伺服系统的滑模变结构控制器设计

伺服系统不确定性和离散指数趋近律造成系统的系统抖振,传统的PID控制方法难以实现系统对精度和稳定性的要求.为了提高控制系统的性能,提出滑模变结构控制问题.采用参数辨识法,分别获取被控对象在空载和满载模型,并将空载测试数据按二阶模型结构辨识得到被控对象近似模型,作为离散滑模控制器设计的标称模型,并采用自适应趋近律设计了离散滑模控制器,分别对被控对象的两个模型进行控制仿真.结果表明,离散滑模变结构控制器能够使伺服系统满足要求,对参数摄动和外部干扰具有较强的鲁棒性,提高了控制器性能,为设计提供了依据.     

无抖振离散滑模输出反馈控制方法及仿真研究

针对离散时间系统,提出了一种基于多速率采样输出反馈和幂次函数趋近律的离散滑模控制方法;理论分析表明,通过引入幂次函数可消除离散滑模控制系统的抖振;采用多速率采样技术,运用不同采样速率下的系统输出值表示系统状态,实现了仅用系统输入输出采样值完成离散滑模控制器的设计,减轻了控制系统设计的复杂性;仿真结果表明,控制器的输出、切换函数、系统的输出均不存在抖振现象,而且控制系统表现出了良好的动态特性。     

移动机器人网络控制系统的输出反馈控制

以线性时不变系统为被控对象,建立了四轮移动机器人网络控制系统的离散数学模型。诱导时延是影响系统性能的关键因素,通过在节点中设置缓冲区的方法可以将网络控制系统中的随机诱导时延转化为确定性时延,从而将网络控制系统由随机系统转化为确定性系统。通过被控对象移动机器人控制实验系统,设计了一个能处理网络诱导时延的输出反馈控制器,分析了采样周期和网络诱导时延对网络控制系统稳定性的影响。仿真结果表明了该控制器和控制策略的正确性及有效性。     

基于模型的网络控制系统稳定性

针对具有时间延迟的网络控制系统被控对象状态无法直接测量得到的情况,设计了状态观测器,并讨论了系统指数稳定性问题．提出了在网络传输信号的时间间隔内依据被控对象模型计算控制信号的开环控制方法,以减少对网络的使用．在此基础土,分别对连续和离散被控对象给出了网络控制系统全局指数稳定的充要条件,该条件受网络信号更新时间、被控对象模型误差及网络引起的时间延迟等因素的影响．仿真示例验证了稳定性条件的有效性。     

一类不确定性网络控制系统的滑模控制器设计

网络诱导时廷是影响网络控制系统稳定性和动态性能的主要因素．针对一类具有不确定性的网络控制系统,给出具有网络诱导时廷及不确定性的被控对象模型,设计其滑模控制器,建立基于滑模反馈控制器的网络控制系统闭环模型．通过Lyapunov方法证明,所得最大允许时延能够保证闭环网络控制系统稳定．仿真例子验证了该方法的正确性和有效性．     

一类非线性大滞后系统自适应积分滑模控制

针对一类非线性大滞后系统, 基于伪偏导数概念的动态线性化非线性系统模型, 利用离散时间预测器技术, 实现了系统原始表达式中滞后环节的隐性表达, 并结合离散积分滑模控制(discrete integral sliding mode control, DISMC)方法, 提出了一种新的无模型自适应离散积分滑模控制(model-free adaptive discrete integral sliding mode control, MFA-DISMC)方案. 该方法的主要特点是控制器设计仅取决于被控对象的输入和输出测量数据. 通过理论分析证明了算法的稳定性, 仿真研究表明, 相比于无模型自适应控制(model-free adaptive control, MFAC)、Smith预估控制、改进的MFAC控制以及比例–积分–微分(proportional-integral-derivative, PID) 控制方法, 本文方法具有更快的响应速度和更强的鲁棒性. 最后, 通过双容水箱液位控制系统的实验研究, 验证了所提出方法的有效性.     

