Impulsive stabilization of a class of nonlinear system with bounded gain error

Considering mechanical limitation or device restriction in practical application, this paper investigates impulsive stabilization of nonlinear systems with impulsive gain error. Compared with the existing impulsive analytical approaches,the proposed impulsive control method is more practically applicable, which includes control gain error with an acceptable boundary. A sufficient criterion for global exponential stability of an impulsive control system is derived, which relaxes the condition for precise impulsive gain efficiently. The effectiveness of the proposed method is confirmed by theoretical analysis and numerical simulation based on Chua＇s circuit.

Study on fast calibration of a ULA's gain and phase error

Array calibration is important in engineering practice. In this paper, fast calibration methods for a ULA's gain and phase errors both in far and near fields are proposed. In the far field, using a single sound source without exact orientation, this method horizontally rotates the array exactly once, performs eigen value decomposition for the covariance matrix of received data, then computes the gain and phase error according to the formulas. In the near field, using the same single sound source, it is necessary to rotate the array horizontally at most three times, build equations according to geometric relations, then solve them. Using the formula proposed in this paper, spherical waves are modified into plane waves. Then eigen values decomposition is performed. These two calibration methods were shown to be valid by simulation and are fast, accurate and easy to use. Finally, an analysis of factors influencing estimation precision is given.

DOA estimation for mixed signals with gain-phase error array

Most of the direction of arrival(DOA) estimation methods often need the exact array manifold, but in actual applications,the gain and phase of the channels are usually inconsistent, which will cause the estimation invalid. A novel direction finding approach for mixed far-field and near-field signals with gain-phase error array is provided. Based on simplifying the space spectrum function by matrix transformation, DOA of far-field signals is obtained. Consequently, errors of the array are acquired according to the orthogonality of far-field signal subspace and noise subspace.Finally, DOA of near-field signals can be estimated. The method merely needs one-dimensional spectrum searching, so as to improve the computational efficiency on the premise of ensuring a certain accuracy, simulation results manifest the effectiveness of the method.

存在幅相误差下的稳健稀疏贝叶斯二维波达方向估计

为减小传感器幅相误差的影响,提升方位估计性能,针对L型传感器阵列提出一种存在幅相误差下的稳健稀疏贝叶斯二维波达方向(Direction-Of-Arrival,DOA)估计方法。引入一个辅助角,将二维DOA估计问题转化为两个一维角度估计问题。利用L型阵列两子阵数据互协方差矩阵的对角线元素向量,构造一个含有幅相误差的稀疏表示模型,采用期望最大算法推导未知参数表达式并进行迭代运算,进而获得离网格和信号精度,利用二者构建新的空间谱函数,通过谱峰搜索估计出辅助角;将求得辅助角代入含有幅相误差的阵列接收数据稀疏表示模型,再次运用稀疏贝叶斯学习方法,估计出入射信号的俯仰角;根据3个角之间的关系,估计出方位角。研究结果表明:该方法实现了方位角和俯仰角的自动匹配,进一步克服了幅相误差对估计性能的影响,提高了方位估计的精度和角度分辨力,尤其是在高信噪比和幅相误差较大情况下优势更明显;仿真结果验证了该方法的有效性。

基于EKF的IPMSM无位置传感器控制估计误差补偿方法

在基于扩展卡尔曼滤波(EKF)法的内置式永磁同步电机无位置传感器控制系统中,电机转速和转子位置的准确估计十分重要。针对相电流增益误差导致的转速和转子位置估计精度下降的问题,提出一种位置估计误差补偿方法。首先,理论推导得出,在扩展卡尔曼滤波器估算过程中,相电流增益误差会使估计转速及转子位置以二倍工频的频率振荡。其次,设计了一种新型结构扩展卡尔曼滤波观测器,即在传统扩展卡尔曼滤波观测器的基础上增加增益误差系数求解环节,以此来降低相电流增益误差引起的估计转速及转子位置的脉动,提高了估计精度。最后,仿真和试验验证了所提补偿方法的可行性。

