基于矢量观测的航天器分段信息融合定姿方法

针对基于MEMS(微机电系统)陀螺和CMOS APS星敏感器的集成惯性/星光姿态确定系统的低精度特点,研究了适用于该定姿系统的基于矢量观测的定姿算法.对于陀螺/星敏感器这种配置模式,有EKF(Extended Kalman Filter)、QUEST、最优REQUEST等几种适用的定姿算法.针对EKF和最优REQUEST算法的不同特点并结合确定性算法QUEST,以四元数为姿态参数,将姿态估计的EKF方法分别与QUEST算法和最优REQUEST算法进行了融合,提出一种分段信息融合的姿态估计器:陀螺漂移估计误差较大时,将EKF与QUEST结合,快速估计出陀螺漂移.当陀螺漂移误差减小到一定程度,再切换为EKF与最优REQUEST算法融合的双重滤波器.仿真比较结果表明,这种分段信息融合的姿态估计器既可以估计姿态参数也可以估计陀螺漂移,并能达到很高的定姿精度.     

Neal-Smith时域PIO预测准则及应用

基于Neal-Smith频域准则,Neal-Smith时域准则(TDNS, Time Domain Neal-Smith criterion)是另一重要的固定翼飞机驾驶员诱发振荡(简称PIO)预测准则,其无需对人机系统的非线性进行任何假设和简化.以某机型为模型,采用TDNS,通过俯仰角闭环操纵误差信号与目标捕获时间之间的关系来同时预测I、II型驾驶员诱发振荡,同时分析了不同速率限制环节对预测结果的影响,基于误差信号的均方差及其二次偏导数,得到了TDNS准则一般计算方法及各个影响因素的关系.结果表明,TDNS准则的计算方法可行、直观、高效.     

Monotonicity-Preserving激波捕捉格式在湍流大尺度模拟中的评估

对高阶激波捕捉格式的性能进行了系统的测评,重点分析了Suresh和Huynh(1997)所提出的Monotonicity-Preserving格式的性能.结果表明Monotonicity-Preserving格式的性能显著优于原始WENO(Weighted Essentially Non-Oscillatory) 格式,和改进型WENO格式相当.对格式的分析进一步表明,迎风型的激波捕捉格式在湍流模拟方面的性能都不及高阶中心格式,其原因归结为激波捕捉格式所包含的线性和非线性耗散.因此,改进高阶激波捕捉格式的关键在于同时降低格式的线性耗散和非线性耗散,以提高格式对湍流脉动能量的保持和对小尺度脉动结构的捕捉能力.     

High-temperature tribological behaviors of a Cr-Si co-alloyed layer on TA15 alloy

A Cr-Si co-alloyed layer was successfully deposited on TA15 alloy by the double glow plasma surface technology to improve its poor wear resistance at elevated temperature.The microstructure,composition,and phase structure of the layer were investigated by SEM,EDS,and XRD.The tribological behaviors of the Cr-Si co-alloyed layer at 20 ℃ and 500 ℃ were analyzed in details.The results indicated that the friction coefficient and wear rate of the Cr-Si coalloyed layer at 20 ℃ and 500 ℃ were much lower than those of the substrate,which was due to higher hardness and superior elastic modulus.This layer may become an approach to effectively improving the wear resistance of TA15 alloy at elevated temperature.     

Performance simulation of high altitude scientific balloons

The design and operation of a high altitude scientific balloon requires adequate knowledge of the thermal characteristics of the balloon to make it safe and reliable. The thermal models and dynamic models of altitude scientific balloons are established in this paper. Based on the models, a simulation program is developed. The thermal performances of a super pressure balloon are simulated. The influence of film radiation property and clouds on balloon thermal behaviors is discussed in detail. The results are helpful for the design and operate of safe and reliable high altitude scientific balloons.     

隐式Runge-Kutta方法在非定常化学非平衡流动中的应用

推导了求解NS方程组的隐式龙格-库塔方法,并从稳定性、精度和效率三方面展开讨论。通过定常和非定常算例对该方法进行验算,分析表明该方法计算结果正确、稳定性好、精度高、效率高,适合求解大型复杂非定常化学非平衡流动。     

Start-up current adaptive control for sensorless high-speed brushless DC motors based on inverse system method and internal mode controller

The start-up current control of the high-speed brushless DC (HS-BLDC) motor is a chal-lenging research topic. To effectively control the start-up current of the sensorless HS-BLDC motor, an adaptive control method is proposed based on the adaptive neural network (ANN) inverse system and the two degrees of freedom (2-DOF) internal model controller (IMC). The HS-BLDC motor is identified by the online least squares support vector machine (OLS-SVM) algo-rithm to regulate the ANN inverse controller parameters in real time. A pseudo linear system is developed by introducing the constructed real-time inverse system into the original HS-BLDC motor system. Based on the characteristics of the pseudo linear system, an extra closed-loop feed-back control strategy based on the 2-DOF IMC is proposed to improve the transient response per-formance and enhance the stability of the control system. The simulation and experimental results show that the proposed control method is effective and perfect start-up current tracking perfor-mance is achieved.     

工业 S型热电偶1100℃以上温度点校准方法

越来越多的单位要求对工业S型热电偶1100℃以上温度点进行校准，但目前没有任何技术规范可供参考。本文就这一需求提供了三种解决方案，并对这三个方案的校准结果及不确定度进行对比分析，为计量机构根据客户的需求制定科学合理的校准方案提供参考。     

基于终端约束的一种速度大小控制方法

为了满足再入机动弹头对落速大小的要求,同时避免复杂的理想速度曲线的设计,提出了一种速度大小控制方案,即在弹头制导和控制系统能力范围内将减速运动规律分为两种不同的形式,并分别推导了系数的具体表达式进而得到了相应的减速指令,分析了采用空气舵对机动弹头的质心和姿态进行控制时的导引与减速指令所需总攻角的计算方法.仿真结果表明,采用该方案对机动目标进行打击时,不但落点精度能满足要求,而且速度大小控制精度也较高.     

电压变化时Boost PFC变换器的混沌和分叉现象

利用小信号模型对开关电源控制器进行设计过程中常出现混沌分叉等不稳定现象。以工程设计的角度,建立了平均电流型BoostPFC的精确电路模型,分析了系统中存在的非线性现象,结合非线性分叉和混沌理论对这类非线性现象进行了详细的分析和推导。