分数阶微积分在图像处理中的研究综述*

综述了关于分数阶微积分理论在数字图像底层处理中的应用研究,具体包括:分数阶微积分和分数阶偏微分方程的基本理论及分数阶傅里叶变换的基本性质;分数阶微分滤波器的构造及在图像增强中的应用研究;分数阶积分滤波器的构造及在图像去噪中的应用研究;分数阶偏微分方程在图像去噪中的应用研究。最后,总结了分数阶微积分理论在图像处理中已取得的研究成果,并结合已有的基于分数阶微积分理论的图像底层处理模型,展望了分数阶微积分理论在图像处理中的应用前景。     

Simultaneous state estimation and parameter identification in linear fractional order systems using coloured measurement noise

In the present paper, the identification and estimation problem of a single-input–single-output (SISO) fractional order state-space system will be addressed. A SISO state-space model is considered in which parameters and also state variables should be estimated. The canonical fractional order state-space system will be transformed into a regression equation by using a linear transformation and a shift operator that are appropriate for identification. The identification method provided in this paper is based on a recursive identification algorithm that has the capability of identifying the parameters of fractional order state-space system recursively. Another subject that will be addressed in this paper is a novel fractional order Kalman filter suitable for the systems with coloured measurement noise. The promising performance of the proposed methods is verified using two stable fractional order systems.     

Subspace-based continuous-time identification of fractional order systems from non-uniformly sampled data

This work focuses on the identification of fractional commensurate order systems from non-uniformly sampled data. A novel scheme is proposed to solve such problem. In this scheme, the non-uniformly sampled data are first complemented by using fractional Laguerre generating functions. Then, the multivariable output error state space method is employed to identify the relevant system parameters. Moreover, an in-depth property analysis of the proposed scheme is provided. A numerical example is investigated to illustrate the effectiveness of the proposed method.     

The Laplace transform in discrete fractional calculus

We develop properties of the Laplace Transform in a discrete, fractional calculus setting, giving a precise treatment to convergence along the way. The end goal is to apply the Laplace Transform Method to solve a fractional initial value problem.     

分数阶系统状态空间描述的数值算法

利用Grünwald-Letnicov分数微积分定义计算分数微积分的数值解,计算精度仅为1阶,不能满足快速收敛性要求.给出并证明了分数阶微积分的高阶近似所应满足的条件,并在此基础上推导出分数阶线性定常系统状态空间描述的数值计算公式.本法不但公式简单易编程,而且具有计算精度高、运算速度快等优点.给出一个粘弹性动态系统的仿真实例,验证了其有效性.     

分数阶微积分流变模型在岩体结构加速流变破坏分析中的应用

针对采用常用的元件模型较好地拟合试验结果时需要的参数较多的缺点,将分数阶微积分理论应用于岩体结构的流变分析.将分数阶微积分的黏弹性模型和黏塑性模型的一维本构关系推广为三维本构关系,推导流变应变增量计算公式.然后将分数阶微积分流变模型应用于不同岩体结构的加速流变破坏分析.结果表明：改变分数阶次时,岩体结构加速流变性态将发生较大变化,分数阶微积分流变模型可较好地描述岩体结构不同的加速流变破坏过程,且模型简单实用.     

豪斯道夫微积分和分数阶微积分模型的分形分析

清晰解读豪斯道夫微积分和分数阶微积分阶数的分形维意义,并比较这2种微积分建模方法的区别与联系.这是首次清晰定量地导出分数阶微积分的分形几何基础.提供豪斯道夫导数模型描述历史依赖过程的几何解释,即初始时刻依赖性问题,并与分数阶导数模型对比.基于本文作者的早期工作,详细描述非欧几里得距离的豪斯道夫分形距离定义——豪斯道夫导数扩散方程的基本解就是基于该豪斯道夫分形距离.该基本解实质上就是目前广泛使用的伸展高斯分布和伸展指数衰减统计模型.     

