Transactions of Nanjing University of Aeronautics & Astronautics
Volume 0,Issue 2,2022 Table of Contents
2022(2):121-142.
DOI: 10.16356/j.1005-1120.2022.02.001
Abstract:
This study conducts an evaluation of air quality， dispersion of airborne expiratory pollutants and thermal comfort in aircraft cabin mini-environments using a critical examination of significant studies conducted over the last 20 years. The research methods employed in these studies are also explained in detail. Based on the current literature， standard procedures for airplane personal ventilation and air quality investigations are defined for each study approach. Present study gaps are examined， and prospective study subjects for various research approaches are suggested.
This study conducts an evaluation of air quality， dispersion of airborne expiratory pollutants and thermal comfort in aircraft cabin mini-environments using a critical examination of significant studies conducted over the last 20 years. The research methods employed in these studies are also explained in detail. Based on the current literature， standard procedures for airplane personal ventilation and air quality investigations are defined for each study approach. Present study gaps are examined， and prospective study subjects for various research approaches are suggested.
2022(2):143-151.
DOI: 10.16356/j.1005-1120.2022.02.002
Abstract:
In-situ exploration of asteroid surfaces is of great scientific significance. Internally actuated rovers have been released to asteroid surfaces but without enough controllability. To investigate the attitude control characteristics of the cubic rover for asteroid surface exploration， a series of experiments are carried out using the self-designed rover and the low-gravity testbed. The experiments focus on two major themes： The minimum flywheel speed for cubic rover to produce a walking motion in different conditions， and the relationship between the rover’s rotation angle and the flywheel speed in twisting motion. The rover’s dynamical descriptions of the walking and twisting motions are first derived. The features and design of the low-gravity testbed are then summarized， including its dynamics， setup， and validation. A detailed comparison between the dynamic model and the experimental results is presented， which provides a basic reference of the cubic rover’s attitude control in low-gravity environments.
In-situ exploration of asteroid surfaces is of great scientific significance. Internally actuated rovers have been released to asteroid surfaces but without enough controllability. To investigate the attitude control characteristics of the cubic rover for asteroid surface exploration， a series of experiments are carried out using the self-designed rover and the low-gravity testbed. The experiments focus on two major themes： The minimum flywheel speed for cubic rover to produce a walking motion in different conditions， and the relationship between the rover’s rotation angle and the flywheel speed in twisting motion. The rover’s dynamical descriptions of the walking and twisting motions are first derived. The features and design of the low-gravity testbed are then summarized， including its dynamics， setup， and validation. A detailed comparison between the dynamic model and the experimental results is presented， which provides a basic reference of the cubic rover’s attitude control in low-gravity environments.
2022(2):152-163.
DOI: 10.16356/j.1005-1120.2022.02.003
Abstract:
Low earth orbit （LEO） mega-constellations can provide global low-latency high bandwidth coverage compared to the terrestrial network. The time-varying topology of satellite networks and the uneven traffic distribution lead to the mismatch between satellites and users， resulting in the waste of satellite resources and the degradation of user performance. Through negotiation with neighbors， the traditional terrestrial cell breathing continuously converges to the optimal cell size in the face of user tides， but this method is difficult to converge timely when facing rapid and extreme flow changes caused by the rapid movement of satellites. This paper presents a fast adaptive cell breathing scheme （FaB） through sub-block division and satellite cell initialization and adjustment. FaB divides the ground into sub-blocks according to the user density. When the satellite moves in the same sub-block， the step size of breathing is adjusted according to the cell size difference between the previous satellite and the current satellite. When the satellite switches between different sub-blocks， the initial value of the cell is determined according to the density of the new sub-block. In addition to negotiating with neighboring satellites， this scheme also introduces location information to directly adjust the parameters of cell breathing and decrease the time of cell breathing convergence. From the real constellation data-driven simulation， we conclude that FaB can quickly adjust the size of the cell with the location changing， and the utilization rate is increased by 2.66 times compared to the method with no cell breathing， and by 2.37 times compared to the method with cell breathing without location information.
