考虑参数摄动的飞行器气动伺服弹性鲁棒稳定性分析研究

高超声速飞行器通常结构整体柔度大、飞控系统权限大、飞行环境复杂、气动加热严重,极易导致由结构、气动、热和控制等耦合引起的气动伺服弹性稳定性问题。由于建模复杂、不确定性多及参数摄动影响,传统的稳定性分析方法不适用分析飞行器气动伺服弹性系统的鲁棒稳定性。利用线性分式变换,考虑多种参数摄动,由子系统到整个闭环系统依次建立气动伺服弹性状态空间模型,并应用结构奇异值?方法分析了系统的鲁棒稳定性。分析结论表明了该建模方法的有效性以及?方法在飞行器气动伺服弹性鲁棒稳定性分析中的应用前景。     

μ-synthisis方法在结构一声耦合系统鲁棒控制中的应用

以在工程中普遍存在的封闭空间结构一声耦合系统为对象，基于鲁棒结构奇异值理论，建立了结构一声耦合系统鲁棒主动控制模型，提出了设计鲁棒μ-synthesis。控制器的方法：通过引入虚拟的不确定块，将耦合系统响应性能的问题转化为广义系统的稳定鲁棒性问题，采用标准D-K迭代法求解该增量系统的稳定鲁棒控制器。封闭空间结构一声耦合系统的控制仿真表明，同鲁棒H∞控制结果相比，μ-synthesis方法对模型不确定性具有良好的稳定鲁棒性和性能鲁棒性。同以往的研究相比，新意在于应用μ-synthesis方法设计了结构一声耦含系统鲁棒控制器，以克服H∞控制器的不足。     

非线性奇异时滞系统的鲁棒同时保性能优化控制

针对一组非线性奇异时滞系统的鲁棒同时保性能控制问题进行研究,用范数有界的不确定参数的微分方程组描述所考虑的系统;基于Lyapunov-Krasovskii泛函和线性矩阵不等式方法给出存在同时保性能控制器的充分条件;对具有线性矩阵不等式约束的凸优化问题求解,进而明确给出使得性能指标函数上界达到最优值控制器的表达式;该控制器的设计方法不仅使得奇异时滞闭环系统组正则、无脉冲、同时鲁棒稳定,而且性能函数上界最优;最后,给出算例验证该方法的有效性。     

基于随机鲁棒优化的导弹姿态控制系统设计

针对多目标优化算法设计的控制系统鲁棒性不强的问题,基于随机鲁棒方法设计了导弹姿态控制系统参数,并进行了对比仿真验证。在确定姿态控制系统结构基础上,根据系统对快速性和稳定性的要求,提出一个包含系统稳定性、时域指标和频域指标项的指标体系。在此基础上,通过对各指标或各指标的不满足概率适当加权,分别为粒子群优化算法和随机鲁棒方法定义适应度函数,并在参数取值区间内对待定控制参数进行寻优,从而实现姿态控制系统参数的优化整定。蒙特卡洛仿真实验表明了随机鲁棒方法用于鲁棒控制系统设计的有效性。     

不确定中立型奇异系统的时滞相关鲁棒H_∞滤波器的设计

研究了不确定中立型奇异系统的时滞相关全阶H∞滤波器的设计问题,利用Lyapunov-Krasovskii泛函方法,得到了以线性矩阵不等式（LMI）表示的滤波误差动态系统的时滞相关的鲁棒H∞性能分析。在此基础上,给出了不确定中立型奇异时滞系统的鲁棒H∞滤波器存在的时滞相关的充分条件。通过数值例子验证了该方法的可行性。     

一种基于最优算法的导弹鲁棒稳定性评估方法

在对参数不确定性导弹控制系统进行多通道鲁棒稳定性评估时,传统方法在计算效率及结果可靠性方面存在不足。提出一种遗传-Nelder-Mead单纯形混合优化算法,利用遗传算法的全局搜索能力,寻找目标函数的近似最优解,并将其作为Nelder-Mead单纯形法搜索的初值,利用Nelder-Mead单纯形法局部寻优的优势,在近似解的邻域内搜索精确解。通过测试函数验证,算法在计算效率和计算精度方面都有很大提升。最后讨论了算法在导弹控制系统鲁棒稳定性评估中的应用价值。     

跨大气层飞行器气动伺服弹性稳定性分析方法研究

跨大气层飞行器通常采用翼身组合体外形,机体结构柔性大,飞行控制系统通道之间交联耦合且通频带宽、再入扰动因素复杂、气动加热严重,上述因素可能导致气动伺服弹性或热气动伺服弹性问题。考虑外界干扰不确定性、飞行器模型摄动和控制通道耦合等因素,跨大气层飞行器需进行多通道交联耦合气动伺服弹性鲁棒稳定性分析。通过弹性飞行器动力学建模、非定常气动力拟合、伺服系统和飞行控制系统建模,建立了气动伺服弹性系统的闭环模型。在此基础上对Nyquist方法、最小奇异值法以及结构奇异值μ方法等气动伺服弹性稳定性分析方法进行了分析与讨论,得出相关结论。     

