一类线性连续切换系统的迭代学习控制

针对有限时间区间内执行重复控制任务的线性连续切换系统,考虑基于迭代学习的跟踪控制问题.假设线性切换系统的切换率在时间域内是任意的,提出该类系统的D型迭代学习控制算法.理论分析表明,当学习增益矩阵满足一定的条件时,D型迭代学习控制算法可以保证切换系统的实际输出在整个运行区间上一致收敛于期望输出,实现完全跟踪控制.数值仿真进一步验证了方法的有效性.     

不确定时变系统的鲁棒学习控制算法

研究不确定性时变系统在有限时间区间上重复作业和在无限时间区间上周期作业的跟踪控制问题. 基于Lyapunov-like方法, 给出了形式简单的鲁棒迭代学习控制和鲁棒重复控制两种算法. 两种学习算法均可弥补单一控制算法的缺陷, 鲁棒控制部分被用来保证闭环系统中所有变量的有界性, 学习控制部分可有效消除系统跟踪误差, 改善系统的跟踪性能. 仿真结果验证了两种学习算法的有效性.     

基于Backstepping的非一致轨迹迭代学习控制研究

针对一类在有限时间区间上可重复运行的高阶混合参数化非线性系统,利用改进Backstepping方法,将参数重组技巧和分段积分机制相结合,提出了一种混合自适应迭代学习控制算法。该算法由参数的微分-差分型自适应律和学习控制律组成,可以处理目标轨线迭代可变的跟踪问题。通过构造Lyapunov-like泛函使得跟踪误差的平方在一个有限时间区间上的积分收敛于零,同时保证所有信号均在有限时间区间内有界。仿真结果说明了所提算法的有效性。     

Lebesgue-p范数意义下区间可调节的变增益加速迭代学习控制

为加快迭代学习控制律的收敛速度,针对线性时不变(LTI)系统,以PD-型学习律为例,提出一种区间可调节的具有指数加速的迭代学习控制算法.首先,根据每次学习效果确定下一次迭代需要修正的区间并在该区间内修正控制律增益;然后,在Lebesgue-p范数意义下分析所提出算法的收敛性并给出其收敛条件;最后,通过理论分析表明,收敛速度主要取决于被控对象、控制律增益、修正指数和学习区间的大小.在相同仿真条件下,与传统算法相比,所提出算法具有更快的收敛速度.     

非线性时变参数不确定系统的自适应迭代学习控制

利用离散时间轴与迭代轴之间的相似性, 提出了一种新的离散时间自适应迭代学习控制 (AILC) 方法来处理带有时变参数不确定性的非线性系统. 与自适应控制相类似, 所提出的 AILC 是基于投影算法的, 因此学习增益可以沿学习轴迭代地调节. 在随机初始状态和参考轨迹迭代变化的条件下, 所提出的 AILC 仍可沿迭代学习轴渐近地实现有限时间区间上的逐点收敛性.     

具有控制时滞和测量数据丢失的直线电机迭代学习控制

针对测量信号存在丢失和控制信号存在时滞的直线电机控制系统,研究PD型迭代学习控制算法的收敛性问题.假设数据丢失描述为概率未知的随机Bernoulli过程,其中丢失概率属于某个已知数值区间,利用超前法解决控制信号存在的时滞问题.基于Bellman-gronwall不等式和$\lambda$范数理论,证明了所提出的迭代学习控制策略能够使系统在有限时间内跟踪期望轨迹.最后通过仿真验证了所提出学习算法的有效性.     

非仿射非线性多智能体系统迭代学习一致跟踪

为了解决非仿射非线性多智能体系统在给定时间区间上一致性完全跟踪问题,基于迭代学习控制方法设计一种分布式一致性跟踪控制算法.首先,由引入的虚拟领导者与所有跟随者组成多智能体系统的通信拓扑,其中虚拟领导者的作用是提供期望轨迹.然后,在只有部分跟随者能够获得领导者信息的条件下,利用每个跟随者及其邻居的跟踪误差构造每个跟随者的迭代学习一致性跟踪控制器.同时采用中值定理将非仿射非线性多智能体系统转化仿射形式,并基于压缩映射方法证明所提算法的收敛性,给出算法的收敛条件.理论分析表明,在智能体的非线性函数未知情况下,利用所提算法可以使非仿射非线性多智能体系统在给定时间区间上随迭代次数增加逐次实现一致性完全跟踪.最后,通过仿真算例进一步验证所提算法的有效性.     

