开通角控制的无刷直流电机转矩脉动抑制新方法

在分析无刷直流电机的等效电路模型和换相过程的基础上,考虑了电磁时间常数和反电势对换相转矩的影响。通过导出换相时关断相电流下降到零的时间和开通相电流上升到最大的时间,分析高、低速运行状态下两者的关系,引入一个开通角的变量,通过控制开通相的开通时刻来抑制换相时的转矩脉动;并且考虑非理想的气隙磁密等因素对开通角进行修正。结合场路耦合的有限元进行仿真,结果表明此思路是可行的。     

小波变换与SVD结合的射频信号消噪方法

射频信号因具备空间远距离传输特性被广泛应用于航天测控等领域,但空间磁场、信道、设备元器件等会引入大量噪声干扰,对射频信号的传播及后续分析处理造成影响。而目前关于射频信号消噪的研究很少,针对此问题,对比研究了传统滤波器消噪、小波阈值法及SVD(Singular Value Decomposition,奇异值分解)法在射频信号消噪方面的应用,仿真分析了各算法对有用射频信号的提取效果,从而发现3种方法均能起到噪声抑制的作用,但是,滤波器法明显会降低信号能量,小波变换法易使重构信号失真,而SVD法则运算时间较长。为此,提出将小波阈值法与SVD相结合,用于射频信号消噪。再通过比对各方法消噪的性能指标,验证了将2种方法结合,可有效提高运算效率及噪声抑制能力。     

一种机载雷达两级降维空时二维自适应处理方法

 提出了一种机载相控阵雷达杂波抑制的两级降维空时自适应处理(STAP)方法,即：先根据杂波分布先验信息进行空时局域化(JDL)降维处理,然后对局域化输出进行多级维纳滤波(MWF),实现二次降维。该方法综合了固定结构和自适应结构降维技术的优点,将JDL处理引入到MWF中,从而有效降低MWF的杂波自由度。计算机仿真和理论分析表明本文方法比JDL自适应处理方法和全空时MWF方法具有更小的运算量,对阵元随机幅相误差具有很好的容差能力,是一种稳健的两级降维自适应处理方法。最后,基于仿真和实测数据的实验验证了算法的有效性。     

风电场雷达杂波动态重构抑制方法

随着风电场的大范围建设，风轮机杂波对雷达的干扰问题日益严重，常规杂波抑制方法难以有效解决风轮机杂波（WTC）干扰问题，因此提出了一种利用动态字典对风轮机杂波进行稀疏重构进而抑制的方法。首先，建立了WTC干扰下的雷达信号模型并分析了风轮机杂波的信号特征。其次，依据WTC的时频特征提出了一种微动参数粗估计方法，利用粗估计结果缩小了字典稀疏重构参数范围，在此基础上利用正交匹配追踪（OMP）算法对字典进行动态生成，并逐级更新字典原子。最后，通过动态字典对风轮机杂波信号进行稀疏重构，从而实现了对WTC的有效抑制。通过仿真实验，分析了风轮机杂波对目标检测的干扰影响，验证了基于动态稀疏重构的风电场杂波抑制方法在不同情况下的有效性。     

Robust H∞ controller design for attitude stabilization of flexible spacecraft with input constraints

This paper addresses the attitude stabilization and vibration suppression problem for flexible spacecraft subject to model parameter uncertainty, controller perturbations, external disturbances and input constraints. The attitude model of flexible spacecraft is described and converted into a state space form in terms of passive and active vibration suppression schemes. A novel state feedback controller is proposed based on the exactly available expectation of a new variable, which is introduced to model a randomly occurring controller gain perturbation. Based on Lyapunov stability theory, sufficient conditions for the existence of the nonfragile H_∞ controller considering input constraints are given based on linear matrix inequalities (LMIs) in terms of additive perturbation and multiplicative perturbation. Then, the developed controller subject to required constraints can be obtained, where the nonfragile property is fully considered to improve the tolerance to uncertainties in the controller. Numerical simulations are performed to demonstrate the effectiveness and superiority of the proposed control strategy in attitude stabilization and vibration suppression, where it should be noted that the passive vibration suppression scheme is superior for high natural frequencies while the active vibration suppression scheme is superior for low natural frequencies. Moreover, the low natural frequencies have more influence on the performance of attitude stabilization and vibration suppression.     

