无人机仿真测试系统设计应用研究

仿真测试系统可以对无人机控制规律进行有效的检测和评估,在无人机研制中起到重要作用。通过研究无人机仿真测试系统工作原理,建立了无人机动力学和运动学数学模型,采用四阶龙格-库塔法进行解算,得到了无人机位置、高度和姿态等信息,对无人机飞行控制的稳定性进行有效验证和评估,并成功运用于某型无人机的研制中。     

Modified unscented Kalman filtering and its application in autonomous satellite navigation

In this paper, a modified unscented Kalman filter (UKF) for nonlinear stochastic systems is proposed, and it is applied to autonomous orbit determination for Earth satellites. Based on some standard results about the boundedness of stochastic processes and a new formulation of the unscented transformation (UT), it is demonstrated that the design of the noise covariance matrix plays an important role in enhancing the filter stability. Furthermore, a particular design of the noise covariance matrix is proposed as a modification of the UKF. The modified UKF is less sensitive to the initial error than the usual one. High performance of the modified UKF is illustrated in comparison with the usual one by using the real data obtained from an Earth sensor.     

某型无人机运动学建模与分析CSCD

采用运动学建模方式对无人机进行总体设计,并通过数字风洞仿真实验对其进行验证,结果表明设计指标正确、合理。     

Temporal and spatial stochastic behaviour of high-frequency slant tropospheric delays from simulations and real GPS data

In this paper, a turbulence theory-based simulation procedure for slant tropospheric delay variations is presented. Based on this procedure tropospheric delay variations are simulated for three different geometric scenarios. The stochastic behaviour of the generated time series is assessed in terms of temporal structure functions. It is shown that the temporal structure functions – in general – follow a 5/3 to 2/3 power-law behaviour. Deviations from this behaviour due to the complex interaction between varying observation geometry and atmospheric/turbulent conditions are discussed.     

A simulation analysis of systematic errors in ion arrival angle and drift velocity from the satellite borne ion drift meter

As one payload of a Chinese seismic satellite program, an ion drift meter (IDM) will measure drift velocity of thermal ions at an altitude of 500 km. Previous works have shown that such instruments use biased grids to create nonuniform potential in the grid planes, which brings systematic errors to the inferred parameters. A commercial finite element analysis software is used to simulate this instrument in the exact size. The error sources from thermal velocity, nonuniform transparency of real grids and potential depression in the grid planes are explained. The simulation results show that the arrival angle and drift velocity will be underestimated in all the conditions and the maximal error will be about −0.87° and −121 m/s, respectively. Furthermore, the relative error of the inferred arrival angle and the drift velocity will be inversely correlated with the arrival angle because of the lensing effect of the potential depression. This simulation provides a quantificational method of evaluating and correcting the data during in situ operation.     

Real-time global MHD simulation of the solar wind interaction with the earth’s magnetosphere

We have developed a real-time global MHD (magnetohydrodynamics) simulation of the solar wind interaction with the earth’s magnetosphere. By adopting the real-time solar wind parameters and interplanetary magnetic field (IMF) observed routinely by the ACE (Advanced Composition Explorer) spacecraft, responses of the magnetosphere are calculated with MHD code. The simulation is carried out routinely on the super computer system at National Institute of Information and Communications Technology (NICT), Japan. The visualized images of the magnetic field lines around the earth, pressure distribution on the meridian plane, and the conductivity of the polar ionosphere, can be referred to on the web site (http://www2.nict.go.jp/y/y223/simulation/realtime/).The results show that various magnetospheric activities are almost reproduced qualitatively. They also give us information how geomagnetic disturbances develop in the magnetosphere in relation with the ionosphere. From the viewpoint of space weather, the real-time simulation helps us to understand the whole image in the current condition of the magnetosphere. To evaluate the simulation results, we compare the AE indices derived from the simulation and observations. The simulation and observation agree well for quiet days and isolated substorm cases in general.     

Study on Simulated Human Load in Unmanned Spaceship

This article introduces the methods for testing and verifying the performance of a new type of oxygen supply apparatus as well as the performance of the Environment Control and Life Support System(ECLSS)in the airtight unmanned space capsule,with a simulated human load instead of animals or human in China's Manned Space Program.The simulated human load also supplies a dummy for the spaceship to instal the envirmental testing equipment,to wear spacesuit,and to match the weight in spaceship.     

Convection of liquid with internal heat release in a rotating container

The convection of heat-generating fluid in a rotating horizontal cylinder is experimentally investigated. The threshold of convection excitation, the structure of convective flows and the heat transfer in the cylinder depending on the heat release capacity, liquid viscosity and aspect ratio of the cavity are studied. It is found that the average convection is excited by the thermovibrational mechanism —the gravity force, rotating in the cavity frame, produces the oscillations of non-isothermal fluid relative to the wall, which in turn result in excitation of mean convective flows. It is shown that the structure of convective flows depends on the dimensionless velocity of rotation. At relatively low rotation velocity the convection develops in the form of a periodic system of vortices regularly distributed along the cylinder axis. The threshold of excitation (critical value of vibration parameter) of three-dimensional vortex structures grows with rotation velocity. Above some definite rotation velocity the convection develops as two-dimensional rolls parallel to the axis of rotation. The threshold of two-dimensional structures excitation does not depend on the rotation velocity. Besides the structure of thermal convective flows the analysis of the relatively weak currents generated by the inertial waves below the threshold of convection is performed.     

系统不确定性边界未知的变结构控制器设计方案

在设计变结构控制器的过程中，确定对象不确定性的范围是一个重要的前提步聚。但是，在某些情况下要确定其边界是相当困难的，或者存在不能精确描述的外部扰动不可能得到其变化的准确范围。针对上述问题，在传统的变结构控制器中加入了对应不确定因素的自适应环节，并证明了该方法设计之控制器的稳定性。仿真结果表明了该法的有效性。     

光学采样成像系统传递函数补偿的仿真研究

简要概述了光学采样成像系统组成及调制传递函数补偿（MTFC）概念；采用计算机仿真的方法模拟成像链路，MTFC是成像链路的一个重要环节，通过改变成像链路中的参数，研究链路中的混叠、光学遥感器噪声、量化、有损压缩对MTFC的影响。