一种网络控制系统时延补偿方法

本文分析介绍了具有随机时延网络控制系统控制器设计及时延补偿方法,采用广义预测控制(GPC)算法设计控制器。针对输出时延通过对时间加上时间戳来估算时间延迟,并采用状态观测器进行时延补偿,而控制时延则采用队列机制,增加缓存器的方法来保证被控对象获得最优控制信号。通过仿真证实该方法的有效性。     

一类多执行机构系的滑模控制设计及其应用

针对一类具有多执行机构的非线性系统,利用滑模控制和backstepping技术,研究了输出跟踪问题.针对执行机构的不同特点,利用离散执行机构实现滑模控制中的不连续控制量,利用连续执行机构实现滑模控制中的连续控制量.然后利用backstepping技术实现连续执行机构的输出对滑模控制中的连续控制量的有限时间收敛.将提出的设计方法应用于导弹直接侧向力与气动力复合控制系统设计,并进行了仿真验证.     

使用低阶参考模型的离散多变量MRACS

本文提出了一种高阶被控对象跟随低阶参考模型的离散多变量模型参考自适应控制系统(MRACS)的设计方法,它利用数字滤波器将系统降阶,通过求解p个一次代数方程而确定的自适应控制输入信号,能够使多变量被控对象的每个多输入单输出(MISO)子系统的输出渐近收敛到对应的单输入单输出(SISO)低阶参考模型的输出,提出的自适应控制器不仅避免了引进正反馈和辅助信号,而且实现了自适应解耦控制,仿真结果表明该控制器具有较好的控制性能。     

具有次优保性能滑动模态的静态输出反馈滑模控制

针对一类不确定系统,提出了一种具有次优保性能滑模面的静态输出反馈滑模控制方法.首先将滑模面的设计问题等价为一个对称矩阵的求解问题,基于等效控制法,推导了保性能滑模面存在的充分条件.然后基于迭代线性矩阵不等式(iterative linear matrix inequality,ILMI)方法,给出了次优保性能线性滑模面的求解算法,最后基于线性矩阵不等式(linearmatrix inequality,LMI)方法,设计了输出反馈滑模控制器,使得闭环系统渐近稳定且切换函数能在有限时间内到达零.该方法首次实现了输出反馈滑模面的优化,且具有保守性小、无需对被控系统模型进行坐标变换的优点.仿真结果验证了本文方法的优越性.     

Output‐feedback‐based sliding mode control for networked control systems subject to packet loss and quantization

In this paper, observer‐based sliding mode control is considered for networked control systems subject to quantization, in which packet dropout may happen when the measurement output is transmitted from the sensor to the controller. Firstly, a compensating scheme is proposed to deal with the effect of packet loss modelled as a Bernoulli process. Then, by means of available output information and state observer, the desirable sliding mode controller is designed. Furthermore, both the reachability and the stochastic stability of sliding mode dynamics can be attained and the corresponding sufficient conditions are derived. Finally, numerical simulation results are provided to illustrate the proposed control law.     

Observer-based output feedback control of networked control systems with non-uniform sampling and time-varying delay

This paper investigates the problem of observer-based output feedback control for networked control systems with non-uniform sampling and time-varying transmission delay. The sampling intervals are assumed to vary within a given interval. The transmission delay belongs to a known interval. A discrete-time model is first established, which contains time-varying delay and norm-bounded uncertainties coming from non-uniform sampling intervals. It is then converted to an interconnection of two subsystems in which the forward channel is delay-free. The scaled small gain theorem is used to derive the stability condition for the closed-loop system. Moreover, the observer-based output feedback controller design method is proposed by utilising a modified cone complementary linearisation algorithm. Finally, numerical examples illustrate the validity and superiority of the proposed method.     

Robust output tracking of constrained perturbed linear systems via model predictive sliding mode control

A robustifying strategy for constrained linear multivariable systems is proposed. A combination of tracking model predictive control with output integral sliding mode techniques is used to completely reject bounded matched perturbations. It can be guaranteed that all constraints on inputs, states, and outputs are satisfied although only output information is used. Finally, real‐world experiments with an unstable plant are presented in order to demonstrate the validity and the effectiveness of the proposed approach.     

