涡轮发动机平衡流形展开模型辨识方法研究

 根据涡轮发动机平衡流形展开模型的特点提出了两步建模方法。将复杂非线性建模转化为静态参数拟合和带约束条件的动态参数最小二乘辨识，根据单轴涡喷发动机气动热力模型辨识算例证明了方法的有效性。     

某型发动机加力燃油总管喷油杆断裂分析

研究了某些发动机在使用中发生的两起加力燃油总管喷油杆断裂故障，通过断口分析，组织检查，喷油杆受力分析等工作，找出喷油杆疲劳断裂失效的根本原因是设计不佳，导致喷油杆根部承受的应力水平较高，另外焊接缺陷是对疲劳裂纹的萌生起到了促进作用，最后提出了预防与改进的措施。     

Vision-based pose estimation for cooperative space objects

Imaging sensors are widely used in aerospace recently. In this paper, a vision-based approach for estimating the pose of cooperative space objects is proposed. We learn generative model for each space object based on homeomorphic manifold analysis. Conceptual manifold is used to represent pose variation of captured images of the object in visual space, and nonlinear functions mapping between conceptual manifold representation and visual inputs are learned. Given such learned model, we estimate the pose of a new image by minimizing a reconstruction error via a traversal procedure along the conceptual manifold. Experimental results on the simulated image dataset show that our approach is effective for 1D and 2D pose estimation.     

FAST FEATURE RANKING AND ITS APPLICATION TO FACE RECOGNITION

A fast feature ranking algorithm for classification in the presence of high dimensionahty and small sample size is proposed. The basic idea is that the important features force the data points of the same class to maintain their intrinsic neighbor relations, whereas neighboring points of different classes are no longer to stick to one an- other. Applying this assumption, an optimization problem weighting each feature is derived. The algorithm does not involve the dense matrix eigen-decomposition which can be computationally expensive in time. Extensive exper- iments are conducted to validate the significance of selected features using the Yale, Extended YaleB and PIE data- sets. The thorough evaluation shows that, using one-nearest neighbor classifier, the recognition rates using 100-- 500 leading features selected by the algorithm distinctively outperform those with features selected by the baseline feature selection algorithms, while using support vector machine features selected by the algorithm show less prominent improvement. Moreover, the experiments demonstrate that the proposed algorithm is particularly effi- cient for multi-class face recognition problem.     

Envelope protection for aircraft encountering upset condition based on dynamic envelope enlargement

Upset condition encountered by an aircraft in flight could pose great threat to flight safety, which is of chief importance in civil aviation. The causal factors have the nonlinear and multiple characteristics, and as a result the conventional envelope protection system cannot successfully do with the condition. So dynamic envelope based on differential manifold theory, which can take more coupling factors into account, is proposed as a basis to design a novel envelope protection system. Then the relationship between the dynamic envelope and the control coefficient or pilot command is obtained, and the result shows that the dynamic envelope can be enlarged with the change of control coefficient. Furthermore, quantification of flight security is realized via defining relative distance between flight state and dynamic envelope, which can detect whether there is a risk for an aircraft in flight. Finally, an envelope protection system based on dynamic envelope enlargement is proposed on the basis. NASA’s Generic Transport Model encountering hazard gust wind in climbing phase is taken as an example to verify the system’s feasibility. The result shows that the system can give a better operation encountering upset condition and to a certain extent reduce the number of accidents or incidents.     

应用三维粒子动态分析仪测量三分支联接流场

应用三维粒子动态分析仪 (3D PDA)测得了矩形截面三分支联接的三维速度分布。在测量中 ,经过理论分析与对比试验 ,选择了蚊香烟雾作为散射粒子。实验结果表明 ,在只有支管进气的情况下 ,在总管的封闭端和支管下游总管壁面处产生了回流 ;以及气流从支管进入总管后由于截面扩张在总管横截面上所诱发的二次流 ,并且二次流现象只发生在支管下游附近的总管横截面上。     

SY汇流板去毛刺技术

结合SY汇流板的结构和加工特点,采用优化加工参数、变更加工条件、改善刀具等方法控制和去除产品钻削加工过程中产生的毛刺。这几种方法经济适用,低成本高效率地应用于实际生产中。     

结冰飞机非线性稳定域确定及安全操纵方法

结冰会恶化飞机的动力学特性,造成飞行包线收缩,威胁飞行安全,研究结冰后飞机的非线性稳定域变化对于驾驶员操纵应对策略设计以及飞行安全的提高具有重要意义。以NASA的GTM为案例飞机,首先对飞机气动参数进行多项式拟合,同时结合结冰因子模型,建立了飞机在结冰条件下的纵向通道动力学模型;然后通过分岔分析方法对飞机在不同程度结冰条件和操纵指令下的飞行状态变化进行了研究,并将其用于指导驾驶员操纵,同时考虑到分岔分析方法的局限性,利用微分流形理论确定了飞行系统的非线性稳定域,并将其作为飞行安全边界;最后针对结冰情形,提出将分岔分析方法与微分流形理论相结合共同用于操纵指导,并进行了操纵时域验证。研究结果表明,结冰会使安全边界收缩,在小扰动的作用下都可能使飞行状态超出安全边界。随着结冰程度增加,飞机的稳定性质甚至会发生变化,此时飞行状态将很难维持在原有的安全边界以内,提出了通过指导驾驶员操纵指令变化使飞行状态到达新的安全边界。研究结果对于飞行安全操纵及边界保护都具有一定的指导意义。      

低成本多小天体并行交会技术

小天体资源开发方兴未艾,为降低开发风险和成本,需要发射无人探测器交会观测多个待选目标小天体。传统多目标探测方案存在无法多次交会、成本高,周期长等不足。提出的低成本多小天体并行交会技术,能够对多小天体探测任务进行解耦,实现基于微纳飞行器的低成本多目标并行交会勘查,从而降低探测成本,缩短探测周期。该技术结合行星借力与不变流形机制构建了低能量星际转移方案。然后引入扰动流形思想,使微纳飞行器能够实现与目标小天体的快速交会。进一步,提出了一种多目标小天体探测全局搜索方法,该方法基于在日地halo轨道上停泊的微纳飞行器集群,逐次确定小天体探测目标,并利用上述方法完成了多微纳飞行器与多小天体的交会。数值仿真结果表明,该方案能够大幅度降低转移过程的燃料消耗,并缩短转移时间。     

空间机械臂位形与基座姿态协同控制研究

针对自由飘浮空间机械臂与基座的运动耦合问题,提出了一种基于不变流形的机械臂位形与基座姿态协同控制算法。在分析了系统可控性的基础上,构造了线性状态反馈下系统的不变流形,并设计了分段连续的镇定控制器。该控制器先将系统状态镇定到不变流形之上,然后沿该流形将系统状态调整到期望值。仿真结果表明,在系统可控的条件下,所提出的协同控制算法能将机械臂位形与基座姿态同时调整到期望状态。