基于深度展开ADMM网络的稳健自适应波束形成

阵列通道间的幅相误差导致导向矢量失配,会严重退化自适应波束形成的性能。现有稳健自适应波束形成(RAB)方法通过引入最差导向矢量失配误差约束或联合估计幅相误差和波束形成器权值矢量,以改善波束形成性能,但这些方法的计算复杂度高,且在有限快拍下性能有限。为此,文中在深度展开框架下提出一种基于交替方向乘子法(ADMM)的RAB网络,以快速实现幅相误差和干扰协方差矩阵的联合估计。首先,建立存在阵列通道幅相误差时的干扰信号稀疏表示模型;然后,根据基于ADMM的幅相误差和干扰稀疏表示系数联合估计算法,设计一种深度展开ADMM(DU-ADMM)网络,该网络的输入为接收到达的干扰信号,输出为幅相误差和干扰稀疏表示系数;最后,利用该网络的输出重构出干扰加噪声协方差矩阵,并生成稳健自适应波束形成器。仿真结果表明,DU-ADMM网络可在单快拍场景下实现RAB,且能够以较少的网络层数更精确地估计出幅相误差,有效降低了计算量,同时可获得更高的输出信干噪比。

幅相误差对体积阵MVDR波束形成的影响

体积阵是一种由多个水听器组成的立体阵列,能够增大潜标接收基阵的孔径,获得较大的空间增益,工程中多将其制作成具有收合、展开功能的阵列应用于低频吊放声呐。由于各水听器通道内器件参数和幅度增益不一致,体积阵的每个阵元接收到的信号之间存在幅相误差。文中通过建立存在幅相误差时的双圆环体积阵模型,从统计学角度分析了幅相误差对其协方差矩阵、最小方差无畸变(MVDR)波束形成器的输出信噪比(SNR)、阵增益以及方位估计精度的影响。计算机仿真结果表明,阵列幅相误差的存在会导致MVDR波束形成器的输出SNR和阵增益降低;对于相位误差而言,当输入SNR在-5 dB以上时,这种影响随输入SNR的增大越来越明显;对于幅度误差而言,当输入SNR在-10 dB以上时,幅度误差对MVDR波束形成器的输出SNR和阵增益的影响会更显著;并且,相比于幅度误差,MVDR波束形成的方位估计精度对相位误差更加敏感。

随机相位对分布式无人机群传输性能的影响

随着无线通信的快速发展,分布式无人机群引发了国内外学者的广泛关注。针对一个分布式无人机群通信系统,分析无人机位置偏移产生的相位误差对系统传输性能的影响。首先,在假设无人机群存在随机相位误差的情况下,考虑目的节点采用等增益合并技术接收来自各个无人机的信号以使系统获得最优的性能。接着,假设无人机通信链路的小尺度衰落服从Nakagami-m分布,推导出系统的中断概率和遍历容量的闭合表达式。最后,利用计算机仿真验证理论分析的正确性,并定量分析无人机数、随机相位误差等关键参数对系统性能的影响,为实际分布式无人机群通信提供参考。

STUDY ON GAIN-SCHEDULING PROBLEM IN FLIGHT CONTROL

Gain-scheduling has got its wide applications in modern flight control, in which control gains are scheduled with variables such as dynamic pressure and Mach number, to meet dynamic response requirements in different flight conditions. Classical gain-scheduling approaches may result in some problems, which can not guarantee global robustness and stability in transitions of different flight conditions. Gain-scheduling problem is systematically investigated from robustness point of view in the paper. Detailed procedures for gain-scheduled controller to achieve both robustness and stability performance are given and applied to a typical flight control system. For switching stability problems of different flight conditions in flight control systems, a new approach is proposed, in which different flight conditions are reduced into a parameter varying plant using interpolation firstly, and then parameter-varying controller design goes next. Though interpolation errors may exist, the robust parameter varying controller design can compensate for those uncertainties and errors, and finally achieve good performance of robustness and switching stability during transitions. Illustrative simulation at last shows satisfactory results.

