In a structural system reliability analysis that lacks probabilistic information, calculating the numerical characteristics of the state functions, especially the first four moments of the state functions, is necessar...In a structural system reliability analysis that lacks probabilistic information, calculating the numerical characteristics of the state functions, especially the first four moments of the state functions, is necessary. Based on that, the structural system reliability is analyzed with a fourth-order moment method. The reliability sensitivity is required to conduct the differential operation of the numerical characteristic functions. A reliability sensitivity analysis formula is then derived in combination with the relation of the differential operation. Based on the matrix theory and Kronecker algebra, this paper systematically derives a matrix expression of the first four moments of the state functions, and establishes the matrix relation between the first four moments of the state functions and those of the basic random variables. On this basis, a differential operation formula of the first four moments of the state functions is further derived against the first four moments of the basic random variables. The vector relation between the state functions and the multidimensional basic random variables is described by means of the matrix operation to extend the operation method. Finally, a concise and intuitive formula is obtained to explore the inherent essential relation between the numerical characteristics of the state functions and those of the basic random variables, leading to a universal equation for the two kinds of numerical characteristics.展开更多
本文基于LLC谐振变换器设计LED驱动器,实现变换器软开关,开关损耗低,驱动器效率高。谐振变换器小信号建模时平均概念被破坏,建模谐振变换器模型使用传统方法时,具有无法得到变换器解析解、阶数高等缺点,导致控制系统难以设计。本文基于...本文基于LLC谐振变换器设计LED驱动器,实现变换器软开关,开关损耗低,驱动器效率高。谐振变换器小信号建模时平均概念被破坏,建模谐振变换器模型使用传统方法时,具有无法得到变换器解析解、阶数高等缺点,导致控制系统难以设计。本文基于美国弗吉尼亚理工大学Fred C. Lee团队提出的小信号模型设计一种LLC谐振变换器分段式PID控制算法,研究了LLC谐振变换器工作原理,基于函数描述法建立等效电路,以开关频率和谐振频率的关系作为分段控制点,得出了各分段传递函数解析式。最后,设计并制作了一个5 W的LED驱动器实验样机,进行了验证分析,实验结果表明所设计的分段式PID控制器对LLC谐振变换器的LED驱动器具有较好控制性能。展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.51135003 and U1234208)the Major State Basic Research Development Program of China(973 Program)(No.2014CB046303)
文摘In a structural system reliability analysis that lacks probabilistic information, calculating the numerical characteristics of the state functions, especially the first four moments of the state functions, is necessary. Based on that, the structural system reliability is analyzed with a fourth-order moment method. The reliability sensitivity is required to conduct the differential operation of the numerical characteristic functions. A reliability sensitivity analysis formula is then derived in combination with the relation of the differential operation. Based on the matrix theory and Kronecker algebra, this paper systematically derives a matrix expression of the first four moments of the state functions, and establishes the matrix relation between the first four moments of the state functions and those of the basic random variables. On this basis, a differential operation formula of the first four moments of the state functions is further derived against the first four moments of the basic random variables. The vector relation between the state functions and the multidimensional basic random variables is described by means of the matrix operation to extend the operation method. Finally, a concise and intuitive formula is obtained to explore the inherent essential relation between the numerical characteristics of the state functions and those of the basic random variables, leading to a universal equation for the two kinds of numerical characteristics.
文摘本文基于LLC谐振变换器设计LED驱动器,实现变换器软开关,开关损耗低,驱动器效率高。谐振变换器小信号建模时平均概念被破坏,建模谐振变换器模型使用传统方法时,具有无法得到变换器解析解、阶数高等缺点,导致控制系统难以设计。本文基于美国弗吉尼亚理工大学Fred C. Lee团队提出的小信号模型设计一种LLC谐振变换器分段式PID控制算法,研究了LLC谐振变换器工作原理,基于函数描述法建立等效电路,以开关频率和谐振频率的关系作为分段控制点,得出了各分段传递函数解析式。最后,设计并制作了一个5 W的LED驱动器实验样机,进行了验证分析,实验结果表明所设计的分段式PID控制器对LLC谐振变换器的LED驱动器具有较好控制性能。
