基于数字波束形成的合成孔径雷达干扰抑制方案

提出一种基于数字波束形成(DBF)的机载SAR自适应干扰抑制方案.该方案根据干扰的方向,在成像的过程中,实时地调整接收波束方向图,使得主波束对准成像区域,同时在干扰方向形成零陷.为了在成像过程中,只对波束进行有限次调整,采用了宽零陷波束形成算法.并对该方案的性能进行分析,仿真表明了该方案的可行性和有效性.     

多阵元天线系统BPSK码元优化聚焦通信

在蜂窝移动通信网络中,多阵元天线系统的BPSK调制码元分布优化问题决定了码间干扰抑制性能和信道优化。提出一种基于S变换和模拟退火算法的多阵元天线系统BPSK调制码元优化分布设计算法,建立多阵元天线系统的信道模型,并进行BPSK调制码元帧格式设计,采用S变换的高斯窗函数进行能量聚集,改变移动通信信道中的时变、空变及多径效应,提高了信道传输性能。仿真实验表明,采用该算法进行蜂窝移动通信网络的天线系统设计,能有效抑制干扰,优化天线阵列分布,提高接收阵元信道冲激响应增益,改善提高通信质量。     

WIFI无线局域网中分层空时分组码检测算法研究

为了增加数据传输速率并且提高频谱利用率,WIFI中采用分层空时分组码,分层空时分组码的检测决定着接收机的性能.本文详细推导了分组干扰抑制算法的原理,并且给出了基于分组干扰抑制的最优排序串行算法,针对该算法需要进行大量的数据排序运算,提出了一种次优排序算法.在WIFI信道环境B下,利用MATLAB对最优与次优排序算法进行仿真.实验结果表明,次优排序算法的性能接近于最优排序算法,但该算法使接收机复杂度大大降低.     

几何平均分解的矢量预编码方案设计

将MIMO信道矩阵几何平均分解,基于迫零准则和最小均方误差准则,提出了新的ZF-VP和MMSE-VP矢量预编码设计方案,并联合信道扩展方法将方案进行简化以降低系统设计复杂度,最后通过V-BLAST算法优化系统检测性能.理论分析和计算机仿真结果表明,本文给出的矢量预编码方案在提升系统误码性能方面明显优于其他次优矢量预编码方案.     

加窗对直扩接收机抗干扰算法影响研究

谱线处理是直扩接收机频域干扰抑制的关键,加窗必然影响频域干扰抑制谱线处理算法性能。针对这一问题,研究了加窗对噪声统计特性的影响,在此基础上推导了加窗情况下部分置零法、门限置零法和门限剪裁法等谱线处理算法的相对信噪比损失,以及门限剪裁的最佳门限值等。数值仿真结果验证了理论推导的正确性。     

WIMAX设备单音干扰抑制功能实现

单音干扰是WiMAX通信系统中的一种常见干扰,在基带处理前引入单音干扰算法能有效抑制单音干扰,提高系统性能。本文提出了一种基于Notch滤波器的抑制固定单音干扰算法及其FPGA逻辑实现方法。文中首先阐述了设计思想,然后讨论Notch滤波器原理及设计方法,最后给出该算法在FPGA中的实现及滤波效果评估。评估测试结果表明该算法不仅可以有效抑制WiMAX通信系统的单音干扰而且易于FPGA逻辑实现。     

网络带宽频间谐振干扰时间-尺度分析

在分组交换网络通信系统中,由于带宽频移键控产生谐振干扰,导致信号传输不稳定,甚至产生误码和丢包。提出一种基于连续小波变换与带宽时延-尺度耦合特性构建的复杂网络带宽频间谐振抗干扰算法。对抗干扰模型进行时间-尺度分析,把干扰信号模型分解成一组带宽双曲调频信号,并分析信号时间平移与尺度伸缩等同效应,有效抑制谐振干扰。仿真验证了算法的有效性,时间-尺度建模分析结果准确,有效抑制了网络带宽频间谐振干扰,大幅降低了复杂分组交换网络通信的误码率,对提高网络安全性能具有积极意义。     

一种强干扰下无线拼接组网临界跨越分析算法

强干扰环境下的无线拼接组网是恶劣环境下组网应用的难点所在。传统方法通常采用盲信号分离算法以及普通小波噪声分离对噪声及干扰进行抑制,但是效果并不理想。提出一种强干扰下基于临界跨越分析算法的无线拼接组网技术,首先对组网呼叫信号与噪声进行分离计算,再对处理后的信号进行白化、临界跨越分析,从而提高系统抗干扰能力,实现可靠组网。在实际恶劣环境下进行仿真实验,结果表明采用临界跨越分析算法,系统的组网干扰分布得到了很好的抑制,组网系统具有很好的抗干扰能力,可以被广泛应用。     

