Transactions of Nanjing University of Aeronautics & Astronautics
Volume 0,Issue 6,2023 Table of Contents
2023(6):627-640.
DOI: 10.16356/j.1005-1120.2023.06.001
Abstract:
This paper addresses the confrontation decision-making problem of unmanned aerial vehicles（UAVs） based on fictitious self-play multi-agent proximal policy optimization. UAV confrontation relies on autonomous decision-making， enabling the UAV to generate action instructions based on environmental information. An innovative autonomous decision-making methodology for UAV confrontations is proposed within the context of red-blue air combat tasks. Initially， the current situation is evaluated by employing the relative angle between the missile attack area and the UAV. Following this， guided by the evaluated scenario， the design of state space， action space， and real-time reward feedback is implemented to streamline the training process. Subsequently， an advanced method is introduced for optimizing strategy through a virtual autonomous agent’s proximity， aiming to derive the advantage function and average strategy from the experience buffer of training data. Ultimately， the efficacy and superiority of the proposed method are validated through simulations of UAVs engaging in red-blue countermeasure tasks.
This paper addresses the confrontation decision-making problem of unmanned aerial vehicles（UAVs） based on fictitious self-play multi-agent proximal policy optimization. UAV confrontation relies on autonomous decision-making， enabling the UAV to generate action instructions based on environmental information. An innovative autonomous decision-making methodology for UAV confrontations is proposed within the context of red-blue air combat tasks. Initially， the current situation is evaluated by employing the relative angle between the missile attack area and the UAV. Following this， guided by the evaluated scenario， the design of state space， action space， and real-time reward feedback is implemented to streamline the training process. Subsequently， an advanced method is introduced for optimizing strategy through a virtual autonomous agent’s proximity， aiming to derive the advantage function and average strategy from the experience buffer of training data. Ultimately， the efficacy and superiority of the proposed method are validated through simulations of UAVs engaging in red-blue countermeasure tasks.
2023(6):641-652.
DOI: 10.16356/j.1005-1120.2023.06.002
Abstract:
This paper proposes a modeling and compensation method for the dynamic coning error parameters of the mechanical dithered laser gyroscope. Firstly， the causes of the dynamic coning error are analyzed in principle， and the deformation of the sensing axis of the laser gyroscope under different external angular acceleration inputs is provided. A compensation model of the dynamic coning error is later established， and the influence of the dynamic coning error is represented by the dynamic coning error coefficient， which is only related to the laser gyro. Then we propose a system level calibration scheme of the dynamic coning error coefficients considering the relationship between the attitude error of the system before and after the coning motion. The existence of the dynamic coning error， as well as the dynamic coning error compensation effect is proved via the coning motion experiment of laser gyroscope and fiber optic gyroscope. Finally， it is verified through the system level vibration test that the dynamic coning error compensation method can effectively reduce the attitude and speed errors of the system in the vibration environment， consequently improving the navigation accuracy of the inertial navigation system in the complex mechanical environment.
This paper proposes a modeling and compensation method for the dynamic coning error parameters of the mechanical dithered laser gyroscope. Firstly， the causes of the dynamic coning error are analyzed in principle， and the deformation of the sensing axis of the laser gyroscope under different external angular acceleration inputs is provided. A compensation model of the dynamic coning error is later established， and the influence of the dynamic coning error is represented by the dynamic coning error coefficient， which is only related to the laser gyro. Then we propose a system level calibration scheme of the dynamic coning error coefficients considering the relationship between the attitude error of the system before and after the coning motion. The existence of the dynamic coning error， as well as the dynamic coning error compensation effect is proved via the coning motion experiment of laser gyroscope and fiber optic gyroscope. Finally， it is verified through the system level vibration test that the dynamic coning error compensation method can effectively reduce the attitude and speed errors of the system in the vibration environment， consequently improving the navigation accuracy of the inertial navigation system in the complex mechanical environment.
2023(6):653-662.