H∞ output tracking control for uncertain networked control systems via a switched system approach

In this paper, the problem of H_∞ output tracking control for networked control systems with random time delays and system uncertainties is investigated. Effective sampling instant that is tightly related with transmission delay from sensor to actuator is proposed to ensure that the random variable time delay is always shorter than one effective sampling period. By using both active time‐varying sampling period strategy and hybrid node‐driven mechanism, the switching instant is coincided with the effective sampling instant. An augmented time‐varying networked tracking system model is provided by including the output tracking error as an additional state. However, random transmission delay causes indeterminate sampling period, which induces infinite subsystems. Gridding approach is introduced to transform the continuous time axis into discrete‐time sequences, which guarantees the finite number of switching rules. By employing multiple Lyapunov–Krasovskii functions, linear matrix inequality (LMI)‐based output tracking H_∞ performance analysis is presented, and robust switching H_∞ model reference tracking controller for networked control systems with communication constraints and system uncertainties is designed to guarantee asymptotic tracking of prescribed reference outputs while rejecting disturbances. Finally, simulation results illustrate the correctness and effectiveness of the proposed approaches. Copyright © 2015 John Wiley & Sons, Ltd.     

Approximate causal output tracking for linear perturbed systems via sliding mode control

ABSTRACT

A new approach to the solution of what is termed causal output tracking problem for linear time-invariant systems in the presence of both matched and unmatched unmodelled disturbances is presented. The proposed solution is addressed through the design of a dynamic steady state estimator based on the desired system structure and an observer, considering the reference as the system output. The unmatched disturbance is estimated and used in the steady state estimator to achieve invariance, while the matched disturbance robustness is provided via sliding mode control using the super-twisting algorithm. A useful application of the presented techniques is output tracking for non-minimum phase systems; thus, the performed simulation results confirm the effectiveness of the proposed control scheme for this kind of systems.     

Output feedback sliding mode control under networked environment

This article considers the problem of sliding mode output feedback control for networked control systems (NCSs). The key idea is to make use of not only the current and previous measurements, but also previous inputs for the reconstruction of the state variables. Using this idea, sliding mode controllers are designed for systems with constant or time-varying network delay. The approach is not only more practical but also easy to implement. To illustrate this, the design technique is applied to an inverted pendulum system.     

Dynamic output feedback integral sliding mode control design for uncertain systems

This paper addresses the problem of designing a dynamic output feedback sliding mode control algorithm for linear MIMO systems with mismatched parameter uncertainties along with disturbances and matched nonlinear perturbations. Once the system is in the sliding mode, the proposed output‐dependent integral sliding surface can robustly stabilize the closed‐loop system and obtain the desired system performance. Two types of mismatched disturbances are considered and their effects on the sliding mode are explored. By introducing an additional dynamics into the controller design, the developed control law can guarantee that the system globally reaches and is maintained on the sliding surface in finite time. Finally, the feasibility of the proposed method is illustrated by numerical examples. Copyright © 2011 John Wiley & Sons, Ltd.     

具有输出/全状态约束的固定时间滑模控制

本文主要解决具有约束的二阶系统的固定时间跟踪控制问题,分别讨论了具有输出约束与具有全状态约束的控制算法设计.首先,为解决输出约束下的固定时间控制问题,本文构建了具有输出约束的新型终端滑模变量,并设计了具有扰动抑制能力的固定时间滑模控制律,保证系统输出始终满足约束条件,同时跟踪误差在固定时间内收敛到原点的充分小的邻域内.进一步,为了处理具有全状态约束的控制问题,本文构建了具有全状态约束的终端滑模变量并设计了相应的固定时间滑模控制律.鉴于系统控制律的不连续性,文章采用非光滑分析及Lyapunov稳定性理论证明了闭环控制系统的稳定性.最后,在数值仿真中,将本文提出的方法与传统固定时间滑模方法进行对比,验证了所建立算法的有效性.     

Robust sampled-data H ∞ output tracking control for a class of nonlinear networked systems with stochastic sampling

In this article, the problem of robust sampled-data H _∞ output tracking control is investigated for a class of nonlinear networked systems with stochastic sampling and time-varying norm-bounded uncertainties. For the sake of technical simplicity, only two different sampling periods are considered, their occurrence probabilities are given constants and satisfy Bernoulli distribution, and can be extended to the case with multiple stochastic sampling periods. By the way of an input delay, the probabilistic system is transformed into a stochastic continuous time-delay system. A new linear matrix inequality-based procedure is proposed for designing state-feedback controllers, which would guarantee that the closed-loop networked system with stochastic sampling tracks the output of a given reference model well in the sense of H _∞. Conservatism is reduced by taking the probability into account. Both network-induced delays and packet dropouts have been considered. Finally, an illustrative example is given to show the usefulness and effectiveness of the proposed H _∞ output tracking design.