非线性迭代学习控制问题的延拓修正牛顿法

对于非线性迭代学习控制问题,提出基于延拓法和修正Newton法的具有全局收敛性的迭代学习控制新方法.由于一般的Newton型迭代学习控制律都是局部收敛的,在实际应用中有很大局限性.为拓宽收敛范围,该方法将延拓法引入迭代学习控制问题,提出基于同伦延拓的新的Newton型迭代学习控制律,使得初始控制可以较为任意的选择.新的迭代学习控制算法将求解过程分成N个子问题,每个子问题由换列修正Newton法利用简单的递推公式解出.本文给出算法收敛的充分条件,证明了算法的全局收敛性.该算法对于非线性系统迭代学习控制具有全局收敛和计算简单的优点.     

一种间歇过程的综合预测迭代学习控制方法

为了提高迭代学习控制方法在间歇过程轨迹跟踪问题中的收敛速度,本文将批次间的比例型迭代学习控制与批次内的模型预测控制相结合,提出了一种综合应用方法.首先根据间歇过程的线性模型,预测出比例型迭代学习控制的系统输出,然后在批次内采用模型预测控制,通过极小化一个二次型目标函数来获得控制增量.该方法可使系统输出跟踪期望轨迹的速度比比例型迭代学习控制方法更快些.最后通过仿真实例验证了该方法的有效性.     

数据丢失对迭代学习控制的影响分析

针对一类线性系统,分析数据丢失对迭代学习控制算法的影响.首先基于lifting方法给出跟踪误差渐近收敛和单调收敛的条件,并分析收敛速度与数据丢失率的关系,结果表明收敛速度随着数据丢失程度的增加而变慢.其次,为抑制迭代变化扰动的影响,给出一种存在数据丢失时的鲁棒迭代学习控制器设计方法,并将控制器设计问题转化为求取线性矩阵不等式的可行解.仿真示例验证了理论分析的结果以及鲁棒迭代学习控制算法的有效性.

     

Convergence Properties of Iterative Learning Control Processes in the Sense of the Lebesgue‐P Norm

This paper addresses the convergence issue of first‐order and second‐order PD‐type iterative learning control schemes for a type of partially known linear time‐invariant systems. By taking advantage of the generalized Young inequality of convolution integral, the convergence is analyzed in the sense of the Lebesgue‐p norm and the convergence speed is also discussed in terms of Q_p factors. Specifically, we find that: (1) the sufficient condition on convergence is dominated not only by the derivative learning gains, along with the system input and output matrices, but also by the proportional learning gains and the system state matrix; (2) the strictly monotone convergence is guaranteed for the first‐order rule while, in the case of the second‐order scheme, the monotonicity is maintained after some finite number of iterations; and (3) the iterative learning process performed by the second‐order learning scheme can be Q_p‐faster, Q_p‐equivalent, or Q_p‐slower than the iterative learning process manipulated by the first‐order rule if the learning gains are appropriately chosen. To manifest the validity and effectiveness of the results, several numerical simulations are conducted. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Comments on “Robust optimal design and convergence properties analysis of iterative learning control approaches” and “On the P-type and Newton-type ILC schemes for dynamic systems with non-affine input factors”

The papers by Xu and Tan [Robust optimal design and convergence properties analysis of iterative learning control approaches, Automatica 38 (2002) 1867-1880], and Xu and Tan [On the P-type and Newton-type ILC schemes for dynamic systems with non-affine input factors, Automatica 38 (2002) 1237-1242], give a convergence analysis for several iterative learning control approaches. Unfortunately, these papers contains several mathematical errors that render the proofs of the claimed results invalid. As there are no obvious ways to correct these errors, the results presented in these papers are questionable.     

基于最小二乘的Q（λ）强化学习算法

通过分析经典的Q（λ）学习算法所存在的经验利用率低、收敛速度慢的问题,根据当前和多步的经验知识样本建立了状态-动作对值函数的最小二乘逼近模型,推导了该逼近函数在一组基底上的权向量所满足的一组线性方程,从而提出了快速而实用的最小二乘Q（λ）算法及改进的递推算法。倒立摆实验表明,该算法可以提高经验利用率,有效加快收敛速度。     

