中远程空地导弹末制导自适应控制

讨论了中远程空导弹的自适应控制规律,基于古典控制器模型,设计了自适应自动驾驶仪：通过适当选择自适应参数,保证了系统良好的动态品质和干扰抑制特性;提出了一种基于李亚诺夫稳定性理论的飞行控制系统方案,推导了自适应控制规律,并对导弹多种飞行高度和初如条件进行了仿真计算,仿真结果表明,所设计的自适应控制系统性能明显优于古典控制回路,具有较好的应用价值。     

Rapid convergence by cascading Applebaum adaptive arrays

An adaptive array architecture is described which has improved convergence speed over the conventional Applebaum array when the eigenvalue spread of the input signal covariance matrix is large. The architecture uses N+1 Applebaum adaptive arrays in a two-layer cascaded configuration. The gain constants in the first layer are set so that large interfering sources are quickly nulled, but small interfering sources are suppressed more slowly. Since the first layer removes the large interfering signals, the gain constant for the second layer can be set to a large value to quickly null the smaller interferers. The adaptation time is examined for several combinations of signal levels and array sizes. It is shown that, in many signal environments, the computational requirements for the cascaded array compare favorably with those of conventional sample matrix inversion (SMI) methods for large arrays     

铁磁性纳米线阵列磁滞回线的模拟

讨论了铁磁性纳米线磁滞回线的特点及其影响因素，使用蒙特卡洛方法模拟了在周期性边界条件下的磁性纳米线阵列的磁滞回线，利用模拟的方法研究了不同长度的混乱度对平均长度相同的铁磁性纳米线阵列磁滞回线的影响。研究发现，铁磁性纳米线阵列的长度的混乱度越高，其磁滞回线的饱和磁场强度随着升高．剩余磁化强度则有所降低。     

Reference Loop Phase Shift in an N-Element Adaptive Array

Adaptive arrays based on the LMS algorithm require the generation of a reference signal which is usually derived from the array output. A particular problem associated with this technique is that of a phase shift in the reference signal loop. The effects of this phase shift on the performance of an N-element adaptive array are discussed. It is shown that a reference loop phase shift causes the array weights to cycle, thereby frequency translating the signals at the output. The weight-cycling frequency is related to various system parameters of an N-element array. In particular, it is observed that the cycling frequency increases as the number of antennas (N) increases.     

Improved Phase-Locked Loop Performance with Adaptive Phase Comparators

A major problem in phase-locked loop (PLL) design is to meet the requirements of both fast signal acquisition and good synchronous mode performance. This relation is reviewed for different types of phase comparators. As a result a new phase-and-frequency comparator is proposed. This comparator is based on an up-down counter principle and can be considered as an adaptive acquisition control circuit. The analysis of a PLL with the proposed phase comparator is based on an exact calculation method for the pull-in time. It is shown that fast signal acquisition is possible without affecting the filtering properties of the loop. Experimental results are given of the acquisition behavior of a second-order type-2 loop which show a good correspondence with the theoretical analysis.     

一种直升机涡轴发动机加速自适应控制研究

提出一种直升机涡轴发动机加速自适应控制方案,它是在ＮＧＧ／ｐ＊２ＰＩＤ控制的基础上加自适应控制律。当发动机性能老化或损伤时,加速时可能引起压气机喘振,这种自适应加速控制方案能适应对象这种性能变化,自动调整方案以消除加速过程出现的喘振现象。这种加速控制比传统的ｗｆ／ｐ＊２开环加速控制具有较高的控制精度,也具有类似高度补偿和喘振恢复项ｐ＊２。这种自适应加速控制只需对原有ＦＡＤＥＣ控制的硬件稍作修改,主要依靠微机控制软件修改就可以将ＦＡＤＥＣ控制提高到自适应控制水平。     

一种鲁棒混合自适应控制器

 目前,国内外关于对象具有干扰或未建模动态时的混合自适应控制,仍处于探索阶段。由于连续对象混合控制系统在某些方面优于全连续或全离散系统,因而引起了国内外学者的重视。 本文提出一种新的适用于受扰对象的混合自适应律,并且从理论上证明了由这种控制律所构成的自适应控制器具有鲁棒稳定性。     

An Adaptive Estimation Algorithm for Time-Varying Bit Synchronizers

This paper presents an adaptive estimation algorithm for bit synchronization, assuming that the parameters of the incoming data process are time varying. The data are linearly related to the state variable to be determined. By employing the Gauss-Markov theorem, the optimal recursive estimate (including the nonstationary property of the system), which is a matrix operation on the transformed data, is obtained. The efficiency of the estimator is measured by the amount of data required and the speed of convergence. Both of these have proved to be of satisfactory and acceptable quality.     

