This paper presents a scheme of fault diagnosis for flexible satellites during orbit maneuver. The main contribution of the paper is related to the design of the nonlinear input observer which can avoid false alarm ar...This paper presents a scheme of fault diagnosis for flexible satellites during orbit maneuver. The main contribution of the paper is related to the design of the nonlinear input observer which can avoid false alarm arising from the disturbance from orbit control force. The effects of orbit control force on the fault diagnosis system for satellite attitude control systems, including the disturbing torque caused by the misalignments and the model uncertainty caused by the fuel consumed, are discussed, where standard Lu- enberger observer cannot work well. Then the nonlinear unknown input observer is proposed to decouple faults from disturbance, Besides, a linear matrix inequality approach is adopted to reduce the effect of nonlinear part and model uncertainties on the observer. The numerical and semi-physical simulation demonstrates the effectiveness of the proposed observer for the fault diagnosis system of the satellite during orbit maneuver.展开更多
为探究双组元空间发动机内自燃推进剂喷雾、燃烧和传热特性,首先对现有MMH/N_(2)O_(4)(甲基肼/四氧化二氮)详细燃烧反应机理进行适当简化,提出适用于三维模拟的MMH/N_(2)O_(4)化学反应动力学模型,并在不同工况下对简化机理的准确性进行...为探究双组元空间发动机内自燃推进剂喷雾、燃烧和传热特性,首先对现有MMH/N_(2)O_(4)(甲基肼/四氧化二氮)详细燃烧反应机理进行适当简化,提出适用于三维模拟的MMH/N_(2)O_(4)化学反应动力学模型,并在不同工况下对简化机理的准确性进行了验证;随后,采用流体体积(volume of fluid,VOF)模型对空间发动机内MMH/N_(2)O_(4)射流撞击雾化过程进行了非稳态模拟,并重点分析了直流互击作用下扇形液膜的形成和演变规律;基于以上化学反应机理及液雾分布模拟结果,在欧拉-拉格朗日体系下构建了离散液滴初始分布,并结合部分搅拌反应器湍流燃烧模型,开展了空间发动机内MMH/N_(2)O_(4)喷雾燃烧及流固耦合传热过程的模拟研究.结果表明,空间发动机内推进剂湍流喷射雾化燃烧过程对壁面冷却液膜的形成和发展具有重要影响,冷却液膜主要出现在燃烧室直线段,在高温燃气与固体域之间建立了一个明显的温度缓冲层,从而实现对发动机壁温的保护.展开更多
This paper investigates a distributed coordination control scheme using an adaptive terminal sliding mode for formation flying spacecraft with coupled attitude and translational dynamics. In order to overcome the sing...This paper investigates a distributed coordination control scheme using an adaptive terminal sliding mode for formation flying spacecraft with coupled attitude and translational dynamics. In order to overcome the singularity of the traditional fast terminal sliding manifold, a novel fast terminal sliding manifold is given. And then, based on the adaptive control method, a continuous robust coordinated controller is designed to compensate external disturbances and to alleviate the chattering phenomenon. The theoretical analysis shows that the coordinated controller can guarantee the finite-time stability of the overall closed-loop system through local information exchange, and numerical simulations also demonstrate its effectiveness.展开更多
基金supported by the National Natural Science Foundation of China (61034005)the Natural Science Foundation of Jiangsu Province (BK2010072)
文摘This paper presents a scheme of fault diagnosis for flexible satellites during orbit maneuver. The main contribution of the paper is related to the design of the nonlinear input observer which can avoid false alarm arising from the disturbance from orbit control force. The effects of orbit control force on the fault diagnosis system for satellite attitude control systems, including the disturbing torque caused by the misalignments and the model uncertainty caused by the fuel consumed, are discussed, where standard Lu- enberger observer cannot work well. Then the nonlinear unknown input observer is proposed to decouple faults from disturbance, Besides, a linear matrix inequality approach is adopted to reduce the effect of nonlinear part and model uncertainties on the observer. The numerical and semi-physical simulation demonstrates the effectiveness of the proposed observer for the fault diagnosis system of the satellite during orbit maneuver.
文摘为探究双组元空间发动机内自燃推进剂喷雾、燃烧和传热特性,首先对现有MMH/N_(2)O_(4)(甲基肼/四氧化二氮)详细燃烧反应机理进行适当简化,提出适用于三维模拟的MMH/N_(2)O_(4)化学反应动力学模型,并在不同工况下对简化机理的准确性进行了验证;随后,采用流体体积(volume of fluid,VOF)模型对空间发动机内MMH/N_(2)O_(4)射流撞击雾化过程进行了非稳态模拟,并重点分析了直流互击作用下扇形液膜的形成和演变规律;基于以上化学反应机理及液雾分布模拟结果,在欧拉-拉格朗日体系下构建了离散液滴初始分布,并结合部分搅拌反应器湍流燃烧模型,开展了空间发动机内MMH/N_(2)O_(4)喷雾燃烧及流固耦合传热过程的模拟研究.结果表明,空间发动机内推进剂湍流喷射雾化燃烧过程对壁面冷却液膜的形成和发展具有重要影响,冷却液膜主要出现在燃烧室直线段,在高温燃气与固体域之间建立了一个明显的温度缓冲层,从而实现对发动机壁温的保护.
基金supported by the National Natural Science Foundation of China(61174037)the National High Technology Research and Development Program of China(863 Program)(2012AA120602CAST20120602)
文摘This paper investigates a distributed coordination control scheme using an adaptive terminal sliding mode for formation flying spacecraft with coupled attitude and translational dynamics. In order to overcome the singularity of the traditional fast terminal sliding manifold, a novel fast terminal sliding manifold is given. And then, based on the adaptive control method, a continuous robust coordinated controller is designed to compensate external disturbances and to alleviate the chattering phenomenon. The theoretical analysis shows that the coordinated controller can guarantee the finite-time stability of the overall closed-loop system through local information exchange, and numerical simulations also demonstrate its effectiveness.