非线性系统在任意初值下的PID型迭代学习控制

针对一类在有限时间区间上重复运行的非线性系统,给出了一种可以解决迭代学习控制中任意初值问题的PID型迭代学习算法及其收敛条件。采用算子理论证明了该算法的收敛性,结果表明该算法不仅有效解决了迭代学习控制的初值问题,而且放宽了收敛条件。仿真分析及与PD型迭代学习控制算法的仿真结果的对比证明,非线性系统在任意初值条件下经过PID型迭代学习后跟踪精度显著提高,输出误差曲线更快速趋于零,表明了该算法的有效性。     

一类控制输入饱和受限的不确定系统滑模控制

本文研究控制输入饱和受限情况下不确定系统的滑模控制问题,其中,被控对象同时存在状态矩阵不确定性和控制增益矩阵不确定性.设计了一种积分型切换面和一个具有特殊结构的滑模控制律,可以在参数不确定和控制受限影响下保证系统状态轨迹有限时间内到达指定的切换面,利用等价控制律方法给出了滑模动态渐近稳定的充分条件.数值仿真例子验证了本文算法的有效性.     

执行器饱和多智能体系统的自适应学习一致性算法

针对一类受到执行器饱和高阶多智能体系统在有限时间区间[0,T]上的精确一致性问题,利用自适应迭代学习控制的方法,设计了具有全饱和差分型自适应更新律的时变增益.通过构造适当的复合能量函数,严格证明了一致性误差向量随着迭代次数趋于无穷而一致趋于零,得到了不依赖于网络通信拓扑矩阵特征值的自适应学习一致性算法.最后,给出一个仿真例子,仿真结果说明了所提算法的有效性.     

Iterative Learning Control for uncertain systems: Robust monotonic convergence analysis

In this paper, we present a novel Robust Monotonic Convergence (RMC) analysis approach for finite time interval Iterative Learning Control (ILC) for uncertain systems. For that purpose, a finite time interval model for uncertain systems is introduced. This model is subsequently used in an RMC analysis based on μ analysis. As a result, we can handle additive and multiplicative uncertainty models in the RMC problem formulation, analyze RMC of linear time invariant MIMO systems controlled by any linear trial invariant ILC controller, and formulate additional straightforward RMC conditions for ILC controlled systems. To illustrate the derived results, we analyze the RMC properties of linear quadratic (LQ) norm optimal ILC.     

Stability analysis of discrete-time iterative learning control systems with interval uncertainty

This paper presents a stability analysis of the iterative learning control (ILC) problem for discrete-time systems when the plant Markov parameters are subject to interval uncertainty. Using the so-called super-vector approach to ILC, vertex impulse response matrices are employed to develop sufficient conditions for both asymptotic stability and monotonic convergence of the ILC process. It is shown that the stability of such interval ILC systems can be determined by checking the stability of the system using only the vertex points of the interval Markov parameters.     

An open-closed-loop iterative learning control approach for nonlinear switched systems with application to freeway traffic control

For nonlinear switched discrete-time systems with input constraints, this paper presents an open-closed-loop iterative learning control (ILC) approach, which includes a feedforward ILC part and a feedback control part. Under a given switching rule, the mathematical induction is used to prove the convergence of ILC tracking error in each subsystem. It is demonstrated that the convergence of ILC tracking error is dependent on the feedforward control gain, but the feedback control can speed up the convergence process of ILC by a suitable selection of feedback control gain. A switched freeway traffic system is used to illustrate the effectiveness of the proposed ILC law.     

Formation control for multi‐agent systems through an iterative learning design approach

This paper deals with formation control problems for multi‐agent systems by using iterative learning control (ILC) design approaches. Distributed formation ILC algorithms are presented to enable all agents in directed graphs to achieve the desired relative formations perfectly over a finite‐time interval. It is shown that not only asymptotic stability but also monotonic convergence of multi‐agent formation ILC can be accomplished, and the convergence conditions in terms of linear matrix inequalities can be simultaneously established. The derived results are also applicable to multi‐agent systems that are subject to stochastic disturbances and model uncertainties. Furthermore, the feasibility of convergence conditions and the effect of communication delays are discussed for the proposed multi‐agent formation ILC algorithms. Simulation results are given for uncertain multi‐agent systems to verify the theoretical study. Copyright © 2012 John Wiley & Sons, Ltd.     

