重力测量稳定平台控制系统设计与实现

介绍了重力测量惯性稳定平台的系统工作原理.设计了一种基于DSP加FPGA架构的嵌入式控制系统.详细描述了控制系统的功能划分以及硬件实现.提出了电流、速度和位置三环回路控制方案.车载测试结果显示稳定平台能实现地垂线跟踪,验证了所设计控制系统的有效性.     

Highest density gates for target tracking

The problem of forming validation regions or gates for new sensor measurements obtained when tracking targets in clutter is considered. Target dynamics and measurement characteristics are modeled with, possible non-Gaussianities or nonlinearities, so that some degree of approximation is usually required in the computation of the filtering densities for the target position and predictive densities for future measurements. Highest density gates (HDGs) are proposed as summaries of the predictive densities. These gates are constructed numerically, via simulation from the filtering density approximation. The algorithm results in gates that are “exact” (up to numerical accuracy) regardless of the approximation used for the filtering density. That is, given an approximation to the filtering density, the gating procedure accounts for all further nonlinearities and non-Gaussianities. Numerical example show that when the predictive density is markedly non-Gaussian, HDGs offer advantages over the more common rectangular and ellipsoidal gates     

网络非法外联监控系统技术探析

内网中的拨号外联行为是一个重大的安全隐患，网络非法外联监控系统可以全面、实时地监控整个单住网络内部的拨号行为。本文介绍了两种主流架构的网络非法外联监控系统，即双机架构与C／S架构，并进行了深入的对比分析，阐述了实际的部署实施策略。     

High-Reliability Strapdown Platforms Using Two-Degree-of-Freedom Gyros

This paper presents a new concept of high-reliability strapdown attitude sensing systems for space vehicles. Each system utilizes a set of redundant two-degree-of-freedom gyros. An optimum system configuration is obtained for maximum system reliability and the best measurement accuracy. Improved accuracy of the final data is obtained by using the least-square data reduction technique. Each system possesses a ?sensor performance management? feature which is capable of failure detection, faulty gyro identification, system reconfiguration, and, possibly, sensor recalibration. Improvement in reliability, as compared to other types of strapdown systems, is demonstrated. Details of the development are described in terms of a system containing four gyros.     

用于SAR运动补偿的DGPS/SINS组合系统研究

使用考虑位置误差相关项的伪距率观测模型 ,研究了用于合成孔径雷达运动补偿的差分 GPS/ SINS伪距率组合系统。结果表明 ,组合系统的长期位置精度能达到 1 m左右。 GPS数据更新率低于 INS,在 GPS测量时间间隔内 ,组合系统的性能仅由 INS决定。虽然 INS误差随时间积累 ,在 GPS数据更新率为 1 s的情况下 ,即使采用中等精度的惯性仪表 ,其相对位置精度为厘米级 (这里相对位置精度指组合系统在 GPS测量时间间隔内位置误差的变化范围)。     

Geostationary Satellite Navigation Systems

The concept of position determination using geostationary satellites as an alternative to the global positioning system (GPS) is studied. The advantage of a geostationary system is that only three, or at most four, satellites are required to cover the continental United States. A total of twelve satellites are sufficient for global coverage (excluding polar regions), or eight if only longitude and latitude, but not altitude, are measured. The system involves the determination of the range to either four geostationary satellites or, if the altitude is not measured, three geostationary satellites. The accuracy of the proposed systems are evaluated to obtain the rms error associated with position determination, and the concept for the implementation of measurements required by the systems is presented. The accuracy of the systems are adequate for civilian use in the continental United States; however, there is a degradation in accuracy as the location of the user approaches the equator.     

Correlation of Multiple-Site Track Data

Tactical air defense systems often require the interchange of target tracking data between two radar sites. This paper presents a systematic and effective procedure, employing correlation gates, for associating , or correlating, track information from one site with that from the other. Using the correlation equation, gate sizes are selected, based on remote and local tracking accuracies, target separation, the number of track coordinates investigated, and the number of successive correlation attempts made, to maximize the selected measure of correlation accuracy. The modeling of physical encounters is discussed and a representative situation is selected for analysis. A variety of correlation procedures are compared in terms of correlation accuracy and ease of implementation.     

Thermal Noise Errors in DF Monopulse Systems Having Log Amplifiers

An analysis of the effects of thermal noise on the accuracy of direction finding (DF) monopulse systems which employ logarithmic amplifiers is presented. Numerical results are presented which indicate that a simple model may be used to compute rms thermal errors for a wide range of signal levels. Analytical results obtained in the limit of large signal-to-noise ratios are compared with standard results used to analyze monopulse systems employing automatic gain control (AGC) circuitry instead of log amplifiers.     