Circular array STAP

Traditionally, space-time adaptive processing (STAP) for airborne early warning (AEW) radar has been applied to uniform linear arrays (ULAs). However, when considering the overall radar system, electronically scanned circular arrays have advantages: a better combination of even and continual angular and temporal coverage, and mechanical simplicity because it does not need to rotate. This paper answers the question “How well does STAP perform when applied to a circular array?” This paper shows that for the AEW mission, circular arrays are indeed STAP compatible. However, when conventional STAP algorithms are used there may be a small loss in performance when compared with a ULA. With some care in the choice and implementation of the STAP algorithm, the majority of the degradation is at close ranges, where the target returns are relatively strong. At long ranges performance is barely affected. A STAP algorithm which compensates for the circular array environment and provides better performance than existing algorithms is presented     

Upper Bound of a Loop Gain in a Power Inversion Adaptive Array

A loop gain is an important parameter in a power inversion adaptive array. The upper bound value of the loop gain is obtained which prevents the array suppressing a desired signal seriously. This result is very useful for determining the loop gain.     

铣削过程在线辨识与极点配置自适应控制

 研究了铣削加工过程的建模、参数在线辨识及自适应控制问题,为铣削过程建立了二阶离散传递函数模型,提出了一种修正的带遗忘因子递推最小二乘参数辨识算法,从而解决了普通递推最小二乘辨识算法中由于递推计算协方差矩阵衰退或膨胀引起辨识结果失真的问题,采用极点配置设计原理,为铣削过程推导了自适应控制的控制律。仿真和实验表明,修正的最小二乘辨识算法和极点配置自适应控制律是正确和可靠的,自适应控制器可获得所需的响应性能。     

A novel model-based multivariable framework for aircraft gas turbine engine limit protection control

Control technologies are innovated to satisfy increasingly complicated control demands of gas turbine engines. In terms of limit protection control, a novel model-based multivariable limit protection control method, which is achieved by adaptive command reconstruction and multiple-control loop selection and switch logic, is proposed in this paper to address the problem of balancing smaller thrust loss and safe operations by comparing with widely-used Min-Max logic. Five different combination modes of control loops, which represent the online control loop of last time instant and that of current time instant, is analyzed. Different command reconstructions are designed for these modes, which is based on static gain conversion of amplitude beyond limits by using an onboard model. The double-prediction based control loop selection and switch logic is developed to choose a control loop appropriately by comparing converted amplitude beyond limits regardless of one or more parameters tending to exceed limits. The proposed method is implemented in a twin-spool turbofan engine to achieve limit protection with direct thrust control, and the loss of thrust is improved by about 30% in comparison with the loss of thrust caused by Min-Max logic when limit protection control is activated, which demonstrates the effectiveness of the proposed method.     

柔性制造系统运行设计的自适应仿真研究

 把控制理论中的自适应控制策略应用到柔性制造系统仿真软件的开发中来,提出了自适应仿真思想用于柔性制造系统运行设计,在一定范围内解决了集成智能仿真环境中对柔性制造系统仿真结果的自动优化等问题,并对自适应仿真进行了展望。     

Two-State Feedback Loop Adaptive Arrays for Pulsed Interference Signals

A two-state feedback loop is presented which increases the effectiveness of an adaptive array in the presence of pulsed interference signals. In the case of the two-state feedback loop, one state permits the maximum adpative response, consistent with the loop stability, and is activated in the presence of an interfering pulse. During the other state, which is activated when the interfering pulse is off, the weights are frozen at the values reached at the end of the last interfering pulse and are maintained until the next disturbance occurs. It is shown that an adaptive array with the proposed two-state loops steers permanent minima in the direction of the interfering signals, irrespective of their duty cycle. The performance of a communication system protected by such an adaptive array improves significantly over one protected by a conventional adaptive array.     

