The consensus problem of the distributed attitude synchronization in the spacecraft formation flying is considered.Firstly,the attitude dynamics of a rigid body spacecraft is described by modified Rodriguez parameters...The consensus problem of the distributed attitude synchronization in the spacecraft formation flying is considered.Firstly,the attitude dynamics of a rigid body spacecraft is described by modified Rodriguez parameters（MRPs）.Then global stable distributed cooperative attitude control laws are proposed for different cases.In the first case,the control law guarantees the state consensus during the attitude synchronization.In the second case,the control law ensures both the attitudes synchronizing to a desired constant attitude and the angular velocities converging at zero.In the third case,an attitude consensus control law with bounded control input is proposed.Finally,the effectiveness and validity of the control laws are demonstrated by simulations of six rigid bodies formation flying.展开更多
Nuclear engineering materials are required to possess outstanding extreme environmental tolerance and irradiation resistance.A promising novel pyrochlore-type of(Sm_(0.2)Eu_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2))2 Hf_(2)O_(7)h...Nuclear engineering materials are required to possess outstanding extreme environmental tolerance and irradiation resistance.A promising novel pyrochlore-type of(Sm_(0.2)Eu_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2))2 Hf_(2)O_(7)high-entropy ceramic(HE-RE2 Hf_(2)O_(7))for control rod was prepared by solid-state reaction method.The ion irradiation of HE-RE_(2) Hf_(2)O_(7)with 400 keV Kr+at 400℃was investigated using a 400 kV ion implanter and compared with single-component pyrochlore Gd2 Hf_(2)O_(7)to evaluate the irradiation resistance.For HE-RE2 Hf_(2)O_(7),the phase transition from pyrochlore to defective fluorite is revealed after irradiation at 60 dpa.After irradiation at 120 dpa,it maintained crystalline,which is comparable to Gd2 Hf_(2)O_(7)but superior to the titanate pyrochlores previously studied.Moreover,the lattice expansion of HE-RE2 Hf_(2)O_(7)(_(0.2)2%)is much lower than that of Gd2 Hf_(2)O_(7)(0.62%),indicating excellent irradiation damage resistance.Nanoindentation tests displayed an irradiation-induced increase in hardness and a decrease in elastic modulus by about 2.6%.Irradiation-induced segregation of elements is observed on the surface of irradiated samples.In addition,HE-RE2 Hf_(2)O_(7)demonstrates a more sluggish grain growth rate than Gd2 Hf_(2)O_(7)at 1200℃,suggesting better high-temperature stability.The linear thermal expansion coefficient of HE-RE2 Hf_(2)O_(7)is 10.7×10-6 K-1 at 298–1273 K.In general,it provides a new strategy for the design of the next advanced nuclear engineering materials.展开更多
基金supported by the National Science Foundation of China (6097406260972119)the Chinese Ministry of Science and Intergovernmental Cooperation Project(2009DFA12870)
文摘The consensus problem of the distributed attitude synchronization in the spacecraft formation flying is considered.Firstly,the attitude dynamics of a rigid body spacecraft is described by modified Rodriguez parameters（MRPs）.Then global stable distributed cooperative attitude control laws are proposed for different cases.In the first case,the control law guarantees the state consensus during the attitude synchronization.In the second case,the control law ensures both the attitudes synchronizing to a desired constant attitude and the angular velocities converging at zero.In the third case,an attitude consensus control law with bounded control input is proposed.Finally,the effectiveness and validity of the control laws are demonstrated by simulations of six rigid bodies formation flying.
基金supported by the Lingchuang Research Project of China National Nuclear Corporation,the National Key Research and Development Program of China(No.2022YFB3504302)the key core technology research project in Beicang District,Ningbo(Grant No.2021BLG009)+4 种基金the key deployment project of the Chinese Academy of Sciences(Grant No.ZDRW-CN-2021-3)the Fujian Provincial Natural Fund Project(Grant No.2021J05101)the Young Elite Scientists Sponsorship Program by CAST(Grant No.2021QNRC001)the independent deployment project of Ganjiang Innovation Research Institute of Chinese Academy of Sciences(Grant No.E055A002)In addition,thanks for the assistance of Jinchi Huang from the School of Energy,Xiamen University for the ion irradiation experiment.
文摘Nuclear engineering materials are required to possess outstanding extreme environmental tolerance and irradiation resistance.A promising novel pyrochlore-type of(Sm_(0.2)Eu_(0.2)Gd_(0.2)Dy_(0.2)Er_(0.2))2 Hf_(2)O_(7)high-entropy ceramic(HE-RE2 Hf_(2)O_(7))for control rod was prepared by solid-state reaction method.The ion irradiation of HE-RE_(2) Hf_(2)O_(7)with 400 keV Kr+at 400℃was investigated using a 400 kV ion implanter and compared with single-component pyrochlore Gd2 Hf_(2)O_(7)to evaluate the irradiation resistance.For HE-RE2 Hf_(2)O_(7),the phase transition from pyrochlore to defective fluorite is revealed after irradiation at 60 dpa.After irradiation at 120 dpa,it maintained crystalline,which is comparable to Gd2 Hf_(2)O_(7)but superior to the titanate pyrochlores previously studied.Moreover,the lattice expansion of HE-RE2 Hf_(2)O_(7)(_(0.2)2%)is much lower than that of Gd2 Hf_(2)O_(7)(0.62%),indicating excellent irradiation damage resistance.Nanoindentation tests displayed an irradiation-induced increase in hardness and a decrease in elastic modulus by about 2.6%.Irradiation-induced segregation of elements is observed on the surface of irradiated samples.In addition,HE-RE2 Hf_(2)O_(7)demonstrates a more sluggish grain growth rate than Gd2 Hf_(2)O_(7)at 1200℃,suggesting better high-temperature stability.The linear thermal expansion coefficient of HE-RE2 Hf_(2)O_(7)is 10.7×10-6 K-1 at 298–1273 K.In general,it provides a new strategy for the design of the next advanced nuclear engineering materials.