Experimental investigation on static/dynamic characteristics of a fast-response pressure sensitive paint

An optical-based technique using Pressure-Sensitive Paint(PSP) is a promising method to measure the distribution of surface pressure on an aerodynamic model. The static and dynamic characteristics of a fast-response PSP that is developed in the Chinese Academy of Sciences(CAS)are analyzed and tested to serve as the basis for experiments on unsteady surface measurement using a fast-response PSP. Two calibration systems used for this study are set up to investigate the temperature dependency, response time, and resolution. A data processing method, used for dynamic data, is analyzed and selected carefully to determine the optimum signal. Results show that the fastresponse PSP can be used normally at temperatures from 25 ℃ to 80 ℃. The effect of temperature on the accuracy of the measurement must be considered when temperatures are beyond the temperature range of 30–40 ℃. The dynamic calibration device with a solenoid valve can achieve a pressure jump within a millisecond order. The resolution is determined by the signal-to-noise ratio of the photo-multiplier tube. Results of the measurement show that the response time of the PSP decreases with a large pressure variation, and the response time is below 0.016 s when the pressure variation is under 40 kPa.     

Monopulse Resolution of Interferometric Ambiguities

Ambiguities in interferometers with high angular accuracy must be resolved to achieve a practical system design. A new technique for ambiguity resolution is described and is based on monopulse circuitry used with the interferometric elements. The overall angular accuracy of the system is achieved by the interferometer; the angular accuracy of the monopulse subsystem is used to resolve interferometric ambiguities. An expression for the probability of correct ambiguity resolution is derived as a function of element size and monopulse accuracy which indicates that high probability of ambiguity resolution results when the size of the interferometric elements are a fraction of the interferometric baseline. Finally, a comparison between conventional monopulse and interferometric system designs is made for the three principal parameters, signal sensitivity, angular accuracy, and field of view, that dictate the appropriate choice for a particular application. Interferometric systems are more appropriate than monopulse systems for those applications in which angular accuracy and field of view are more important than signal sensitivity.     

分布式电推进飞机动力系统评估优化方法

以电推进飞机的动力系统作为研究对象,开展了以下研究工作：采用电力系统潮流计算方法,分析了采用高压直流供电体制的分布式电推进飞机电气系统,模拟了其在稳定运行状态与断路故障状态下的能量流动关系,同时分析了直流电压等级对电气系统的影响。搭建了完整的分布式电推进飞机动力系统仿真模型,依据基于时间和基于高度的飞行剖面,对比分析了纯电推进与涡轮电推进架构在推进功率、推进效率与航程3个评价指标上的优劣。建立了动力系统典型部件的参数化模型,并使用符号规划算法对建立的参数化模型进行了优化计算,比较了传统涡轮推进与涡轮电推进架构下动力系统质量与燃油消耗率间的优化权衡关系。研究结果为分布式电推进飞机混合动力系统的设计提供了有价值的正向设计方法。     

Radar Altimeter Optimization for Geodesy Over the Sea

The optimum processor and its accuracy limit for radar altimetry for geodetic use over the sea are studied with a model accounting for random surface reflectivity, sea height variation, additive noise, and pointing errors, and allowing for arbitrary antenna patterns, signal modulations, and other system parameters. The ?threshold? case solution (which can have any specified accuracy) dictates a signal modulation bandwidth just shy of resolving the sea height variation and/or illuminated sea area (as scaled into time delay and ?smeared? by pointing errors). For such a modulation a relatively complete solution is obtained. These results are used to determine practical radar altimeter designs, additionally accounting for antenna size, stability, and peak power restraints. Conditions allowing neglecting of limiting or complicating effects due to temporally varying reflectivity, sea height, and vehicle position are given and shown to be satisfied for a typical satellite.     

Accuracy and Error Sens-itivities for Circular Scan Correlator Systems

Correlation guidance systems are being developed and implemented as a means of improving the performance of tactical and strategic missiles. Performance predictions for these systems often neglect the actual correlator structure due to the mathematical difficulties associated with analyzing practical operating correlation systems. In this paper accuracy predictions and error sensitivities to systematic error sources are presented for a circular scan correlation system using the tracking form of the modified difference squared correlation algorithm. In addition, the sine/cosine modulation required to generate the X and Y tracking commands is considered, as well as unequal range and azimuth resolution. The techniques developed to perform this analysis can be easily applied in a simplified fashion to noncircular scan systems and to correlators using a product correlation algorithm.     

Effects of Modulation Nonlinearity on the Range Response of FM Radars

The effect of modulation nonlinearity on the range response of FM radars with harmonic processing and ?triangle? modulation is derived. The nonlinearity may be desirable or undesirable; that is, the sidelobe level of the range response may be decreased or increased depending on the shape and amount of nonlinearity. The results of this paper may be used to predict the actual range laws of existing ?linear? FM radars; or, alternately, to specify the desired amount of modulation nonlinearity for new FM radars so that superior sidelobe suppression can be realized.     

