By recording nocturnally migrating passerines with tracking radar we have investigated how coastlines affect the migrants＇ flight paths. Birds could use coastlines as an orientation aid or as a reference cue to compe...By recording nocturnally migrating passerines with tracking radar we have investigated how coastlines affect the migrants＇ flight paths. Birds could use coastlines as an orientation aid or as a reference cue to compensate for wind drift while mi- grating. However, on the small scale of Falsterbo Peninsula in southern Sweden, we found very little effect of coastlines on migrants flight paths, irrespective of altitude. We tracked 2 930 migrants in three autumn and two spring seasons, at altitudes from 60 up to 3 000 meters. We compared tracks of migrants flying in three different areas, which correspond to the three main coastlines, and can demonstrate that the orientation of the tracks did not differ in a way consistent with the coastlines between the areas in autumn, and showed only a slight effect in spring. This is in accordance with earlier infrared device monitoring in Falsterbo, but contrary to earlier visual observations. It supports the view of nocturnally migrating passerines as mainly broad-front migrants. Even though the coastlines on the scale of the peninsula affected the flight paths very little, it is possible that the coastline has an effect on a larger regional scale, by migrants avoiding long sea crossings and thereby being funneled towards the peninsula, but this remains to be investigated [Current Zoology 60 （5）： 660-669, 2014].展开更多
Airborne area-array whisk-broom imaging systems typically adopt constant-speed scanning schemes.For large-inertia scanning systems,constant-speed scanning requires substantial time to complete the reversal motion,redu...Airborne area-array whisk-broom imaging systems typically adopt constant-speed scanning schemes.For large-inertia scanning systems,constant-speed scanning requires substantial time to complete the reversal motion,reducing the system's adaptability to high-speed reversal scanning and decreasing scanning efficiency.This study proposes a novel sinusoidal variable-speed roll scanning strategy,which reduces abrupt changes in speed and acceleration,minimizing time loss during reversals.Based on the forward image motion compensation strategy in the pitch direction,we establish a line-of-sight(LOS)position calculation model with vertical flight path correction(VFPC),ensuring that the central LOS of the scanned image remains stable on the same horizontal line,facilitating accurate image stitching in whisk-broom imaging.Through theoretical analysis and simulation experiments,the proposed method improves the scanning efficiency by approximately 18.6%at a 90o whiskbroom imaging angle under the same speed height ratio conditions.The new VFPC method enables wide-field,high-resolution imaging,achieving single-line LOS horizontal stability with an accuracy of better than O.4 mrad.The research is of great significance to promote the further development of airborne area-array whisk-broom imaging technology toward wider fields of view,higher speed height ratios,and greater scanning efficiency.展开更多
The UAVs （unmanned aerial vehicles） and the use of graphical data files of extension KML （keyhole markup language） have become popular nowadays. The KML files are associated to the Google Earth applications. Devel...The UAVs （unmanned aerial vehicles） and the use of graphical data files of extension KML （keyhole markup language） have become popular nowadays. The KML files are associated to the Google Earth applications. Developed by Microdrone company for planning, overflight simulation and data flight analysis, the program mdCockpit was used in this experiment. The UAV Microdrone＇s flight path was programmed in two ways： using geo referenced images from Google Earth and entering points coordinates into the program. These points have had their geographical decimal coordinates collected by GPS （global positioning system） （RTK （real time kinematic）） method. The aim here is to describe a way of evaluating the difference between the alternatives of flight planning. A flight path, defined a route with 22 points, was also simulated in the program mdCockpit. The points were collected and saved, while the images captured by the program went automatically forming a georeferenced mosaic. A comparison between the differences of coordinates to each point was made by choosing on the images and also by a RTK positioning. The result was up to 14.20 m to a 100 m flight height. There is a significant change of position and this can result in unwanted over flights in locations or even jeopardizing the safety of air activity.展开更多
