非线性动力响应分析的双θ法

本文在二次加速度插值模式的基础上,提出了动力响应分析的双θ法及加权平均法。这两个方法,加速度的截断误差(精度)是O(△t~(3)),是无条件稳定的,有较好的人工阻尼性质,没有超越现象。比现有的逐步积分法有明显的优点。     

一种新型综合性靶场安全系统及其检验测试结果

本文首先简要介绍战略导弹发射场和航天发射场靶场安全系统的作用、特点、主要技术要求,接着介绍按美国空军航天司令部要求,由空军研究所开发的基于GPS弹道测量技术,外测、遥测、遥控综合为一体的机动型靶场安全系统——BMRST的构成及其经多种检验测试的结果。     

工艺模型驱动的物料动态精准配送技术

针对飞机装配车间传统“领料式”物料配送存在的弊端,提出了一种工艺模型驱动的物料动态精准配送方法,构建了飞机装配车间物料精准配送管理系统,阐述了系统构建涉及的关键技术难点,采用基于模型的三维可视化消耗式BOM重构方式,建立与设计了模型动态同步精准的MBOM工艺模型,利用RFID技术的优点实时获取物料信息,通过iGPS系统引导AGV物料运输平台来实现装配站位物料的高精度配送。     

Sliding mode control design for oblique wing aircraft in wing skewing process

When the wing of Oblique Wing Aircraft (OWA) is skewed, the center of gravity, inertia and aerodynamic characteristics of the aircraft all significantly change, causing an undesirable flight dynamic response, affecting the flying qualities, and even endangering the flight safety. In this study, the dynamic response of an OWA in the wing skewing process is simulated, showing that the three-axis movements of the OWA are highly coupled and present nonlinear characteristics during the wing skewing. As the roll control efficiency of the aileron decreases due to the shortened control arm in an oblique configuration, the all-moving horizontal tail is used for additional roll and the control allocation is performed based on minimum control energy. Given the properties of pitch-roll-yaw coupling and control input and state coupling, and the difficulty of establishing an accurate aerodynamic model in the wing skewing process due to unsteady aerodynamic force, a multi-loop sliding mode controller is formulated by the time-scale separation method. The closed-loop simulation results show that the asymmetric aerodynamics can be balanced and that the velocity and altitude of the aircraft maintain stable, which means that a smooth transition is obtained during the OWA’s wing skewing.     

Stall flutter prediction based on multi-layer GRU neural network

The modeling of dynamic stall aerodynamics is essential to stall flutter, due to the flow separation in a large-amplitude pitching oscillation process. A newly neural network based Reduced Order Model (ROM) framework for predicting the aerodynamic forces of an airfoil undergoing large-amplitude pitching oscillation at various velocities is presented in this work. First, the dynamic stall aerodynamics is calculated by solving RANS equations and the transitional SST-γ model. Afterwards, the stall flutter bifurcation behavior is calculated by the above CFD solver coupled with structural dynamic equation. The critical flutter speed and limit-cycle oscillation amplitudes are consistent with those obtained by experiments. A newly multi-layer Gated Recurrent Unit (GRU) neural network based ROM is constructed to accelerate the calculation of aerodynamic forces. The training and validation process are carried out upon the unsteady aerodynamic data obtained by the proposed CFD method. The well-trained ROM is then coupled with the structure equation at a specific velocity, the Limit-Cycle Oscillation (LCO) of stall flutter under this flow condition is predicted precisely and more quickly. In order to predict both the critical flutter velocity and LCO amplitudes after bifurcation at different velocities, a new ROM with GRU neural network considering the variation of flow velocities is developed. The stall flutter results predicted by ROM agree well with the CFD ones at different velocities. Finally, a brief sensitivity analysis of two structural parameters of ROM is carried out. It infers the potential of the presented modeling method to depict the nonlinearity of dynamic stall and stall flutter phenomenon.     

航空发动机全飞行包线稳态划分方法研究

航空发动机在鲁棒控制器设计过程中存在飞行包线区域难以系统划分的问题,为此,提出基于推力耗油率特性和基于动压耗油率特性的航空发动机飞行包线划分法。根据某型涡扇发动机在全包线范围内稳态工作时的推力、耗油率及动压特性,结合大气条件的客观规律,通过两种划分方法将飞行包线划分为65 个区域,用每个区域对应标称点的参数代替其周围小偏差区域和边界点参数。通过对该发动机全包线内各区域标称点与边界点参数的对比,证明两种方法均对全飞行包线划分有效,可为后续航空发动机控制器设计提供理论基础。     

一种计算开伞动载的实用方法

依据海因里奇开伞动力理论,在计算个表充满时间的连续方程中,考虑了伞顶孔,伞顶部分大透气量织物面积,以及伞衣中、下部分织物透气量对开伞动载的影响。引用了非线性的阻力特征文化曲线［２］,计算伞衣充气过程中阻力特征的变化。并考虑了伞衣充气过程初始瞬时的阻力特征,假设在伞衣初始充气时期的一段时间中,进气口直径为常值,数值上等于［４（ＣＡ）０／Ｃ（ｓｔ）π）］（１／２）。计算实例表明,计算结果与实测数据相比较,其一致性是比较满意的。     

分布参数液体管道的分段近似状态空间模型

分别提出了分布参数层流和湍流液体管道的分段近似状态空间模型,模型考虑了稳态摩擦和频率相关摩擦损失两种情况,层流管道的分段近似状态空间模型是线性的,而湍流管道的是非线性的。包括频率相关摩擦损失的模型比只考虑稳态摩擦损失的模型更精确地描述流体管道的瞬变过程,但模型的阶次成倍地增加了。用单根管道阀门关断的水击问题仿真计算对模型进行了验证,采用２个分段的分段近似状态空间模型的计算结果已经与特征线方法的计算结果吻合较好。     

量化对遥感图像质量的影响

文章定义了航天遥感图像的信噪比 (SNR) ,调制传递函数 (MTF) ,动态范围 (DR) ,并在理论上推导了它们与量化位数b的关系     

单幅图像的三维重构视觉系统特征点提取算法的研究与实现

实现基于单幅二维图像不标定欧氏重构三维场景的关键技术之一是有效提取彩色伪随机编码图像特征角点。为给图像特征点匹配提供更多的样本信息,采用定位于彩色图像Harris算子探测特征角点,并动态给出角点响应的自适应阈值条件。特征点提取实验及三维欧氏重构结果证实了该方法的适用性和有效性。