基于永磁磁链在线辨识的永磁同步电机无速度传感器控制

在无速度传感器控制条件下,研究了基于MRAS的永磁同步电机永磁磁链在线辨识系统。仅辨识速度和永磁磁链两个参数,使得辨识模型满秩,避免了出现设置不同初值获得不同永磁磁链辨识值的问题,确保了参数估计的收敛性和唯一性。分析了欠秩问题的本质,分别推导了速度和永磁磁链的辨识自适应律。仿真结果表明:该控制系统在转速和负载突变下均能准确跟踪转子的速度,具有良好的鲁棒性和动态性能,同时降低了系统参数敏感性。     

一种永磁同步电机谐波抑制的工程化方法

提出了一种抑制永磁同步电机电流谐波的工程化方法。对相电流谐波进行坐标变换和低通滤波,提取出其中5次、7次谐波的直流分量,求解高次谐波稳态电压方程,再通过坐标反变换计算出电压谐波补偿量,最后注入PARK逆变换输出电压中作为SVPWM计算单元输入,可以抑制相电流中的5次、7次谐波。试验结果证明所提工程化方法是可行和有效的。     

Multipath mitigation method based on Gaussian mixture model in RF relative measurement

Radio Frequency (RF) technology represents a high-precision relative navigation solution that has significant potential for application to earth-orbiting satellites. In precision applications, multipath errors dominate the total error because observables, which are used to estimate carrier-phase integer ambiguity, are not always subject to a Gaussian distribution when dual-frequency ambiguity estimation methods are used in the presence of multipath. As it has been shown that ranging observables obey a Gaussian mixture distribution, this study proposes improvements to the accuracy of estimation based on multipath mitigation founded on the Gaussian mixture model. To this end, such a model is created for integer ambiguity resolution in the presence of multipath, using which the theoretical error in dual-frequency ambiguity estimation is derived. Expectation Maximization (EM), which aids dual-frequency ambiguity estimation, is subsequently proposed to reduce the effect of multipath errors. Finally, two experimental scenarios are implemented to test the performance of the proposed method. The results show that EM-aided dual-frequency ambiguity estimation reduces the range error to approximately 20% in comparison with simple dual-frequency ambiguity estimation. Therefore the proposed technique is effective for multipath mitigation in RF relative measurement.     

Experimental and numerical study of chaff cloud kinetic performance under impact of high speed airflow

To solve the kinetic and diffusion problem of surface-type infrared decoy, multi-chaff kinetic models are established and chaff cloud holistic kinetic performance are analyzed under the impact of high speed airflow in this work. Chaffs rotate rapidly during the motion under the impact of high speed airflow. The rotation speed is correlated with lift, position of pressure center and aerodynamic damping. Computational Fluid Dynamics (CFD) is used to compute the aerodynamic coefficients of chaff. It is found that there exists serious aerodynamic interference which mainly relates to the overlapping area and distance among chaffs during the diffusion of chaff cloud. The chaff wind tunnel test and rocket sled experiment are carried out to verify the credibility of the models in this work. Then, the variation of chaff cloud expectation and extremum are analyzed to achieve the holistic kinetic and diffusing performance of chaff cloud. Simulation results demonstrate that the chaffs diffuse rapidly under the impact of high speed airflow and chaff cloud can be formed rapidly within 0.5?s. The shape of the chaff cloud is similar to cone that forms a certain angle with the horizontal plane and most chaffs focus on the second half.     

PBT钝感高能推进剂高温力学性能调节技术研究

为了改善PBT类型钝感高能推进剂的高温力学性能,分析了推进剂高温力学性能的影响因素,研究了中性键合剂粒度、用量以及固化网络交联分子量对高温性能的影响,并进一步考察了组合键合剂技术(中性键合剂+醇胺键合剂)在三种不同燃速(高燃速、中燃速、低燃速)配方中的使用效果。研究表明:(1)醇胺键合剂对HMX粒子表面缺乏有效的化学键合,HMX能部分溶解在极性增塑剂A3中,形成软界面层,这两点使得试样拉伸过程中HMX的表面容易"脱湿",影响高温力学性能。(2)通过调整固化参数和交联剂用量,控制交联分子量,优化固化网络,并结合组合键合剂技术,能获得高、低、常温力学性能优良的PBT钝感高能推进剂配方,当NPBA的用量为0.08%～0.10%,交联分子量Mc达到8000～10000时,推进剂的高温抗拉强度大于550kPa,伸长率达到40%以上。     