ZAM BIA＇S third largest city Ndola, headquarters of the country＇s famed copper-mining region known as the Copperbelt, has long wished for a modern air- port. Now the wish is to materialize with a $500-mil- lion faci...ZAM BIA＇S third largest city Ndola, headquarters of the country＇s famed copper-mining region known as the Copperbelt, has long wished for a modern air- port. Now the wish is to materialize with a $500-mil- lion facility on the drawing board. The project is being developed by the Aviation Industry Corp. of China （AVIC）, a company involved in the production of military aircraft and information and communications technology products as well as construction of commercial airports. The artistic impressions of the airport developed by AVIC include a terminal, aircraft and other vehicle parking spaces, and a hotel. At the time of writing this, the Zambian Government was looking for over $500 million so that construction could begin on the 2,000-hectare site in a forest reserve west of the city.展开更多
Aimed at the safety of helicopter flight in the highly dynamic wind field of urban lowaltitude environment,a wind field simulation and reconstruction method based on unsteady Reynolds-Averaged Navier-Stokes(RANS)and S...Aimed at the safety of helicopter flight in the highly dynamic wind field of urban lowaltitude environment,a wind field simulation and reconstruction method based on unsteady Reynolds-Averaged Navier-Stokes(RANS)and Snapshot Proper Orthogonal Decomposition(Snapshot POD)is proposed in this paper.A comprehensive flight simulation platform is developed,integrating the simulated wind field,a helicopter flight dynamic model,an explicit ModelFollowing Control System(MFCS),and a simplified precision pilot model.Focusing on the issue of airflow disturbances from nearby obstacles in urban environments,a spatiotemporal,dualsource wind-induced threat identification model is established,which fuses turbulence threat and operational exceedance threat,and is incorporated into the construction of safety maps used for trajectory planning.The neighborhood search strategy of the A*algorithm is improved to enhance the trajectory's environmental adaptability,forming an automatic helicopter flight simulation method for complex urban wind environments,integrating wind field prediction,trajectory planning,and flight simulation.Applied to real-world environment flight simulation,the Improved Safety Map-based A*method(I-SM-A*)can reduce the number of path nodes and approach the target faster compared with the Traditional A*method(Trad-A*).The designed trajectory can effectively isolate the wind-induced threat caused by the building airflow.This results in a reduction in pilot workload,as evidenced by decreases of 10.6%and 8.0%in the time and frequency domains,respectively.The flight simulation platform can accurately track the designed trajectory and achieve reliable automatic flight planning in complex urban windy environments.展开更多
During path planning, it is necessary to satisfy the requirements of multiple objectives. Multi-objective synthesis is based on the need of flight mission and subjectivity inclination of decision-maker. The decision-m...During path planning, it is necessary to satisfy the requirements of multiple objectives. Multi-objective synthesis is based on the need of flight mission and subjectivity inclination of decision-maker. The decision-maker, however, has illegibility for under- standing the requirements of multiple objectives and the subjectivity inclination. It is important to develop a reasonable cost performance index for describing the illegibility of the decision-maker in multi-objective path planning. Based on Voronoi dia- gram method for the path planning, this paper studies the synthesis method of the multi-objective cost performance index. Ac- cording to the application of the cost performance index to the path planning based on Voronoi diagram method, this paper ana- lyzes the cost performance index which has been referred to at present. The analysis shows the insufficiency of the cost per- formance index at present, i.e., it is difficult to synthesize sub-objective flmctions because of the great disparity of the sub-objective fimctions. Thus, a new approach is developed to optimize the cost performance index with the multi-objective fuzzy optimization strategy, and an improved performance index is established, which could coordinate the weight conflict of the sub-objective functions. Finally, the experimental result shows the effectiveness of the proposed approach.展开更多