Low earth orbit （LEO） mega-constellations can provide global low-latency high bandwidth coverage compared to the terrestrial network. The time-varying topology of satellite networks and the uneven traffic distribution lead to the mismatch between satellites and users， resulting in the waste of satellite resources and the degradation of user performance. Through negotiation with neighbors， the traditional terrestrial cell breathing continuously converges to the optimal cell size in the face of user tides， but this method is difficult to converge timely when facing rapid and extreme flow changes caused by the rapid movement of satellites. This paper presents a fast adaptive cell breathing scheme （FaB） through sub-block division and satellite cell initialization and adjustment. FaB divides the ground into sub-blocks according to the user density. When the satellite moves in the same sub-block， the step size of breathing is adjusted according to the cell size difference between the previous satellite and the current satellite. When the satellite switches between different sub-blocks， the initial value of the cell is determined according to the density of the new sub-block. In addition to negotiating with neighboring satellites， this scheme also introduces location information to directly adjust the parameters of cell breathing and decrease the time of cell breathing convergence. From the real constellation data-driven simulation， we conclude that FaB can quickly adjust the size of the cell with the location changing， and the utilization rate is increased by 2.66 times compared to the method with no cell breathing， and by 2.37 times compared to the method with cell breathing without location information.
YANG Hai
,
GUO Bingli
,
PANG Chengguang
,
CUI Xinbin
,
REN Huilin
,
ZHOU Huichao
,
KANG Chengbin
,
HUANG Shanguo
2022(2):164-175.
DOI: 10.16356/j.1005-1120.2022.02.004
Abstract:
Frequent inter-satellite link （ISL） handovers will induce service interruption in large-scale space information networks， since traditional distributed/centralized routing strategy-based route convergence/update will consume considerable time （compared with ground networks） derived from long ISL delay and flooding between hundreds or even thousands of satellites. During the network convergence/update stage， the lack of up-to-date forwarding information may cause severe packet loss. Considering the fact that ISL handovers for close-to-earth constellation are predictable and all the ISL handover information could be stored in each satellite during the network initialization， we propose a self-update routing scheme based on open shortest path first （OSPF-SUR） to address the slow route convergence problem caused by frequent ISL handovers. First， for predictable ISL handovers， forwarding tables are updated according to locally stored ISL handover information without link state advertisement （LSA） flooding. Second， for unexpected ISL failures， flooding could be triggered to complete route convergence. In this manner， network convergence time is radically descended by avoiding unnecessary LSA flooding for predictable ISL handovers. Simulation results show that the average packet loss rate caused by ISL handovers is reduced by 90.5% and 61.3%compared with standard OSPF （with three Hello packets confirmation） and OSPF based on interface state （without three Hello packets confirmation）， respectively， during a period of topology handover. And the average end-to-end delay is also decreased by 47.6%， 9.6%， respectively. The packet loss rate of the proposed OSPF-SUR does not change along with the increase of the frequency of topology handovers.
Frequent inter-satellite link （ISL） handovers will induce service interruption in large-scale space information networks， since traditional distributed/centralized routing strategy-based route convergence/update will consume considerable time （compared with ground networks） derived from long ISL delay and flooding between hundreds or even thousands of satellites. During the network convergence/update stage， the lack of up-to-date forwarding information may cause severe packet loss. Considering the fact that ISL handovers for close-to-earth constellation are predictable and all the ISL handover information could be stored in each satellite during the network initialization， we propose a self-update routing scheme based on open shortest path first （OSPF-SUR） to address the slow route convergence problem caused by frequent ISL handovers. First， for predictable ISL handovers， forwarding tables are updated according to locally stored ISL handover information without link state advertisement （LSA） flooding. Second， for unexpected ISL failures， flooding could be triggered to complete route convergence. In this manner， network convergence time is radically descended by avoiding unnecessary LSA flooding for predictable ISL handovers. Simulation results show that the average packet loss rate caused by ISL handovers is reduced by 90.5% and 61.3%compared with standard OSPF （with three Hello packets confirmation） and OSPF based on interface state （without three Hello packets confirmation）， respectively， during a period of topology handover. And the average end-to-end delay is also decreased by 47.6%， 9.6%， respectively. The packet loss rate of the proposed OSPF-SUR does not change along with the increase of the frequency of topology handovers.
