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Dendritic solidification experiments during multiple parabolic aircraft maneuvers for ironcarbon type alloys and superalloys show increased dendritic spacing in lowgravity periods.


Nonlinear loop simulations of real time kinematic (RTK) tracking during highg aircraft maneuvers with vehicleinduced blockages are used to illustrate the filtering method and it s robustness.


Instructors train pilots to fly the full range of aircraft maneuvers or capabilities necessary to accomplish the unit's flying mission.




 It is well known that an Inertial Navigation System(INS) can proyide accurate continuous navigation information in a short period of time, but its errors increase with time. On the other hand, the velocity errors of a Doppler Radar(DR) do not accumulate with time, but the velocity accuracy is poor due to outer disturbances and inherent uncertainties. A DopplerAided Inertial Navigation System (DINS) incorporates the advantages of both INS and DR to give a system which can provide accurate navigation information... It is well known that an Inertial Navigation System(INS) can proyide accurate continuous navigation information in a short period of time, but its errors increase with time. On the other hand, the velocity errors of a Doppler Radar(DR) do not accumulate with time, but the velocity accuracy is poor due to outer disturbances and inherent uncertainties. A DopplerAided Inertial Navigation System (DINS) incorporates the advantages of both INS and DR to give a system which can provide accurate navigation information for a long period of time. An optimum incorporation of the two systems can be accomplished by means of a Kalman filter. From the system point of view, the crux of improving the navigation performance of DINS is to increase the estimating ability of the Kalman filter, that is, to enhance the observability of the state variables. The common me thod applied to analyze the performance of a Kalman filter is the covariance analysis, which can get the estimation effects of the Kalman filter. But it proves to be very difficult for us to employ covariance analysis to make clear the relation between the state estimation and aircraft maneuvers and to make clear the connections among the state variables themselves. This paper, however, chooses an intuitive method, which directly inves tigates the relations between state variables and measurement values. By using this method, the observabilities of both a DopplerAided Strapdown Inertial Navigation System(DSINS) and a DopplerAided Platform Inertial Navigation System(DPINS) are studied. The effects of different types of maneuvers on the system observability are discussed in detail, and major sim ilarities and differences between the characteristics of DSINS and those of DPINS in maneuvers are pointed out particularly. Finally, a sample system, with all its numerical values included, is given.  多卜勒/惯性组合导航系统(DINS)是较复杂的卡尔曼滤波系统。提高DINS的导航性能的关键在于提高卡尔曼滤波器对误差状态的可观测性[1]、[2]。若用通常的可观测性分析法对DINS的可观测性进行研究,不但分析过程复杂,并且难以具体判定不同的飞行动作对于提高各个误差状态的可观测性的作用[3]。本文采取直接从误差状态与量测值的关系入手来分析系统可观测性的方法,详细研究了增强DINS误差状态可观测性的条件和如何利用飞机的机动飞行来实现这些条件;不仅分析了在不同的飞行动作时各个误差状态是否可观测,而且还比较出它们的可观测性程度以及相互之间的联系。最后,通过计算机仿真给出在飞机做弯道飞行时,误差状态可观测性提高的效果。  Based on Bifurcation Analysis and catastrophe theory, a novel theoretical method to forecast jump bifurcation phenomena in the control space is established with nonlinear mathematical models. The jump bifurcation is a type of phenomenon which often occurs in the aircraft maneuvers, such as rapidroll divergence departure, entry into stall and then into spin from steady, straight flight, or recovery into the state of low angle of attack from high angle of attack. Apparently prediction of these phenomena... Based on Bifurcation Analysis and catastrophe theory, a novel theoretical method to forecast jump bifurcation phenomena in the control space is established with nonlinear mathematical models. The jump bifurcation is a type of phenomenon which often