一种小区重叠干扰下的通信滤波器噪声抑制算法

小区域重叠干扰下的通信滤波器通信信号由于受到外界环境的干扰通常极不稳定,传统噪声抑制方法只适用于平稳信号,无法实现复杂环境下通信滤波器噪声的抑制,提出一种基于自适应非线性滤波的小区重叠干扰下通信滤波器噪声抑制算法,对小区重叠干扰下的通信信号进行预增强处理,对得到的通信信号和既定阈值进行比较,判断是否需要进行噪声抑制,为小区重叠干扰下的通信滤波器噪声抑制提供有效依据。假设小区重叠干扰喜爱通信滤波器接收信号是同步的,给出采样结果。对滤波器的估计方差和条件方差进行计算,求出背景噪声和干扰剩余之和的方差,通过自适应改变非线性变换的非线性部分的变化曲线,实现小区域重叠干扰下的通信滤波器噪声抑制。仿真实验结果表明,所提方法具有很高的噪声抑制性能。     

认知无线电网络的干扰信道学习算法

认知无线电网络的信道受到干扰情况下,学习性能不好,导致信道失衡。传统的认知无线电网络的干扰信道学习算法采用多模盲均衡宽带压缩频谱联合特征识别算法,当干扰强度较大时,学习均衡性能不好。提出一种基于线性预编码设计的协作频谱共享的认知无线电网络的干扰信道学习算法。通过协作中继方式在服务PU的同时获得传输机会,并给出了PU/SU联合优化的预编码矩阵进行算法改进,采用Jakes功率谱,组成新的云计算联合服务器接收端和发射端节点定位训练序列,将PU、SU预编码矩阵设计问题分解,采用干扰信道学习算法,得到正交通信信道载波均衡控制方程,实现干扰信道的学习算法改进。仿真结果表明,本文算法能有效提高信道学习性能,抗干扰能力增强,吞吐率比传统方法提高35%,展示较好的网络通信性能。     

Distributed fixed-Time secondary control for islanded microgrids: Tackling abnormal data

This paper deals with the distributed secondary control problem for multiple distributed generators in an islanded microgrid. A distributed fixed-time secondary controller is designed for each generator using only its neighbors’ information, where saturation functions are introduced to the designed controllers to constrain the adverse influence of abnormal data from neighbors. Several indicator variables are introduced to reformulate the saturation function to reduce conservatism. The objective of this paper is to realize the recovery of the frequency and voltage as well as the active power-sharing within a fixed time. The fixed-time convergence of the proposed distributed control algorithm is analyzed through rigorous analysis. Also, the upper bound of the settling time is derived, which does not depend on the system’s initial state. Finally, a simulation example is utilized to verify the effectiveness of the proposed distributed control scheme by using the MATLAB/SimPowerSystems toolbox.     

Real time observer and control scheme for a wind turbine system based on a high order sliding modes

The introduction of advanced control algorithms may improve considerably the efficiency of wind turbine systems. This work proposes a high order sliding mode (HOSM) control scheme based on the super twisting algorithm for regulating the wind turbine speed in order to obtain the maximum power from the wind. A robust aerodynamic torque observer, also based on the super twisting algorithm, is included in the control scheme in order to avoid the use of wind speed sensors. The presented robust control scheme ensures good performance under system uncertainties avoiding the chattering problem, which may appear in traditional sliding mode control schemes. The stability analysis of the proposed HOSM observer is provided by means of the Lyapunov stability theory. Experimental results show that the proposed control scheme, based on HOSM controller and observer, provides good performance and that this scheme is robust with respect to system uncertainties and external disturbances.     

Improved krill herd algorithm based sliding mode MPPT controller for variable step size P&O method in PV system under simultaneous change of irradiance and temperature

In recent years, Photovoltaic (PV) systems have been received great attention all over the words as they are sustainable, unlimited and environmentally friendly energy. However, it is required for the PV system to apply a tracking controller to guarantee efficient operation by extracting the maximum power, which named maximum power point tracking (MPPT) method. Due to the simple structure, the conventional perturb and observe (P&O) MPPT algorithm is very popular in the literature. Nevertheless, conventional methods show inaccurate performance, particularly when high variations occur in irradiance, resulting in fluctuations around the MPP. To deal with these challenges, a novel technique on the basis of the variable-step size of P&O MPPT and sliding mode controller (SMC) adjusted by the θ-modified krill herd (θ-MKH) algorithm is presented. The θ-MKH algorithm is utilized to fine-tune the optimal SMC parameters to drive the variable step of the classical P&O algorithm. Simulations are prepared to compare the performance of the suggested scheme with conventional methods by considering simultaneous fast changes of irradiance and temperature. The results show that the suggested scheme have proper performance in both transient and steady-state, particularly under quickly varying climate circumstances.     