一类分数阶复杂网络混沌系统的投影同步

根据分数阶系统的相关理论研究了一类分数阶复杂网络混沌系统的投影同步问题,给出了分数阶复杂网络以及分数阶时滞复杂网络系统实现投影同步的充分性条件,仿真结果表明了方法的正确性.     

一类耦合分数阶反应–扩散系统的边界控制

针对带有空间变化的反应项的耦合分数阶反应–扩散系统边界镇定问题,利用反步法设计了用于Robin边界条件的状态反馈控制.通过可逆的积分变换将原耦合系统转化为一个稳定的目标系统.利用变量代换和逐次逼近法分析了核函数矩阵的存在唯一性.借助分数阶Lyapunov直接法证明了闭环系统的Mittag-Leffler稳定性.数值仿真验证了所提出方法的有效性.     

Pseudo-state feedback stabilization of commensurate fractional order systems

This paper addresses the problem of pseudo-state feedback stabilization of commensurate fractional order systems (FOS). In the proposed approach, Linear Matrix Inequalities (LMI) formalism is used to check if the pseudo-state matrix eigenvalues belong to the FOS stability region of the complex plane. A review of LMI stability conditions is first proposed for fractional order 0<ν<1 and 1<ν<2. The paper then focuses particularly on the case 0<ν<1 as the stability region is non-convex and associated LMI condition is not as straightforward to obtain as in the case 1<ν<2. A new LMI stability condition is thus proposed. Based on this condition, a necessary and sufficient LMI method for the design of stabilizing controllers is given. This method paves the way for extension to FOS of various LMI-based results. Among these possible extensions, a first result on robust control of polytopic fractional order systems is given in this paper.     

分数微积分理论在非线性车辆悬架滑模控制中的应用

基于分数微积分理论,提出分数阶”天棚”阻尼控制概念,并以它控制的悬架为参考模型,提出一个控制效果理想、鲁棒性好的悬架滑模控制的新策略,并应用于非线性悬架的动力学控制中．文中给出了一种精度较高,收敛稳定的分数阶系统的数值算法,最后对非线性悬架的滑模主动控制进行数值仿真,验证了新控制策略优良的控制效果．     

Event-triggered fuzzy adaptive control of incommensurate fractional order nonlinear systems

This paper focuses on the event-triggered control of nonstrict-feedback incommensurate fractional order systems with external disturbances. To release more communication resources and reduce the triggered time instant, we adopt the relative-threshold-based event-triggered strategy and prove that the Zeno behavior does not exist. We utilize the fuzzy systems to approximate the nonlinear systems and design an adaptive update law to estimate the approximation errors and external disturbances. To conquer the dimension explosion phenomenon in the backstepping process, we design a fractional order filter and apply the dynamic surface control technique. The closed-loop system is semiglobally stable and the tracking error converges to a small neighborhood of equilibrium point under the proposed control approach. Finally, the validity of the developed controller is verified by the simulation examples.     

分数阶控制器的数字实现及其特性

针对分数阶控制器数值计算和应用难的问题,研究了分数阶控制器的数字实现方法和控制特性．取Grunwald-Letnikov定义有限项,并直接离散化,得到有限记忆数字实现法;利用Tustin算子生成函数把分数阶微分由复频域变换到Z域,然后用连分式展开式CFE(continued fraction expansion)近似展开,可得到Tustin CFE数字实现法．两种方法的频域对比分析表明Tustin CFE法优于有限记忆法．采用设计的分数阶控制器的数字实现方法,对分数阶控制器和传统PID控制器的控制性能进行了对比实验分析．研究结果表明:分数阶控制器对非线性具有较强的控制能力．     

Controllability of fractional dynamical systems with distributed delays in control using ψ-Caputo fractional derivative

This research investigates the controllability of linear and non-linear fractional dynamical systems with distributed delays in control using the $\psi$-Caputo fractional derivative. For controllability of linear systems, the positive definiteness of Grammian matrix, which is characterized by Mittag–Leffler functions, is used to provide necessary and sufficient conditions. For the controllability of non-linear systems, the iterative technique with the completeness of $X$ is used to obtain sufficient conditions. Using the $\psi$-Caputo fractional derivative, this study is new since it investigates the ideas of controllability. A couple of numerical results are offered to explain the theoretical results.     

