监测功率晶体管的V_(BE)实现过流保护的研究

监测 V_(BE)参数作为功率晶体管过流保护的取样信号是一种新方法。本文用实验验证了 V_(BE)在一定范围内是随 I_C 的增大而线性地增大的,其平均变化率不超过0.038V/A。根据此方法设计的保护电路用于单个晶体管时,也能对过流起到安全保护的作用,并用实验得到证明。     

Influence of measure-density on combustor characteristics

The apparatus of scan measurement was used to gather the temperature pattern at the combustor outlet,where the average working temperature of gas was about 1700Kand the maximum temperature was about 1 950K.Consequently,the measurement part was cooled by water or air.Usually,for intermittent measurement devices,the interval of circle angel could be changed to get a high-density temperature distribution.A continuous measurement manner was adopted to get point in circle.The angle between two measurepoints was 1.286°.The annular combustor outlet was about 40to 50mm in height,where 5or 6measure points were usually arranged.In this device,10measure points were arranged in a range of 45.5mm.Four thermocouples were arranged in circle to obtain 2 800measure-points of the temperature field in a single experiment.Data were drawn from the whole datasheet at intervals.Each group of data whose number decreased in turn,included temperature points of 2 800,1 400,700,and 350,respectively.Several groups of temperature distributions with different densities were established.Subsequently,data processing was conducted to calculate the main combustor characteristics,including arithmetic or integral average temperature,OTDF(overall temperature distribution factor)and RTDF(radial temperature distribution factor).It is found that the data from different groups with different measuring densities result in significant difference on the combustor characteristics.The veracity of temperature characteristics increases with the growing measure-density.     

Multi-coset angular sampling-based compressed sensing of blade tip-timing vibration signals under variable speeds

Blade Tip-Timing (BTT) has been regarded as a promising way of on-line blade vibration monitoring. But blind multi-band BTT vibration reconstruction is a big challenge under variable speeds and under-sampling. In order to deal with it, a novel Compressed Sensing (CS) method is proposed based on Multi-Coset Angular Sampling (MCAS) in this paper. First, multi-coset sampling scheme of BTT vibration signals is presented. Then the CS model of BTT vibration signals is derived in order domain. A sufficient condition of the number of BTT sensors is derived for perfect reconstruction and optimal placement of BTT sensors is determined by minimizing the condition number. In the end, numerical simulations are done to validate the proposed method and the performances of four reconstruction algorithms are compared, i.e., Orthogonal Matching Pursuit (OMP), Multiple Signal Classification (MUSIC), Basis Pursuit Denoising (BPDN) and Modified Focal Underdetermined System Solver (MFOCUSS). Influences of the sensor placement, the number of BTT sensors and measurement noises on the reconstruction performances are also testified. The results demonstrate that the proposed method is feasible and the overall performance of the BPDN algorithm is the best among the four algorithms. Also the reconstruction performance decreases with the accelerations of rotating speed.     

一种非规则采样航空时序数据异常检测方法

航天器遥测数据的实时异常检测对于航天任务具有重要意义。以往方法大都考虑规则采样且缺失率较低的时序数据,然而航空时序数据具有维度大、噪声多、缺失率高、采样间隔不规则等特点,因此异常检测任务较为困难。针对非规则采样且具有缺失值的多维航空时序数据提出非规则采样多维时序数据异常检测（IMAD）算法。首先,采用带有可训练迟滞项的门控循环单元（GRU-D）对缺失值和非规则采样的时序数据进行建模;然后,采用变分自编码器建立随机性模型,学习正常时序数据的分布,从而对噪声数据具有鲁棒性;最后,利用基于极值理论的自适应阈值确定法确定合适阈值进行异常检测。结果显示,在两个真实航空时序数据集上,IMAD具有超出当前最新异常检测算法的性能;多个实验表明,IMAD在缺失率、参数以及数据集变化时,能够维持较好的异常检测效果,具有较强的鲁棒性。     

基于小样本的试验系统可信度评估方法

针对小样本试验数据信息匮乏、难以利用概率统计方法进行可信度评估的问题,将重抽样方法与小样本区间估计方法相融合,提出了小样本试验系统新型可信度评估方法。利用重抽样理论,获取多个具有相同样本量的相似小样本。根据灰色系统理论,提出了改进的灰色置信度及置信区间的定义及计算方法。并在此基础上通过求公共区间的方式计算原小样本数据的灰色置信区间。该置信区间在相同的置信度下,区间宽度更窄,精度更高。通过算例仿真,验证了上述方法的合理性、有效性,对工程试验中的小样本数据系统评估提供了一定的方法指导。      

天文观测相机的视频处理电路的设计

在讨论传统的天文观测相机视频处理方式的基础上,设计了以高集成度的专用CCD视频信号处理芯片TDA8783为核心的相机视频处理电路方案.对所设计的视频处理电路进行了软硬件联调测试,仿真和实验的结果表明,电路系统运行稳定,噪声低,方案对后续观测相机系统的小型化具有较好的参考意义.     

用重要性抽样方法估计分组码同时纠错和检错时的性能

研究用重要性抽样仿真方法估计线性分组码同时纠错和检错时的不可检错误概率。从理论上得到了最佳偏置转移概率和仿真效率的表达式。对 (1 5,7) BCH码和 (2 3,12 ) Golay码的仿真表明,重要性抽样是一种非常有效的仿真方法。     

一种基于数字采样技术的电压波动测量系统CSCD

本文针对电能质量计量校准领域中电压波动参数的测量问题进行研究,通过比较现有电压波动信号的检测方法,结合数学模型分析,提出一种基于Agilent 3458A采样器的电压波动信号交流采样均方根值检测法。并搭建电压波动信号测量系统,通过实验,实现了测量电压波动频率范围可覆盖0.008Hz^40Hz,波动值范围为0.1%~30%。     

月面复杂地形表层采样可采点确定方法

表层采样是获取地外天体特性的重要手段,是目前原位探测与采样返回样品获取的重要方式。实施月球表层采样过程中,月面复杂地形将对大尺度采样器工作带来约束。结合一类大尺度表层采样器,分析了月面复杂地形的影响,提出了表层采样的可采样充分条件,构建了以可视区分区、分区延伸、局部平均法向量稀疏、基点包覆检测相结合的并行可采点确定方法。仿真结果表明,该方法可准确确定复杂地形下表层采样可采点,分区并行计算可有效提升可采点的确定效率。     

月面无人自主采样返回任务动力下降点确定及验证

动力下降点确定是实施月面软着陆的重要环节,是多系统间复杂迭代的过程,涉及轨道设计、制导律设计、着陆目标的采样区确定、着陆及起飞安全分析。其设计结果直接影响了最终着陆点的位置和着陆过程的着陆安全,也间接影响采样安全和采样工程目标的实现结果。针对嫦娥五号在实施月面软着陆前确定动力下降点的任务需求,提出了通过多次轨道控制与最优标称制导轨迹搜索联合控制策略的动力下降点确定方法。首先,根据月面无人自主采样返回任务设计总结了动力下降点确定原理和约束条件;然后,详细论述了月面无人自主采样返回任务软着陆过程动力下降点确定方法;最后,通过嫦娥五号在着陆前主要的几次轨控实施结果分析了其对动力下降点的影响,同时综合了着陆区地形分析及着陆、起飞安全性分析,对动力下降点进行确定并根据最终在轨飞行结果进行验证。验证结果表明,基于“逐次逼近寻优方法”的月面软着陆环节动力下降点的确定方法有效,可以为后续地外天体软着陆等任务提供参考和借鉴。