基于遗传算法的PID控制器参数优化研究

针对PID控制器在不同的应用系统,需要动态调整PID控制参数的问题,提出了基于遗传算法的PID自适应参数优化方案。该方案通过将PID控制器产生的误差作为目标函数,利用遗传算法实现对PID控制器参数的自动调整。为了提高参数的优化效率,文章通过对交叉算子和变异算子的自适应处理,提高了PID控制器的性能。实验测试表明,文章设计的PID参数优化策略比普通的基于遗传算法优化策略效率平均高14.7%。     

基于Pareto遗传算法的虚拟企业收益分配优化研究

现有的虚拟企业收益分配方法以单一过程为前提,着重于直接分析并提供最终收益分配方案,而没有考虑到时间因素在整个运营过程中的影响,忽略了各影响因素的动态性。本文在虚拟企业的收益分配中增加了时间因素,同时引入激励机制,并结合满意度建立了多目标优化模型,采用Pareto遗传算法进行了优化分析。算例表明所建模型在分析此类问题时较已有方法有一定改善。     

一种基于数字波束形成的抑制星载SAR距离模糊的方案

天线波束形成是改善星载合成孔径雷达(SAR)距离模糊的主要手段之一.提出一种宽零陷波束形成算法,该算法能够在星载SAR模糊区回波方向形成特定深度的宽零陷,从而对模糊区回波进行有效抑制.以一个星载SAR系统为实例,对该方案的性能进行了分析,仿真结果显示该方案的可行性和有效性.     

A family of variable step-size sparsity-aware SSAF algorithms with individual-weighting-factors under model-driven method

Recently, the sparsity-aware sign subband adaptive filter algorithm with individual-weighting-factors (S-IWF-SSAF) was devised. To accomplish performance enhancement, the variable parameter S-IWF-SSAF (VP-S-IWF-SSAF) algorithm was developed through optimizing the step-size and penalty factor, respectively. Different from the optimization scheme, we devise a family of variable step-size strategy S-IWF-SSAF (VSS-S-IWF-SSAF) algorithms based on the transient model of algorithms via minimizing the mean-square deviation (MSD) on each iteration with some reasonable and frequently adopted assumptions and Price's theorem. And in order to enhance the tracking capability, an effective reset mechanism is also incorporated into the proposed algorithms. It is worth mentioning that the presented algorithms could acquire lower computational requirements and exhibit higher steady-state estimation accuracy obviously and acceptable tracking characteristic in comparison to the VP-S-IWF-SSAF algorithm. In addition, the stable step-size range in the mean and mean square sense and steady-state performance are concluded. And the computational requirements are exhibited as well. Monte-Carlo simulations for system identification and adaptive echo cancellation applications certify the proposed algorithms acquire superior performance in contrast to other related algorithms within various system inputs under impulsive interference environments.     

Robust integral backstepping control for sensorless IPM synchronous motor controller

In this paper, a sensorless speed control for interior permanent magnet synchronous motors (IPMSM) is designed by combining a robust backstepping controller with integral actions and an adaptive interconnected observer. The IPMSM control design generally requires rotor position measurement. Then, to eliminate this sensor, an adaptive interconnected observer is designed to estimate the rotor position and the speed. Moreover, a robust nonlinear control based on the backstepping algorithm is designed where an integral action is introduced in order to improve the robust properties of the controller. The stability of the closed-loop system with the observer–controller scheme is analyzed and sufficient conditions are given to prove the practical stability. Simulation results are shown to illustrate the performance of the proposed scheme under parametric uncertainties and low speed. Furthermore, the proposed integral backstepping control is compared with the classical backstepping controller.     

Active fault tolerant control scheme for aircraft with dissimilar redundant actuation system subject to hydraulic failure

In this paper, an active fault tolerant control (AFTC) scheme is proposed for more electric aircraft (MEA) equipped with dissimilar redundant actuation system (DRAS). The effect of various fault/failure of hydraulic actuator (HA) on the system performance is analyzed in this work. In nominal condition, the state feedback control law is designed for primary control surfaces. In the presence of fault/failure of certain HA, control allocation (CA) scheme together with integral sliding mode controller (ISMC) is retrofitted with existing control law and engaged the secondary (redundant) actuators into the loop. A modified recursive least square (RLS) algorithm is proposed to identify the parametric faults in HA and to measure the effectiveness level of the actuator. In an event of failure of all HA’s in the system, electro hydraulic actuators (EHA) are taken in loop to bring the system back to its nominal operation. In order to stabilize the closed-loop dynamics of HA and EHA, fractional order controllers are designed separately for each actuator. Simulations on the lateral directional model of aircraft demonstrated the effectiveness of the proposed scheme as compared to the existing methods in the literature.     

基于Web服务的电力市场交易计划分布式计算模型

对电力市场中的日交易计划的模型和计算流程进行了分析,并结合当前分布计算的热点技术Web服务技术,给出了一个基于Web服务的分布式日交易计划计算模型,该模型可以有机的对现有算法和代码进行有机的集成,具有很好的扩展性和适用性.