广义时滞系统的降维观测器设计

讨论广义时滞系统的降维观测器的设计方法．通过引入矩阵的广义逆矩阵,给出在一定条件下降维观测器的具体形式,然后分别利用广义逆矩阵及Lyapunov函数方法给出这些条件成立的具体条件及验证方法。最后给出一个例子来说明方法的有效性。     

基于谱分解的中立型时滞系统观测器

针对线性中立型时滞系统, 利用线性算子半群的谱分解理论进行观测器设计. 在中立型项的范数小于一的条件下, 利用谱理论并结合投影算子, 将无穷维系统解的相空间分解为有限维不稳定广义特征子空间和无限维稳定广义特征子空间的直和. 进而利用线性算子半群的无穷小生成元得到具有积分微分形式的观测器方程, 并证明了观测器误差方程的渐近稳定性. 数值实验证实了所提设计方法的有效性.     

基于神经网络干扰观测器的一类不确定非线性MIMO系统H_∞跟踪控制

针对一类具有未知外部干扰及内部不确定性的非线性MIMO系统,提出了基于神经网络干扰观测器的鲁棒跟踪控制方法,用于降低控制器对干扰的要求.设计了基于神经网络的干扰观测器,以逼近由外部干扰、内部不确定性和子系统的交叉耦合组成的复合干扰.根据Lyapunov稳定性理论的参数更新律及所设计的控制器,保证了系统中所有信号的最终一致有界性,并获得了给定的跟踪性能指标.仿真结果证明了该方法的有效性.     

基于故障跟踪估计器的非线性时滞系统故障诊断

提出一种可有效检测和估计一类非线性时滞系统故障的故障跟踪估计器.根据预测控制和迭代学习控制的思想,在所选取的优化时域长度内,通过迭代算法调节故障跟踪估计器中的可调参数,使之逼近系统中实际发生的故障.与以往基于观测器的故障诊断方法不同的是,故障跟踪估计器可同时检测和估计系统中发生的故障,而且针对不同类型的故障亦有很好的适应性.仿真结果表明了所提出算法的可行性和有效性.     

具有输出时延的网络控制系统故障检测

考虑一类具有长时延的网络控制系统,假定其传感器到控制器之间存在输出时延,对其进行故障检测研究.建立具有时延补偿功能的故障观测器,得到状态估计误差方程.基于离散切换系统理论,将观测器系统的稳定条件归结为一个线性矩阵不等式.当系统正常时,只要给定的矩阵不等式条件成立,该观测器系统就是渐近稳定的.当系统发生故障时,观测器残差能够迅速发生跳变,从而检测出故障的发生.仿真示例验证了方法的有效性.     

Effect of slow display on detectability when browsing large image datasets

Abstract— In this work, the effect of display temporal characteristics on detectability of signals was studied by comparing detection performance with a slow liquid‐crystal‐display (LCD) monitor and a fast, cathode‐ray‐tube (CRT) monitor when browsing multi‐slice image datasets in stack‐mode presentation. Thirteen readers evaluated 200 image sequence pairs in a two‐alternative forced choice experiment. The image sets consisted of three‐dimensional cluster lumpy backgrounds and were presented to the readers in two display devices: a three‐million‐pixel medical color LCD and a color desktop CRT. For the LCD, many inter‐gray‐level transitions are on the order of 50–60 msec, which was almost twice the frame time. The CRT had 2–5‐msec inter‐gray‐level transitions. The reader study was performed with a graphical‐user interface programmed using direct calls to OpenGL libraries to precisely control the browsing speed. The results were analyzed in terms of the difference in reader performance for each reader and each display, between a browsing speed of 20 and 50 frames per sec (fps). Average reader performance difference between 20 and 50 fps was measured to be 0.049 and 0.156 for the CRT and LCD monitors, respectively. The corresponding drop in reader performance associated with slow display was 0.11.     

一种改进线性扩张状态观测器的自抗扰控制宽频带振荡抑制方法研究

针对自抗扰控制策略在并网系统参数变化时能否维持逆变器接入弱电网的稳定性展开了进一步研究。首先,建立了计及频率耦合的自抗扰控制型并网逆变器等效单输入单输出序阻抗模型,并采用Nyquist稳定判据定量分析逆变器输出功率、电网短路比、锁相环以及自抗扰控制器参数变化对并网系统稳定性的影响。其次,针对上述参数变化所导致的弱电网下自抗扰控制型逆变器稳定性降低、宽频带振荡等问题,提出了一种改进线性扩张状态观测器(enhanced linear expansion state observer, e-LESO)的自抗扰控制宽频带振荡抑制方法。通过在传统一阶自抗扰控制器中LESO内部增添比例支路和滤波环节,重塑自抗扰控制型并网逆变器输出阻抗,拓宽其中频段(100 Hz~1 kHz)内呈正阻尼特性的频率范围,从而增强自抗扰型并网逆变器鲁棒性,实现宽频带振荡抑制。最后,通过仿真验证了所提方法的有效性。     

一种永磁同步电机无模型超螺旋快速终端滑模控制方法

针对内置式永磁同步电机(interior permanent magnet synchronous motor, IPMSM)由于内部参数变化、外部扰动等各种不确定性因素导致控制性能不佳的问题,提出一种无模型超螺旋快速终端滑模控制方法。首先,建立考虑IPMSM不确定性的新型超局部模型,结合超螺旋算法和快速终端切换函数设计无模型超螺旋快速终端滑模控制器,确保系统状态有限时间收敛,并有效减小抖振。其次,设计扩展滑模扰动观测器精准估计超局部模型中的未知部分,并前馈补偿给设计的控制器,进一步提升系统的抗干扰能力和跟踪性能。最后,通过与PI控制和传统无模型滑模控制进行仿真实验对比,验证了该方法具有更快的收敛速度和更强的鲁棒性。     

Extended state observer-based finite-region control for 2-D Markov jump systems

In this article, an extended state observer-based finite-region control scheme is presented for two-dimensional Markov jump systems with unknown mismatched disturbances. The mathematical model of the two-dimensional Markov jump systems is built on the well-known Roesser model. By establishing special recursive formulas and utilizing the 2-D Lyapunov function theory, sufficient conditions are obtained, which prove that the resultant system is finite-region bounded, if some linear matrix inequalities are achieved. Then, we provide an algorithm to solve the extended state observer-based controller gains. With the proposed control scheme, the external disturbances can be actively rejected from the system outputs. To conclude, a numerical example based on the Darboux equation is provided to demonstrate the validity and effectiveness of the devised control scheme.