2020中美阿火星探测任务分析

2020年为火星探测大年,各国相继赶在发射窗口发射自己的火星探测器,截至目前成功赶上发射窗口的国家,按时间先后分别为阿联酋、中国和美国。给出了2020年火星探测发射和到达窗口的“猪排”能量图,从有效载荷、发射窗口、运载火箭、地火转移轨道、火星俘获及着陆、通信等方面,对3个国家发射的探测器进行了对比分析,给出2020年三国火星探测各环节的关键参数,并提取出共同点及不同的特殊之处。     

Standing window of oblique detonation with pathological behaviour

Standing of an Oblique Detonation Wave (ODW) on a wedge within combustor is the prerequisite of thrust generation for ODW engine which is regarded as a novel and conceptual propulsion device with hypersonic flight Mach number. Usually a standing window of ODW is defined as the wedge angle ranged from the ODW detached angle from wedge (upper limit) to the angle that a Chapman-Jouguet (CJ) detonation occurs (lower limit). For pathological detonation cases, however, the CJ detonation cannot be achieved, and thus the lower limit of the standing window of ODW should be revisited. In present study, two types of reactions in hypersonic incoming flow that include the behavior of pathological detonation, that is, the single-step irreversible reaction with mole variation and the two-step irreversible reactions with exothermic process followed by endothermic process, have been used for studying standing behavior of ODW. The steady detonation polar analysis of ODW is carried out for both reaction systems. The results reveal that the reaction with more mole decrement and the reactions with stronger endothermic process show the pathological detonation feature and therefore modify the lower limit of standing window of ODW. Three equivalent parameters are proposed to quantitatively measure the standing window range of ODW from points of view of thermodynamics, Mach number of incoming flow and heat effect of reactions. It is found that the standing window of ODW is determined by the specific heat ratio, the overdrive degree of detonation and the endothermic level of the hypersonic incoming flow, regardless of whether the detonation is pathological or not.     

Variable slip window technology in transition detection on pitching airfoil

In the pitching motion, the unsteady transition and relaminarization position plays an important role in the dynamic characteristics of the airfoil. In order to facilitate the computer to automatically and accurately calculate the position of the transition and relaminarization, a Variable Slip Window Technology (VSWT) suitable for airfoil dynamic data processing was developed using the S809 airfoil experimental data in this paper and two calculation strategies, i.e., global strategy and single point strategy, were proposed: global strategy and single point strategy. The core of the VSWT is the selection of the window function h and the parameters setting in the h function. The effect of the VSWT was evaluated using the dimensionless pulse strength value (INB), which can be used to evaluate the signal characteristics, of the root mean square (RMS) value of the fluctuating pressure. It is found that: the h function characteristics have a significant influence on the VSWT. The suitable functions are H_n function constructed in this paper and step function. For the left boundary of the magnified area, the step function can obtain the largest INB value, but the robustness is not good. The H₁ function (Gaussian-like function, n = 1) can show higher robustness while ensuring a large INB value. The two computing strategies, which are single point strategy and global strategy, have their own advantages and disadvantages. The former strategy, that is the single point strategy, can achieve a higher INB value, but the RMS magnification at the feature position needs to be known in advance. Although the INB value obtained by the latter strategy, that is the global strategy, is slightly smaller than the calculation results of the former strategy, it is not necessary to know the RMS magnification at the feature position in advance. So the global strategy has better robustness. The experimental data of NACA0012 airfoil was used to further validate the developed VSWT in this paper, and the results show that the VSWT developed in this paper can still double the INB value of the transition/relaminarization position. The VSWT developed in this paper has certain practicability, which is convenient for the computer to automatically determine the transition/relaminarization characteristics.     