一类不确定非线性系统的指数镇定控制

研究一类不确定非线性系统的鲁棒镇定问题。应用输入/输出反馈线性化法和李亚普诺夫方法,提出了一种基于不确定项上界的连续型鲁棒镇定控制器设计方法。所提出的鲁棒镇定控制器不仅可确保相应闭环系统的可观状态指数稳定、内部状态一致最终有界,而且计算简单,更易实现。最后给出了一个仿真算例,仿真结果证明了所提方法的可行性与有效性。     

基于μ综合的防空导弹自动驾驶仪设计

针对防空导弹自动驾驶仪设计中存在的建模误差,提出了μ综合自动驾驶仪的设计方法,通过引入虚拟不确定块将控制系统的鲁棒性能问题转化为广义系统的鲁棒稳定问题,采用标准的D-K迭代法求解系统的鲁棒控制器.仿真结果表明,基于标准弹道上某特征点的一个确定数学模型设计的μ综合自动驾驶仪,可控制导弹沿标准弹道的全弹道稳定准确地飞行.系统对模型不确定性具有较好的鲁棒稳定性和鲁棒性能.     

飞行器大包线鲁棒飞行控制律设计

对于飞行器随环境改变而参数变化范围较大的问题,研究采用鲁棒控制方法进行控制律设计。重点研究被控对象不确定的建模问题。将飞行器参数变化视为飞行器对象的不确定性,分别给出了时域和频域两种不确定性的建模方法。采用时域状态空间模型不确定性的线性分式变换描述方法,对某飞行器进行了大包线范围的μ综合鲁棒控制律设计。设计仿真结果表明,控制系统不但具有鲁棒稳定性,而且具有鲁棒性能。     

Stability of the Third Generation Intensifier under Illumination

The stability under illumination of transmission-mode GaAs photocathode sealed in the third generation intensifier is investigated by use of spectral response testing instruments. The variations of spectral response with the illumination times under weak and intense illumination are compared. The variations of photoemission performance parameters are also characterized. The results show that during initial several weak illuminations photocathode behaves no evident decay and a maximum sensitivity is achieved, while under intense illumination the sensitivity of photocathode begin to decrease largely at the first illumination. The calculated performance parameters show that the variation of surface escape probability with illumination times is a direct cause of instability of photocathode. It is also found that under intense illumination peak wavelength is moved towards short-wave and peak response is decreased, which shows that the ability of long-wave response of photocathode is decreased.     

Passive Acoustic Radar for Detecting Supersonic Cruise Missile

A Passive Acoustic Radar is presented as a necessary complement to electromagnetic wave radar, which will be expected to be an effective means for detecting cruise missiles. Acoustic characteristics of supersonic flying projectiles with diverse shapes are expounded via experiment. It is pointed out that simulation experiment could be implemented using bullet or shell instead of cruise missile. Based on theoretical analysis and experiment, the ““acoustic fingerprint““ character of cruise missile is illustrated to identify it in a strong noise environment. After establishing a locating mathematical model, the technique of acoustic embattling is utilized to resolve a problem of confirming the time of early-warning, considering the fact that velocity of sound is much slower than that of light. Thereby, a whole system of passive acoustic radar for detecting supersonic cruise missile is formed.     

Design and Analysis of Test Schemes of Static Postponing Time on Shrapnels Used to Riot Control

The test scheme of static postponing time given in our actual national military test standard on shrapnels used to control riot is a nine-point test scheme on the combined action of three kinds of temperatures and three kinds of pressures,the consumed ammunitions are more excessive. Statistic analysis and tentative checkout about a lot of test data are done,feasibility gists are put forward for optimizing of the test design scheme. The optimizing design and data analysis of test scheme of the item are done by managing uniformity design theory, two scientific and reasonable six-point test schemes are confirmed. The feasibility and reliability of the optimizing design schemes put forward above are proved ulteriorly by test validating. The gained schemes not only have good design uniformity and little ammunition wastage and meet the test demand, but also have better forecast ability for the result data of other points using the mathematic models from the actual test points.     