输入增益未知非参数不确定系统的准最优学习控制

为解决一类非参数不确定系统在任意初态且输入增益未知情形下的轨迹跟踪问题, 提出准最优误差跟踪学习控制方法.该方法综合准最优控制和迭代学习控制两种技术设计控制器, 在构造期望误差轨迹的基础上, 根据控制Lyapunov函数及Sontag公式给出标称系统的优化控制, 以鲁棒方法和学习方法相结合的策略处理非参数不确定性.闭环系统经过足够次迭代运行后, 经由实现系统误差对期望误差轨迹在整个作业区间上的精确跟踪, 获得系统状态对参考信号在预设的部分作业区间上的精确跟踪.仿真结果表明所设计学习系统在收敛速度方面快于非优化设计.     

Adaptive iterative learning control for switched nonlinear continuous-time systems

In this paper, an adaptive iterative learning control (ILC) method is proposed for switched nonlinear continuous-time systems with time-varying parametric uncertainties. First, an iterative learning controller is constructed with a state feedback term in the time domain and an adaptive learning term in the iteration domain. Then a switched nonlinear continuous-discrete two-dimensional (2D) system is built to describe the adaptive ILC system. Multiple 2D Lyapunov functions-based analysis ensures that the 2D system is exponentially stable, and the tracking error will converge to zero in the iteration domain. The design method of the iterative learning controller is obtained by solving a linear matrix inequality. Finally, the efficacy of the proposed controller is demonstrated by the simulation results.     

Consensus seeking via iterative learning for multi‐agent systems with switching topologies and communication time‐delays

This paper deals with the high‐precision consensus seeking problem of multi‐agent systems when they are subject to switching topologies and varying communication time‐delays. By combining the iterative learning control (ILC) approach, a distributed consensus seeking algorithm is presented based on only the relative information between every agent and its local (or nearest) neighbors. All agents can be enabled to achieve consensus exactly on a common output trajectory over a finite time interval. Furthermore, conditions are proposed to guarantee both exponential convergence and monotonic convergence for the resulting ILC processes of multi‐agent consensus systems. In particular, the linear matrix inequality technique is employed to formulate the established convergence conditions, which can directly give formulas for the gain matrix design. An illustrative example is included to validate the effectiveness of the proposed ILC‐motivated consensus seeking algorithm. Copyright © 2016 John Wiley & Sons, Ltd.     

A New Approach For Stability Analysis Of Time‐Dependent Switched Continuous‐Time Linear Systems

In this paper, a new approach for stability analysis of time‐dependent switched linear systems is proposed. System equivalence is the main idea in this new approach, which derives a switched discrete linear parameter‐varying system from the switched continuous‐time linear switched system with interval dwell time, and the stability properties of the two corresponding systems are proved to be equivalent. Then, by applying a quadratic Lyapunov function approach for the equivalent switched discrete system, the stability of the switched continuous‐time linear system can be established without checking any average dwell time condition. Finally the computation complexity is analyzed, and mode incidence matrix is introduced to reduce the computation cost.     

Adaptive ILC algorithms of nonlinear continuous systems with non-parametric uncertainties for non-repetitive trajectory tracking

In this article, two adaptive iterative learning control (ILC) algorithms are presented for nonlinear continuous systems with non-parametric uncertainties. Unlike general ILC techniques, the proposed adaptive ILC algorithms allow that both the initial error at each iteration and the reference trajectory are iteration-varying in the ILC process, and can achieve non-repetitive trajectory tracking beyond a small initial time interval. Compared to the neural network or fuzzy system-based adaptive ILC schemes and the classical ILC methods, in which the number of iterative variables is generally larger than or equal to the number of control inputs, the first adaptive ILC algorithm proposed in this paper uses just two iterative variables, while the second even uses a single iterative variable provided that some bound information on system dynamics is known. As a result, the memory space in real-time ILC implementations is greatly reduced.