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21.
为研究高精度的液压缸位置跟踪控制问题,设计了高速开关阀和换向阀组合控制液压缸的结构方案,并通过实验分析了高速开关阀的静态流量特性。建立了液压缸的连续可微摩擦模型,利用粒子群优化算法对其参数进行辨识。建立了系统的非线性数学模型,基于非连续参数映射和反步法设计了直接自适应鲁棒控制器,通过参数在线自适应调节来更新估计值和鲁棒反馈项支配参数不确定性,实验结果表明:在跟踪幅值为5mm,频率为0.4Hz的正弦信号时,最后一个周期的最大跟踪误差、平均跟踪误差及其标准差分别为0.638、0.25mm和0.405mm,与传统PID控制器相比,控制精度显著提升,旨在为实现高精度的数字阀控位置伺服技术提供有价值的参考。 相似文献
22.
为有效检测热障涂层(TBCs)表面裂纹,进行了热障涂层表面裂纹水浸超声检测技术的应用研究。以常用的大气等离子喷涂(APS)热障涂层作为试验材料,采用水浸超声检测回波声程差和C扫描图像对不同深度、宽度和长度的热障涂层表面裂纹进行了表征。结果表明:热障涂层基体材料对热障涂层表面裂纹的检测效果无明显影响;通过优化检测参数和合理选用仪器探头,利用水浸超声方法可实现对热障涂层表面深度为0.1 mm、长度为2 mm裂纹的有效检测;水浸超声检测技术可以获得裂纹的长度、深度参数,是解决热障涂层表面裂纹检测问题的有效方法。 相似文献
23.
《中国航空学报》2020,33(2):391-406
A thermal-solid-liquid complex operational environment induces structural interface developing a typical coupling sliding/impact wear behavior. It results in contact damage until systems fail, which may cause significant economic losses and catastrophic consequences. The key point of solving this problem is to reveal the coupling damage mechanism of the sliding/impact behavior in typical systems and life characterization under a complicate evolving environment. This has been a hot topic in the area of mechanical reliability. The main work in this paper can be concluded as follows. Firstly, the main industries in which the “sliding/impact behavior” takes place have been introduced. Then, existing studies on the wear mechanism and degree analysis are presented, which includes surface morphology analysis, wear debris analysis, and wear degree measurement. Meanwhile, existing problems in theoretical modeling and experiments in current research are summarized, so as to point out a bright direction for future research on wear prediction. They include interface contact modeling, mathematic coupling mechanism modeling, wear equation establishment, and wear life characterization, which can provide some new ideas for improving the existing studies on the sliding/impact wear behavior. 相似文献
24.
对于翼型气动隐身设计问题,设计变量的配置对设计结果影响很大,而简单地增加设计变量不能保证得到理想的结果。提出一种适用于代理模型全局优化的自适应参数化方法:利用全局敏感性分析方法——基本效应法,得到设计空间关于目标函数的敏感区域信息,并以此为根据增加设计变量;利用节点插入算法将低维样本在高维空间内进行重构,避免了重新取样的工作量。相对于传统固定设计空间维度方法,自适应参数化方法在设计空间的敏感区域扩展维度,能够更加精准地描述外形并反映目标的变化趋势。通过飞翼布局翼型的气动隐身优化算例,证实自适应参数化方法可以大幅提高优化设计质量和效率。 相似文献
25.
《中国航空学报》2020,33(3):792-804
SiCp/Al composites have excellent comprehensive properties and have been widely used in aerospace, automotive industry and other fields. Due to the huge difference in performance between SiC particles and matrix alloys, traditional fusion welding methods are difficult to meet the join requirements of SiCp/Al composites. Friction stir joining (friction stir welding), as a solid phase joining process, has been proved to be a new technology with fine prospect in joining SiCp/Al composites compared with fusion welding process. Although some progress has been made in recent years, there are still full of challenges. In this paper, the research status of friction stir joining of SiCp/Al composites in recent years is expatiated, including the weldability of SiCp/Al composites, the macrostructure and the microstructure of joints, mechanical properties of joints, and tool wear and monitoring. Furthermore, the existing challenges of friction stir joining of SiCp/Al composites are summarized and the future development directions are prospected. 相似文献
26.
葛宁 《南京航空航天大学学报》2018,50(2):145-156
首先,对美国20世纪70年代以来各时期涡轴发动机发展规划及其性能演变过程进行了梳理,并分析了不同循环类型及循环参数的选择,进行了性能统计分析。然后,介绍了直升机/发动机一体化设计理论的基础与方法。最后本文提出新一代超低排放涡轴发动机的概念,指出降低总耗油量的同时提高功重比,才能实现超低排放。 相似文献
27.
Yeerang Lim Youeyun Jung Hyochoong Bang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(10):2661-2672
This study presents model predictive formation control based on an eccentricity/inclination vector separation strategy. Alternative collision avoidance can be accomplished by using eccentricity/inclination vectors and adding a simple goal function term for optimization process. Real-time control is also achievable with model predictive controller based on convex formulation. Constraint-tightening approach is address as well improve robustness of the controller, and simulation results are presented to verify performance enhancement for the proposed approach. 相似文献
28.
29.
针对拦截高速目标的作战特点,分析了比例导引(PN)与反比例导引(RPN)的捕获区。首先,通过分析拦截弹与目标的相对运动关系,推导得到了顺轨和逆轨的零控拦截条件,此条件由目标和拦截弹的速度前置角以及二者速度比确定;其次,以拦截弹和目标速度前置角为坐标系,推导得到了PN以及RPN捕获区以及各自导航比设置范围。PN的捕获区由逆轨零控拦截条件以及与其相切且斜率为1/(N-1)的两条直线构成,RPN的捕获区由顺轨零控拦截条件以及与其相切且斜率为1/(-N-1)的两条直线构成;然后,利用函数对称性将PN与RPN捕获区转换到同一坐标区间,得到了相同条件下RPN捕获区要大于PN捕获区的结论;最后,开展了四种情形下的仿真,验证了本文捕获区分析的合理性及有效性。 相似文献
30.
《中国航空学报》2021,34(4):241-252
Particle-tool interactions, which govern the synergetic deformation of SiC particle reinforced Al matrix composites under mechanical machining, strongly depend on the geometry of particle position residing on cutting path. In the present work, we investigate the influence of cutting path on the machinability of a SiCp/Al composite in multi-step ultra-precision diamond cutting by combining finite element simulations with experimental observations and characterization. Be consistent with experimentally characterized microstructures, the simulated SiCp/Al composite is considered to be composed of randomly distributed polygonally-shaped SiC particles with a volume fraction of 25vol%. A multi-step cutting strategy with depths of cut ranging from 2 to 10 μm is adopted to achieve an ultimate depth of cut of 10 μm. Intrinsic material parameters and extrinsic cutting conditions utilized in finite element simulations of SiCp/Al cutting are consistent with those used in corresponding experiments. Simulation results reveal different particle-tool interactions and failure modes of SiC particles, as well as their correlations with machining force evolution, residual stress distribution and machined surface topography. A detailed comparison between numerical simulation results and experimental data of multi-step diamond cutting of SiCp/Al composite reveals a substantial impact of the number of cutting steps on particle-tool interactions and machined surface quality. These findings provide guidelines for achieving high surface finish of SiCp/Al composites by ultra-precision diamond cutting. 相似文献