气压高度表辅助下GPS接收机自备完善性监测可用性研究

 对我国范围内飞机非精密进场及终端航行时全球定位导航系统（ＧＰＳ）接收机自备完善性监测（ＲＡＩＭ）的可用性进行了研究，分析了气压高度表辅助和故障偏置大小对ＧＰＳＲＡＩＭ可用性的影响。结果表明：气压高度表与ＧＰＳ组合是提高ＲＡＩＭ可用性的有效措施；过大或过小的偏置误差将产生较小的漏警概率，而中等大小的故障偏置则产生较大的漏警概率     

Estimating Bias in Loran Lines of Position

A method of determining bias in calculated Loran-C coordinates is presented. The bias in calculated coordinates results from the complexity of the propagation problem. To remove the bias, a bias function is determined by regression analysis using observed time differences. Two examples of application to field data are given.     

速率偏频激光陀螺偏频速率模糊PID自适应控制的设计与实现

应用模糊 PID自适应技术设计并实现了激光陀螺偏频速率的控制系统,结果表明 :偏频台速率平稳性优于 3.1 2× 1 0 - 4;角速率正反换向速度快,在± 60°/ s之间的转换时间约为 1 4 ms,而且换向过程速率超调很小。该控制系统在实际系统中得到了良好的应用     

Multisensor multitarget bias estimation for general asynchronous sensors

A novel solution is provided for the bias estimation problem in multiple asynchronous sensors using common targets of opportunity. The decoupling between the target state estimation and the sensor bias estimation is achieved without ignoring or approximating the crosscovariance between the state estimate and the bias estimate. The target data reported by the sensors are usually not time-coincident or synchronous due to the different data rates. Since the bias estimation requires time-coincident target data from different sensors, a novel scheme is used to transform the measurements from the different times of the sensors into pseudomeasurements of the sensor biases with additive noises that are zero-mean, white, and with easily calculated covariances. These results allow bias estimation as well as the evaluation of the Cramer-Rao lower bound (CRLB) on the covariance of the bias estimate, i.e., the quantification of the available information about the biases in any scenario. Monte Carlo simulation results show that the new method is statistically efficient, i.e., it meets the CRLB. The use of this technique for scale and sensor location biases in addition to the usual additive biases is also presented.     

基于惯性系的光纤寻北仪双位置寻北算法

由低精度光纤陀螺(Fiber Optical Gyroscope,FOG)组成的寻北仪具有结构简单、成本低的优点,但易受地磁和车上复杂外部环境的影响.针对低精度FOG存在地磁零位,寻北仪对外部晃动敏感的缺陷,通过对陀螺进行地磁零位补偿保证陀螺零偏稳定性,在此基础上提出了基于惯性系的双位置寻北算法.算法分别在两个对位进行惯性系寻北,利用双位置对消原理获得不受陀螺固定零偏影响的方位角并完成水平陀螺固定零偏的估计.实验结果表明,陀螺零偏稳定性0.15(°)/h,加速度计零偏稳定性150μg的惯性器件精度下,车上寻北误差1倍标准差小于4.5mil、极差小于10mil、对准时间小于5min.与传统双位置算法相比,所提算法在晃动基座条件下具有对准精度高,环境适应性强的优点.     

基于变偏置电流控制方式的磁悬浮轴承系统控制策略

建立了五自由度磁悬浮轴承试验系统,介绍了变偏置电流控制方式的工作原理,采用H_∞控制策略设计数字控制器,根据系统固有频率处转子的振幅选择加权函数,将转速信号引入数字控制器,研究了变偏置电流控制时系统的动态性能,并与恒定偏置电流控制时系统的动态性能进行比较.研究结果表明,变偏置电流控制不会恶化系统的动态性能,同时能减少磁悬浮轴承25%以上的总电流消耗.      

On-orbit real-time magnetometer bias determination for micro-satellites without attitude information

Due to the disadvantages such as complex calculation, low accuracy of estimation, and being non real time in present methods, a new real-time algorithm is developed for on-orbit magnetometer bias determination of micro-satellites without attitude knowledge in this paper. This method uses the differential value approach. It avoids the impact of quartic nature and uses the iterative method to satisfy real-time applications. Simulation results indicate that the new real-time algorithm is more accurate compared with other methods, which are also tested by an experiment system using real noise data. With the new real-time algorithm, a magnetometer calibration can be taken on-orbit and will reduce the demand for computing power effectively.     