任意采样率变换数字重构滤波器设计

针对理想重构函数在数字信号域不可实现而直接截取性能较差的情况,根据信号重构理论和FIR（Finite Impulse Response,有限脉冲响应）滤波器窗函数设计法,分析不同窗函数、不同截取长度对重构滤波器的影响,提出一种凯塞窗任意采样率变换数字重构滤波器设计方法.该方法通过选择合适的窗参数、截取长度、重构滤波器时域精度和量化位数,有效控制阻带最小衰减抑制数字重构镜像.设计的数字重构滤波器已成功应用于某卫星基带调制解调器,符合镜像抑制大于65 dB的性能要求.     

航空精密工件电火花加工微型方窗口研究

在电火花加工中,零件参数的选择对加工工艺指标起着重要作用,只有正确选择电参数才能加工出品质优良的产品。影响电参数选择的因素主要有:电极材料、工件材料、放电面积、表面粗糙度、放电间隙、电极损耗和加工速度等。主要针对微型方窗口的加工确定电极材料、放电间隙、加工速度等电参数,并对上述分析方法进行延伸扩展。     

A380客舱窗框结构设计的分析与研究

A380作为新一代大型客机的代表,数量庞大的大尺寸舷窗设计是众所瞩目的关键课题之一。通过与其他机型采用的窗框方案对比,重点分析A380窗框结构方案的优势,研究窗框结构的受载情况,将静力试验数据与有限元分析结果对比验证,从主结构的材料选用方面将A380的锻件窗框与不同材料的窗框进行对比分析。结果表明:A380客舱窗框结构的设计概念与现有机型相比,有效降低了加工复杂性、制造风险及研制成本,可为后续机型的窗框设计提供借鉴和参考。     

巧用Creat（）和SyntaxFromSQL（）函数创建动态数据窗口

本文以两个实例介绍了在PB环境下，利用Creat()和SyntaxfromSQL()函数创建动态数据窗口的设计方法。     

面向卫星多目标重复观测任务的分层聚类规划

针对敏捷卫星多目标重复观测任务规划面临的可行任务执行序列集合规模庞大困难,提出了一种任务执行序列时间解耦的分层聚类任务规划方法。该方法以规划过程中的可观测窗口和任务执行窗口为聚类对象,通过单次可观测窗口聚类和多次任务执行窗口聚类将任务集合按任务窗口属性分解为一系列时间解耦的小规模集合,在两次任务执行窗口聚类间使用基于贪婪优化的搜索算法对聚类生成的小规模任务集合分别进行集合内任务规划,最后将各集合的任务规划结果合并后得到所有任务的执行序列。仿真结果表明,该分层聚类方法可有效降低全局优化复杂度,消解不同优先级观测任务的冲突,提高任务规划质量,能够在不降低目标点观测完成率的前提下对有多个观测机会的目标点进行重复观测,且算法稳定性好,能在数秒内得出规划结果,适用于星上自主任务规划。     

基于自适应容积卡尔曼滤波方法的涡扇发动机气路部件故障诊断

针对涡扇发动机气路部件故障诊断中参数存在不同的噪声统计特性,提出了一种自适应平方根容积卡尔曼滤波(ASRCKF)器的自适应滤波方法.该方法直接利用基于3阶容积积分方法近似发动机的非线性统计特性,用于替代非线性无迹卡尔曼滤波方法的系统模型,避免了滤波过程参数选取的问题;采用移动窗口法对噪声协方差矩阵进行自适应估计,提高了算法对不同统计特性噪声的自适应能力和滤波精度.通过对发动机气路部件健康参数蜕化过程仿真结果表明:ASRCKF方法相比平方根容积卡尔曼滤波(SRCKF)方法,精度提高40%~50%,对不同噪声信号具有更好的适应能力.      

机场着陆排序的一种滑动窗优化算法

对交通拥挤时的终端区进场飞机进行合理的排序,是空中交通流量管理的一个重要研究内容。当降落飞机架次较多时,目前的各种算法因计算量太大而实时性不好。基于飞机进场时位置的调整受一定限制,通过分析窗体的大小与位置限制和步长的关系,对计算量的影响提出了滑动窗的方法,并给出了通过采用滑动窗方法可以减少运算量的理论证明。最后通过仿真对该方法进行了验证。