A high-precision nominal flight profile,involving controllers′intentions is critical for 4Dtrajectory estimation in modern automatic air traffic control systems.We proposed a novel method to effectively improve the a...A high-precision nominal flight profile,involving controllers′intentions is critical for 4Dtrajectory estimation in modern automatic air traffic control systems.We proposed a novel method to effectively improve the accuracy of the nominal flight profile,including the nominal altitude profile and the speed profile.First,considering the characteristics of trajectory data,we developed an improved K-means algorithm.The approach was to measure the similarity between different altitude profiles by integrating the space warp edit distance algorithm,thereby to acquire several fitted nominal flight altitude profiles.This approach breaks the constraints of traditional K-means algorithms.Second,to eliminate the influence of meteorological factors,we introduced historical gridded binary data to determine the en-route wind speed and temperature via inverse distance weighted interpolation.Finally,we facilitated the true airspeed determined by speed triangle relationships and the calibrated airspeed determined by aircraft data model to extract a more accurate nominal speed profile from each cluster,therefore we could describe the airspeed profiles above and below the airspeed transition altitude,respectively.Our experimental results showed that the proposed method could obtain a highly accurate nominal flight profile,which reflects the actual aircraft flight status.展开更多
Uncertain factors such as atmospheric density,aerodynamic coefficients,and aircraft mass can have a catastrophic impact on the flight safety of entry vehicles(EVs).It is crucial for EVs to quickly generate safe entry ...Uncertain factors such as atmospheric density,aerodynamic coefficients,and aircraft mass can have a catastrophic impact on the flight safety of entry vehicles(EVs).It is crucial for EVs to quickly generate safe entry trajectories that consider the impact of uncertainties to execute complex flight tasks such as online target changing.Given this challenge,a rapid generation method of safe entry trajectories is proposed,which is based on the drag-acceleration-profile method employed during space shuttle entry flights.This method can efficiently generate a safe,feasible trajectory while accounting for the influence of uncertain factors.Compared to traditional drag-acceleration-profile methods,the proposed method incorporates the influence of uncertain factors on the boundaries of the flight corridor.It establishes an uncertain flight corridor model,thereby ensuring the safety of the reference flight profile designed within this corridor under actual uncertain flight conditions.Additionally,a simplified design approach for the reference flight profile enables the rapid generation of satisfactory profiles through straightforward parameter iteration or optimization.Simulations demonstrate that this method can efficiently plan gliding flight trajectories that meet safety requirements,exhibiting potential for online trajectory generation and maneuverability assessment.展开更多
Air-breathing hypersonic vehicle has great military and potential economic value due to its characteristics:high velocity,long range,quick response.Therefore,the development of hypersonic vehicle and its guidance and ...Air-breathing hypersonic vehicle has great military and potential economic value due to its characteristics:high velocity,long range,quick response.Therefore,the development of hypersonic vehicle and its guidance and control technology are reviewed in this paper.Firstly,the development and classification of hypersonic vehicles around the world are summarized,and the geometric configuration and mission profile of typical air-breathing hypersonic vehicle are given.Secondly,the control difficulties of air-breathing hypersonic vehicle are introduced,including integrated design of engine and fuselage,static instability,strong nonlinearity,uncertain aerodynamic parameters,etc.According to its control requirements,the control methods considering external disturbance,fault-tolerant control methods,anti-saturation methods,and prescribed performance control methods considering transient performance constraints are summarized respectively.The classification and comparison of various control methods are given,and the frontiers of theoretical development are analyzed.Finally,considering the effects of composite disturbances,the design of terminal guidance law under multiple constraints is overviewed,including guidance law with angle constraint,velocity constraint,acceleration constraint and time constraint.Similarly,the classification of guidance law design methods under different constraints,their advantages as well as the future development trend and requirements are introduced.展开更多
One of the important questions in space biology is the mechanisms underlying plant responses to an outer space environment,i.e.,how gene expression is altered in space.In this study,the transcriptome of Arabidopsis th...One of the important questions in space biology is the mechanisms underlying plant responses to an outer space environment,i.e.,how gene expression is altered in space.In this study,the transcriptome of Arabidopsis thaliana seedlings was analyzed as a part of Germany SIMBOX(science in microgravity box)spaceflight experiment on Shenzhou 8 spacecraft.This experiment involved the following treatments:spaceflight with microgravity(Fμg),spaceflight with 1g centrifugal force(F 1g),and ground 1g control(G 1g).Gene chips were used to screen gene expression differences in Arabidopsis thaliana seedlings among these treatments.Microarray analysis revealed that 621 genes were differentially expressed in samples Fμg vs.G 1g,249 genes in samples F 1g vs.G 1g,and 368 genes in samples Fμg vs.F 1g.Gene ontology analysis indicated that the genes were involved in metabolism of stress response,gravitropic response,and DNA damage and repair,suggesting that plants adjust these metabolic pathways to space environmental stress,microgravity,and radiation.展开更多
基金supported by the National Natural Science Foundation of China(Nos.61174180,U1433125)the Jiangsu Province Science Foundation (No.BK20141413)the Chinese Postdoctoral Science Foundation (No.2014M550291)
文摘A high-precision nominal flight profile,involving controllers′intentions is critical for 4Dtrajectory estimation in modern automatic air traffic control systems.We proposed a novel method to effectively improve the accuracy of the nominal flight profile,including the nominal altitude profile and the speed profile.First,considering the characteristics of trajectory data,we developed an improved K-means algorithm.The approach was to measure the similarity between different altitude profiles by integrating the space warp edit distance algorithm,thereby to acquire several fitted nominal flight altitude profiles.This approach breaks the constraints of traditional K-means algorithms.Second,to eliminate the influence of meteorological factors,we introduced historical gridded binary data to determine the en-route wind speed and temperature via inverse distance weighted interpolation.Finally,we facilitated the true airspeed determined by speed triangle relationships and the calibrated airspeed determined by aircraft data model to extract a more accurate nominal speed profile from each cluster,therefore we could describe the airspeed profiles above and below the airspeed transition altitude,respectively.Our experimental results showed that the proposed method could obtain a highly accurate nominal flight profile,which reflects the actual aircraft flight status.