机动目标“当前”统计模型与自适应跟踪算法

本文提出机动目标“当前”统计模型的概念并建议用修正的瑞利-马尔科夫过程描述目标随机加速机动的统计特性。文中指出了在机动目标运动模型中状态（机动加速度）估值与状态噪声之间的内在联系。在此基础上提出了具有机动加速度均值及方差自适应的卡尔曼滤波算法。对一维和三维的情形进行了计算机模拟。计算结果表明,在仅对目标位置进行观测的情况下,这类自适应估值算法无论对高度机动或无机动的目标均可绘出较好的位置、速度及加速度估值。     

Control-Loop Noise in Adaptive Array Antennas

Adaptive array receiving antennas can be designed to sense the external noise field and to optimize the array illumination function. A substantial improvement in signal-to-noise ratio can be obtained with adaptive arrays when the external noise field is nonuniformly distributed in angle. The external noise process may be time varying and contain both discrete sources and continuously distributed sources. Two adaptive array implementations which maximize the signal-to-noise ratio are described in this paper. Expressions are derived for control-loop noise, i.e., the variance of the array element weights, and for the additional noise in the array output due to this element weight noise. It is shown that both the element weight noise and the array convergence rate are determined by the eigenvalues of the noise covariance matrix.     

Adaptive image segmentation using genetic and hybrid search methods

This paper describes an adaptive approach for the important image processing problem of image segmentation that relies on learning from experience to adapt and improve the segmentation performance. The adaptive image segmentation system incorporates a feedback loop consisting of a machine learning subsystem, an image segmentation algorithm, and an evaluation component which determines segmentation quality. The machine learning component is based on genetic adaptation and uses (separately) a pure genetic algorithm (GA) and a hybrid of GA and hill climbing (HC). When the learning subsystem is based on pure genetics, the corresponding evaluation component is based on a vector of evaluation criteria. For the hybrid case, the system employs a scalar evaluation measure which is a weighted combination of the different criteria. Experimental results for pure genetic and hybrid search methods are presented using a representative database of outdoor TV imagery. The multiobjective optimization demonstrates the ability of the adaptive image segmentation system to provide high quality segmentation results in a minimal number of generations     

Adaptive processing at the subarray level

This paper describes a class of partially adaptive arrays with adaptive processing applied to the outputs of steered subarrays. The problem is to detect a signal or estimate its direction of arrival in the presence of jammers. The advantage of applying adaptive processing to subarrays is that it requires much less CPU time than the corresponding fully adaptive processing. The subarray processing equations for the two kinds of problem are described. In this paper, we compare partially adaptive processing performance with fully adaptive processing performance in the case of the following antenna and signal sources:

• •- array with regularly spaced sensors ;
• •- between 20 and 100 elements ;
• •- between 3 and 20 subarrays ;
• •- a single jammer ;
• •- desired signal from the antenna zenith.

We suggest a method for determining the optimal subarray configurations in this case. An example is given to show that the performance of an antenna with five subarrays is comparable to that of a fully adaptive thirty-element array for eliminating a single jammer with a target at the zenith.     

An Lms Adaptive Array Using a Pilot Signal

A least mean square (LMS) adaptive array requires a reference signal. When the desired signal contains a pilot signal, it may be used as the reference signal. In this paper the steady-state performance of an LMS adaptive array in which the pilot signal is used as the reference signal is examined. It is shown that the LMS adaptive array occasionally suppresses the desired signal. The loop gain, which is an important parameter, is also considered.     

Costas array generation and search methodology

Costas arrays are permutation matrices that provide sequencing schemes for frequency hop in FSK waveforms. Such frequency-shift keying (FSK) waveforms can be designed to have nearly ideal ambiguity function properties in both the time and frequency directions: the Costas property permits at most one coincident tone in autocorrelations in both time and frequency. Costas arrays are found by number-theoretic generators and their extensions, and by exhaustive search methods. Two new extensions of number-theoretic methods are introduced here that find two new Costas arrays. All Costas arrays for orders 24, 25, and 26 are disclosed here, including previously unknown examples.