occurs in the aircraft maneuvers, such as rapidroll divergence departure, entry into stall and then into spin from steady, straight flight, or recovery into the state of low angle of attack from high angle of attack. Apparently prediction of these phenomena in the control space will be of much help in the design of control law. By means of studying singular lines in the bifurcation surfaces, we get the critical values of control surfaces avoiding rapidroll divergence and provide the guide to extend rapidtoll maneuver scope. According to the change of numbers and stability of equilibrium solutions in the bifurcation surfaces, the thesis works out the control law of bringing planes entry into stall, spin, then returning to stable and controllable state at low angle of attack. The calculation of time history proves the conclusion.  本文以分歧突变理论为基础,采用非线性数学模型,建立了求解分歧面的理论方法。文中通过对分歧面的分析研究,得到了避免飞机出现急滚发散的舵面极限值;通过分析分歧面上平衡解的个数和稳定性的变化情况,设计了使飞机进入或退出失速尾旋的操纵规律。经时间历程验证,所得结论正确可靠。  Integration of a Strapdown Inertial Navigation System (SINS) with a Global Positioning System (GPS) receiver presents many advantages. With thisintegrated design approach, the authors overcome some of the recognized limitations of an INS such as: (1) unbounded position error and pilot initialization,(2) standalone GPS limitations such as poor satellite geometry and dynamicnoise. This paper discusses the synergistic effect obtainable with such an approach,and emphasizes Kalman filter design, system configurations... Integration of a Strapdown Inertial Navigation System (SINS) with a Global Positioning System (GPS) receiver presents many advantages. With thisintegrated design approach, the authors overcome some of the recognized limitations of an INS such as: (1) unbounded position error and pilot initialization,(2) standalone GPS limitations such as poor satellite geometry and dynamicnoise. This paper discusses the synergistic effect obtainable with such an approach,and emphasizes Kalman filter design, system configurations and performanceevaluation. This paper analyzes a specific example and the key features of suchan analysis are: (1) A comprehensive digital computer simulation is developed. (2) Covariance analysis results are presented to demonstrate the improved performance of the proposed integrated system composed of medium accuracy strapdown instrument package and C/A Code GPS receiver under different flight scenarios. In the covariance analysis just mentioned, the authors show that beforeloss of the GPS signal, the navigation errors are bounded by the GPS solutionaccuracy. North, East and vertical velocity errors are 0.07, 0.1 and 0.08m/s(1σ), respectively. North and East positions and altitude errors are 11, 15 and20m (1σ) for precise position locating. During the 180sec GPS signal outagedue to aircraft maneuvers and/or radio noise jamming, the position error increases from 18m to 80m, the horizontal velocity error goes from 0.1m/s to0.7m/s. As a result of inertial velocity aiding, fast reacquiring of the jammedor masked satellite signal can be realized, the navigation error quickly returnsto its full operational values. Accurate and rapid INS inflight alignment canbe accomplished in aircraft straight flight and turns by using GPS measurements. Initial rms azimuth alignment errors are reduced from about 35 arcminto about 2, 5 arcmin in less than 3 minutes. In this paper the authors show that the present integrated system approachallows the error estimation filter design to be less dependent on strict modellingof error dynamics, and that the system can be implemented with a modulardesign approach and is costeffective and reliable.  采用卡尔曼滤波器进行最优组合的GPS/捷联惯性组合导航系统是一种精度高、成本效益好、功能可靠的导航系统。它既能增强GPS接收机的抗干扰能力又能抑制惯导的积累误差。机动飞行和干扰环境下所进行的模拟计算表明,采用C/A码GPS接收机和低精度(0.1°/h陀螺,1×10~(3)加速度计)捷联惯导所组成的系统,定位精度可达20m(1σ),速度精度约为0.1m/s(1σ)。与纯惯导相比,性能精度约提高2个数量级。系统具有对惯性元件进行测漂补偿,对GPS用户钟差进行估计校正和实现惯性平台空中对准的功能,能缩短地面准备时间,提高飞行器的快速反应能力,是一种在航空、航天等领域中有着广阔应用前景的导航定位系统。   << 更多相关文摘 
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