DOI: 10.16356/j.1005-1120.2023.06.003
Abstract:
Ice crystal icing has the potential to induce engine damage or flameout， posing a serious threatening to flight safety. Therefore， it is of great importance to improve the precision of ice crystal icing prediction. Considering the effect of blade thickness， we develop a numerical model to simulate the entire process of ice crystal icing. The influences of airflow parameters， ice crystal suction position and blade thickness are examined on the characteristics of ice crystal melting and accumulation. The findings show a high melting rate of ice crystals at high air velocities， accompanied by a relatively short heat transfer duration， resulting in a low liquid water content. The trajectories of ice crystals at different suction positions are simulated， which reveals that elastic collision occurs at the first two blades， while adhesion takes place at the last three blades. The effect of blade thickness is found to be significant. The ice accumulation area is expanded， the main ice accumulation is shifted toward stators backwards， and the ice accumulation in each stator is more concentrated after taking blade thickness into account.
Ice crystal icing has the potential to induce engine damage or flameout， posing a serious threatening to flight safety. Therefore， it is of great importance to improve the precision of ice crystal icing prediction. Considering the effect of blade thickness， we develop a numerical model to simulate the entire process of ice crystal icing. The influences of airflow parameters， ice crystal suction position and blade thickness are examined on the characteristics of ice crystal melting and accumulation. The findings show a high melting rate of ice crystals at high air velocities， accompanied by a relatively short heat transfer duration， resulting in a low liquid water content. The trajectories of ice crystals at different suction positions are simulated， which reveals that elastic collision occurs at the first two blades， while adhesion takes place at the last three blades. The effect of blade thickness is found to be significant. The ice accumulation area is expanded， the main ice accumulation is shifted toward stators backwards， and the ice accumulation in each stator is more concentrated after taking blade thickness into account.
2023(6):663-677.
DOI: 10.16356/j.1005-1120.2023.06.004
Abstract:
The rotating engine components subject to Coriolis and centrifugal forces exhibit distinctive ice accretion characteristics when an aircraft operates under supercooled large droplet conditions. This study establishes the mathematical model of the ice accretion on rotating components of engine entry and considers the dynamic characteristics of terminal velocity， deformation， breakup， splash， and rebound of supercooled large droplets. The multiple reference frame method is employed to deal with the fluid flow and heat transfer under the rotating condition. A three-dimensional numerical simulation is conducted to investigate the droplet impingement and ice accretion characteristics of entry components， including the inlet lip， spinner， and fan blades. The simulation results at rotational speeds of 0， 2 000， and 4 100 r/min show that the ice accretion on the inlet lip moves towards the outer surface of the inlet lip from the inner surface as the rotational speed increases. Moreover， the ice accretion on the blades is mainly concentrated at the blade root， and the ice accumulation decreases with the increase of rotational speed. The ice thickness on the inlet lip and spinner increases with increased rotational speed. The maximum ice thickness on the inlet lip and spinner under the rotational speed of 4 100 r/min increases by 0.27 and 2.46 times， respectively， compared to the stationary condition. This work can serve as a reference for developing subsequent anti/de-icing technology.
The rotating engine components subject to Coriolis and centrifugal forces exhibit distinctive ice accretion characteristics when an aircraft operates under supercooled large droplet conditions. This study establishes the mathematical model of the ice accretion on rotating components of engine entry and considers the dynamic characteristics of terminal velocity， deformation， breakup， splash， and rebound of supercooled large droplets. The multiple reference frame method is employed to deal with the fluid flow and heat transfer under the rotating condition. A three-dimensional numerical simulation is conducted to investigate the droplet impingement and ice accretion characteristics of entry components， including the inlet lip， spinner， and fan blades. The simulation results at rotational speeds of 0， 2 000， and 4 100 r/min show that the ice accretion on the inlet lip moves towards the outer surface of the inlet lip from the inner surface as the rotational speed increases. Moreover， the ice accretion on the blades is mainly concentrated at the blade root， and the ice accumulation decreases with the increase of rotational speed. The ice thickness on the inlet lip and spinner increases with increased rotational speed. The maximum ice thickness on the inlet lip and spinner under the rotational speed of 4 100 r/min increases by 0.27 and 2.46 times， respectively， compared to the stationary condition. This work can serve as a reference for developing subsequent anti/de-icing technology.
2023(6):678-687.
