Robust exponential stabilization of uncertain nonholonomic chained systems based on visual feedback

The visual serving stabilization for a kind of nonholonomic mobile robots with uncalibrated camera parameters is investigated based on the visual feedback and the state and input transformations. The authors obtain a new uncertain model of the nonholonomic kinematic system in the image plane,which is a chained form with uncalibrated visual parameters,from the camera robotic system. A new time varying feedback controller is proposed for the exponential stabilization of the nonholonomic chained system with unknown parameters by using state-scaling and switching technique.The exponential stability of the closed loop system is rigorously proved.Simulation results demonstrate the effectiveness of the proposed methods.     

反推技术及其在不确定系统中的应用

从控制学科的角度,综述了反推技术的产生、发展、主要方案及其特点。着重叙述了该技术在状态反馈非线性不确定系统、输出反馈非线性不确定系统、离散时间非线性不确定系统、线性不确定系统和随机非线性不确定系统等五个方面的应用形势与进展情况。同时,清楚地指出了反推技术在不确定系统应用中存在的问题,并且就这些问题提出了相应的解决途径和方法。     

Robust Feedback Controller for Exponential Stability of Nonlinear Systems with Mismatched Uncertainties

The robust stabilization of nonlinear systems with mismatched uncertainties is investigated. Based on the stability of the nominal system, a new approach to synthesizing a class of continuous state feedback controllers for uncertain nonlinear dynamical systems is proposed. By such feedback controllers, the exponential stability of uncertain nonlinear dynamical systems can be guaranteed. The approach can give a clear insight to system analysis. An illustrative example is given to demonstrate the utilization of the approach developed. Simulation results show that the method presented is practical and effective.     

不确定模糊系统的静态输出反馈-迭代算法

研究连续不确定T-S模糊系统的静态输出反馈控制问题。连续不确定T-S模糊系统的静态输出反馈控制稳定性的充分条件是根据可解的双线性矩阵不等式给出的。为了计算连续不确定T-S闭环模糊系统的静态输出反馈增益,提出了基于迭代线性矩阵不等式的算法。用数值仿真例子说明了该迭代线性矩阵不等式算法的有效性和收敛性。     

欠驱动VTOL空间飞行器系统的非线性跟踪控制

研究了欠驱动VTOL(垂直上升和垂直着陆)空间飞行器在各种输入耦合时的非线性跟踪控制问题。VTOL空间飞行器是具有三个自由度,两个控制输入的欠驱动系统。首先,通过控制输入和坐标变换,系统的动力学方程被变换成二阶链式形式。其次,利用后推法(backstepping)的思想推导出保证系统渐近收敛于给定轨迹的时变反馈控制规律。该方法将系统分解为低阶子系统来处理,利用中间虚拟控制变量和部分Lyapunov函数简化了控制器的设计。仿真结果证明了所设计控制器的有效性。     

线性不确定系统的鲁棒容错H∞控制设计

研究了线性不确定系统的鲁棒容错H∞控制问题.当系统既有状态滞后,又有控制输入滞后,而且状态和控制输入的不确定项均满足匹配条件时,运用线性矩阵不等式(LMI)方法,提出了一种针对不确定系统的鲁棒容错反馈控制设计方法.利用该方法设计的闭环系统,不仅在传感器发生故障时具有完整性,而且对于系统的参数不确定性具有鲁棒性.以设计实例及仿真结果验证了这种方法的有效性.     

参数不确定Liu混沌系统的模糊反馈控制

研究了新近提出的Liu混沌系统的模糊控制方法。在用T-S模糊模型重构了系统结构的基础上,利用反馈控制思想,设计了Liu混沌系统的模糊控制方法,并通过Lyapunov函数的推导得到了系统以衰减率α全局渐近稳定的充分条件。该方法适用于参数确定的系统和含有不确定参数的系统。文章对两种情况均进行了仿真实验。所有的控制参数可以通过LMI方法得到,仿真结果验证了该控制方法的有效性。该模糊控制方法在连续混沌系统中具有通用性。     

Adaptive failure compensation for uncertain systems with multiple inputs

The aim of this paper is to develop controllers for uncertain systems in the presence of stuck type actuator failures. A new scheme is proposed to design output feedback controllers for a class of uncertain systems having redundant control inputs, with which the relative degrees of transfer functions are different. To deal with these inputs using backstepping technique, a pre-filter is introduced before each actuator such that its output is the input to the actuator. The orders of the pre-filters are chosen properly to ensure all their inputs can be designed at the same step in the systematic design. To compensate for the effects of possible failed actuators, more uncertain parameters than system parameters are required to be identified. With the proposed scheme, the global boundedness of the closed-loop system can still be ensured and the system output can be regulated to a specific value when some of the actuators' outputs are stuck at unknown fixed values.     

