卫星SAR载荷蓄电池充电器的建模分析与设计

随着现代商业卫星的发展，低成本、重量轻、多功能、高集成的微纳合成孔径雷达(SAR)卫星迎来加速发展的阶段。由于SAR载荷工作时间短、峰值功率大的特点，需专门为SAR载荷配置一组高压载荷蓄电池，在相同电流下，可输出更大功率。针对高压载荷蓄电池恒流恒压充电的需求，提出采用推挽变换器的隔离升压充电器方案，搭建了推挽变换器的小信号模型，采用峰值电流控制的双环控制策略实现恒流恒压充电控制，最后在充电器样机上进行了实验验证。实验结果验证了分析的正确性与设计的有效性，可以满足SAR载荷蓄电池充电的要求。     

高温环境下角接触球轴承磨损寿命分析

针对高温环境下轴承材料性质和润滑状态变化，造成轴承磨损加剧，过早丧失精度的问题。首先开展高温环境下轴承用材料的摩擦磨损试验，获取材料的磨损系数。在此基础上，考虑温度、润滑、轴承材料属性等对轴承磨损性能的影响，建立高温角接触球轴承磨损模型，通过数值求解探讨工况参数和结构参数等对轴承磨损性能的影响，并评估轴承的磨损寿命。结果表明：对于高温轴承材料无磁合金GH05，在高温300 ℃摩擦状态下平均磨损系数为2.5×10^-7 mm²/N；随着载荷、转速、温度的增加，轴承内、外滚道的磨损率均不断增大，其中内圈磨损率大于外圈，内圈磨损特性决定着轴承的磨损寿命；载荷和转速是决定轴承磨损寿命的主要因素，轴承主结构参数对磨损寿命具有重要影响，通过结构优化可提高轴承磨损寿命。     

船舶混合动力系统与智能能量管理控制策略研究进展

开发新型动力系统和智能控制策略是解决节能减排的重要技术方向。本文首先对混合动力系统的配置和拓扑结构进行归类与比较，对控制策略中涉及的智能算法进行归纳和总结；其次，对新型动力船舶在动力系统和控制算法使用情况进行阐释；最后，从不同角度对混合动力系统以及能量管理系统的发展趋势进行展望，为绿色船舶混合动力系统开发以及能量管理系统的研发提供了参考依据。     

基于Q-Learning的深度神经网络自适应退避策略

针对无人机自组织网络,结合Q-Learning和深度神经网络,提出一种自适应退避策略,以提高基于竞争的MAC协议通信性能.以Matlab为仿真平台,仿真比较了自适应退避策略与二进制指数退避策略的性能.     

基于改进的SqueezeNet直升机滚动轴承故障诊断

针对现有基于卷积神经网络的故障诊断方法存在模型参数量和计算量大的问题，提出一种改进的SqueezeNet模型应用于直升机滚动轴承故障诊断。该模型借鉴VGG16模型的思想，在经典的SqueezeNet基础上，采用3个3×3卷积核代替1个7×7卷积核，实现了在相同感知野条件下增加网络容量、增强非线性、减少网络参数量，采用卷积层、池化层和Fire模块、池化层两大结构交替的方式组成模型特征提取层，在保障特征提取能力的情况下，进一步减少了网络参数量。通过轴承数据开展模型故障诊断实验，结果表明该模型诊断精度达到99.65%，与传统卷积神经网络及经典的SqueezeNet模型相比诊断精度相当，而计算量与参数量最大缩减约6倍和36倍。     

A hybrid chemical modification strategy for monocrystalline silicon micro-grinding: Experimental investigation and synergistic mechanism