DOI: 10.16356/j.1005-1120.2023.06.005
Abstract:
In order to prevent the formation of runback ice and achieve dry anti-icing effect while reducing energy consumption， a low-energy consumption dry anti-icing technology is developed. Based on the principle of thermal anti-icing， the idea of water shedding is introduced to keep the impact water liquid at a lower surface temperature. Superhydrophobic materials are used to promote water shedding as the main protection method to increase water shedding and reduce heat exchange time. The runback of liquid water on the surface and the energy consumption of surface heat exchange are reduced. The formation of runback ice is suppressed to achieve anti-ice effect and reduce energy consumption. The test results show that the low-energy dry anti-icing technology can significantly inhibit the formation of leading edge ice and runback ice， and reduce the required power compared with traditional thermal protection methods.
In order to prevent the formation of runback ice and achieve dry anti-icing effect while reducing energy consumption， a low-energy consumption dry anti-icing technology is developed. Based on the principle of thermal anti-icing， the idea of water shedding is introduced to keep the impact water liquid at a lower surface temperature. Superhydrophobic materials are used to promote water shedding as the main protection method to increase water shedding and reduce heat exchange time. The runback of liquid water on the surface and the energy consumption of surface heat exchange are reduced. The formation of runback ice is suppressed to achieve anti-ice effect and reduce energy consumption. The test results show that the low-energy dry anti-icing technology can significantly inhibit the formation of leading edge ice and runback ice， and reduce the required power compared with traditional thermal protection methods.
2023(6):688-702.
DOI: 10.16356/j.1005-1120.2023.06.006
Abstract:
At present， research on the anti-icing heat loads of propeller aircraft is inadequate， while predicting the distribution of anti-icing heat loads is crucial for designing propeller aircraft anti-icing systems. A three-dimensional propeller is simulated based on the multiple reference frame and Messinger thermodynamic model to analyze the effect of the anti-icing heat load. The results indicate that the majority of the anti-icing heat loads concentrates at the leading edge of the blade， with an initial increase and subsequent decrease along the spreading direction. As the incoming flow speed increases， both the value and range of anti-icing power initially increase and then decrease. The influence of the angle of attack is negligible due to the rotating effect. The anti-icing power increases linearly as the temperature drops. Considering the provisions in Appendix C of CCAR-25， when the rotation speed is 660 r/min， the chordwise upward limit is 12.1%， the chordwise downward limit is 6.7%， and the maximum anti-icing power density is 9.5 kW/m2. The anti-icing power of the single propeller exceeds 1.96 kW. This study provides a scientific explanation for the surface anti-icing of propeller aircraft and a theoretical basis for the installation of anti-icing systems on propeller aircraft.
At present， research on the anti-icing heat loads of propeller aircraft is inadequate， while predicting the distribution of anti-icing heat loads is crucial for designing propeller aircraft anti-icing systems. A three-dimensional propeller is simulated based on the multiple reference frame and Messinger thermodynamic model to analyze the effect of the anti-icing heat load. The results indicate that the majority of the anti-icing heat loads concentrates at the leading edge of the blade， with an initial increase and subsequent decrease along the spreading direction. As the incoming flow speed increases， both the value and range of anti-icing power initially increase and then decrease. The influence of the angle of attack is negligible due to the rotating effect. The anti-icing power increases linearly as the temperature drops. Considering the provisions in Appendix C of CCAR-25， when the rotation speed is 660 r/min， the chordwise upward limit is 12.1%， the chordwise downward limit is 6.7%， and the maximum anti-icing power density is 9.5 kW/m2. The anti-icing power of the single propeller exceeds 1.96 kW. This study provides a scientific explanation for the surface anti-icing of propeller aircraft and a theoretical basis for the installation of anti-icing systems on propeller aircraft.
2023(6):703-713.
