehicular activity （EVA） needs， we propose a new design of movable handrail to benefit the EVA of astronauts. Specifically， we fully consider the hand force characteristics of astronauts in the pressurized spacesuit and design the parameters for geometric dimension and spring stiffness of each operating component in the movable handrail. In addition， in order to meet the needs of astronauts to operate the movable handrail with one hand during EVA， each operating component can be self-lock. Dynamics simulation analysis of each operating component is performed with ADAMS software. Simulation results show that operating components can be locked under appropriate operating force. We develop an engineering prototype of the extravehicular movable handrail based on the design and analysis result. Experimental verifications are carried out in terms of function， environment and ergonomics， which show that the proposed prototype can not only realize the clamping of the extravehicular fixed handrail but also freely adjust its own length and angle. In addition， the measured operating force is basically consistent with the theoretical value， and there is little change in the operating force before and after the force and thermal environment tests. All these experiments show that the proposed movable handrail has good adaptability to low-orbit environment of the space station.
2024(1):122-134.
DOI: 10.16356/j.1005-1120.2024.01.010
Abstract:
Accurate pose estimation of space non-cooperative targets with a monocular camera is crucial to space debris removal， autonomous rendezvous， and other on-orbit services. However， monocular pose estimation methods lack depth information， resulting in scale uncertainty issue that significantly reduces their accuracy and real-time performance. We first propose a multi-scale attention block （MAB） to extract complex high-dimensional semantic features from the input image. Second， based on the MAB module， we propose a dense multi-scale attention network （DMANet） for estimating the 6-degree-of-freedom （DoF） pose of space non-cooperative targets， which consists of planar position estimation， depth position estimation， and attitude estimation branches. By introducing an Euler angle-based soft classification method， we formulate the pose regression problem as a classical classification problem. Besides， we design a space non-cooperative object model and construct a pose estimation dataset by using Coppeliasim. Finally， we thoroughly evaluate the proposed method on the SPEED+， URSO datasets and our dataset， compared to other state-of-the-art methods. Experiment results demonstrate that the DMANet achieves excellent pose estimation accuracy.
Accurate pose estimation of space non-cooperative targets with a monocular camera is crucial to space debris removal， autonomous rendezvous， and other on-orbit services. However， monocular pose estimation methods lack depth information， resulting in scale uncertainty issue that significantly reduces their accuracy and real-time performance. We first propose a multi-scale attention block （MAB） to extract complex high-dimensional semantic features from the input image. Second， based on the MAB module， we propose a dense multi-scale attention network （DMANet） for estimating the 6-degree-of-freedom （DoF） pose of space non-cooperative targets， which consists of planar position estimation， depth position estimation， and attitude estimation branches. By introducing an Euler angle-based soft classification method， we formulate the pose regression problem as a classical classification problem. Besides， we design a space non-cooperative object model and construct a pose estimation dataset by using Coppeliasim. Finally， we thoroughly evaluate the proposed method on the SPEED+， URSO datasets and our dataset， compared to other state-of-the-art methods. Experiment results demonstrate that the DMANet achieves excellent pose estimation accuracy.
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