Improved Interference Suppression Algorithm Against Broadband BPSK Interference

An improved polar exciser （IMPE） interference suppression method against broadband constant envelope binary phase shift keying （BPSK） interference is proposed. The disadvantage of traditional polar exciser （PE） is the performance degradation when the power of interference is low, i.e., the threshold effect. The proposed improved PE （IMPE） algorithm can overcome the threshold effect of PE by introducing compression gain （CG） metric, which forces PE suppressor active only at larger jammer-to-signal ratio （JSR） and switch to matched filter （MF） at lower JSR. Theoretical analysis and numerical simulations show the exactness of CG as a switching metric and the validity of the IMPE algorithm.

基于辅助阵元的幅相误差和DOA同时估计算法

针对阵元幅相误差使波达方向(direction of arrival,DOA)估计精度下降的问题,提出了一种阵元幅相误差和DOA同时估计算法。该算法通过在阵列一侧设置少量已校正阵元,改变了误差矩阵的结构,并根据改变后的矩阵特征构造了变换矩阵,通过构造的变换矩阵和子空间算法,实现了对阵元幅相误差和DOA的同时估计。此外,该算法能够解决信源功率存在较大差异时误差估计不准的问题,实现了高精度的误差和角度的同时估计。计算机仿真结果证明了所提算法的正确性和有效性。

Polynomial-Based Evaluation of the Impact of Aperture Phase Taper on the Gain of Rectangular Horns

The aperture phase taper due to quadratic phase errors in the principal planes of a rectangular horn imposes signifi-cant constraints on the on-axis far-field gain of the horn. The precise calculation of gain reduction involves Fresnel integrals;therefore, exact results are obtained only from numerical methods. However, in horns’ analysis and design, simple closed-form expressions are often required for the description of horn-gain. This paper provides a set of simple polynomial approximations that adequately describe the gain reduction factors of pyramidal and sectoral horns. The proposed formulas are derived using least-squares polynomial regression analysis and they are valid for a broad range of quadratic phase error values. Numerical results verify the accuracy of the derived expressions. Application examples and comparisons with methods in the literature demonstrate the efficacy of the approach.

基于稀疏贝叶斯学习的稳健STAP算法

为了提高阵列幅相误差和格点失配情况下稀疏恢复空时自适应处理(sparse recovery space-time adaptive processing,SR-STAP)算法的性能,提出一种基于稀疏贝叶斯学习的稳健SR-STAP算法。首先,利用空时导向矢量的Kronecker结构构建SR-STAP误差信号模型;然后,利用贝叶斯推断和最大期望算法迭代求取角度多普勒像和误差参数;最后,利用求解参数估计精确的杂波加噪声协方差矩阵并计算权矢量。仿真实验表明,所提算法能够显著提高稀疏信号模型失配时的目标检测性能。

开关磁阻电机电流跟踪变增益鲁棒控制

针对开关磁阻电机(SRM)传统滞环控制电流跟踪效果差和转矩脉动大的问题,提出一种变增益鲁棒控制方法。基于SRM极端位置磁化曲线,建立考虑磁饱和效应的SRM非线性解析模型,实现了电机增量电感和反电动势的在线估计。为克服模型不确定造成的估计偏差,设计SRM电流鲁棒控制器,利用反馈增益对增量电感和反电动势的估计偏差进行在线补偿,提高电流跟踪控制精确度。基于Lyapunov直接法对SRM电流控制器进行分析设计,保证了控制系统的稳定性。在此基础上,采用线性转矩模型和误差补偿设计新型转矩-电流转换器,实现转矩到电流的精确映射,间接完成转矩平滑控制。实验结果表明,SRM变增益鲁棒控制器的电流跟踪均方根误差和转矩脉动系数均低于传统滞环控制,具有更好的电流跟踪性能和转矩脉动抑制能力,有效提高了SRM驱动性能。

