变结构控制在基于脉冲比例阀的燃油调节系统中的应用

针对航空发动机燃油控制系统中二阶非定常执行机构通常出现设计困难的问题,介绍一种变结构控制方法,将二阶非定常执行机构变成确定的一阶惯性环节,该方法既充分利用其优点"不变性"又可以规避其突出缺点"抖振",特别适用于驱动脉冲比例调节阀;同时提出脉冲比例阀的变结构调节中遇到的实际问题(例如微分的精度问题)的解决办法,以及影响该方法可行性的若干必要条件。结果表明:符合条件时变结构控制在基于脉冲比例阀的燃油调节系统中是可行的。     

再入飞行器和模型转换雷诺数计算

本文采用近似的激波关系、球锥体压力分布、平衡气体状态方程、边界层厚度计算公式及转捩准则等,按照流管法计算了4种再入飞行器的外流转捩雷诺数和转捩距离,并给出了高硅氧、碳石英、碳碳球锥模型的转捩雷诺数范围,对再入飞行器和模型的计算结果作了分析和比较。     

纳米碳粉掺杂对激光烧蚀GAP的推进性能影响

实验以含能聚合物聚叠氮缩水甘油醚(Glycidyl azide polymer,GAP）作为激光烧蚀微推力器的靶材。通过对不同浓度纳米碳粉掺杂和靶材厚度下激光烧蚀GAP的比冲、冲量耦合系数和能量转化效率测量，结合靶材喷射羽流图像，分析了纳米碳粉掺杂提高激光烧蚀聚合物靶材推进性能的机理，给出纳米碳粉掺杂的适用方式。实验结果表明：透射式下，掺杂纳米碳粉之后，聚合物对激光的吸收大幅增强，但激光烧蚀推进性能不随掺杂浓度增加而显著提升；纳米碳粉吸收激光能量形成温度极高的局部热区促进聚合物中化学能的释放，是推进性能提升的主要原因；掺杂纳米碳粉之后的GAP烧蚀深度降低，表现出面吸收特性；随着靶材厚度的增加，未完全烧蚀的工质质量增加，使得靶材的利用率大大降低，导致聚合物推进性能下降。实验中掺杂3%纳米碳粉、厚度为54 μm的GAP靶材最优能量转化效率超过250%，适合作为透射式激光烧蚀微推力器的靶材。     

A novel architecture of electro-hydrostatic actuator with digital distribution

To address the flow imbalance rapidly of the asymmetric Electro-Hydrostatic Actuator (EHA), this paper presents a novel architecture of asymmetric EHA with the Digital Distribution (EHA-DD). It also improves the flow nonlinearity and control accuracy of the pump, especially in the low-speed condition. The digital distribution with two High-Speed on–off Valves (HSVs) not only balances flow instead of the check valves, but also replaces the pump at the low-speed to control output flow by adjusting the PWM signal. The pump and HSVs are the crucial components to control flow output. Firstly, the flow calculation models of the pump and the duty ratio inversed model of the HSV are obtained through experimental tests and the identification method. To get the control input signal for the required flow, the pump speed and PWM duty ratio for the HSVs are inversed to compensate for flow output. Further, a multimode digital flow distribution control method based on pump speed, mainly including the pump-controlled mode for large flow demand and valve-controlled mode for little flow demand, is proposed to control the accurate flow output actively. The step extension experiments based on the flow calculation models are conducted on the EHA-DD prototype under elastic, opposite varying load. The results demonstrate that the EHA-DD realizes little position error by accurate flow control, and it is also beneficial to improve the service life of the pump.     