不确定广义系统的镇定

针对输出反馈下不确定广义系统的可镇定问题,从状态反馈下闭环广义系统的稳定性问题入手,利用矩阵不等式,依次给出不确定广义系统可镇定、关联不确定广义大系统的分散可镇定、以及关联不确定广义大系统在执行器故障、传感器故障下分散可镇定的充分条件。由此推广到输出反馈,给出了输出反馈意义下的广义系统可镇定、关联不确定广义大系统的分散可镇定、以及关联不确定广义大系统在执行器故障、传感器故障下分散可镇定的充分条件(即完整性设计)。其中反馈控制器的设计方法简明而又统一,便于应用。最后用数值例子来验证所给结果的有效性。     

随机时延网络控制系统的鲁棒H∞状态反馈控制

研究了含有双随机时延的不确定网络控制系统的鲁棒H_∞状态反馈控制问题。将传感器到控制器和控制器到执行器的网络时延建模为相互独立的连续时间离散状态的马尔可夫随机过程。基于此网络环境,构造时延依赖的控制器,将不确定网络控制系统转化为马尔可夫跳变系统。通过Lyapunov Krasovskii泛函方法和新的矩阵不等式技术,给出了系统随机稳定且满足H_∞性能的充分条件,并以矩阵不等式形式给出了相应的控制器设计方法。最后,给出了仿真算例,验证了该方法的有效性。     

一类不确定离散切换广义系统的一致有限时间稳定准则

利用Lyapunov like函数方法和线性矩阵不等式（linear matrix inequality, LMI）技术研究了一类不确定离散时间切换广义系统的一致有限时间稳定和状态反馈镇定问题。首先,在任意给定的切换规则且假定不确定参数项范数有界的情况下,给出了保证不确定离散切换广义系统一致有限时间有界和有限时间稳定的充分条件和状态反馈控制器的设计方法,然后利用Matlab中的LMI工具箱对建立的LMI问题进行求解。最后的仿真算例验证了所提方法的有效性。     

Disturbance Attenuation State-Feedback Control for Uncertain Interconnected Systems

This paper studies the problem of robust H∞ control design for a class of uncertain interconnected systems via state feedback. This class of systems are described by a state space model, which contains unknown nonlinear interaction and time-varying norm-bounded parametric uncertainties in state equation. Using the Riccati-equation-based approach we design state feedback control laws, which guarantee the decentralized stability with disturbance attenuation for the interconnected uncertain systems. A simple example of an interconnected uncertain linear system is presented to illustrate the results.     

具有状态和控制时滞系统的鲁棒容错控制研究

研究一类不确定时滞系统的鲁棒容错控制问题。针对既有状态滞后,又有控制输入滞后,且假定状态和控制输入的不确定项均是范数有界的线性系统,通过引入无记忆状态反馈控制器,基于Lyapunov稳定性理论和LMI方法,给出了一个在传感器完全失效或执行器完全失效故障情况下具有鲁棒容错性能的充分条件,并用求解线性矩阵不等式组方便地得到容错控制器设计结果。最后用算例验证了该设计方法的有效性和可行性。     

Further results on limitations of sampled-data feedback

To control continuous-time uncertain dynamical systems with sampled data-feedback is prevalent today,but the sampling rate is usually not allowed to be arbitrarily fast due to various physical and/or computational constrains.In this paper,the authors examine the limitations of sampled-data feedback control for a class of uncertain systems in continuous-time,with sampling rate not necessary fast enough and with the unknown system structure confined to a set of functions with both linear and nonlinear growth.The limitations of the sampled-data feedback control for the uncertain systems are established quantitatively,which extends the existing related results in the literature.     

不确定离散广义系统的鲁棒无源控制

将严格无源的概念引入到离散广义系统中 ,研究了具有未知定常不确定参数的离散广义系统在有界外部输入作用下的鲁棒无源控制问题 ;利用线性矩阵不等式 ,给出了不确定离散广义系统广义二次稳定且从外部输入到被调输出之间是严格无源的 ,并在此基础上给出存在状态反馈控制器 ,使得闭环系统广义二次稳定且从外部输入到被调输出之间是严格无源 ,同时给出相应的依赖于矩阵不等式的解的控制器构造 ;数值算例说明了结论的有效性。     

基于模糊自适应的微型飞行器姿态控制

针对一类不确定非线性系统,基于李亚普诺夫稳定性理论提出了模糊自适应算法.将系统分为标称模型和包含建模误差、参数变化、干扰及未建模动态等在内的混合干扰项,用模糊自适应控制实时逼近系统各个不确定参数,用鲁棒反馈控制消除系统的外部干扰.由于模糊自适应控制是对系统输入系数矩阵和系统函数向量的不确定部分的每一个分量进行实时逼近,所以系统控制的精确性得到了提高,有较好的鲁棒性.模糊逻辑系统的计算量相对较少,从而能够很好地完成系统输出信号的渐近跟踪.给出了控制算法的稳定性证明,并对微型飞行器的姿态控制系统进行了仿真研究,仿真结果验证了算法的有效性.     

严格耗散广义系统的鲁棒性分析与控制

考虑不确定广义系统的鲁棒耗散性分析与控制,其中各不确定参数矩阵具有线性分式形式。针对确定广义系统建立耗散性与正实性之间的等价关系,将不确定广义系统的鲁棒耗散性分析与控制转化为确定广义系统的耗散性分析与控制,利用线性矩阵不等式,给出了不确定广义系统鲁棒严格耗散的充要条件及状态反馈鲁棒严格耗散控制器的设计方法。通过一个数值算例说明所给设计方法的有效性。     

Adaptive Output Feedback Regulation for a Class of Uncertain Feedforward Time-Delay Nonlinear Systems

This paper addresses the global output feedback regulation problem for a class of uncertain feedforward time-delay nonlinear systems. Unlike to the previous works, the nonlinear functions in the class of systems under consideration are dominated by an input-output function multiplied by an unknown parameter and linear unmeasured states. By using only one dynamic gain and an appropriate Lyapunov-Krasovskii functionals, it is shown that the closed-loop system is globally asymptotically stable. Finally, a numerical example is provided to illustrate the effectiveness of the proposed design scheme.