基于状态全反馈的动态迟滞非线性系统

该文针对不平滑、多映射动态迟滞非线性系统,提出了一种基于神经网络自适应控制方案.在该方案中,通过利用神经网络来逼近模型误差,避免了目前常用逆模型补偿方案中,需求取复杂逆模型的问题.应用Lyapnov稳定定理,证明了整个闭环系统的跟踪误差及神经网络权值将收敛到零点一个有界邻域内.仿真结果表明,所提出的控制方案能够有效补偿迟滞非线性对系统的影响.     

基于状态观测器的迟滞非线性系统输出反馈控制

利用Preisach模型与其边界线之间的映射关系建立了容易在线更新的迟滞模型．将模型和径向基网络相结合，针对一类动态多映射迟滞非线性系统设计了输出反馈控制器．应用LyaPunov定理得到系统控制律和神经网络权值更新律，从而保证了闭环系统的跟踪误差及网络权值偏差收敛到原点的某个有界邻域内．     

基于状态全反馈的动态迟滞非线性系统自适应控制

该文针对不平滑、多映射动态迟滞非线性系统，提出了一种基于神经网络自适应控制方案。在该方案中，通过利用神经网络来逼近模型误差，避免了目前常用逆模型补偿方案中，需求取复杂逆模型的问题。应用Lyapnov稳定定理，证明了整个闭环系统的跟踪误差及神经网络权值将收敛到零点一个有界邻域内。仿真结果表明，所提出的控制方案能够有效补偿迟滞非线性对系统的影响。     

基于遗传算法的时频域模型降阶方法

本文提出了一种基于遗传算法的时频域智能模型降阶新方法。通过发挥遗传算法的优点和引入添加微变异种群等新策略、轮流评价新策略，使得本方法具有智能和高效的特点，具有良好的工程应用价值。     

振动系统的时频域仿真分析研究

将有限自由度振动系统物动力学方程化为系统的状态方程和传递函数，以状态变量分析法和机械阻抗分析法代替振动模态分析法，直接运用MATLAB仿真功能及其控制系统工具箱函数，对振动系统进行了时频域仿真分析，并通过实例进行了说明，为振动系统的分析与设计提供一种工具。     

迟滞非线性系统的建模与控制

介绍了对不平滑、多映射迟滞非线性系统的研究成果,重点阐述了迟滞建模与控制器设计的研究现状.详细地分析比较了Preisach模型和线性迟滞模型优缺点.在控制器设计方法方面,比较了常用的两类基于逆模型补偿方案的特点、差别和适应范围,并扼要论述了其他控制方案.最后,对迟滞研究中仍需解决的问题和未来发展方向进行了探讨.     

迟滞非线性动态系统神经网络自适应控制

为了减轻非线性动态系统中未知迟滞(Hysteresis)的不良影响,该文提出了一类Backlash型迟滞模型。将有限数量不同宽度的Backlash(Matlab／Simulink)算子进行叠加,来仿真执行器中的迟滞非线性动态。用此模型,提出了基于径向基函数神经网络的自适应控制方案,以控制伴有未知迟滞的非线性动态系统。该方案采用了动态逆的思想及伪控制的概念。利用Lyapunov稳定理论,设计了两个鲁棒控制项,保证动态系统的稳定性、系统中所有信号有界和误差收敛到起点的领域内。通过Matlab／Simulink仿真实验,证明了所提出方案的有效性。     

基于坐标变换和仿射映射辨识迟滞非线性模型

运用坐标变换方法和仿射映射的有关原理,对迟滞系统的输入信号进行变换映射.利用集合理论证明了变换后,迟滞的输入输出集合是双射的,从而对在光滑周期信号作用下的一类迟滞非线性进行建模.不仅建立了动态迟滞模型,而且也建立了相应的动态逆模型.仿真试验验证了所提出方法的有效性.     

基于坐标变换和仿射映射辨识迟滞非线性模型

运用坐标变换方法和仿射映射的有关原理,对迟滞系统的输入信号进行变换映射。利用集合理论证明了变换后,迟滞的输入输出集合是双射的,从而对在光滑周期信号作用下的一类迟滞非线性进行建模。不仅建立了动态迟滞模型,而且也建立了相应的动态逆模型。仿真试验验证了所提出方法的有效性。     

基于函数链神经网络的非线性系统稳态模型辨识及应用

利用函数链神经网络的非线性映射能力和快速收敛特性，将良好的推广能力视为网络评价函数的约束条件，以改善网络的泛化特性，提高系统的稳态辨识精度，仿真和实际应用结果表明，具有收敛快，辨识精度高，所需样本少等优点。该方法在ＳＯ３磺化过程非线性系统建模中得到应用。     

A parametric frequency response method for non-linear time-varying systems

A new parametric frequency response algorithm is introduced to investigate linear and non-linear dynamic systems with time-varying parameters. In the new algorithm the time-varying parameters are regarded as additional inputs of the systems and the non-linear generalised frequency response functions for multi-input-single-output systems are then employed to obtain Zadeh's system functions from a differential equation representation. The parametric frequency response method reveals how the time-varying parameters affect the behaviour of the systems through a time-varying term. The new method can be applied to both linear and non-linear time-varying systems.     

Learning-based frequency response function estimation for nonlinear systems

In this paper, we perform the nonlinear frequency response function (FRF) estimation for a class of nonlinear systems. Two non-parametric estimation techniques are considered: radial basis function neural network (RBF-NN)-based estimation and support vector machine (SVM)-based estimation. Based on the system's available observations, the proposed estimation models are used to predict its frequency response. Simulation results are provided to demonstrate the model implementation. Finally, a comparative study is carried out to evaluate the effectiveness of the RBF-NN and SVM schemes, which has demonstrated that the SVM outperformed RBF-NN in the FRF estimation.     