西安某粘接材料厂室内供暖、热水系统的设计

基于厂方对供热系统的要求,根据供热建筑物、机房和可利用设施的实际情况,采用一台换热器,通过阀门的切换,实现了供暖和供热水的分段运行。将蒸汽发生器的进水与系统补水有机地整合为一个系统,有效地解决了机房面积过小的实际困难。利用自来水的压力和热水箱与浴室的高差解决了热水供应的实际问题。     

SAR performance-based fault diagnosis for electro-hydraulic control system: A novel FDI framework for closed-loop system

Model-based fault diagnosis serves as an efficient and powerful technique in addressing fault detection and isolation (FDI) issues for control systems. However, the standard methods and their modifications still encounter some difficulties in algorithm design and application for complex higher-order systems. To avoid these difficulties, a novel fault diagnosis framework based on multiple performance indicators of closed-loop control system is proposed. Under this framework, a so-called performance residual vector is constructed to measure the differences between the real system and the nominal model in terms of system stability, accuracy, and rapidity (SAR) respectively. The criteria for quantification, normalization of the SAR residuals and the explicit mappings between the thresholds and the required performance are given. FDI can be easily achieved simultaneously by monitoring the normalized residual vector length and direction in the SAR performance residual space. A case study on electro-hydraulic servo control system of turbofan engine is adopted to demonstrate the effectiveness of the proposed method.     

射流管伺服阀前置级压力特性

为分析射流管伺服阀射流管喷嘴高压射流区的特性,建立了射流管伺服阀前置级数学模型,得到了射流管偏移值、射流管喷嘴半径和接收孔半径对接收器压力分布、喷嘴出口流速及接收器的左右孔恢复压力的影响规律.流场分析发现射流管喷嘴的高速射流出口处容易产生旋涡,且存在环状负压效应.结果表明:高压射流状态下,射流管喷嘴半径增大,恢复压力增加;接收孔半径增大,恢复压力降低.接收孔半径与射流管喷嘴半径之比的最佳取值区间为[1.3,1.5].当射流管偏移值增大时,在偏移值增大一侧,射流管与接收孔之间的有效流体接收面积增大,射流管与接收孔之间的流体旋涡扩大,内部流场环状负压效应增加,接收孔恢复压力降低.      

双独立闭环复合液压伺服控制体系的分析

针对现有几种液压伺服控制系统的优缺点,基于高性能和节能这一发展趋势,提出基于伺服电机、定量泵、蓄能器和伺服阀的双独立闭环的新型复合控制体系.分析了其结构特点,建立了数学模型并进行了仿真分析和实验验证,证明新型控制体系充分发挥了各个控制环节的效能,实现了流量适应,较现有的控制方案简单可靠,在综合指标方面有了很大的提高,适合机载液压系统和弹载液压系统.      

基于气动热力模型的FADEC系统FHA方法

从适航规章对全权限数字发动机控制(full authority digital engine control,简称FADEC)系统的安全要求出发,结合功能危险分析(functional hazard assessment,简称FHA)的一般原则和FADEC系统的特点,得到了FADEC系统FHA的分析要素.根据分析要素中的工具与数据需求,将航空发动机气动热力模型用于可调放气活门(variable bleed valve,简称VBV)控制功能失效危险分析,结果表明:①该模型能够辅助确定FADEC系统功能失效的发动机影响;②FADEC系统功能危险的模型分析方法通过定量分析确定发动机影响的危险等级,为FHA提供直观的参考依据,可作为对专家经验的补充.      

激光冲击强化提高主动连杆振动疲劳性能

针对某型发动机放气活门主动连杆转接R处的疲劳断裂问题,进行了主动连杆激光冲击强化工艺研究;完成了原型件和激光冲击强化、喷丸及加大R3种处理工艺后主动连杆振动疲劳对比试验.结果表明,在317MPa的应力水平下,激光冲击强化、喷丸和加大R后主动连杆疲劳寿命分别为原型件的5.24倍、3.89倍及1.36倍;与其它2种工艺相比,激光冲击强化具有强化效果好、工艺稳定性高、易于实现等优点,是截至目前减少主动连杆疲劳断裂故障的最佳处理工艺.主动连杆激光冲击强化后表面粗糙度较小,产生深度约1.4mm的高数值残余压应力层,表层晶粒细化至纳米晶并伴随高密度位错.三者共同作用可以有效缓解转接R处的应力集中,抑制疲劳裂纹在转接R处的萌生和扩展,是主动连杆振动疲劳寿命提高的主要原因.