共查询到20条相似文献,搜索用时 93 毫秒
1.
In tracking optical beams from a source, a pointing error signal is derived from photodetecting the field in the receiver focal plane. This error signal is then used in some manner to control a gimballed system that continually points the receiver optics toward the source. When the source field undergoes turbulent transmission, the optical beam is attenuated and scattered, and the field is randomly defocused at the receiver. In this case the pointing error of the tracking system will evolve as a random vector process in time, statistically related to the random scattering, the photodetection process, and the dynamics of the gimballing system. Such vector processes have probability densities that satisfy well-known differential equations. These equations are derived in terms of accepted scattering models and tracking systems, assuming quadranttype error detectors are used in the focal plane. Approximate solutions are obtained and analyzed for typical operating conditions, and the manner in which the degree of scattering degrades the entire pointing operation is shown. 相似文献
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Boussalis D. Bayard D.S. Ih C. Wang S.J. Ahmed A. 《IEEE transactions on aerospace and electronic systems》1993,29(4):1204-1215
The authors describe an experimental study of adaptive pointing and tracking control for flexible spacecraft conducted on a complex ground experiment facility. The algorithm used is based on a multivariable direct model reference adaptive control law. Several experimental validation studies performed using this algorithm for vibration damping and robust regulation are extended by addressing the pointing and tracking problem. As is consistent with an adaptive control framework, the plant is assumed to be poorly known to the extent that only system level knowledge of its dynamics is available. Explicit bounds on the steady-state pointing error are derived as functions of the adaptive controller design parameters. It is shown that good tracking performance can be achieved in an experimental setting by adjusting adaptive controller design weightings according to the guidelines indicated by the analytical expressions for the error 相似文献
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Lee A.Y. Yu J.W. Kahn P.B. Stoller R.L. 《IEEE transactions on aerospace and electronic systems》2002,38(2):502-514
Preliminary error budgets for the pointing knowledge, control, and stability of the Space Interferometry Mission (SIM) spacecraft are constructed using the specifications of commercial off-the-shelf attitude determination sensors, attitude control actuators, and other spacecraft capabilities that have been demonstrated in past missions. Results obtained indicate that we can meet all the presently known spacecraft pointing requirements. A large number of derived requirements are generated from this study. Examples are specifications on attitude determination sensors, attitude control actuators, minimum settling time after a rest-to-rest spacecraft slew. Preliminary error budgets constructed in this study must be updated to reflect the changing spacecraft design and requirements 相似文献
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对影响定向通信系统天线波束指向误差的因素进行了分析,给出了一种特殊情形下波束指向误差与姿态角的关系式,同时给出了一般情形下基于最小二乘估计的波束指向误差与姿态角关系的推导方法.给出的关系式和方法对分析定向通信系统波束指向误差提供了理论依据,有助于评估定向通信系统的波束对准情况. 相似文献
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A new method of reducing target glint errors in radar systems is presented. The target is modeled as n reflectors whose magnitudes and phases are known. The reflector positions are described by a dynamical model driven by white Gaussian noise. The resulting vibrations of the target reflectors produce glintlike pointing errors in the radar system. An extended Kalman filter is developed to estimate the positions of the target reflectors; this information is used to substantially reduce the pointing error due to glint. Data illustrating this glint reduction is given. The model is extended by the inclusion of clutter effects modeled in the same fashion as the glint phenomenon. The results presented indicate the limits of usefulness of this technique as a function of both receiver noise and relative clutter amplitude. 相似文献
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Greene M. Walls J. Stensby J. 《IEEE transactions on aerospace and electronic systems》1988,24(6):817-820
A recently proposed method of reducing target glint errors in radar systems using extended Kalman filtering is further extended with the inclusion of and compensation for clutter effects. A discrete target model and discrete Kalman filter (DKF) are used. Simulation results demonstrating the DKF are presented, and the limits on the effectiveness of the method are investigated. The major advantage of the DKF is that it can be implemented in software in the digital processor of the radar, offering flexibility over continuous time filters. The ability of the filter to reduce clutter effects further demonstrates the usefulness of this technique for radar pointing error reduction 相似文献
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Missile terminal guidance seekers that employ optical, infrared, or radar sensors to acquire, lock-on, and track their target are subject to a missile-to-target line-of-sight pointing error during the acquisition phase. The error is due primarily to missile navigation errors (attitude and position) and inaccuracies in predicting the target location. The computational process to obtain the seeker-to-target pointing vector is formulated. Linear perturbation ion of the pointing vector yields the pointing-angle error tions.quaons. A simple quantitative example is given. 相似文献
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A typical function of an angle tracking loop is to keep a radar antenna pointed at a target. The error in pointing is directly related to successful operation of the tracking device; therefore, its behavior is of interest. For a tracker with a general polynomial nonlinearity, an arbitrary initial pointing error, and a bounded deterministic input, a method is developed for finding upper bounds on the magnitude of the tracking error using Volterra series techniques. Convergence regions of the Volterra series are also obtained. Applications of these results are made to a second-order tracking device. 相似文献
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正态分布百分位值和百分率的置信限和容忍限公式 总被引:22,自引:4,他引:22
建立了正态分布置信限曲线方程,给出了其百分位值和百分率的置信限公式和容忍限公式。该公式对完全数据、不完全数据和无失效数据均适用,并且可综合利用当前数据和经验数据。 相似文献
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在协同制导条件下,建立了导引头最大预定指向角误差模型,分析了各种因素对协同制导条件下导引头最大预定指向角误差的影响。结果表明,雷达测角误差和系统时延是影响协同制导中末交班导引头最大指向角误差的主要因素。 相似文献
11.
