Novel attitude determination method by integration of electronic level meter,INS, and low-cost turntable for level attitude evaluation and calibration of INS

Attitude references are greatly needed for the evaluation and calibration of Inertial Navigation Systems (INSs), which are widely used in gravimeter, marine, and aeronautical navigation. High-accuracy turntable, INS, and Global Navigation Satellite System have been utilized to verify the performance of relatively low-accuracy INS. The accuracy requirement of the attitude reference continuously increases with the rapid improvement of inertial sensors and navigation algorithms. However, the cost of attitude determination system increases rapidly with the increase of attitude accuracy requirement. To solve this limitation, the integration of level meter, INS, and low-cost turntable is proposed to provide level attitude, such as roll and pitch. The turntable is utilized to rotate the INS. An integration model of the level meter and INS is built to estimate the level attitude and reduce the cost of the turntable. The proposed method successfully avoids the dependence on high-accuracy turntables. An observability degree analysis is conducted to improve the level attitude accuracy further. The simulation and turntable test results indicate that the proposed method can provide high-accuracy level attitude without high-accuracy INS or turntable and is applicable to error calibration and attitude evaluation of INS.     

Real-time modular dynamic modeling for compression system of altitude ground test facilities

Modeling of a centrifugal compressor is of great significance to surge characteristics and fluid dynamics in the Altitude Ground Test Facilities (AGTF). Real-time Modular Dynamic System Greitzer (MDSG) modeling for dynamic response and simulation of the compression system is introduced. The centrifugal compressor, pipeline network, and valve are divided into pressure output type and mass flow output type for module modeling, and the two types of components alternate when the system is established. The pressure loss and thermodynamics of the system are considered. An air supply compression system of AGTF is modeled and simulated by the MDSG model. The simulation results of mass flow, pressure, and temperature are compared with the experimental results, and the error is less than 5%, which demonstrates the reliability, practicability, and universality of the MDSG model.     

A novel temperature-compensation method based on correlation analysis for multi-FOG INS

Aimed at improving the bias stability of Fiber-Optic Gyroscope (FOG)-based inertial navigation systems in environments of various ambient temperatures, a novel temperature-compensation method based on a correlation analysis of the same batch of FOGs is proposed. The empirical mode decomposition method was employed to filter the high-frequency noises of the FOGs. Then, the correlation information of the multiple FOGs was used to analyze the feasibility of the method. Eventually, the same residual error of the FOGs was compensated via the simple piecewise linear models. The experimental results indicate that excellent compensation effects for both high- and low-accuracy FOGs are achieved using the proposed method. Specifically, the accuracies of high-accuracy FOGs are improved by approximately 33.9%, 20%, and 31.2%, while those of low-accuracy FOGs are improved by approximately 39.1%, 20.8%, and 26.1%. The method exhibits the merits of simplicity, validity, and stability, and thus is expected to be widely used in engineering applications.     

Modularity,reconfigurability, and autonomy for the future in spacecraft: A review

The shape of a spacecraft is transitioning from monolithic, manual, and static to modular, autonomous, and dynamic. Modular Reconfigurable Spacecrafts (MRSs) offer better solutions than traditional monolithic spacecrafts in several aspects, and may become the next generation of spacecraft systems with efficient design, fast deployment, flexible application, and convenient management. This paper reviews the development and technology of MRS from three aspects: Modularity, reconfigurability, and autonomy. Despite the progress of research on MRS, there is still a lack of unified standards and little understanding of related concepts. Based on the understanding of basic concepts, the studies conducted on MRS are reviewed to identify technical requirements and solutions. Aiming at the future development trend of MRS, a novel modular self-reconfigurable spacecraft, referred to as MagicSat, is proposed. Furthermore, the MagicSat system composition, advantages, and application prospects are studied. The enabling technologies and major challenges of MRS are further analyzed in terms of modularization, integrated management, and self-reconfiguration technologies. Finally, the future development trend of MRS technology is predicted, and corresponding suggestions are provided.     