电学前沿计量技术在航天型号保障中的应用

针对航天器中电学基准的长期稳定性、多种传感器输出电信号的线性度、电脉冲测量的时延等多个航天电测领域的难题,提出采用电学量子计量技术和计算基准技术的解决方案,可以10^-9量级的不确定度测量航天器中电阻基准短期变化量,从而推算出长期变化量,对航天器的稳定控制具有重要作用;可以极小的不确定度校准多种传感器输出的毫伏、微伏量级电压的线性度,对航天传感器测量准确度具有重要意义;可在10^-9秒量级确定电脉冲测量中电阻引入的时延,对航天器电推进系统的控制具有重要作用。     

低利用率下民机结构维修间隔确定模型

制定民用飞机结构维修大纲的核心内容之一是确定结构维修间隔,现有的分析模型普遍没有综合考虑民机利用率对维修间隔各指标的影响。以民机在环境损伤下的金属结构维修间隔为研究背景,综合考虑利用率对确定结构维修间隔各个指标的影响,应用K-means算法和AHP （Analytic Hierarchy Process）-熵值法,建立了一种某型国产民机低利用率下金属结构环境损伤维修间隔的确定模型,并通过选取相似机型的典型结构进行了实例验证。分析结果表明：所建模型与飞机利用率匹配关系良好,符合工程实际,在一定程度上解决了国产民机制定维修大纲的过程中,由于缺少运营数据和维修数据而导致维修间隔的确定偏于主观的问题。     

碳基高导热材料及其在航天器上的应用

在分析航天器对于高导热材料的需求及应用特点的基础上,将碳基导热材料分为高导热石墨扩热板和高导热柔性石墨膜,总结了其在航天器上的典型应用场景.高导热柔性石墨膜可用于复杂结构等温化设计、柔性热传输等,高导热石墨扩热板可用于大功率元器件或设备扩热与传输.针对现有柔性导热材料柔韧性差、尺寸小、厚度薄等应用瓶颈,采用固相发泡技术...     

某航空发动机轴承钢球失效分析

针对某航空发动机轴承钢球的表面剥落及裂纹故障,利用视频显微镜、扫描电镜等设备对故障钢球剥落表面进行宏、微观检查,明确了钢球表面剥落性质为滚动接触疲劳;通过裂纹断口分析、能谱分析及金相检查等手段,确定了钢球裂纹是在淬火过程中温度过高导致的淬火裂纹,同时钢球组织中存在带状碳化物,对淬火裂纹的产生有一定的促进作用。淬火裂纹在钢球工作过程中并未扩展,但引起钢球表面发生接触疲劳剥落。建议在钢球热处理过程中,严格控制热处理工艺参数,保证热处理温度和保温时间的稳定。     

波浪前缘静子叶片对高速轴流风扇单音噪声的影响

航空发动机压气机噪声与大型风洞压缩机噪声问题日益凸显,相关研究机构迫切需求新的降噪手段以指导大型叶轮机械降噪设计。为了探索波浪前缘静子叶片在大型叶轮机械降噪中的应用前景,采用非定常雷诺平均Navier-Stoke（URANS）方程与FW-H方程混合方法对基准静子叶片和3种波浪前缘静子叶片的降噪效果进行了数值模拟,研究对象静子来流平均马赫数约为0.49,基于静子叶片弦长的雷诺数约为1 040 000。数值预测结果显示：波浪前缘静子叶片可以显著降低高速轴流风扇单音噪声,但会对风扇的气动性能产生少许不利影响;相较于基准静子叶片,3种波浪前缘静子叶片可以在1BPF时降低风扇入口声功率级0.97~1.5 dB,2BPF时降低风扇入口声功率级2.89~4.9 dB,3BPF时降低风扇入口声功率级3.32~4.72 dB;同时,总压比降低0.1%~0.8%,等熵效率降低0.1%~0.3%。进一步研究表明：不同频率下声源振幅和相位关系是风扇单音噪声强度的主要影响因素,总的来说,幅值的增加会降低声源强度,然而通过改变声源相位关系的降噪方式则需要兼顾径向模态与波长两个方面。