基于多载频MIMO雷达的Radon-Fourier变换盲速旁瓣抑制

 长时间相干积累方法Radon-Fourier变换(RFT)中盲速旁瓣(BSSL)现象会导致雷达虚警增加、目标检测性能降低。针对BSSL问题,给出了一种基于多输入多输出(MIMO)雷达多载频设计的BSSL抑制方法。首先根据载频与BSSL分布的关系,详细推导了BSSL不交叠的约束条件;然后基于该约束条件给出了具体的载频设计公式。利用设计的载频可得到具有不交叠BSSL的两个RFT输出,通过联合处理这两个RFT输出,可实现BSSL抑制。给出了BSSL抑制性能的评价方法。理论分析和数值实验结果表明,本文算法能够在不降低RFT相干积累性能的同时,有效实现BSSL抑制。     

空间站柔性太阳电池翼对日跟踪控制

空间站柔性太阳电池翼高稳定对日跟踪驱动控制,对于保障空间站长期在轨能源安全和平稳运行具有重要意义。在推导柔性太阳电池翼动力学模型、柔性体模态分析和截断、Alpha对日定向装置机电系统模型、非线性传动系统模型的基础上,对空间站柔性太阳电池翼对日跟踪控制系统进行设计。采用Heaviside五次样条变速规划、位置和速度两级闭环、速度环陷阱滤波器柔性振动抑制的组合方案,实现空间站柔性太阳电池翼高稳定驱动控制。通过对典型工况的仿真校核,验证所设计的控制方案可实现跟踪精度优于0.3°、速度偏差±0.005(°)/s、稳定度优于7%@0.065(°)/s的性能指标。同时,Alpha对日定向装置的启动和变速过程中驱动力矩不大于30 N·m,稳速运行期间驱动力矩不大于5 N·m。各项性能指标要好于国际空间站Alpha对日定向装置,满足使用要求。     

基于深度学习的SAR图像质量提升方法研究

提升合成孔径雷达(SAR)图像质量以增强其可判读性,一直是SAR图像处理中的关键问题。近年来,深度学习在光学图像处理中取得显著的成功,并逐步应用到SAR图像质量提升领域。对深度学习在SAR图像质量提升中的关键应用进行综述,对深度学习在SAR图像质量提升中采用的典型网络进行了介绍,并从SAR图像旁瓣抑制、超分辨(SR)处理和图像融合3个方面对深度学习的应用进行阐述。最后,分析与探讨了基于深度学习的SAR图像质量提升中的关键问题及进一步研究方向。     

LPV modeling and controller design for body freedom flutter suppression subject to actuator saturation

In recent years, the Active Flutter Suppression (AFS) employing Linear Parameter-Varying (LPV) framework has become a hot spot in the research field. Nevertheless, the flutter suppression technique is facing two severe challenges. On the one hand, due to the fatal risk of flight test near critical airspeed, it is hard to obtain the accurate mathematical model of the aeroelastic system from the testing data. On the other hand, saturation of the actuator may degrade the closed-loop performance, which was often neglected in the past work. To tackle these two problems, a new active controller design procedure is proposed to suppress flutter in this paper. Firstly, with the aid of LPV model order reduction method and State-space Model Interpolation of Local Estimates (SMILE) technique, a set of high-fidelity Linear Time-Invariant (LTI) models which are usually derived from flight tests at different subcritical airspeeds are reduced and interpolated to construct an LPV model of an aeroelastic system. And then, the unstable aeroelastic dynamics beyond critical airspeed are ‘predicted’ by extrapolating the resulting LPV model. Secondly, based on the control-oriented LPV model, an AFS controller in LPV framework which is composed of a nominal LPV controller and an LPV anti-windup compensator is designed to suppress the aeroelastic vibration and overcome the performance degradation caused by actuator saturation. Although the nominal LPV controller may have superior performance in linear simulation in which the saturation effect is ignored, the results of the numerical simulations show that the nominal LPV controller fails to suppress the Body Freedom Flutter (BFF) when encountering the actuator saturation. However, the LPV anti-windup compensator not only enhances the nominal controller’s performance but also helps the nominal controller to stabilize the unstable aeroelastic system when encountering serious actuator saturation.     

一种简化的机载MIMO雷达杂波特征相消器

针对机载多输入多输出(MIMO)雷达杂波抑制问题,提出一种简化的杂波特征相消器(EC).根据杂波在空时二维平面的先验分布离线构造杂波子空间.以此替代由协方差矩阵特征值分解(EVD)得到的杂波子空间,从而将最优权简化为一个确知投影矩阵与目标信号空时二维导向矢量的乘积,避免了传统EC方法中复杂的协方差矩阵估计和EVD运算,...