2022(2):176-185.
DOI: 10.16356/j.1005-1120.2022.02.005
Abstract:
The formation problem of multi-agent systems via coordinated control is investigated， where the multiple agents can achieve the common velocity with leader and avoid collision during the evolution. In the real-world situation， the communication is often disturbed and inaccurate. Hence， the unknown disturbances are considered in the velocity measurements， which is assumed to be bounded and does not need to be modelled. Moreover， a complicated nonlinear interaction among agents is presented in the design of control. Based on the existing work of multi-agent systems， a flocking control protocol is proposed to address the formation problem in the dynamic topology. The stability analysis is given to prove that the velocities of all agents can converge to the velocity of leader and the stable motion with collision avoidance can be achieved eventually. Finally， some simulations are presented to verify the effectiveness of the proposed algorithm.
The formation problem of multi-agent systems via coordinated control is investigated， where the multiple agents can achieve the common velocity with leader and avoid collision during the evolution. In the real-world situation， the communication is often disturbed and inaccurate. Hence， the unknown disturbances are considered in the velocity measurements， which is assumed to be bounded and does not need to be modelled. Moreover， a complicated nonlinear interaction among agents is presented in the design of control. Based on the existing work of multi-agent systems， a flocking control protocol is proposed to address the formation problem in the dynamic topology. The stability analysis is given to prove that the velocities of all agents can converge to the velocity of leader and the stable motion with collision avoidance can be achieved eventually. Finally， some simulations are presented to verify the effectiveness of the proposed algorithm.
2022(2):186-200.
DOI: 10.16356/j.1005-1120.2022.02.006
Abstract:
To solve the problem of altitude control of a tilt tri-rotor unmanned aerial vehicle （UAV） in the transition mode， this study presents a grey wolf optimization （GWO） based neural network adaptive control scheme for a tilt tri-rotor UAV in the transition mode. Firstly， the nonlinear model of the tilt tri-rotor UAV is established. Secondly， the tilt tri-rotor UAV altitude controller and attitude controller are designed by a neural network adaptive control method， and the GWO algorithm is adopted to optimize the parameters of the neural network and the controllers. Thirdly， two altitude control strategies are designed in the transition mode. Finally， comparative simulations are carried out to demonstrate the effectiveness and robustness of the proposed control scheme.
To solve the problem of altitude control of a tilt tri-rotor unmanned aerial vehicle （UAV） in the transition mode， this study presents a grey wolf optimization （GWO） based neural network adaptive control scheme for a tilt tri-rotor UAV in the transition mode. Firstly， the nonlinear model of the tilt tri-rotor UAV is established. Secondly， the tilt tri-rotor UAV altitude controller and attitude controller are designed by a neural network adaptive control method， and the GWO algorithm is adopted to optimize the parameters of the neural network and the controllers. Thirdly， two altitude control strategies are designed in the transition mode. Finally， comparative simulations are carried out to demonstrate the effectiveness and robustness of the proposed control scheme.
2022(2):201-218.
DOI: 10.16356/j.1005-1120.2022.02.007
Abstract:
This paper is focused on control design for high-precision satellite rendezvous systems. A relative motion model of leader-follower satellites described by relative orbit elements （ROE） is adopted， which has clear geometric meaning and high accuracy. An improved repetitive control （IRC） scheme is proposed to achieve high-precision position and velocity tracking， which utilizes the advantage of repetitive control to track the signal precisely and conquers the effects of aperiodic disturbances by adding a nonsingular terminal sliding mode （NSTSM） controller. In addition， the nonlinear state error feedback （NLSEF） is used to improve the dynamic performance of repetitive controller and the radial basis function （RBF） neural networks are employed to approximate the unknown nonlinearities. From rigorous Lyapunov analysis， the stability of the whole closed-loop control system is guaranteed. Finally， numerical simulations are carried out to assess the efficiency and demonstrate the advantages of the proposed control scheme.
