Stabilization and H∞ Control of Nonlinear Switched Hamiltonian Systems Subject to Actuator Saturation

This paper investigates the stabilization and H_∞ control problem of nonlinear switched Hamiltonian systems (NSHSs) subject to actuator saturation (AS) under arbitrary switching paths. First, based on the saturating actuator property, an appropriate state feedback is designed under a realistic assumption for the stabilization of NSHSs with AS. Then, an H_∞ controller is designed for NSHSs subject to AS with external disturbances in order to attenuate the disturbances. Futhermore, the results obtained for NSHSs are applied to study the stabilization and H_∞ control of switched nonlinear systems with AS via the Hamiltonian realization method. Finally, simulation examples show the efficiency of the methods and results proposed in this paper.     

Robust Stability and Stabilization of Positive Interval Systems Subject to Actuator Saturation

This paper addresses the stabilization problem for a class of uncertain positive linear systems (PLSs) in the presence of saturating actuators. The objective is to obtain sufficient conditions for the robust stability of PLSs and to design robust state feedback control laws such that the closed‐loop uncertain system is asymptotically stable and positive at the origin with a large domain of attraction. Several sufficient conditions for robust stabilization and positivity are derived via the Lyapunov function approach and convex analysis method for both the discrete‐time and the continuous‐time cases, respectively. The state feedback controller design and the estimation of the domain of attraction are presented by solving a convex optimization problem with linear matrix inequalities (LMIs) constraints. A numerical example is given to show the effectiveness of the proposed methods.     

Active Disturbance Rejection Control for Teleoperation Systems with Actuator Saturation

In this paper, stabilization of a nonlinear bilateral teleoperation system with time delays and actuator saturation is investigated via active disturbance rejection control (ADRC). An linear extended state observer is introduced to deal with the lumped system uncertainties. Lyapunov functions are given to prove the stabilization of the closed‐loop bilateral teleoperation system. Two Phantom Premium 1.5 HighForce (HF) robot manipulators are used in experiments to demonstrate the effectiveness of the proposed method in this paper.     

Human-in-the-Loop Consensus Control for Nonlinear Multi-Agent Systems With Actuator Faults

This paper considers the human-in-the-loop leader-following consensus control problem of multi-agent systems(MASs)with unknown matched nonlinear functions and actuator faults.It is assumed that a human operator controls the MASs via sending the command signal to a non-autonomous leader which generates the desired trajectory.Moreover,the leader’s input is nonzero and not available to all followers.By using neural networks and fault estimators to approximate unknown nonlinear dynamics and identify the actuator faults,respectively,the neighborhood observer-based neural fault-tolerant controller with dynamic coupling gains is designed.It is proved that the state of each follower can synchronize with the leader’s state under a directed graph and all signals in the closed-loop system are guaranteed to be cooperatively uniformly ultimately bounded.Finally,simulation results are presented for verifying the effectiveness of the proposed control method.     

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。     

一类带死区输入的非线性不确定系统滑模自适应控制

研究一类参数不确定和带有未知死区的非线性系统滑模自适应控制问题。将死区分解为两部分,被控系统中有两类不确定性的系统参数,一类是常值的未知系统参数;另一类是时变的未知系统参数和部分未知的死区。采用滑模控制和自适应控制相结合的方式,第一类不确定性可以由自适应控制来处理,而第二类不确定性可以由滑模控制来处理,即滑模自适应控制器。为了消除滑模控制所带来的抖振,引入边界层。采用’Lyapunov函数证明了系统的稳定性。仿真实验表明方法的可行性。     

输入饱和的一类切换系统神经网络跟踪控制

针对单输入单输出系统研究一种在任意切换下的跟踪控制问题,系统包含未知扰动和输入饱和特性.首先,利用高斯误差函数描述一个连续可导的非对称饱和模型.其次,利用径向基神经网络（Radial basis function neural network,RBF NN）逼近未知的系统动态.最后,基于公共的Lyapunov函数构造状态反馈控制器.设计的控制器避免过多参数调节从而减轻计算负荷.结果展示本文给出的状态反馈控制器可以保证闭环系统的所有信号是半全局一致有界的,并且跟踪误差可收敛到零值小的领域内.最后的仿真结果进一步验证提出方法的有效性.     

针对一类执行器故障连续系统的保性能控制设计

本文利用线性矩阵不等式 (LMI)方法 ,讨论了一类存在执行器故障不确定连续系统的保性能控制问题 ,给出了故障时系统保性能状态反馈控制器存在的充分条件并应用基于LMI的凸优化方法实现了针对系统故障的最优保性能状态反馈控制器设计。仿真实例验证了该方法的有效性。     

不确定非线性系统控制方法概述

不确定非线性系统的控制是目前国内外自动控制领域研究的一个热点。主要总结了近年来不确定非线性系统的控制方法，并分析了各种方法的优缺点。最后探讨了这一研究领域的研究趋向。     

非线性机械系统PID控制渐近稳定性分析

应用Lyapunov直接稳定性理论和LaSalle不变性原理, 证明了不确定非线性机械系统常用线性PID控制的半全局渐近稳定性. 同时证明了为提高系统的响应速度而发展的一种非线性PI加D (NPI-D)控制系统的全局渐近稳定性. 两自由度机器人系统的数值仿真结果验证了NPI-D控制的良好性能.     

Sliding Mode Control for Uncertain Switched Systems with Partial Actuator Faults

This paper considers the sliding mode control for a class of uncertain switched systems with partial actuator faults. By employing a weighted sum of the input matrices, a common integral sliding surface is designed. Moreover, the exponential stability of the sliding mode dynamics is analyzed by adopting the multiple Lyapunov function method and the average dwell time strategy. It is shown that the state trajectory can be driven onto the proposed sliding surface despite the presence of parameter uncertainties, external disturbances, and actuator faults. A numerical example is given to demonstrate the effectiveness of the proposed method.     

