一类饱和非线性系统抗饱和控制器设计

针对一类饱和非线性系统研究抗饱和控制器综合问题. 基于线性分式表示技术(LFR), 该类非线性系统可转化为带有满足扇形区间不等式条件的非线性函数及额外线性分式约束的饱和线性系统. 基于二次Lyapunov 方程并利用广义扇形区间不等式条件处理饱和非线性项, 提出了基于LMI 条件的非线性抗饱和控制器综合方法. 数值仿真验证了所提出方法的有效性.

     

执行器饱和的线性连续系统的镇定

针对控制系统中广泛存在饱和问题,主要研究执行器饱和线性连续系统的镇定问题并进行吸引域估计。首先根据Finsler’s引理和Lyapunov函数方法研究系统稳定的充分条件,得到执行器饱和控制系统稳定的新判据。其次,在稳定条件下,应用凸组合方法和新引入的自由权矩阵使得系统吸引域估计具有更小的保守性,将所得非线性矩阵不等式转化为线性矩阵不等式,给出求解最大吸引域的优化方法和状态反馈控制器的设计方案。最后通过仿真算例验证结果的有效性和可行性。     

含状态时滞及执行器饱和不确定系统反馈镇定及L2增益分析

研究了具有控制饱和状态时滞不确定系统的L2控制问题,提出了状态反馈方法,利用Lyapunov函数可获得时滞相关的线性矩阵不等式.线性矩阵不等式条件可保证闭环系统无干扰时鲁棒内稳定性和在某椭球内预先给定的有干扰时L2性能水平,该不等式通过引入辅助矩阵解除了执行器饱和对系统的影响而更易于实现且减小了保守性.采用线性矩阵不等式技术,将控制器存在的充分条件转化为凸优化问题.在此基础上设计了系统的状态反馈控制器,最后用数值仿真验证了所提出方法的可行性.     

运用线性反馈分析设计饱和线性系统

给出了状态反馈控制饱和单输入系统以及动态输出反馈单输出饱和线性系统是全局渐近稳定还是区域渐近稳定的充分性条件,并在区域渐近稳定的情况下计算其不变吸引椭球.对于控制饱和系统,运用Ricatti方程迭代法设计控制器,以使所得椭球尽量大.仿真算例说明了所提出方法的有效性.     

带有饱和执行器的T-S离散模糊系统的LQ模糊控制

研究了带有饱和执行器的Takagi-SugenoT-S离散模糊系统的LQ模糊控制问题,利用Lyapunov稳定理论、PDC(平行分配补偿)技术以及线性矩阵不等式方法,得到了闭环模糊系统的渐近稳定的充分条件,给出了闭环系统的LQ模糊控制律的设计方法和吸引域的一个估计,并建立了闭环系统的LQ性能函数上界的计算公式.进一步,针对两类优化问题,即:LQ性能最小化问题和吸引域最大化问题,给出了相应的带有线性矩阵不等式约束的计算方法.最后,一个仿真例子说明了所给方法的有效性.     

一类切换时滞奇异系统的状态反馈H∞控制

研究一类由任意有限多个时滞奇异子系统组成的切换系统的状态反馈H∞控制问题。利用Lyapunov函数方法和凸组合技术,给出由矩阵不等式表示的控制器存在的充分条件,并设计了相应的子控制器和切换规则。采用变量替代方法,将该矩阵不等式转换为一组线性矩阵不等式(LMIs),最后给出一个求解状态反馈控制器增益矩阵的仿真算例。研究结果表明,通过切换,闭环系统在整个状态空间上的每个点都满足H∞性能,并不要求每个子系统在整个状态空间上都满足H∞性能,甚至也不要求其渐进稳定。     

一类切换线性奇异系统的状态反馈H∞控制*

研究了一类由任意多个子系统组成的线性切换奇异系统的状态反馈H∞控制问题。采用共同Lyapunov函数方法和凸组合技术,给出由矩阵不等式表示的使闭环系统渐近稳定且满足H∞性能的控制器存在的充分条件, 并设计了相应的子控制器和切换策略。采用矩阵变换,将矩阵不等式等价转换为一组线性矩阵不等式。数值算例说明了所提方法的有效性和可行性。     

广义时滞系统的状态反馈H∞控制

考虑一类广义时滞系统的状态反馈H∞控制问题，目的是设计状态反馈控制律，使得闭环系统渐近稳定，且满足一定的H∞性能指标，控制律的设计只需求解一组LMI。数值算例说明了所给方法的有效性。     

具有执行器饱和特性的不确定系统预测控制器设计

针对具有执行器饱和特征的不确定系统,提出了一种带有状态观测器的新型预测控制器设计方法.该方法在滚动优化的每一步,采用带有饱和特性的反馈控制结构得到一个最优控制律.使无穷时域性能指标最小.考虑在状态不完全已知的情况下,设计了带有状态观测器的预测控制器,并通过观测器参数调整使闭环系统渐近稳定.通过仿真实验验证了所设计控制器的有效性.     