麦克风阵列幅相误差校准的最小二乘系统辨识研究

阵列幅相误差显著降低了麦克风阵列的声源定位算法性能,研究了一种麦克风阵列幅相误差有源宽带近场校准方法。该方法采用一个校准源,线性正弦扫频信号作为激励信号,它先对阵列接受到的信号进行幅值和相位补偿,以阵列中的一个阵元作为参考阵元,把参考阵元与待校准阵元当作单输入单输出线性系统,然后通过递推最小二乘(RLS)系统辨识算法获得用于通道校准的FIR滤波器。用三维声强探头阵列进行校准和声源定位实验,验证了所提出的校准方法实用有效。

基于IESKF的激光惯性里程计实现方法研究

针对主流的激光里程计方案存在精度较低和计算耗时严重的问题,提出一种基于迭代误差状态卡尔曼滤波器的IMU与LiDAR紧耦合的里程计方案,将IMU预积分结果与特征点云匹配结果融合得到高精度位姿,并且使用等效卡尔曼增益公式,降低计算维度,提高系统运行效率。对比分析了主流里程计方案与本方案在位姿估计精度和时效性上的表现,结果表明,本方案在满足系统实时性的前提下,能有效提高里程计的精度。

MIMO系统中基于代价函数和排序模式的MMSE SIC检测器

针对多输入多输出空间多路复用系统,提出了一种基于代价函数和排序模式的多个并行分支的最小均方误差连续干扰消除检测器;具体而言,设计了选择规则来选择代价函数性能最好的分支,并通过利用不同的检测排序模式使得每个分支中的SIC算法按照信号干扰噪声比由高到低来检测信号,从而实现完全检测分集;为了进一步降低算法的计算复杂度,还提出了一种采用递归最小二乘算法的有效自适应接收机来更新滤波器权值向量,从而获得基于递归最小二乘算法的MB-SIC接收机的自适应实现;此外,还对提出的检测器在比特差错概率性能方面进行了分析;仿真结果表明,相比于现有的检测算法,提出的算法不仅具有较低的计算复杂度,而且能获得更好的误码率性能。

基于三稳态随机共振的BPSK信号检测算法

基于高斯白噪声下BPSK信号接收误码率较高的问题,提出了一种基于三稳态随机共振系统来降低BPSK信号误码率的方法。首先,基于随机共振的BPSK通信系模型,推导了系统的输出信噪比及信噪比增益的表达式。其次,以信噪比增益为衡量指标,探究了系统参数a、b、c和噪声强度D对共振输出的影响。研究表明,随着噪声强度的增加,输出信噪比呈现单峰结构;信噪比增益始终大于1,峰值随着系统参数b的增大而逐渐增大,但随着系统参数a和c的增大而减小。最后,在强噪声背景下,对BPSK信号的传统接收方案和所提方法的误码率进行仿真对比分析,结果证实信号在经过随机共振系统后,时域图像更为清晰,毛刺明显减少,频谱幅值是传统方法的4.613倍。

弹载雷达阵列幅相误差校正及目标超分辨技术

传统波束形成方法受瑞利限约束,不能有效分辨主瓣内的两个目标,在阵列存在幅相误差时,参数估计精度和分辨率都会下降。针对该问题,研究了利用强回波信号校正二维面阵幅相误差的方法,并给出了采用平滑多重信号分类(MUSIC)算法处理相干回波信号的阵列平滑方法。仿真实验证明了幅相误差估计算法的有效性,说明了幅相误差对目标分辨的影响较大,在校正后可以恢复目标角度超分辨性能。

基于模糊滑模的爬壁机器人末端自动控制方法

由于爬壁机器人在末端控制过程中,易受信号强度变化、网络配置高低和传感器性能等因素的干扰,导致爬壁机器人末端控制速度和稳态值较低、误差较大的问题。为此,提出基于模糊滑模的爬壁机器人末端自动控制方法。首先,利用刚体上6个特征点的单方向增量,得到爬壁机器人的末端位置;然后,通过基于再生权最小二乘法,结合最优剪枝极限学习机法,对得到的末端位置进行误差补偿,以此来提高控制精度;最后,使用模糊滑模理论,推导出一种基于等效控制和切换控制的模糊滑模控制器,实现爬壁机器人的末端自动控制。实验结果表明,所提方法的自动控制速度和稳态值较高,能够有效降低自动控制误差。