DOI: 10.16356/j.1005-1120.2023.06.007
Abstract:
Aircraft wing icing detection is a crucial task during high-altitude flights because ice accumulation on the leading edge of wings can change their aerodynamic shape and reduce lift capacity. This paper proposes a rotated object detection method called RA-CenterNet， based on the CenterNet model， to overcome the limitations of existing icing detection approaches that either rely on operator experience or require high engineering implementation and hardware development costs. To address the specific icing area directions presented in wind tunnel experimental datasets， a novel angle prediction branch network that enables precise calibration of rotated targets is designed. Additionally， the convolutional block attention module （CBAM） is incorporated to enhance the feature extraction ability of the neural network for ice-shaped boundaries. Comparative experiments are conducted to validate the performance of the proposed method against other rotated object detection approaches and the baseline network. The results demonstrate that our RA-CenterNet method has a significant competitive advantage over the mainstream rotation-based object detection algorithms.
Aircraft wing icing detection is a crucial task during high-altitude flights because ice accumulation on the leading edge of wings can change their aerodynamic shape and reduce lift capacity. This paper proposes a rotated object detection method called RA-CenterNet， based on the CenterNet model， to overcome the limitations of existing icing detection approaches that either rely on operator experience or require high engineering implementation and hardware development costs. To address the specific icing area directions presented in wind tunnel experimental datasets， a novel angle prediction branch network that enables precise calibration of rotated targets is designed. Additionally， the convolutional block attention module （CBAM） is incorporated to enhance the feature extraction ability of the neural network for ice-shaped boundaries. Comparative experiments are conducted to validate the performance of the proposed method against other rotated object detection approaches and the baseline network. The results demonstrate that our RA-CenterNet method has a significant competitive advantage over the mainstream rotation-based object detection algorithms.
2023(6):714-726.
DOI: 10.16356/j.1005-1120.2023.06.008
Abstract:
The numerical simulation method combining solidification/melting model and volume of fluid （VOF） model is used to study the freezing behavior of double-droplet continuously impacting cold surfaces with varying wettability under low-velocity conditions. The droplet spreading and phase transition processes under two contact modes （diffusion contact and contraction contact） are compared. The simulation results indicate that the coalescence of droplets has a significant impact on their morphology. When two droplets continuously impact the hydrophilic surface， the maximum spreading factor of diffusion contact increases by 26%—38% compared with that of a single droplet impact， and the maximum spreading factor of contraction contact increases by 15%—30% compared with that of a single droplet impact. On superhydrophobic surfaces， the maximum spreading coefficient difference between single and double-droplet impacts is less than 2%， which can be ignored. In addition， an analysis is conducted on the collision between double droplets and superhydrophobic surfaces at low temperatures， and the impact patterns of complete rebound， partial rebound， and full adhesion on droplet aggregation and solidification processes under different contact modes are obtained.
The numerical simulation method combining solidification/melting model and volume of fluid （VOF） model is used to study the freezing behavior of double-droplet continuously impacting cold surfaces with varying wettability under low-velocity conditions. The droplet spreading and phase transition processes under two contact modes （diffusion contact and contraction contact） are compared. The simulation results indicate that the coalescence of droplets has a significant impact on their morphology. When two droplets continuously impact the hydrophilic surface， the maximum spreading factor of diffusion contact increases by 26%—38% compared with that of a single droplet impact， and the maximum spreading factor of contraction contact increases by 15%—30% compared with that of a single droplet impact. On superhydrophobic surfaces， the maximum spreading coefficient difference between single and double-droplet impacts is less than 2%， which can be ignored. In addition， an analysis is conducted on the collision between double droplets and superhydrophobic surfaces at low temperatures， and the impact patterns of complete rebound， partial rebound， and full adhesion on droplet aggregation and solidification processes under different contact modes are obtained.
2023(6):727-737.
DOI: 10.16356/j.1005-1120.2023.06.009
Abstract:
In order to reduce operator fatigue and accelerate aircraft cabin assembly， supernumerary robotic limbs （SRLs） are developed for overhead work in cabin assembly task. The SRLs assist workers in supporting the ceiling to achieve single-person operation via dual three-degree-of-freedom robotic limbs， which are mounted on the human shoulder. The proposed robot can replace the original two-person operation mode， which reduces labor costs and avoids the burden of supporting tasks on workers. A flexible saddle-liked wearable backpack and a flexible end-effector are designed to improve the wearing comfort and environmental adaptability. At the same time， to ensure the safety of human-robot collaboration， the SRLs are designed to address the issues by sensor detection， tendon-driven decoupling mode selection and motion parameter limitation. Moreover， a position compensation control algorithm is designed based on the ergonomic kinematics model to avoid the interference caused by human perturbation. A force compensation control algorithm is designed based on the admittance control principle to improve the operational stability. Experimental results show that the proposed position algorithm reduces the end position error by more than 74%， compared with the original error. The proposed force algorithm can control the single robotic limb of the SRLs to output target force of 5 N for meeting the requirement.