基于频域、时域相结合的自适应图像超分辨率重建

基于最大后验概率(MAP)的超分辨率(SR)重建的研究重点是规则化项的选择,且其大都在频域中实现,为此提出一种基于频域、时域相结合的图像SR重建方法.首先,根据不同图像的特点,定义了频域规则化项(FR)和时域规则化项(TR);然后,给出了图像重建模型,引入频域、时域自适应权值来加强算法的自适应性;最后,运用共轭梯度法推导出重建迭代计算公式.实验表明,所提出的算法具有良好的收敛性和精确性.     

MLP-based adaptive neural control of nonlinear time-delay systems with the unknown hysteresis

In this note, the authors study the tracking problem for uncertain nonlinear time-delay systems with unknown non-smooth hysteresis described by the generalised Prandtl–Ishlinskii (P-I) model. A minimal learning parameters (MLP)-based adaptive neural algorithm is developed by fusion of the Lyapunov–Krasovskii functional, dynamic surface control technique and MLP approach without constructing a hysteresis inverse. Unlike the existing results, the main innovation can be summarised as that the proposed algorithm requires less knowledge of the plant and independent of the P-I hysteresis operator, i.e. the hysteresis effect is unknown for the control design. Thus, the outstanding advantage of the corresponding scheme is that the control law is with a concise form and easy to implement in practice due to less computational burden. The proposed controller guarantees that the tracking error converges to a small neighbourhood of zero and all states of the closed-loop system are stabilised. A simulation example demonstrates the effectiveness of the proposed scheme.     

Fault estimation observer design for a class of nonlinear multiagent systems in finite‐frequency domain

This paper focuses on the fault estimation observer design problem in the finite‐frequency domain for a class of Lipschitz nonlinear multiagent systems subject to system components or actuator fault. First, the relative output estimation error is defined based on the directed communication topology of multiagent systems, and an observer error system is obtained by connecting adaptive fault estimation observer and the state equation of the original system. Then, sufficient conditions for the existence of the fault estimation observer are obtained by using a generalized Kalman‐Yakubovich‐Popov lemma and properties of the matrix trace, which guarantee that the observer error system satisfies robustness performance in the finite‐frequency domain. Meanwhile, the pole assignment method is used to configure the poles of the observer error system in a certain area. Finally, the simulation results are presented to illustrate the effectiveness of the proposed method.     

Computer aided design of multivariable nonlinear control systems using frequency domain techniques

The application of frequency domain methods to the study of a class of multivariable nonlinear feedback systems is considered within the context of a comprehensive interactive graphics design procedure and a new computational method is outlined for the determination of limit cycle operation which emphasises the effects of off diagonal system elements. It is shown how compensation can be applied using classical graphical design methods to avoid critical regions in the frequency domain. Two examples of use are given.     

Output frequency response function of nonlinear Volterra systems

An expression for the output frequency response function (OFRF), which defines the explicit analytical relationship between the output spectrum and the system parameters, is derived for nonlinear systems which can be described by a polynomial form differential equation model. An effective algorithm is developed to determine the OFRF directly from system simulation or experimental data. Simulation studies demonstrate the significance of the OFRF concept, and verify the effectiveness of the algorithm which evaluates the OFRF numerically. These new results provide an important basis for the analytical study and design of a wide class of nonlinear systems in the frequency domain.     

Output frequency response characteristics of nonlinear systems. Part I: general multi-tone inputs

A systematic algorithm for determining the output frequencies generated by a nonlinear system subject to a general multi-tone input, including a bias input, is presented. The algorithm is very efficient, and circumvents many of the difficulties of ‘duplicate frequencies’ that are often generated using previous methods. The inclusion of the dc bias component in the analysis is also important because of the significant effect that non-zero mean inputs can have on nonlinear system response. The algorithm is straightforward to implement on a computer, and the results are illustrated by means of an example.     

Fault estimation observer design for discrete‐time systems in finite‐frequency domain

This paper proposes a framework of fault estimation observer design in finite‐frequency domain for discrete‐time systems. First, under the multiconstrained idea, a full‐order fault estimation observer in finite‐frequency domain is designed to achieve fault estimation by using the generalized Kalman–Yakubovich–Popov lemma to reduce conservatism generated by the entire frequency domain. Then, a reduced‐order fault estimation observer is constructed, which results in a new fault estimator to realize fault estimation using current output information. Furthermore, by introducing slack variables, improved results on full‐order fault estimation observer and reduced‐order fault estimation observer design with finite‐frequency specifications are obtained such that different Lyapunov matrices can be separately designed for each constraint. Simulation results are presented to illustrate the advantages of the theoretic results obtained. Copyright © 2014 John Wiley & Sons, Ltd.     

Output frequency response characteristics of nonlinear systems. Part II: overlapping effects and commensurate multi-tone excitations

The output response of nonlinear systems is strongly dependent on the extent to which different input frequency combinations/intermodulations overlap one another and contribute to a common output frequency component. This makes it hard to determine the actual number of output frequencies, or to determine which of the many possible combinations contribute to a specified output frequency of interest. Systematic algorithms are presented for resolving these issues in a manner, which is both efficient and straightforward to implement on a computer. Three broad classes of input are considered: multi-tone, but nominally incommensurate sinusoids; multi-tone, harmonically related sinusoids and multi-tone excitations that are equi-spaced in frequency. The considered inputs also admit the possibility of a dc bias component since this can significantly affect the system response. The algorithms are therefore applicable to a broad range of practical inputs, and their use and benefits are illustrated with several examples.