Satellite formation keeping through inter-satellite electromagnetic force provides an attractive alternative for future space missions due to its distinct advantages of no propellant consumption or plume contamination...Satellite formation keeping through inter-satellite electromagnetic force provides an attractive alternative for future space missions due to its distinct advantages of no propellant consumption or plume contamination as compared to conventional approaches.However,the internal force nature as well as the high nonlinearity and coupling of electromagnetic force brings new control challenges for this novel technique.In this paper,analysis on the dynamics characteristics and special control issues in the presence of electromagnetic force is carried out on the basis of the derived relatively translational dynamics.Considering the model uncertainties,external disturbances and sensor noise,a combined nonlinear control scheme involving feed-forward and feedback control components is proposed for electromagnetic-force-based formation keeping.The feed-forward component is directly obtained through desired configuration and dynamics under nominal conditions while the feedback component is realized utilizing active disturbance rejection control methodology with some reasonable improvement.Numerical simulation is presented to verify the feasibility and validity of the combined control scheme.展开更多
The Hunga Tonga-Hunga Ha’apai eruption on January 15,2022 was one of the most explosive volcanic eruptions of the 21st century and has attracted global attention.Here we show that large numbers of the volcanic aeroso...The Hunga Tonga-Hunga Ha’apai eruption on January 15,2022 was one of the most explosive volcanic eruptions of the 21st century and has attracted global attention.Here we show that large numbers of the volcanic aerosols from the eruption broke through the tropopause into the lower stratosphere,forming an ash plume with an overshooting top at 25-30 km altitude.In the four days following the eruption,the ash plume moved rapidly westward for nearly 10,000 km under stable stratospheric conditions characterized by strong tropical easterlies,weak meridional winds and weak vertical motion.The intrusion of the ash plume into the stratosphere resulted in a marked increase in atmospheric aerosol loading across northern Australia,with the aerosol optical depth(AOD)observed by satellites and sun-photometers peaking at 1.5 off the coast of northeastern Australia;these effects lasted for nearly three days.The ash plume was characterized by fine-mode particles clustered at a radius of about 0.26μm,with an observed peak volume of 0.25μm^(3)μm^(-2).The impact of the ash plume associated with the Hunga Tonga eruption on the stratospheric AOD and radiative balance in the tropical southern hemisphere is remarkable,with an observed volcanic-induced perturbation of the regional stratospheric AOD of up to 0.6.This perturbation largely explains an instantaneous bottom(top)of the atmosphere radiative forcing of-105.0(-65.0)W m^(-2)on a regional scale.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11172322)
文摘Satellite formation keeping through inter-satellite electromagnetic force provides an attractive alternative for future space missions due to its distinct advantages of no propellant consumption or plume contamination as compared to conventional approaches.However,the internal force nature as well as the high nonlinearity and coupling of electromagnetic force brings new control challenges for this novel technique.In this paper,analysis on the dynamics characteristics and special control issues in the presence of electromagnetic force is carried out on the basis of the derived relatively translational dynamics.Considering the model uncertainties,external disturbances and sensor noise,a combined nonlinear control scheme involving feed-forward and feedback control components is proposed for electromagnetic-force-based formation keeping.The feed-forward component is directly obtained through desired configuration and dynamics under nominal conditions while the feedback component is realized utilizing active disturbance rejection control methodology with some reasonable improvement.Numerical simulation is presented to verify the feasibility and validity of the combined control scheme.
基金supported by the National Science Fund for Distinguished Young Scholars(41825011)the National Natural Science Foundation of China(42175153 and 42030608)the Basic Research Fund of Chinese Academy of Meteorological Sciences(2021Y001)。
文摘The Hunga Tonga-Hunga Ha’apai eruption on January 15,2022 was one of the most explosive volcanic eruptions of the 21st century and has attracted global attention.Here we show that large numbers of the volcanic aerosols from the eruption broke through the tropopause into the lower stratosphere,forming an ash plume with an overshooting top at 25-30 km altitude.In the four days following the eruption,the ash plume moved rapidly westward for nearly 10,000 km under stable stratospheric conditions characterized by strong tropical easterlies,weak meridional winds and weak vertical motion.The intrusion of the ash plume into the stratosphere resulted in a marked increase in atmospheric aerosol loading across northern Australia,with the aerosol optical depth(AOD)observed by satellites and sun-photometers peaking at 1.5 off the coast of northeastern Australia;these effects lasted for nearly three days.The ash plume was characterized by fine-mode particles clustered at a radius of about 0.26μm,with an observed peak volume of 0.25μm^(3)μm^(-2).The impact of the ash plume associated with the Hunga Tonga eruption on the stratospheric AOD and radiative balance in the tropical southern hemisphere is remarkable,with an observed volcanic-induced perturbation of the regional stratospheric AOD of up to 0.6.This perturbation largely explains an instantaneous bottom(top)of the atmosphere radiative forcing of-105.0(-65.0)W m^(-2)on a regional scale.