Geolocation of a known altitude object from TDOA and FDOA measurements

Most satellite systems for locating an object on Earth use only time difference of arrival (TDOA) measurements. When there are relative motions between an emitter and receivers, frequency difference of arrival (FDOA) measurements can be used as well. Often, the altitude of an object is known (it is zero, for example) or can be measured with an altimeter. Two sets of geolocation solutions are proposed which exploit the altitude constraint to improve the localization accuracy. One is for TDOAs alone and the other for the combination of TDOA and FDOA measurements. The additional complexity by imposing the constraint is a one-dimensional Newton's search and the rooting of a polynomial. The covariance matrices of the new estimators are derived under a small measurement noise assumption and shown to attain the constrained Cramer-Rao lower bound (CRLB). When there is a bias error in the assumed altitude, using the altitude constraint will introduce a bias to the solution. Since applying the constraint decreases the variance, there is a tradeoff between variance and bias in the mean square error (MSE). The maximum allowable altitude error such that the constraint solution will remain superior to the unconstraint is given. Simulation results are included to corroborate the theoretical development.     

基于最大似然估计的TDOA/FDOA无源定位偏差补偿算法

在到达时差/到达频差(TDOA/FDOA)无源定位系统中,定位问题的非线性使得定位的结果存在偏差,特别是在噪声较大或者接收站布站不合理的情况下,定位的偏差尤其显著。针对这一问题,提出了一种基于最大似然估计的偏差补偿算法。该方法分为3步:首先,利用最大似然估计器对目标的位置和速度进行求解;其次,通过利用目标定位的估计值和含噪的测量值,对目标的位置和速度偏差值进行理论分析和推导;最后,将最大似然估计解减去理论偏差值,得到经过偏差补偿的新的目标定位解。理论分析和实验仿真证明,在一定噪声的情况下,所推导的目标位置和速度的理论偏差值与实际偏差值相符,并且经过偏差补偿后的定位算法,在保持目标定位的均方根误差(RMSE)与原最大似然算法一致的情况下,目标的位置和速度偏差值远远小于原最大似然算法的偏差值,目标定位精度得到了有效的提高。     

神经网络在发动机自适应建模中的应用研究

提出了一种新的基于神经网络的发动机自适应实时模型的建模方法。建模的思想是认为发动机的任何非额定工作都将导致其输出参数的变化,因而可以把这些参数偏离正常工作参数值的变化量,也就是输出偏离量,用来表征发动机的非额定工作情况。把它们作为增广的状态变量,设计卡尔曼滤波器对其进行最优估计,然后用这些输出偏离量的估计值,通过由BP神经网络训练出来的可测输出偏离量与未测输出偏离量的映射关系来校正机载发动机模型的计算输出,使之与真实发动机的输出一致,从而使实时机载模型获得对任何发动机非额定工况的自适应能力。      

Analysis of Modeling and Bias Errors in Discrete-Time State Estimation

This paper concerns the effects of modeling and bias errors in discrete-time state estimation. The newly derived algorithms include the effect of correlation between plant and measurement noise in the system. The effects of nonzero mean noise terms and bias errors are considered. With plant or measurement matrix errors, divergence can occur. The local or linear sensitivity approach to error analysis, where the sensitivity is defined as a partial derivative with respect to a variable parameter taken about the modeled value, will not show this divergence due to neglect of higher order terms. Approximate algorithms are presented which circumvent the problem inherent in the local sensitivity approach. These make use of a "conditional bias" concept which views system error as a bias, conditioned on knowledge of the state estimates. It is shown that the actual error in optimum estimation is orthogonal to the residue error for suboptimum estimation where the residue error is defined as the difference between the actual estimation error and the optimum estimation error. Two examples, one concerning an integrated navigation system, demonstrate the theoretical results.     

Phase Monopulse Error Due to Nonuniform Noise Background

A phase monopulse antenna system can be used for the high accuracy tracking of active or passive objects in space or on earth. Far-field noise sources that are present in the background of the object being tracked will introduce an offset or bias error in the determination of the angle of incidence of the coherent sinusoidal wave received from the source. The dependency of this bias error upon the nonuniformity of the noise background or equivalently upon the asymmetry of the antenna patterns about the direction to the signal being tracked is determined. Although the variance in the measurement of the sinusoidal source direction can be reduced by increasing the post detection integration time, it is shown that the bias or offset error is unaffected by this change. In order to decrease the offset or bias error the predetection bandwidth must be reduced.     

Model QA3000 Q-Flex accelerometer high performance test results

Q-Flex quartz flexure suspension technology has evolved to produce a world class accelerometer with thousands of units delivered in 1991. The Sundstrand Model QA3000 Q-Flex design achieves a new level of inertial grade performance while maintaining a competitive market price. The specification for the QA3000, supported by actual performance data, depicts performance characteristics superior in both bias and scale factor. Long term measurements display bias and scale factor repeatability obtained across temperature over a period of three years. These data exhibit improved thermal behavior with reduced errors. Reaction time and radiation data highlight the performance of the hybrid position detector circuit     

The Low-Energy Telescope (LET) and SEP Central Electronics for the STEREO Mission