不确定分数阶多涡卷混沌系统自适应重复学习同步控制

研究了不确定分数阶多涡卷混沌系统的自适应重复学习同步控制问题.通过利用滞环函数,设计了一类参数可调的分数阶多涡卷混沌系统.针对这类分数阶多涡卷混沌系统,在考虑非参数化不确定性、周期时变参数化不确定性、常参数化不确定性和外部扰动情况下,提出了一种重复学习同步控制方案.利用自适应神经网络技术补偿了系统中的函数型不确定性,通过自适应重复学习控制技术处理了周期时变参数化不确定性,并利用自适应鲁棒学习项处理了神经网络逼近误差和干扰的影响,实现了主系统和从系统的完全同步.综合利用分数阶频率分布模型和类Lyapunov复合能量函数方法证明了同步误差的学习收敛性.数值仿真验证了所提方法的有效性.     

分数阶线性系统的内部和外部稳定性研究

介绍了分数阶线性定常系统的状态方程描述和传递函数描述．运用拉普拉斯变换和留数定理，给出并证明了分数阶线性定常系统的内部和外部稳定性条件，并讨论了其相互关系．以一个粘弹性系统的实例验证了上述方法的正确性．     

分数阶Genesio Tesi系统的混沌及自适应同步

对具有五次方非线性项的分数阶Genesio-Tesi系统的混沌及自适应同步进行了研究.首先分析了该系统平衡点的稳定性,并发现该系统满足出现双涡卷混沌吸引子的必要条件.然后研究了在阶数相同和不同的两种情况下的吸引子以及系统随阶数变化的分岔情况.该系统在两种情况下存在混沌的最小有效维数分别为2.784和2.793.基于分数阶系统的稳定性理论,实现了该分数阶系统的自适应混沌同步.数值模拟验证了所设计的自适应控制器和未知参数的辨识观测器的有效性.     

Routh table test for stability of commensurate fractional degree polynomials and their commensurate fractional order systems

A Routh table test for stability of commensurate fractional degree polynomials and their commensurate fractional order systems is presented via an auxiliary integer degree polynomial. The presented Routh test is a classical Routh table test on the auxiliary integer degree polynomial derived from and for the commensurate fractional degree polynomial. The theoretical proof of this proposed approach is provided by utilizing Argument principle and Cauchy index. Illustrative examples show efficiency of the presented approach for stability test of commensurate fractional degree polynomials and commensurate fractional order systems. So far, only one Routh-type test approach [1] is available for the commensurate fractional degree polynomials in the literature. Thus, this classical Routh-type test approach and the one in [1] both can be applied to stability analysis and design for the fractional order systems, while the one presented in this paper is easy for peoples, who are familiar with the classical Routh table test, to use.     

基于分数阶微分自适应算法的煤尘图像滤噪

针对传统的煤尘图像滤噪方法迭代过程长、滤噪效果不理想、纹理保持能力差等问题,对现有的滤噪方法进行改进,建立了基于分数阶微分模型的自适应滤噪算法。改进算法对参数u的变化梯度进行调整,从整数阶扩展到分数阶;根据区域特征分别对算法中的各项参数进行自适应选择。实验结果表明,改进后的滤噪算法收敛速度快,迭代次数少,滤噪效果好,纹理保持能力强,且其检测滤噪效果能力的量化指标获得了很好的改善。     

一种分数阶预测控制器的研究与实现

本论文研究了一种新型预测控制器RTD-A的分数阶实现方法及应用. 与常规控制器比较, RTD-A控制器具有参数意义明确, 易于整定和实施的优点. 论文将RTD-A控制器扩展到分数阶形式, 并与经Z-N法整定的分数阶PI?D1控制器和Wang-Juang-Chan法整定的PID控制器进行了比较. 所提出的分数阶预测控制器在设定值跟踪, 克服负荷扰动, 鲁棒性等方面都有较理想的控制性能. 仿真结果验证了这种分数阶预测控制器的有效性.