Carrier-based aircraft endow aircraft carriers with powerful combat capabilities but also bring about safety issues for carrier-based aircraft landing.Therefore,it is necessary to study the accuracy,speed and orbit-ch...Carrier-based aircraft endow aircraft carriers with powerful combat capabilities but also bring about safety issues for carrier-based aircraft landing.Therefore,it is necessary to study the accuracy,speed and orbit-changing ability of carrier-based aircraft to follow ideal glide trajectories.Based on the control strategy of the US military’s‘magic carpet’technology,with the E-2C as the target,decoupling the trajectory angle control and angle of attack control,a double-layer dynamic inverse landing flight trajectory incremental modal control method is designed.The simulation results show that the designed control law can accurately track the glide command,while maintaining the angle of attack and velocity,and has good control performance;provide the correction capability of carrier-based aircraft to correct back to−3.5°under different trajectory angle states,as well as the correction capability and boundary when there are different altitude deviations during the final landing phase.展开更多
文摘By recording nocturnally migrating passerines with tracking radar we have investigated how coastlines affect the migrants＇ flight paths. Birds could use coastlines as an orientation aid or as a reference cue to compensate for wind drift while mi- grating. However, on the small scale of Falsterbo Peninsula in southern Sweden, we found very little effect of coastlines on migrants flight paths, irrespective of altitude. We tracked 2 930 migrants in three autumn and two spring seasons, at altitudes from 60 up to 3 000 meters. We compared tracks of migrants flying in three different areas, which correspond to the three main coastlines, and can demonstrate that the orientation of the tracks did not differ in a way consistent with the coastlines between the areas in autumn, and showed only a slight effect in spring. This is in accordance with earlier infrared device monitoring in Falsterbo, but contrary to earlier visual observations. It supports the view of nocturnally migrating passerines as mainly broad-front migrants. Even though the coastlines on the scale of the peninsula affected the flight paths very little, it is possible that the coastline has an effect on a larger regional scale, by migrants avoiding long sea crossings and thereby being funneled towards the peninsula, but this remains to be investigated [Current Zoology 60 （5）： 660-669, 2014].
基金Supported by the National Key Research and Development Program(2023YFC3107602)。
文摘Airborne area-array whisk-broom imaging systems typically adopt constant-speed scanning schemes.For large-inertia scanning systems,constant-speed scanning requires substantial time to complete the reversal motion,reducing the system's adaptability to high-speed reversal scanning and decreasing scanning efficiency.This study proposes a novel sinusoidal variable-speed roll scanning strategy,which reduces abrupt changes in speed and acceleration,minimizing time loss during reversals.Based on the forward image motion compensation strategy in the pitch direction,we establish a line-of-sight(LOS)position calculation model with vertical flight path correction(VFPC),ensuring that the central LOS of the scanned image remains stable on the same horizontal line,facilitating accurate image stitching in whisk-broom imaging.Through theoretical analysis and simulation experiments,the proposed method improves the scanning efficiency by approximately 18.6%at a 90o whiskbroom imaging angle under the same speed height ratio conditions.The new VFPC method enables wide-field,high-resolution imaging,achieving single-line LOS horizontal stability with an accuracy of better than O.4 mrad.The research is of great significance to promote the further development of airborne area-array whisk-broom imaging technology toward wider fields of view,higher speed height ratios,and greater scanning efficiency.
文摘The UAVs （unmanned aerial vehicles） and the use of graphical data files of extension KML （keyhole markup language） have become popular nowadays. The KML files are associated to the Google Earth applications. Developed by Microdrone company for planning, overflight simulation and data flight analysis, the program mdCockpit was used in this experiment. The UAV Microdrone＇s flight path was programmed in two ways： using geo referenced images from Google Earth and entering points coordinates into the program. These points have had their geographical decimal coordinates collected by GPS （global positioning system） （RTK （real time kinematic）） method. The aim here is to describe a way of evaluating the difference between the alternatives of flight planning. A flight path, defined a route with 22 points, was also simulated in the program mdCockpit. The points were collected and saved, while the images captured by the program went automatically forming a georeferenced mosaic. A comparison between the differences of coordinates to each point was made by choosing on the images and also by a RTK positioning. The result was up to 14.20 m to a 100 m flight height. There is a significant change of position and this can result in unwanted over flights in locations or even jeopardizing the safety of air activity.