For high performance manufacturing of micro parts and features, a hybrid chemical modification strategy is proposed to decrease critical energy barrier of mechanical removal of hard and brittle crystal material by refining localized machining condition. The strategy, namely UV-light and IR-laser hybrid chemical modification (UVIR-CM) strategy, includes two steps, an ultraviolet light (UV-light) catalytic advanced oxidation and an infrared laser (IR-laser) assisted selective modification based on Fenton liquid–solid reaction for monocrystalline silicon. The modification effects of UVIR-CM strategy were investigated by surface morphology micro-observation, cross-section transmission electron microscopy (TEM) observation, Raman spectroscopy analysis and nanoindentation test. Experimental results demonstrated that varied degrees of laser texturing appeared on different strategy samples’ IR-laser scanned area. And the IR-laser thermal damage has been successfully inhibited due to the refraction and reflection of energy by bubbles in liquid medium. But for the UVIR-CM strategy, a uniform and amorphous silicate layer is detected in a certain boundary. The UV-light promotes oxidation cycle ability of the chemical solution and ensures sufficient oxide modified layer for subsequent step. Attributing to synergism of photochemical, photothermal and kinetic effects induced by IR-laser, the modified layer displays layered structure with about 600 nm thickness, (2.7 ± 0.60) GPa nanohardness, and (93.7 ± 22.9) GPa indentation modulus. And the layered structure is amorphous layer, nanocrystal and micro-twins layer from the surface to the interior of sample. Consequently, it reveals that the subsequent mechanical removal will become easy due to decreasing energy barrier of monocrystalline silicon in selective area. Meanwhile, its original excellent mechanical properties also are maintained under a certain depth. The results contribute to develop a novel combined micro-machining technology to achieve collaborative manufacturing of structure shape and surface integrity for micro parts and feature.     

An innovative constraining ring rolling process for manufacturing conical rings with thin sterna and high ribs

Conical rings with thin sterna and high ribs (CRTSHR) are key bearing-load parts of aerospace equipment, which are required to be manufactured with high performance and efficiency. Traditional ring rolling is the most preferred method for manufacturing high-performance ring parts, but it can hardly achieve the forming of CRTSHR due to the extreme geometry of CRTSHR. To solve this difficulty, an innovative constraining ring rolling process (CRR) is proposed in this paper to manufacture CRTSHR. To evaluate the proposed CRR and reveal its deformation behaviors, a thermomechanical coupled FE model for CRR of CRTSHR is established. Then, the experiment for CRR of CRTSHR is performed on a modified ring rolling machine, which proves that CRR of CRTSHR is feasible and the established FE model is reliable. Based on the reliable FE model, the metal flow mode in deformed CRTSHR is analyzed, and the deformation characteristics such as the stress state, strain distribution and the evolution of power parameters in CRR of CRTSHR are revealed. Finally, the influences of key parameters such as the friction factor between ring and molds, the diameter of idle roll and the feed velocity of idle roll on CRR of CRTSHR are investigated by FE simulation.     

Transition control of a tail-sitter unmanned aerial vehicle with L1 neural network adaptive control

The main task of this work is to design a control system for a small tail-sitter Unmanned Aerial Vehicle(UAV) during the transition process. Although reasonable control performance can be obtained through a well-tuned single PID or cascade PID control architecture under nominal conditions, large or fast time-varying disturbances and a wide range of changes in the equilibrium point bring nonlinear characteristics to the transition control during the transition process, which leads to control prec...     

基于低轨全覆盖卫星星座的反向缝建链策略

低轨卫星星座的拓扑设计是天地一体化网络部署中较为重要的一环。在低轨卫星网络中，如何设计星座拓扑来提升卫星网络的稳定性与传输性能，是亟待解决的问题。提出一种基于轨道覆盖带方法的低轨持续全覆盖卫星星座设计方法，通过该方法构建低轨卫星星座，满足覆盖性能，可有效减少卫星切换的次数。基于构建的星座拓扑，制定邻轨k最近邻星的反向缝建链策略，优化设计链路长度和链路持续时长，获取网络传输性能与稳定性的平衡。仿真结果表明:通过上述方法设计出的星座，在满足对地持续全覆盖性能的情况下，相较于轨道覆盖带方法切换次数减少10%;邻轨k最近邻星策略相较于最短建链策略，拓扑稳定性能提升79.62%，使网络拓扑稳定性与传输性能达到更优的平衡。     

On a plastic instability criterion for ultra-large radial-axial ring rolling process with four guide rolls

A dynamic mechanical model is proposed to describe the complexing actions of all the rolls on the ring during the ultra-large radial-axial ring rolling(RARR) process with four guide rolls. Based on the model, the calculation models for bending moment and normal stress at any section of the ring are deduced by force method. If the maximum section bending normal stress exceeds the yield stress of the ring materials, the ring will be distorted thus leading to the instability of the RARR process. Ac...