This paper is focused on control design for high-precision satellite rendezvous systems. A relative motion model of leader-follower satellites described by relative orbit elements （ROE） is adopted， which has clear geometric meaning and high accuracy. An improved repetitive control （IRC） scheme is proposed to achieve high-precision position and velocity tracking， which utilizes the advantage of repetitive control to track the signal precisely and conquers the effects of aperiodic disturbances by adding a nonsingular terminal sliding mode （NSTSM） controller. In addition， the nonlinear state error feedback （NLSEF） is used to improve the dynamic performance of repetitive controller and the radial basis function （RBF） neural networks are employed to approximate the unknown nonlinearities. From rigorous Lyapunov analysis， the stability of the whole closed-loop control system is guaranteed. Finally， numerical simulations are carried out to assess the efficiency and demonstrate the advantages of the proposed control scheme.
2022(2):219-230.
DOI: 10.16356/j.1005-1120.2022.02.008
Abstract:
Given external disturbances and system uncertainties， a nonsingular fast terminal sliding mode control （NFTSMC） method integrated a nonlinear disturbance observer （NDO） is put forward for quadrotor aircraft. First， a NDO is proposed to estimate the actual values of uncertainties and disturbances. Second， the NFTSM controller based on the reaching law is designed for the attitude subsystem （inner loop）， and the control strategy can ensure Euler angles’ fast convergence and stability of the attitude subsystem. Moreover， the NFTSMC strategy combined with backstepping is proposed for the position subsystem （outer loop）， which can ensure subsystem tracking performance. Finally， comparative simulations show the trajectory tracking performance of the proposed method is superior to that of the traditional sliding mode control （SMC） and the SM integral backstepping control under uncertainties and disturbances.
Given external disturbances and system uncertainties， a nonsingular fast terminal sliding mode control （NFTSMC） method integrated a nonlinear disturbance observer （NDO） is put forward for quadrotor aircraft. First， a NDO is proposed to estimate the actual values of uncertainties and disturbances. Second， the NFTSM controller based on the reaching law is designed for the attitude subsystem （inner loop）， and the control strategy can ensure Euler angles’ fast convergence and stability of the attitude subsystem. Moreover， the NFTSMC strategy combined with backstepping is proposed for the position subsystem （outer loop）， which can ensure subsystem tracking performance. Finally， comparative simulations show the trajectory tracking performance of the proposed method is superior to that of the traditional sliding mode control （SMC） and the SM integral backstepping control under uncertainties and disturbances.
9 A Parallel Integration Method of Cooperative Target-Localization and Cooperative Self-localization
2022(2):231-238.
DOI: 10.16356/j.1005-1120.2022.02.009
Abstract:
When a group of mobile agents track a target， they can locate themselves and the target in a cooperative manner. To maximize the group advantage， a parallel integration strategy of cooperative target-localization（CTL） and cooperative self-localization（CSL） is designed. Firstly， a global cost function containing the agents’ positions and the target’s position is established. Secondly， along with the agents’ positions being re-estimated during CTL， the U-transform is employed to propagate the error covariance of the position estimations among the agents. The simulation results show that， the proposal exploits more information for locating the target and the agents than the cases where CTL and CSL run separately， and the global optimal position estimations of the agents and the target are obtained.
When a group of mobile agents track a target， they can locate themselves and the target in a cooperative manner. To maximize the group advantage， a parallel integration strategy of cooperative target-localization（CTL） and cooperative self-localization（CSL） is designed. Firstly， a global cost function containing the agents’ positions and the target’s position is established. Secondly， along with the agents’ positions being re-estimated during CTL， the U-transform is employed to propagate the error covariance of the position estimations among the agents. The simulation results show that， the proposal exploits more information for locating the target and the agents than the cases where CTL and CSL run separately， and the global optimal position estimations of the agents and the target are obtained.