文摘ZAM BIA＇S third largest city Ndola, headquarters of the country＇s famed copper-mining region known as the Copperbelt, has long wished for a modern air- port. Now the wish is to materialize with a $500-mil- lion facility on the drawing board. The project is being developed by the Aviation Industry Corp. of China （AVIC）, a company involved in the production of military aircraft and information and communications technology products as well as construction of commercial airports. The artistic impressions of the airport developed by AVIC include a terminal, aircraft and other vehicle parking spaces, and a hotel. At the time of writing this, the Zambian Government was looking for over $500 million so that construction could begin on the 2,000-hectare site in a forest reserve west of the city.
基金supported by the National Natural Science Foundation of China(No.11972190)。
文摘Aimed at the safety of helicopter flight in the highly dynamic wind field of urban lowaltitude environment,a wind field simulation and reconstruction method based on unsteady Reynolds-Averaged Navier-Stokes(RANS)and Snapshot Proper Orthogonal Decomposition(Snapshot POD)is proposed in this paper.A comprehensive flight simulation platform is developed,integrating the simulated wind field,a helicopter flight dynamic model,an explicit ModelFollowing Control System(MFCS),and a simplified precision pilot model.Focusing on the issue of airflow disturbances from nearby obstacles in urban environments,a spatiotemporal,dualsource wind-induced threat identification model is established,which fuses turbulence threat and operational exceedance threat,and is incorporated into the construction of safety maps used for trajectory planning.The neighborhood search strategy of the A*algorithm is improved to enhance the trajectory's environmental adaptability,forming an automatic helicopter flight simulation method for complex urban wind environments,integrating wind field prediction,trajectory planning,and flight simulation.Applied to real-world environment flight simulation,the Improved Safety Map-based A*method(I-SM-A*)can reduce the number of path nodes and approach the target faster compared with the Traditional A*method(Trad-A*).The designed trajectory can effectively isolate the wind-induced threat caused by the building airflow.This results in a reduction in pilot workload,as evidenced by decreases of 10.6%and 8.0%in the time and frequency domains,respectively.The flight simulation platform can accurately track the designed trajectory and achieve reliable automatic flight planning in complex urban windy environments.
文摘During path planning, it is necessary to satisfy the requirements of multiple objectives. Multi-objective synthesis is based on the need of flight mission and subjectivity inclination of decision-maker. The decision-maker, however, has illegibility for under- standing the requirements of multiple objectives and the subjectivity inclination. It is important to develop a reasonable cost performance index for describing the illegibility of the decision-maker in multi-objective path planning. Based on Voronoi dia- gram method for the path planning, this paper studies the synthesis method of the multi-objective cost performance index. Ac- cording to the application of the cost performance index to the path planning based on Voronoi diagram method, this paper ana- lyzes the cost performance index which has been referred to at present. The analysis shows the insufficiency of the cost per- formance index at present, i.e., it is difficult to synthesize sub-objective flmctions because of the great disparity of the sub-objective fimctions. Thus, a new approach is developed to optimize the cost performance index with the multi-objective fuzzy optimization strategy, and an improved performance index is established, which could coordinate the weight conflict of the sub-objective functions. Finally, the experimental result shows the effectiveness of the proposed approach.
基金supported by the Aeronautical Science Foundation of China under grant 20230007003002.
文摘Carrier-based aircraft endow aircraft carriers with powerful combat capabilities but also bring about safety issues for carrier-based aircraft landing.Therefore,it is necessary to study the accuracy,speed and orbit-changing ability of carrier-based aircraft to follow ideal glide trajectories.Based on the control strategy of the US military’s‘magic carpet’technology,with the E-2C as the target,decoupling the trajectory angle control and angle of attack control,a double-layer dynamic inverse landing flight trajectory incremental modal control method is designed.The simulation results show that the designed control law can accurately track the glide command,while maintaining the angle of attack and velocity,and has good control performance;provide the correction capability of carrier-based aircraft to correct back to−3.5°under different trajectory angle states,as well as the correction capability and boundary when there are different altitude deviations during the final landing phase.
