翼柱型药柱固体火箭发动机工作过程仿真

将翼柱型药柱的18个关键尺寸定义成可变多数，通过人机交互输入具体的数值，构造任意烧去肉厚下的药柱模型，并计算该模型的体积。由Ab=△V／△e计算燃烧面积的大小，并进而计算出燃烧室压强和发动机推力。把任意烧去肉厚下的药柱模型和相对应时刻的压强-时间、推力-时间坐标制作成幻灯文件，通过计算机显示器屏幕连续演示，达到动画模拟的效果。     

铝合金氧化物夹杂超声波检测技术

针对航天器用铝合金内部的氧化物夹杂缺陷的检测难题,开展了超声波检测技术试验研究,采用一种基于过盈配合和快速氧化原理的铝合金氧化物夹杂缺陷模拟方法进行了氧化物缺陷模拟,并对缺陷的微观组织和成分进行分析,分析结果验证了氧化物夹杂缺陷的制作有效性。测试结果表明机械C型扫描能够有效分辨Φ1.2 mm当量左右的夹杂缺陷,其直观性、耦合稳定性和重复性相较手动扫描,检测效果更优。该方法已应用于航天器铝合金产品氧化物夹杂检测,效果良好。     

退火温度对高纯钨靶显微组织和内应力的影响

采用热等静压工艺制备了高纯钨靶,并在不同温度下对其进行退火处理。采用金相显微镜、TEM、XRD和硬度计对不同温度退火的高纯钨靶的显微组织和内应力进行表征。结果表明:高纯钨靶经1200℃真空退火后,保留了热等静压后的细晶组织,晶粒未发生长大,但是位错密度却大幅度减小,晶格畸变率下降,硬度值降低,这是由于退火处理使热等静压高纯钨靶发生回复,内应力得以释放。当退火温度低于1200℃时,钨靶的内应力去除不完全,当退火温度高于1 200℃时钨靶的晶粒开始长大,故热等静压高纯钨靶的最佳退火温度是1 200℃。     

An internal power angle control strategy for high-speed sensorless brushless DC motors

High-speed Brushless DC Motors(BLDCMs) usually adopt a sensorless control strategy and operate in three-phase six-state drive mode. However, the sampling errors of the rotor position and the driving method increase the Internal Power Angle(IPA), resulting in a decrease in the efficiency of the system. Conventional IPA reduction strategies are either sensitive to motor parameters, or ignore diode freewheeling during the commutation process, or require additional current sensors. In this paper, a ...     

BDS-3 PPP模糊度固定实现及精度评估

精密单点定位(PPP)模糊度固定(AR)能够显著提升精密定位的收敛速度和精度。通过在BDS-2和BDS-3之间添加系统间偏差的方法实现BDS-3的模糊度固定,并基于全球MGEX测站静态、仿动态数据和车载实验数据全面评估了BDS-3模糊度固定的效果。结果表明,相对于浮点解,BDS-3 PPP模糊度固定能够显著提升PPP的精度,在东北天3个方向上静态解算精度提升依次为37.4%、26.2%和20.1%;仿动态解算精度提升依次为38.3%、27.2%和11.1%;车载动态实验BDS-3模糊度固定精度在三维方向上综合提升为40.4%。此外,模糊度固定后,以浮点解稳定后的两倍定位精度为基准,在东北天方向上,静态定位时间提升程度依次为63.5%、64.0%和40.3%;仿动态定位时间提升程度依次为58.7%、56.8%和25.4%;车载实验在三维方向的收敛时间为30.0 min。以上结果证明了所提方法的有效性及BDS-3模糊度固定的性能提升。     

液体火箭发动机端面密封用石墨材料内部缺陷检测工艺方法

介绍了石墨材料的制造工艺和缺陷类型,并结合液体火箭发动机端面密封的工作特性,阐明了端面密封用石墨材料内部缺陷检测的必要性。对目前通用的无损检测方法进行了对比分析,确定了适用于液体火箭发动机端面密封用石墨材料内部缺陷的X射线检测方法,并对X射线检测过程中图像灰度、对比度、电压、电流、滤片及积分时间等关键工艺参数的影响因素进行了对比分析,确定了石墨材料内部缺陷检测的工艺参数设置准则及高精度检测方法,实现了石墨材料内部孔隙的可视化仿真分析,并提出了一种基于图像处理的石墨材料气孔率统计计算方法,最终建立了液体火箭发动机端面密封用石墨材料内部典型缺陷的特征标样。     

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.     

二次燃烧对自力弹射内弹道影响分析

目前弹射所用低温药柱的燃烧平衡产物中含有可燃气体成分,遇初容室内氧气后发生二次燃烧,影响初容室内流场与弹射内弹道特性。为了分析二次燃烧对自力弹射方案内弹道的影响,建立了自力弹射可压缩流动仿真模型,结合有限速率化学反应模型与动网格技术,利用PISO(压力隐式算子分裂法)算法对控制方程进行数值求解。计算结果表明,二次燃烧使得初容室初始压力峰值时刻提前,并影响初始压力峰值大小。仿真分析结果为自力弹射内弹道设计提供了理论参考。     

访问AutoCAD 图形方法综述

当前AutoCAD的图形输出存在着很多对外不公开文件格式,为实现加工信息的集成及数控加工,必须对AutoCAD的图形文件进行访问、读取、转化成我们所需要的格式,所以对访问AutoCAD图形文件的方法必须进行深入分析,详细地论述访问AutoCAD的图形文件的LISP、VBA、DXF、Ob jectX ARX等各种方法的优缺点,从而可根据不同的开发环境,选择合适的开发方法,以提高工作效率。     

Stability of spinning satellite under axial thrust and internal mass motion

This paper considers a spinning rigid body and a particle with internal motion under axial thrust. This model is helpful for gaining insights into the nutation anomalies that occurred near the end of orbit injections performed by STAR-48 rocket motors. The stability of this system is investigated by means of linearized equations about a uniform spin reference state. In this model, a double root does not necessarily imply instability. The resulting stability condition defines a manifold in the parameter space. A detailed study of this manifold and the parameter space shows that the envelope of the constant solutions is in fact the stability boundary. Only part of the manifold defines a physical system and the range of frequency values that make the system unstable is restricted. Also it turns out that an increase of the spring stiffness, which restrains the internal motion, does not necessarily increase the stability margin. The application of the model is demonstrated using the orbit injection data of ESA's Ulysses satellite in 1990.