Passive localization by a single moving observer using TOA only with unknown SRI: Observability analysis and algorithm

Passive localization by a single moving observer using Time of Arrival (TOA) only with an unknown Signal Repetition Interval (SRI) is investigated in this paper. Observability analysis is performed first. The observability condition for uniquely determining the emitter position and SRI is derived. The conditional Cramer-Rao Lower Bound (CRLB) is also analyzed. It is found that the ambiguity of the SRI integer of the first TOA does not affect the theoretical estimation precision of the emitter position and SRI. A Reference-Fixed Differential TOA (RFDTOA)-based Iterative Maximum Likelihood Estimator (IMLE) is proposed, which only needs O(M) computational operations. Theoretical analysis and simulation results show that the Mean Square Error (MSE) of the proposed algorithm could attain the CRLB with moderate Gaussian measurement noise.     

一种可靠的MDIO接口逻辑设计

本文介绍了一种可靠的MDIO 接口逻辑设计的方法。目前已使用在AFDX交换机专用集成电路芯片上。该设计采用VHDL 进行描述,并使用Modelsim进行了仿真,结果表明,该设计的正确性和可靠性。同时在AFDX交换机板级调试过程中,也验证了设计的正确性。     

亚轨道飞行器发动机故障下飞行程序设计方法

针对亚轨道飞行器单台发动机发生故障情况,提出了基于正指数攻角的发动机故障下飞行程序设计方法,给出了不同故障时刻的仿真结果,并与正常飞行情况进行了比较.仿真结果表明,对于不同故障时刻,该方法均能够在满足弯矩约束、攻角限制的情况下使得故障飞行器安全到达预定高度,为后续应急返回机动飞行提供有利的飞行条件.     

喷油杆与凹腔支板稳定器近距匹配雾化特性

以水和煤油为雾化介质,采用马尔文激光粒度仪研究了来流马赫数为0.16~0.24、喷雾压差为0.30~0.90MPa、喷油杆与凹腔支板稳定器间隔为31.5mm且顺喷时液雾在轴向不同位置处的雾化特性.研究结果表明:液滴索太尔平均直径(SMD)随来流马赫数增大而减小,随喷雾压差升高而减小,但凹腔支板稳定器下游远方截面的液滴SMD在主流区对马赫数不敏感,在回流区对喷雾压差不敏感.此外,喷油杆下游液滴SMD沿轴向逐渐减小,沿径向在主流区逐渐增大,在回流区逐渐减小.      

Computational aerodynamic analysis on perimeter reinforced （PR）-compliant wing

Abstract Implementing the morphing technique on a micro air vehicle （MAV） wing is a very chal- lenging task, due to the MAWs wing size limitation and the complex morphing mechanism. As a result, understanding aerodynamic characteristics and flow configurations, subject to wing structure deformation of a morphing wing MAV has remained obstructed. Thus, this paper presents the investigation of structural deformation, aerodynamics performance and flow formation on a pro- posed twist morphing MAV wing design named perimeter reinforced （PR）-compliant wing. The numerical simulation of two-way fluid structure interaction （FSI） investigation consist of a quasi- static aeroelastic structural analysis coupled with 3D incompressible Reynolds-averaged Navier- Stokes and shear-stress-transport （RANS-SST） solver utilized throughout this study. Verification of numerical method on a rigid rectangular wing achieves a good correlation with available exper- imental results. A comparative aeroelastic study between PR-compliant to PR and rigid wing per- formance is organized to elucidate the morphing wing performances. Structural deformation results show that PR-compliant wing is able to alter the wing＇s geometric twist characteristic, which has directly influenced both the overall aerodynamic performance and flow structure behavior. Despite the superior lift performance result, PR-compliant wing also suffers from massive drag penalty, which has consequently affected the wing efficiency in general. Based on vortices investigation, the results reveal the connection between these aerodynamic performances with vortices formation on PR-comoliant wing.     

样本重复使用失效响应曲线分析结构可靠度方法

用基于样本重复使用失效响应曲线逼近法,为充分利用迭代过程中的样本点,提出了样本重复使用的思想,并由此发展出一种结构可靠度的计算方法.利用可靠度指标作为收敛条件,从迭代收敛后的所有样本点中选取靠近失效界线处的样本点构造失效曲线响应函数,最后通过蒙特卡洛抽样的方法计算可靠度.多个算例表明:该响应函数避免了对传统意义上的功能函数响应面的模拟,降低了模型维数,又由于适当地 引入了带交叉项、具有曲线旋转功能的响应函数,因此能够很好地逼近失效曲线,有效地提高可靠度计算精度.