Underwater vehicles operating in complex ocean conditions present difficulties in determining accurate dynamic models. To guarantee robustness against parameter uncertainty, an adaptive controller for dive-plane contr...Underwater vehicles operating in complex ocean conditions present difficulties in determining accurate dynamic models. To guarantee robustness against parameter uncertainty, an adaptive controller for dive-plane control, based on Lyapunov theory and back-stepping techniques, was proposed. In the closed-loop system, asymptotic tracking of the reference depth and pitch angle trajectories was accomplished. Simulation results were presented which show effective dive-plane control in spite of the uncertainties in the system parameters.展开更多
This paper addresses the problem of synchronized path following of multiple homogenous underaetuated autonomous underwater vehicles （AUVs）. The dedicated control laws are categorized into two envelopes： One is stee...This paper addresses the problem of synchronized path following of multiple homogenous underaetuated autonomous underwater vehicles （AUVs）. The dedicated control laws are categorized into two envelopes： One is steering individual underwater vehicle to track along predefined path, and the other is ensuring tracked paths of multiple vehicles to be synchronized, by means of decentralized speed adaption under the constraints of multi-vehicle communication topology. With these two tasks formulation, geometric path following is built on Lyapunov theory and baekstepping techniques, while injecting helmsman behavior into classic individual path following control. Synchronization of path parameters are reached by using a mixture of tools from linear algebra, graph theory and nonlinear control theory. A simple but effective control design on direct inter-vehicle speed adaption with minimized communication variables, enables the multi-AUV systems to be synchronized and stabilized into an invariant manifold, and all speeds converge to desired assignments as a byproduct. Simulation results illustrate the performance of the synchronized path following control laws proposed.展开更多
A new kind of glass-ceramic phosphor, which contains crystalline phases with green emissions, is explored. The glassceramic is prepared through semi-melt-quenching procedure with a nominal composition of （Ca0.99Eu0.0...A new kind of glass-ceramic phosphor, which contains crystalline phases with green emissions, is explored. The glassceramic is prepared through semi-melt-quenching procedure with a nominal composition of （Ca0.99Eu0.01）3Si2O7. The greenemitting crystals are precipitated and identified to be β-Ca2SiO4： Eu2＋ which is responsible for 510 nm-peaked much broader band emissions holding at 1550 ℃ for half an hour. In terms of the available light scattering theory, the appearance of opaque is discussed by closely associating with size and morphology of luminous β-Ca2SiO4 crystalline phase in glass.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No.50909025/E091002
文摘Underwater vehicles operating in complex ocean conditions present difficulties in determining accurate dynamic models. To guarantee robustness against parameter uncertainty, an adaptive controller for dive-plane control, based on Lyapunov theory and back-stepping techniques, was proposed. In the closed-loop system, asymptotic tracking of the reference depth and pitch angle trajectories was accomplished. Simulation results were presented which show effective dive-plane control in spite of the uncertainties in the system parameters.
基金supported by the EU FP6 FreeSubNet project under Grant No.036186the National Science Foundation of China under Grant No.51079061+1 种基金the Key Laboratory of Education Ministry for Image Processing and Intelligent Control,Huazhong University of Science and Technology under Grant No. 200804supported by the European Marie Curie Fellowship
文摘This paper addresses the problem of synchronized path following of multiple homogenous underaetuated autonomous underwater vehicles （AUVs）. The dedicated control laws are categorized into two envelopes： One is steering individual underwater vehicle to track along predefined path, and the other is ensuring tracked paths of multiple vehicles to be synchronized, by means of decentralized speed adaption under the constraints of multi-vehicle communication topology. With these two tasks formulation, geometric path following is built on Lyapunov theory and baekstepping techniques, while injecting helmsman behavior into classic individual path following control. Synchronization of path parameters are reached by using a mixture of tools from linear algebra, graph theory and nonlinear control theory. A simple but effective control design on direct inter-vehicle speed adaption with minimized communication variables, enables the multi-AUV systems to be synchronized and stabilized into an invariant manifold, and all speeds converge to desired assignments as a byproduct. Simulation results illustrate the performance of the synchronized path following control laws proposed.
基金supported by the National Natural Science Foundation of China(Nos.50872091 and 21076161)the Key Discipline of Materials Physics and Chemistry of Tianjin(Nos.2006ZD30 and 10SYSYJC28100)
文摘A new kind of glass-ceramic phosphor, which contains crystalline phases with green emissions, is explored. The glassceramic is prepared through semi-melt-quenching procedure with a nominal composition of （Ca0.99Eu0.01）3Si2O7. The greenemitting crystals are precipitated and identified to be β-Ca2SiO4： Eu2＋ which is responsible for 510 nm-peaked much broader band emissions holding at 1550 ℃ for half an hour. In terms of the available light scattering theory, the appearance of opaque is discussed by closely associating with size and morphology of luminous β-Ca2SiO4 crystalline phase in glass.