Distributed Control of Nonlinear Uncertain Systems: A Cyclic-small-gain Approach

This paper presents a cyclic-small-gain approach to distributed control of nonlinear multi-agent systems for output agreement. Through a novel nonlinear control law design, the output agreement problem is transformed into a stabilization problem, and the closed-loop multi-agent system is transformed into a large-scale system composed of input-to-state stability (ISS) subsystems which are interconnected with each other through redefined outputs. By forcing the redefined outputs to go to arbitrarily small neighborhoods of the origin, practical consensus is achieved for the agents in the sense that their outputs ultimately converge to each other within an arbitrarily small region. A recently developed cyclic-small-gain result is adopted to assign appropriately the ISS gains to the transformed interconnected system. Moreover, if the system is disturbancefree, then consensus can be guaranteed. Interestingly, the closedloop multi-agent system is also robust to bounded time-delays and disturbances in information exchange.      

一类非线性不确定系统的鲁棒自适应控制

针对一类含有未知参数和动态不确定的非线性系统，基于Lyapunov递推设计方法设计了状态反馈控制器，并提出了鲁棒自适应控制算法。所设计的控制器不仅可保证闭环系统的全局稳定性。而且使得系统对于所有允许的不确定系统状态全局一致终值有界。仿真结果表明了本文方法所设计的控制器的有效性和可行性。     

Robust Control for a Class of Uncertain Switched Fuzzy Systems with Saturating Actuators

This paper investigates the robust control problem for a class of uncertain switched fuzzy systems with saturating actuators. The asymptotical stability for fuzzy subsystems subject to actuator saturation is not assumed. Based on the multiple Lyapunov functions method, we design a switching law and a state feedback control law such that the closed‐loop system is asymptotically stable. Additionally, the estimation of the domain of attraction is presented by solving an optimization problem. Finally, simulation results verify the feasibility and effectiveness of the proposed method.     

Analysis and Design of Time-Delay Impulsive Systems Subject to Actuator Saturation

This paper investigates the exponential stability and performance analysis of nonlinear time-delay impulsive systems subject to actuator saturation. When continuous dynamics is unstable, under some conditions, it is shown that the system can be stabilized by a class of saturated delayed-impulses regardless of the length of input delays. Conversely, when the system is originally stable, it is shown that under some conditions, the system is robust with respect to sufficient small delayed-impulses....     

含有广义饱和函数的全局渐近稳定非线性PID控制

为解决传统饱和函数条件比较苛刻的问题,本文提出了一种饱和函数,并将其应用于线性PD(比例-微分)+非线性PI (比例-积分)控制律.应用李亚普诺夫稳定性定理和拉萨尔不变原理推导了非线性PID控制律全局渐近稳定条件.为提高非线性PID控制精度,以位置跟踪误差绝对值时间积分和关节力矩输出误差绝对值时间积分为目标函数,以全局渐近稳定性条件以及关节额定驱动力矩为约束条件,应用多目标遗传算法NSGA-II(non-dominated sorted genetic algorithm-II)进行非线性PID控制律参数整定.选择优化后位置跟踪误差绝对值时间积分最小的饱和函数,并研究含有该饱和函数的非线性PID控制律对模型不确定性、输入干扰力矩和噪声的鲁棒性.与传统PID控制律和含有传统饱和函数的非线性PID控制律相比,本文方法的位置跟踪精度分别提高了近2个数量级和1个数量级.提出的饱和函数在靠近平衡点处具有较强反作用,使误差快速收敛于平衡点,有助于提高非线性PID控制律的位置跟踪精度以及鲁棒性.     

执行器故障下不确定非线性系统的鲁棒保成本控制

对一类执行器故障的非线性不确定系统,研究了具有L2增益扰动衰减性能指标约束的鲁棒保成本控制器的设计问题.提出了更实际、更一般的执行器故障模型；给出了具有L2增益扰动衰减性能的鲁棒保成本控制系统的概念和属性.采用HJI不等式方法,导出了故障闭环系统渐近稳定、具有给定的抗干扰能力和成本函数有上界的充分条件.仿真实例验证了结论的有效性.     

Tracking Control of Leader-follower Multi-agent Systems Subject to Actuator Saturation

This paper addresses the tracking problem of leaderfollower multi-agent systems subject to actuator saturation. A leader node or command generator is considered, which generates the desired tracking trajectory. To track such a leader, a new family of scheduled low-and-high-gain feedback controllers is designed for each follower, provided that the linear dynamic mode is asymptotically null controllable with bounded controls, and such control laws rely on the asymptotic property of a class of parametric algebraic Ricatti equations. We show that if the associated undirected graph of the system is connected, with the proposed control law, all the followers can track the leader eventually. A simulation example is finally given to illustrate the performance of the proposed control scheme.      

执行器故障不确定非线性系统最优自适应输出跟踪控制

本文针对一类具有执行器故障的多输入多输出（Multi-input multi-output,MIMO）不确定连续仿射非线性系统,提出了一种最优自适应输出跟踪控制方案.设计了保证系统稳定性的不确定项估计神经网络权值调整算法,仅采用评价网络即可同时获得无限时域代价函数和满足哈密顿-雅可比-贝尔曼（Hamilton-Jacobi-Bellman,HJB）方程的最优控制输入.考虑执行器卡死和部分失效故障,设计最优自适应补偿控制律,所设计的控制律可以实现对参考输出的一致最终有界跟踪.飞行器控制仿真和对比验证表明了本文方法的有效性和优越性.