应用标校卫星鉴定测控系统精度方法探讨

根据标校卫星的用途及所需提供的高精度比较标准等技术要求,针对星载比较标准及靶场数据处理状况,提出了改进和提高测控系统精度鉴定的技术途径.探讨和提出了4种类型的数据处理技术和方法,简述了它们的思路和关键技术,分析了应用条件和特点.其中.第1种方法是目前使用的经典鉴定方法;后3种方法（自鉴定方法、精确标准鉴定方法和融合处理鉴定方法）都充分利用了星上测量资源、卫星轨道运动特性以及优良的差分、自校准等融合处理技术,它们都明显优于经典鉴定方法.可以使标校卫星提供更精确的比较标准,扩大其目前的功能和用途.特别是融合处理鉴定方法,不仅可以精确地评定定位系统测量精度,而且可以为测速系统精度评定提供一种良好的技术途径.     

Range and Bearing Estimation in Passive Sonar

Passive sonar systems are used for estimating the range and bearing of signal sources, such as ships or submarines. In this study, the Cramer-Rao bounds on estimation errors are used as measures of the accuracy of the estimates. The bounds show how parameters such as observation time, signal bandwidth, signal-to-noise ratio, and array geometry can be chosen to obtain maximum accuracy. When the array geometry satisfies certain conditions, the bound for range estimate is shown to be independent of the actual source bearing and the bound for bearing estimate independent of both the range and bearing of the source. It is also shown that the same conditions on array geometry ensure that the range or bearing estimation accuracy is not degraded when tne other pammeter is not known.     

非正侧视阵列机载雷达多空间角补偿算法

 非正侧阵列机载雷达的杂波分布随距离变化而变化,各距离单元的杂波分布不再满足独立同分布条件,造成统计型空时自适应处理(STAP)处理器性能下降。本文提出了一种多空间角补偿(MSAC)的非正侧视机载雷达杂波抑制方法,该方法先通过角度-多普勒补偿(ADC)预处理以消除在谱中心处的杂波非均匀,然后采用MSAC法在多个多普勒方向使参考单元和待检测单元的杂波谱保持一致,从而进一步消除在其余方位的杂波非均匀。仿真结果表明了该方法的性能明显优于ADC法,且运算量增加不多。     

Linearization errorʼs measure and its influence on the accuracy of MEKF based attitude determination method

Multiplicative Extended Kalman Filter (MEKF) is one of the most widely used satellite attitude estimation methods. However, the linearization error?s influence is an inherent limitation of this method. In this paper, we aim to analyze this linearization error in the typical satellite attitude determination system with star sensors and gyros. The formulation of linearization error is first derived and the curvature metric is then employed to measure the linearization error. Additionally, we show the reason why linearization error has influence on the performance of MEKF. Based on these analyses, we point out that star sensors? sampling frequency, initial estimated error and accuracy of gyro?s measurement model are the factors that could enlarge the system model?s linearization error. They all affect the linearization error and attitude determination accuracy by decreasing the predicted accuracy. More concretely, the influence of star sensor?s sampling frequency is large, while initial estimated error and gyro?s measurement error within a certain range have little influence on MEKF. Finally, combined with plenty of experiments, validity of the above analyses is verified.     

神经网络最优闭环制导律设计

对于复杂的非线性导弹制导系统 ,很难求得其解析的最优制导律 ,只能求得开环的数字解 ,不能适用于具有时变不确定性的导弹制导系统。利用神经网络的学习和推广能力 ,对开环的数字最优制导律进行离线的学习 ,作为闭环的神经最优制导律在线应用。研究分别选择系统状态变量和视线角速率等不同的神经网络输入对制导系统性能的影响 ,以及各种制导律的鲁棒性问题 ,并采用模块化神经网络结构提高神经网络的学习和推广能力 ,仿真结果得到一些有益的结论。     

基于适航要求的飞机和发动机多余度信号表决设计

为保证机双发或4发在相同油门杆／操纵杆角度下的推力／功率一致,发动机控制系统可使用来自飞机的环境温度、 压力信号。适航要求当飞机信号发生错误时发动机推力变化不超过3%,因此发动机控制系统需要具备飞机信号容错能力。为满 足以上要求,以发动机传感器信号为基准,根据适航条件计算飞机各信号的加权系数,综合发动机传感器基准信号、飞机信号加权 系数及其优先级顺序,设计出飞发系统之间多余度信号加权平均综合表决算法。结果表明：利用该算法,在同时满足飞机多台发 动机推力一致性需求和适航要求的前提下,可选择出精度、可信度较高的信号,在信号选择状态发生变化时,能够保证发动机推力 平稳过渡。