摘要：Various micro-mechanical and micro-structural influences on fatigue crack growth resistance of the material have been investigated over the years. It is widely recognized that resistance to fatigue crack growth can be differentiated into ‘intrinsic＇ and ‘extrinsic＇. The separation of intrinsic and extrinsic crack growth resistance has constituted a major theme of fatigue research in the last 30 years, with the concept of crack closure or crack tip shielding being used to rationalize a wide range of micro-structural and mechanical influences on fatigue crack growth behavior. An accurately quantitative understanding of intrinsic and extrinsic effects on crack growth is essential to directed alloy design for improved fatigue resistance, and/or improved structural service life. This paper presents a compliance-based crack closure measurement method and a multi-mechanism based analytical model for the separation of intrinsic and extrinsic material fatigue resistance, with application in characterizing the fatigue performance of two high strength damage tolerant airframe AI alloys.

摘要：为提高系统在大扰动下的响应的快速性和鲁棒性,针对纯电动汽车上的DC-DC变换器,设计了一种基于prescribed convergence law(PCL)算法的鲁棒滑模控制器。以Buck变换器为例,验证该滑模算法在有限时间内的收敛性,并与PI和传统滑模控制效果进行对比。结果表明:1无扰动时,PCL滑模算法稳态精度高,调节时间短,输出纹波小;2输入电压和负载电阻大扰动时,PCL滑模算法响应速度更快,鲁棒性更强。

摘要：燃料电池作为分布式信息能源系统中的重要能量发生装置,在能源网络安全中发挥着重要作用。但由于燃料电池输出电压较低且随负载波动范围较大,需采用高增益DC-DC变换器实现后级负载的安全稳定工作。该文以一款输出串联Boost变换器为研究对象,为提高功率变换器抵抗内外干扰的能力,采用微分平坦控制理论设计电压外环和电流内环。此外,利用扰动观测器对系统寄生参数进行等效估计,提高系统抵抗内部参数摄动的能力;同时实时估计出负载电流和输入电压,减少传感器使用数量以降低系统成本。最后,通过1个240W的实验样机对所提出的控制器性能进行验证。

摘要：针对传统Boost变换器电压增益低、开关器件电压应力大不适用于燃料电池/光伏发电系统的问题,提出一种新型非隔离高增益DC/DC变换器。该拓扑采用浮地并联结构,主电路上下对称,并结合开关电容单元有效提高了变换器的电压增益;此外变换器还具有开关器件低电压应力、低电流应力、电感电流自动均流的优点,多电感并联的结构则有利于提升变换器的功率等级。详细分析了所提变换器的工作原理与稳态特性,并设计了相应的高阶滑模控制策略以提高变换器的鲁棒性。最后,通过仿真与试验验证了理论分析的正确性。