The Low-Energy Telescope (LET) is one of four sensors that make up the Solar Energetic Particle (SEP) instrument of the IMPACT investigation for NASA’s STEREO mission. The LET is designed to measure the elemental composition, energy spectra, angular distributions, and arrival times of H to Ni ions over the energy range from ～3 to ～30 MeV/nucleon. It will also identify the rare isotope ³He and trans-iron nuclei with 30≤Z≤83. The SEP measurements from the two STEREO spacecraft will be combined with data from ACE and other 1-AU spacecraft to provide multipoint investigations of the energetic particles that result from interplanetary shocks driven by coronal mass ejections (CMEs) and from solar flare events. The multipoint in situ observations of SEPs and solar-wind plasma will complement STEREO images of CMEs in order to investigate their role in space weather. Each LET instrument includes a sensor system made up of an array of 14 solid-state detectors composed of 54 segments that are individually analyzed by custom Pulse Height Analysis System Integrated Circuits (PHASICs). The signals from four PHASIC chips in each LET are used by a Minimal Instruction Set Computer (MISC) to provide onboard particle identification of a dozen species in ～12 energy intervals at event rates of ～1,000 events/sec. An additional control unit, called SEP Central, gathers data from the four SEP sensors, controls the SEP bias supply, and manages the interfaces to the sensors and the SEP interface to the Instrument Data Processing Unit (IDPU). This article outlines the scientific objectives that LET will address, describes the design and operation of LET and the SEP Central electronics, and discusses the data products that will result.     

切向流与偏流相互干扰对穿孔板声阻抗的影响

对切向流和偏流相互干扰如何影响穿孔板声阻抗进行了细致的实验研究,结果表明:切向流削弱了偏流对穿孔板声阻的调控,但在较高偏流速度下,偏流对穿孔板声阻的影响仍起主导作用;此外,不同的偏流方式(吹气或吸气)与切向流干扰对穿孔板声阻抗的影响有明显区别。最后,尝试通过有效流量系数把不同实验条件下的数据关联起来。     

中国股票市场中的现状偏好现象研究

理性人假设历来饱受诟病,现状偏好现象在成熟资本市场广泛存在.西方行为金融学学者提出了现状偏好理论,而该理论在我国鲜有实证支持.尝试提出了以中国股票市场的正负收益率对换手率的不对称影响来衡量现状偏好现象的理论,选择了我国2011年1月4日至2012年9月28日之间上交所和深交所挂牌的主板A股的数据进行实证分析,发现中国股票市场存在明显的现状偏好现象,并计算出该时期上交所主板A股的现状偏好系数为9.61％,上交所主板A股的现状偏好系数为11.11％.     

Receiver clock-based integrity monitoring for GPS precision approaches

The errors in the vertical position and clock bias estimates obtained from GPS pseudo-range measurements are highly correlated. Therefore, the error in a vertical position estimate can be predicted if we know the clock bias estimation error. The latter can be estimated if the clock bias changes smoothly and, therefore, predictably. The current technology appears capable of manufacturing clocks which can meet this smoothness requirement for airborne use within the constraints of size, weight, and cost. We discuss the theoretical basis and present empirical data from laboratory and field experiments with a commercial rubidium standard to explore the benefits of integrity monitoring for precision approaches based on the receiver clock.     

Multiple Gaussian Targets: The Track-on-Jam Problem

When a radar with amplitude comparison monopulse arithmetic encounters signals from multiple Gaussian sources it will "point" to the centroid of the incident radiation. The probability density function (pdf) of the monopulse ratio when N independent samples of difference and sum signals are processed in a maximum likelihood receiver is derived. For finite jam-to-noise ratio the estimate has a bias which is independent of N. The variance in the estimate does however depend upon N. Central moments of order less than or equal 2N - 2 exist and are given by a simple formula. Plots of the pdf and its bias and variance for various jam-to-noise ratios, locations of the centroid with respect to the boresight direction, and number of samples processed are presented in the accompanying figures.     

Multipath Angle Error Reduction Using Multiple-Target Methods

The usual methods of reducing multipath angle errors in monopulse tracking radar achieve only limited success because they do not attack the root of the problem. A more correct approach is to accept the multipath signal as a second target and utilize a two-target signal processor which angle tracks both wavefronts. The processor will decouple the return signals so that relatively interference-free data on both waves are obtained. In this paper a signal processor for separating signal from (N - 1) multipath components is developed. The processor is then specialized to the case of only one multipath signal and evaluated by a computer simulation. Data show that large improvements are possible as compared to the usual monopulse tracking system. In particular, the usual large bias errors at low elevation angles are eliminated. Tracking precision compares favorably with the theoretically best possible for two-target tracking systems.     

挠性陀螺寻北中的航向误差

陀螺两位置寻北中存在非线性航向误差,其测量航向角与真实的航向角差值的大小随真实航向角的变化而变化,呈现出近似为正（余）弦曲线的波动形式。本文分析了挠性陀螺寻北系统中航向效应产生机理。介绍了陀螺两位置寻北原理及误差模型,重点分析了挠性陀螺仪零次项漂移和一次项漂移对航向误差的影响,推导了误差公式,估计了两位置寻北中陀螺仪精度对测量精度的影响,寻北试验的结果验证了理论分析结论。