用DFT计算立方氮化硼的状态方程及体积模量

立方氮化硼的高硬度起因于硼原子和氮原子形成的B-N sp3键很强。为获得对B-Nsp3键的定量认识,用DFT计算了它在常压到百万大气压(0-100GPa)范围内的状态方程(EOS)及体积模量。采用保模赝势模拟硼原子和氮原子,分别根据GGA、LDA进行相关计算。计算结果表明,立方氮化硼的体积模量B0为372.8±2.2GPa~395.8±0.2GPa,GGA对B-N sp3键的计算偏弱。     

导弹复合控制系统的模糊逻辑控制分配

针对空空导弹复合控制系统中的控制分配问题,提出了一种模糊逻辑控制分配算法。采用动态面控制方法设计了复合控制量的控制律。在设计过程中,利用扩张状态观测器估计汇总不确定项,并采用光滑二阶滑模控制算法设计了控制律,达到了提高鲁棒性和削弱抖振现象的目的。应用模糊逻辑控制分配算法将复合控制量分解为直接力控制指令和舵偏角控制指令。为了检验所设计的复合控制系统的控制效果,对采用基于模糊逻辑控制分配算法的复合控制系统和传统的气动力控制系统进行了对比仿真实验。仿真结果表明,所设计的复合控制系统具有更好的控制效果。     

ESO-based event-triggered attitude control of spacecraft with unknown actuator faults

An event-triggered control strategy based on extended state observer (ESO) is proposed for the attitude tracking problem of small plug-and-play spacecraft with uncertain inertia parameters, external disturbances, and actuator faults. A simplified controller is developed based on the angular velocity and the general disturbances estimated by the provided ESO using the information of the system inputs and the angular velocities. In the designed event-triggered sampling mechanism, a state-dependent event-triggered strategy determines the triggering instant of the controller to reduce the frequency of information transmission between the controller and the actuator. In comparison with the previous literature, this paper considers uncertain inertia parameters, external disturbances, and actuator faults as general disturbances estimated by ESO, especially for the actuator faults. The inputs of ESO are the error of the angular velocities, which can simplify the controller design. Moreover, the designed ESO can effectively attenuate the influence of measured noises generated by the gyroscopes. The proposed event-triggered policy balances the performance of event-triggering and the control stability performance, which reduces the final state convergence regions without increasing more triggering times compared to existing studies. Furthermore, the investigated policy achieves Zeno-free triggering. Numerical simulations verify theoretical results.     

一种基于链路状态的舱内环境自适应干扰消除算法

针对舱内无线光传输系统多种干扰问题,比如多径损耗和突发干扰等,提出一种基于链路状态的自适应干扰消除技术,该方法分析舱内链路状态,完成链路状态估计,采用环境自适应的变遗忘因子RLS（recursive least squares）算法,针对不同链路状态采取差异化的干扰消除策略,以提高舱内通信质量。仿真结果表明：该算法在尽力避免增加算法复杂度的条件下,相对于传统固定遗忘因子算法,在平稳状态下优先保证传输的误码性能,在链路状态变化时具有更好的收敛性能,灵活适应了舱内多种传输情况。     

A novel approach of testability modeling and analysis for PHM systems based on failure evolution mechanism

Prognostics and health management (PHM) significantly improves system availability and reliability, and reduces the cost of system operations. Design for testability (DFT) developed concurrently with system design is an important way to improve PHM capability. Testability modeling and analysis are the foundation of DFT. This paper proposes a novel approach of testability modeling and analysis based on failure evolution mechanisms. At the component level, the fault progression-related information of each unit under test (UUT) in a system is obtained by means of failure modes, evolution mechanisms, effects and criticality analysis (FMEMECA), and then the failure-symptom dependency can be generated. At the system level, the dynamic attributes of UUTs are assigned by using the bond graph methodology, and then the symptom-test dependency can be obtained by means of the functional flow method. Based on the failure-symptom and symptom-test dependencies, testability analysis for PHM systems can be realized. A shunt motor is used to verify the application of the approach proposed in this paper. Experimental results show that this approach is able to be applied to testability modeling and analysis for PHM systems very well, and the analysis results can provide a guide for engineers to design for testability in order to improve PHM performance.     

基于增广观测器的非线性系统执行器故障诊断

针对一类满足李普希茨条件的非线性系统,提出了一种新的执行器故障诊断方法。将执行器故障作为增广状态向量的一部分构造一个增广系统,然后利用线性矩阵不等式方法设计一个增广状态观测器,能够同时获得原系统的状态和执行器故障的渐近估计。利用李亚普诺夫理论分析了增广状态观测器的稳定性和收敛性。最后,将所提出的方法用于卫星姿态控制系统执行器的故障诊断,仿真结果验证了该方法的有效性。     

考虑人及组织因素的航天工程项目风险分析模型

针对人及组织因素是造成航天工程项目风险的重要原因,在揭示了人及组织因素产生航天工程项目风险的机理基础上,构建了考虑人及组织因素的航天工程项目风险分析模型。模型首先评价人及组织因素对航天工程元器件建造工作质量的影响,接着测度工作质量与不同缺陷类型之间的一致性概率,并应用Poisson分布计算缺陷严重性,最后根据贝叶斯定理对元器件先验失效率进行修正,通过一个经过数据处理的航天工程项目对所构建的模型和方法进行了验证。     

SpaceWire CODEC的容错设计和实现

对SpaceWire CODEC进行容错设计是提高其可靠性的重要途径.分析SpaceWire协议的容错性能,介绍SpaceWire CODEC的容错设计方法,通过故障汇入和仿真验证了容错设计的有效性.