The performance of a steered beam adaptive array as a function of the beam pointing error is examined. The purpose is to determine how close the steered beam has to be to the actual desired signal arrival angle for good performance. It is shown that the beam pointing error that can be tolerated is essentially a question of dynamic range. The greater the desired signal dynamic range that must be accommodated by the array, the more accurate the beam pointing angle must be. 相似文献
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区间数据整体估计方法 总被引:1,自引:1,他引:0
提出了一种区间数据整体估计方法, 给出整体分布参数的最佳线性无偏估计量及其协方差矩阵, 得到了正态分布、Weibull分布等位置-尺度分布族区间数据百分位值和百分率的置信限估计.该方法可以将不同条件下的试验数据作为一个整体进行统计推断, 将传统的只适用于完全数据的回归分析推广到工程中常见的区间数据的情况. 相似文献
14.
Arnon S. Rotman S. Kopeika N.S. 《IEEE transactions on aerospace and electronic systems》1998,34(2):590-596
An important aspect in satellite optical communication is to obtain minimum bit error rate (BER) using minimum power. This aim can be achieved with very small transmitter beam divergence angles. The disadvantages of too narrow divergence angle is that the transmitter beam may sometimes miss the receiver satellite, due to pointing vibrations. A mathematical model of communication and tracking systems that optimize the BER as function of the transmitter gain is derived 相似文献
15.
Haber F. Bar-Ness Y. Yeh C.C. 《IEEE transactions on aerospace and electronic systems》1983,(6):795-804
The steady state properties of an adaptive array utilizing prior knowledge of both approximate signal arrival direction and signal characteristics are presented. The method combines the features of a directionally constrained array and an array with a self-generated reference signal. Explicit results are obtained for output signal, interference, and noise powers assuming a single interferer is present. The inclusion of a self-generated reference circuit is shown to reduce the sensitivity to pointing error typical of arrays utilizing a zero order directional constraint, the improvement being a consequence of the reduction of the desired signal component fed back to the sidelobe canceling circuit. A relationship between the degree of sensitivity reduction and the quality of the reference signal is developed. Results of computations of signal to interference plus noise ratios for a 7-element 10-wavelength nonuniformly spaced array as a function of pointing error are presented. These results show the behavior with one interferer inside and outside the beamwidth of the quiescent array and with multiple interferers for various degrees of perfection of the reference generating circuit. In all cases the computations confirm that the otherwise severe effects of small pointing errors are substantially reduced. 相似文献
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Two basic concepts of rate aided tracking and position aided tracking are applied to a conventional pointing system in order to improve performance. The aided track signals are derived in an inertial space format and are generated from a Kalman filter algorithm. Computational results are included to show the interplay between the conventional pointing system and the aided track filter. 相似文献
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Corrections of pointing data provided by gimbal readout transducers can be used to compensate for the errors that arise because of gimbal misalignments and inaccuracies in transducer readout. This paper reviews the sources of pointing error in precision gimbaled pointing systems and describes the techniques for determining them. In particular, a method of calibration that is suitable for systems in which constraints on gimbal travel preclude the use of conventional calibration procedures is presented, and the pointing readout accuracy that can be achieved by this method is evaluated. 相似文献