2022(2):239-249.
DOI: 10.16356/j.1005-1120.2022.02.010
Abstract:
In cryogenic wind tunnel tests， piezoelectric stacks are adopted to realize the vibration control of the cantilever sting. However， the free stroke and blocking force of the piezoelectric stack would decrease dramatically as the temperature decreases. This paper proposes a convenient and effective warming structure for the piezoelectric stack， which could keep it working at operating temperatures when the ambient temperature drops. The piezoelectric stack actuator is wrapped with the heating film， and this resulting assembly is then wrapped with the aerogel material for thermal insulation. Both ends of the piezoelectric stack actuator make direct contact with the payload structure. Both one-dimensional and two-dimensional theoretical analyses of the heating conduction problem of the piezoelectric stack actuator are conducted. These analyses results are compared with those of the finite element simulation analysis. The finite element method results show a good consistency with the two-dimensional theoretical results， and a slight deviation of only 0.91 K is observed， indicating its potential for protecting piezoelectric stacks at low temperatures.
In cryogenic wind tunnel tests， piezoelectric stacks are adopted to realize the vibration control of the cantilever sting. However， the free stroke and blocking force of the piezoelectric stack would decrease dramatically as the temperature decreases. This paper proposes a convenient and effective warming structure for the piezoelectric stack， which could keep it working at operating temperatures when the ambient temperature drops. The piezoelectric stack actuator is wrapped with the heating film， and this resulting assembly is then wrapped with the aerogel material for thermal insulation. Both ends of the piezoelectric stack actuator make direct contact with the payload structure. Both one-dimensional and two-dimensional theoretical analyses of the heating conduction problem of the piezoelectric stack actuator are conducted. These analyses results are compared with those of the finite element simulation analysis. The finite element method results show a good consistency with the two-dimensional theoretical results， and a slight deviation of only 0.91 K is observed， indicating its potential for protecting piezoelectric stacks at low temperatures.
2022(2):250-262.
DOI: 10.16356/j.1005-1120.2022.02.011
Abstract:
The main focus of this paper is to investigate the influence of hygrothermal aging on tensile strength of epoxy resin matrix composites. Firstly， tests of water absorption and moisture induced tensile strength degradation of glass fiber reinforced polymer （GFRP） are conducted. Results show that the moisture absorption behavior of the GFRP follows the Fick’s law， and its tensile strength retention decreases notably in the early hygrothermal aging stage and then gradually approaches a constant. Then， microscale longitudinal and transverse strength prediction models for unidirectional fiber reinforced composites are proposed. They are moisture concentration dependent and reflect the inherent probability of failures of fiber and matrix （or fiber/matrix interface）.The moisture diffusing analysis demostrates that the proposed models can predict degradation of tensile strength of epoxy resin matrix composites undergoing different hygrothermal durations. The proposed models are validated by the experiments of hygrothermal residual strength of the GFRP mentioned above.
The main focus of this paper is to investigate the influence of hygrothermal aging on tensile strength of epoxy resin matrix composites. Firstly， tests of water absorption and moisture induced tensile strength degradation of glass fiber reinforced polymer （GFRP） are conducted. Results show that the moisture absorption behavior of the GFRP follows the Fick’s law， and its tensile strength retention decreases notably in the early hygrothermal aging stage and then gradually approaches a constant. Then， microscale longitudinal and transverse strength prediction models for unidirectional fiber reinforced composites are proposed. They are moisture concentration dependent and reflect the inherent probability of failures of fiber and matrix （or fiber/matrix interface）.The moisture diffusing analysis demostrates that the proposed models can predict degradation of tensile strength of epoxy resin matrix composites undergoing different hygrothermal durations. The proposed models are validated by the experiments of hygrothermal residual strength of the GFRP mentioned above.
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