Super-resolution Restoration of Remote-sensing Images

A novel image restoration scheme, which is super-resolution image restoration algorithm Poisson-maximum-afterword-probability based on Markvo constraint （MPMAP） combined with evaluating image detail parameter D, has been proposed. The advantage of super-resolution algorithm MPMAP incorporated with parameter D lies in the fact that superresolution algorithm MPMAP model is discrete, which is in accordance with remote-sensing imaging model, and the algorithm MPMAP is proved applicable to linear and non-linear imaging models with a unique solution when noise is not severe. According to simulation experiments for practical images, super-resolution algorithm MPMAP can retain image details better than most of traditional restoration methods; at the same time, the proposed parameter D can help to identify real point spread function （PSF） value of degradation process. Processing result of practical remote-sensing images by MPMAP combined with parameter D are given, it illustrates that MPMAP restoration scheme combined PSF estimation has a better restoration result than that of Photoshop processing, based on the same original images. It is proved that the proposed scheme is helpful to offset the lack of resolution of the original remote-sensing images and has its extensive application foreground.     

Design and Simulation of TF and TA Controller for Missile

A nonlinear terrain following(TF) and terrain avoidance(TA) controller is proposed for missile control systems. Based on classical TF algorithm (adaptive angle method), a new method for TF controller is proposed by using angle of attack. A method of obtaining terrain outline data from digital elevation map (DEM) for TF control is discussed in order to save store space. A TA algorithm is proposed by using bank-to-turn technique. The block control model, which is suitable for backstepping design, is given for nonlinear model of missile. Making full use of the characteristics of the system and combining block control principle and backstepping technique, a robust controller design method is proposed. Uncertainties in every sub-block are allowed, and can be canceled by using the idea of nonlinear damping. It is proved that the state tracking errors are converged to a neighborhood of the origin exponentially. Finally, nonlinear six-degree-of-freedom simulation results for the missile model are presented to demonstrate the effectiveness of the proposed control law.     

Design of Non-fragile Satisfactory Estimator for Linear Continuous Perturbed Stochastic Systems

The design problem of non-fragile estimator is addressed for a class of perturbed linear continuous systems. The perturbations occur on the plant and estimator parameters. The estimator designed should force the error system to achieve the desired decay rate and force the steady error variance less than the specified upper bound irrdevancy of the admissible plant perturbations and estimator perturbations. Consistency problem of the decay rate with the variance upper bound is first considered via linear matrix inequality （LMI） approach. The solution of the estimator parameter under specifications to be consistent is then discussed. The consistency condition of specifications and estimator parameter solution are transformed to feasible or minimum problems subject to a set of LMI respectively. The method is illustrated by a numerical example.     

An Improved Scene-based Nonuniformity Correction Algorithm for Infrared Focal Plane Arrays Using Neural Networks

The improved scene-based adaptive nonuniformity correction （NUC） algorithms using a neural network （NNT） approach for infrared image sequences are presented and analyzed. The retlna-like neural networks using steepest descent model was the first proposed infrared focal plane arrays （IRFPA） nonuniformity compensation method, which can perform parameter estimation of the sensors over time on a frame by frame basis. To increase the strength and the robustness of the NNT algorithm and to avoid the presence of ghosting artifacts, some optimization techniques, including momentum term, regularization factor and adaptive learning rate, were executed in the parameter learning process. In this paper, the local median filtering result of Xij （ n ） is proposed as an alternative value of desired network output of neuron Xij （ n ）, denoted as Tij （ n ）, which is the local spatial average of Xij （ n ） in traditional NNT methods. Noticeably, the NUC algorithm is inter-frame adaptive in nature and does not rely on any statistical assumptions on the scene data in the image sequence. Applications of this algorithm to the simulated video sequences and real infrared data taken with PV320 show that the correction results of image sequence are better than that of using original NNT approach, especially for the short-time image sequences （several hundred frames） subjected to the dense impulse noises with a number of dead or saturated pixels.     

Piecewise Filter of Infrared Image Based on Moment Theory

The disadvantages of IR images mostly include high noise, blurry edge and so on. The characteristics make the existent smoothing methods ineffective in preserving edge, To solve this problem, a piecewise moment filter （PMF） is put forward. By using moment and piecewise linear theory, the filter can preserve edge. Based on the statistical model of random noise, a related-coefficient method is presented to estimate the variance of noise. The edge region and model are then detected by the estimated variance. The expectation of first-order derivatives is used in getting the reliable offset of edge. At last, a fast moment filter of double-stair edge model is used to gain the piecewise smoothing results and reduce the calculation. The experimental result shows that the new method has a better capability than other methods in suppressing noise and preserving edge.     

Bistatic Sonar Localization Based on Best Linear Unbiased Estimation

A best linear unbiased estimation （BLUE） algorithm for bistatic sonar localization is proposed. The Cramer-Rao bound for bistatic Sonar and the geometrical dilution of precision （GDOP） in different conditions are given. The simulation results show that the location accuracy of BLUE algorithm is higher than the weighted least square method.     

Research on Gear-broken Fault Diagnosis in a Tank Gearbox

A fault diagnosis method of working position gear in a tank gearbox is put forward based on simulating the fault of working position gear in an actual tank, extracting the envelope of vibration signal by Hilbert transformation amplitude demodulation method, and zooming the low-frequency band to envelope signal.