基金supported by the National Nature Science Foundation of China(92271108,62173336)
文摘Uncertain factors such as atmospheric density,aerodynamic coefficients,and aircraft mass can have a catastrophic impact on the flight safety of entry vehicles(EVs).It is crucial for EVs to quickly generate safe entry trajectories that consider the impact of uncertainties to execute complex flight tasks such as online target changing.Given this challenge,a rapid generation method of safe entry trajectories is proposed,which is based on the drag-acceleration-profile method employed during space shuttle entry flights.This method can efficiently generate a safe,feasible trajectory while accounting for the influence of uncertain factors.Compared to traditional drag-acceleration-profile methods,the proposed method incorporates the influence of uncertain factors on the boundaries of the flight corridor.It establishes an uncertain flight corridor model,thereby ensuring the safety of the reference flight profile designed within this corridor under actual uncertain flight conditions.Additionally,a simplified design approach for the reference flight profile enables the rapid generation of satisfactory profiles through straightforward parameter iteration or optimization.Simulations demonstrate that this method can efficiently plan gliding flight trajectories that meet safety requirements,exhibiting potential for online trajectory generation and maneuverability assessment.
基金co-supported by the National Natural Science Foundation of China(No.12102343)the Key Program of the National Natural Science Foundation of China(No.U2013206)+1 种基金Shanghai Space Science and Technology Innovation Fund,China(No.SAST2020-072)the Fundamental Research Funds for the Central Universities,China(No.D5000210833)。
文摘Air-breathing hypersonic vehicle has great military and potential economic value due to its characteristics:high velocity,long range,quick response.Therefore,the development of hypersonic vehicle and its guidance and control technology are reviewed in this paper.Firstly,the development and classification of hypersonic vehicles around the world are summarized,and the geometric configuration and mission profile of typical air-breathing hypersonic vehicle are given.Secondly,the control difficulties of air-breathing hypersonic vehicle are introduced,including integrated design of engine and fuselage,static instability,strong nonlinearity,uncertain aerodynamic parameters,etc.According to its control requirements,the control methods considering external disturbance,fault-tolerant control methods,anti-saturation methods,and prescribed performance control methods considering transient performance constraints are summarized respectively.The classification and comparison of various control methods are given,and the frontiers of theoretical development are analyzed.Finally,considering the effects of composite disturbances,the design of terminal guidance law under multiple constraints is overviewed,including guidance law with angle constraint,velocity constraint,acceleration constraint and time constraint.Similarly,the classification of guidance law design methods under different constraints,their advantages as well as the future development trend and requirements are introduced.
基金supported by the National Key Basic Research Program (Grant No. 2011CB710902)China Manned Space Engineering ProgramInternational S&T Cooperation Program of China
文摘One of the important questions in space biology is the mechanisms underlying plant responses to an outer space environment,i.e.,how gene expression is altered in space.In this study,the transcriptome of Arabidopsis thaliana seedlings was analyzed as a part of Germany SIMBOX(science in microgravity box)spaceflight experiment on Shenzhou 8 spacecraft.This experiment involved the following treatments:spaceflight with microgravity(Fμg),spaceflight with 1g centrifugal force(F 1g),and ground 1g control(G 1g).Gene chips were used to screen gene expression differences in Arabidopsis thaliana seedlings among these treatments.Microarray analysis revealed that 621 genes were differentially expressed in samples Fμg vs.G 1g,249 genes in samples F 1g vs.G 1g,and 368 genes in samples Fμg vs.F 1g.Gene ontology analysis indicated that the genes were involved in metabolism of stress response,gravitropic response,and DNA damage and repair,suggesting that plants adjust these metabolic pathways to space environmental stress,microgravity,and radiation.