一种估计奇异摄动饱和系统稳定域的方法

针对奇异摄动饱和系统, 提出了一种估计其稳定域的降阶方法. 结合饱和函数的特殊性质, 证明了此类系统的稳定域可分解为伴随系统的不变集与一个足够大球体的笛卡尔积. 将原系统稳定域估计问题转化为低阶伴随系统稳定域的估计问题, 利用线性矩阵不等式(Linear matrix inequality, LMI)优化方法估计伴随系统的稳定域以减少保守性. 本方法不仅可以克服奇异摄动饱和系统的奇异性, 还可以一定程度克服系统的``维数灾'等问题.     

Output-feedback control for switched linear systems subject to actuator saturation

This article is devoted to the output-feedback ?_∞ control problem for switched linear systems subject to actuator saturation. We consider both continuous- and discrete-time switched systems. Using the minimal switching rule, nonlinear output feedbacks expressed in the form of quasi-linear parameter varying system are designed to satisfy a pre-specified disturbance attenuation level defined by the regional ?₂ (?₂)-gains over a class of energy-bounded disturbances. The conditions are expressed in bilinear matrix inequalities and can be solved by line search coupled with linear matrix inequalities optimisation. A spherical inverted pendulum example is used to illustrate the effectiveness of the proposed approach.     

Quantised feedback control for bilinear systems with actuator saturation

This paper is concerned with quantised feedback control problems for bilinear systems with actuator saturation. We propose two types of quantisers. For the first quantiser, quantised input and quantised state are considered. For the second quantiser, quantised control input is only investigated. A designed state feedback controller guarantees that the resulting closed-loop system is convergent to a small neighbourhood around the origin for every initial condition emanating from the large admissible domain. Sufficient conditions for feasibility are derived in terms of linear matrix inequalities. Several examples are presented to demonstrate the applicability of the proposed approach.     

Anti‐windup design for uncertain nonlinear systems subject to actuator saturation and external disturbance

A novel anti‐windup design method is provided for a class of uncertain nonlinear systems subject to actuator saturation and external disturbance. The controller considered incorporates both an active disturbance rejection controller as well as an anti‐windup compensator. The dynamical uncertainties and external disturbance are treated as an extended state of the plant, and then estimate it using an extended state observer and compensate for it in the control action, in real time. The anti‐windup compensator produces a signal based on the difference between the controller output and the saturated actuator output, and then augment the signal to the control to deal with the windup phenomenon caused by actuator saturation. We first show that, with the application of the proposed controller, the considered nonlinear system is asymptotically stable in a region including the origin. Then, in the case that the controller in linear form, we establish a linear matrix inequality‐based framework to compute the extended state observer gain and the anti‐windup compensation gain that maximize the estimate of the domain of attraction of the resulting closed‐loop system. The effectiveness of the proposed method is illustrated by a numerical example. Copyright © 2016 John Wiley & Sons, Ltd.     

Overall convergence rate of delta operator systems subject to actuator saturation

In this paper, overall convergence rate is considered for a delta operator system with actuator saturation. A saturation feedback law is presented for the delta operator system to obtain a desired overall convergence rate. Some properties on the overall convergence rate are revealed for time‐optimal actuator saturation delta operator systems. Limitations on the overall convergence rate are also investigated by proposed methods. An optimization problem is solved through a linear matrix inequality method to obtain the domain of attraction and overall convergence rate. Two numerical examples are provided to demonstrate the effectiveness of the proposed techniques. Copyright © 2017 John Wiley & Sons, Ltd.     

Analysis and design for singular discrete linear systems subject to actuator saturation

A method to estimate the domain of attraction for a singular discrete linear system under a saturated linear feedback is established. Simple conditions are derived in terms of an auxiliary feedback matrix for determining if a given ellipsoid is contractively invariant. These conditions are expressed in terms of linear matrix inequalities. The largest contractively invariant ellipsoid can also be determined by solving an optimization problem with linear matrix inequality constraints. This result is extended to the design of feedback gain that results in the largest contractively invariant ellipsoid, which is also a linear matrix inequality optimization problem. A numerical example demonstrates the applicability and effectiveness of the presented method. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Improved delay‐dependent stabilization of time‐delay systems with actuator saturation

This paper addresses the controller synthesis problem of linear time‐delay systems subjected to saturating control. Delay‐dependent regional stabilization criteria are derived based on Lyapunov–Krasovskii approach by using both the polytopic or dead‐zone representation of the saturation function. The main contribution of the paper lies in developing less conservative convex criterion in terms of LMIs to obtain superior results. On the basis of the derived stabilization criterion, an optimization problem is defined to compute the stabilizing state feedback gains with an aim to maximize the stabilizing region while guaranteeing the asymptotic stability of the closed‐loop system. Considering three numerical examples, an assessment of the polytopic and dead‐zone nonlinearity approaches is made. Copyright © 2012 John Wiley & Sons, Ltd.     

Analysis and design of delta operator systems with nested actuator saturation

In this paper, the problem of estimating the domain of attraction is considered for delta operator systems subject to nested actuator saturation. A set invariance condition is established for the delta operator system with nested actuator saturation in terms of auxiliary feedback matrices. Based on the set invariance condition, an optimisation approach is proposed to estimate the domain of attraction for the delta operator system. Thereby, the partial results of nested actuator saturation for both continuous-time systems and discrete-time systems are extended to delta operator system framework. A numerical example is provided to illustrate the effectiveness of the proposed design techniques.