In order to reduce operator fatigue and accelerate aircraft cabin assembly， supernumerary robotic limbs （SRLs） are developed for overhead work in cabin assembly task. The SRLs assist workers in supporting the ceiling to achieve single-person operation via dual three-degree-of-freedom robotic limbs， which are mounted on the human shoulder. The proposed robot can replace the original two-person operation mode， which reduces labor costs and avoids the burden of supporting tasks on workers. A flexible saddle-liked wearable backpack and a flexible end-effector are designed to improve the wearing comfort and environmental adaptability. At the same time， to ensure the safety of human-robot collaboration， the SRLs are designed to address the issues by sensor detection， tendon-driven decoupling mode selection and motion parameter limitation. Moreover， a position compensation control algorithm is designed based on the ergonomic kinematics model to avoid the interference caused by human perturbation. A force compensation control algorithm is designed based on the admittance control principle to improve the operational stability. Experimental results show that the proposed position algorithm reduces the end position error by more than 74%， compared with the original error. The proposed force algorithm can control the single robotic limb of the SRLs to output target force of 5 N for meeting the requirement.
2023(6):738-752.
DOI: 10.16356/j.1005-1120.2023.06.010
Abstract:
In application scenarios such as smart cities， a single wireless communication technology cannot cover complex network environments， while different communication technologies cannot communicate with each other， making it impossible to take full advantage of different wireless communication technologies. Therefore， we design a device that can communicate with multiple wireless communication nodes， which is called wireless heterogeneous communication modules （WHCM）. WHCM is used as a hub to build a communication heterogeneous mesh network （CHMN）. CHMN consists of nodes with multiple wireless communication protocols. We propose an AD HOC on-demand multi-path distance vector （AOMDV） routing protocol based on CHMN networks， named CH-AOMDV. CH-AOMDV is able to identify different types of communication protocols during the route initiation and path establishment process. It can also identify the communication distance， data transmission rate， energy and the load capacity of each node in CHMN. Simulations with NS-2 show that the performance of the CHMN is better than that of the traditional network when the distribution density between nodes is higher in terms of packet delivery rate， average end-to-end delay， throughput rate and routing overhead. This work proposes a new method of implementing CHMN and the corresponding routing protocol CH-AOMDV. The proposed protocol is superior to the other three protocols， improves network lifecycle， throughput and packet delivery rate， and reduces node overhead and average end-to-end delay. The protocol is useful for CHMN.
In application scenarios such as smart cities， a single wireless communication technology cannot cover complex network environments， while different communication technologies cannot communicate with each other， making it impossible to take full advantage of different wireless communication technologies. Therefore， we design a device that can communicate with multiple wireless communication nodes， which is called wireless heterogeneous communication modules （WHCM）. WHCM is used as a hub to build a communication heterogeneous mesh network （CHMN）. CHMN consists of nodes with multiple wireless communication protocols. We propose an AD HOC on-demand multi-path distance vector （AOMDV） routing protocol based on CHMN networks， named CH-AOMDV. CH-AOMDV is able to identify different types of communication protocols during the route initiation and path establishment process. It can also identify the communication distance， data transmission rate， energy and the load capacity of each node in CHMN. Simulations with NS-2 show that the performance of the CHMN is better than that of the traditional network when the distribution density between nodes is higher in terms of packet delivery rate， average end-to-end delay， throughput rate and routing overhead. This work proposes a new method of implementing CHMN and the corresponding routing protocol CH-AOMDV. The proposed protocol is superior to the other three protocols， improves network lifecycle， throughput and packet delivery rate， and reduces node overhead and average end-to-end delay. The protocol is useful for CHMN.
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