正则系统在Lebesgue-p范数意义下的快速迭代学习控制

针对一类线性正则系统,传统迭代学习控制算法收敛速度较低的问题,设计了一种快速迭代学习控制算法。该算法在传统P型迭代学习控制算法基础上,增加了由相邻两次迭代时跟踪误差构成的上一次差分信号和当前差分信号,并在Lebesgue-p范数度量意义下,利用卷积推广的Young不等式严格证明了,当迭代次数趋于无穷大时,系统的跟踪误差收敛于零,并给出了算法的收敛条件。该算法与传统P型迭代学习控制算法相比,不仅提高了收敛速度,而且还避免了采用λ范数度量跟踪误差的缺陷,最后通过仿真结果进一步验证了所提算法的有效性。     

迭代学习控制与二维分析

本文探讨了在学习时间有限和元情形下用二维系统方法分析迭代学习控制的可能性，给出线性离散系统在开环与闭环学习中各种学习律下的稳定与收敛的充要条件，并比较了各种学习律的收敛速度，指出随着学习次数的增加，在一定条件下，Ｐ型学习与其它类型的学习算法具有相同的收敛速度。     

改进的时不变系统PD型迭代学习控制算法

针对时不变线性系统的迭代学习控制问题,提出了一种改进的时不变系统的PD型迭代学习控制算法,理论证明了系统满足收敛条件时的改进算法是收敛的。仿真实例分析表明,改进的算法利用最新算出的控制分量代替旧的控制分量,使系统的实际输出以更快的收敛速度逼近系统的理想输出。     

一阶强双曲分布参数系统的迭代学习控制

研究了一阶强双曲分布参数系统的迭代学习控制问题.首先利用Fourier变换和半群方法导出了系统状态的适应解.进而基于强双曲条件和Plancheral定理,在允许迭代过程中初值存在一定偏差条件下,给出并证明了系统在P型迭代学习控制算法下的收敛条件.最后应用实例说明了所提方法的有效性.     

测量数据丢失的一类非线性系统迭代学习控制

迭代学习控制方法应用于网络控制系统时,由于通信网络的约束导致数据包丢失现象经常发生.针对存在输出测量数据丢失的一类非线性系统,研究P型迭代学习控制算法的收敛性问题.将数据丢失描述为一个概率已知的随机伯努利过程,在此基础上给出P型迭代学习控制算法的收敛条件,理论上证明了算法的收敛性,并通过仿真验证理论结果.研究表明,当非线性系统存在输出测量数据丢失时,迭代学习控制算法仍然可以保证跟踪误差的收敛性.     

离散非线性系统的迭代学习轨迹跟踪鲁棒算法优化及应用

针对一类存在随机输入状态扰动、输出扰动及系统初值与给定期望值不严格一致的离散非线性重复系统,提出了一种P型开闭环鲁棒迭代学习轨迹跟踪控制算法．基于λ范数理论证明了算法的严格鲁棒稳定性,并通过多目标函数性能指标优化P型开闭环迭代学习控制律的增益矩阵参数,保证了优化算法下系统输出期望轨迹跟踪误差的单调收敛性,达到提高学习算法收敛速度和跟踪精度的目的．最后应用于二维运动移动机器人的实例仿真,验证了本文算法的可行性和有效性．     

时变非线性系统迭代学习控制遗忘因子算法

针对迭代学习P型控制算法对初始偏差和输出误差扰动的敏感性问题,研究了一种带有遗忘因子的时变非线性系统的迭代学习控制方法.在有扰动的情况下,利用迭代学习过程记忆的期望轨迹,期望控制以及跟踪误差,通过有界学习增益和批次时变因子设计学习控制器,并基于算子理论给出了控制算法存在的充分必要条件及其收敛性分析,改善了系统的鲁棒性和动态特性.最后以注塑机的注射速度控制仿真验证了本文算法的有效性.     

离散非线性系统开闭环P型迭代学习控制律及其收敛性

本文在讨论了一般开环与闭环迭代学习控制的不足后，针对一类离散非线性系统，提出了新的开闭环ＰＧ型迭代学习控制律，给出了它的收敛性证明，仿真结果表明：开闭环Ｐ型迭代律优于单纯的开环或产才环Ｐ型迭代 律。     

Robust optimal design and convergence properties analysis of iterative learning control approaches

In this paper, we address four major issues in the field of iterative learning control (ILC) theory and design. The first issue is concerned with ILC design in the presence of system interval uncertainties. Targeting at time-optimal (fastest convergence) and robustness properties concurrently, we formulate the ILC design into a min-max optimization problem and provide a systematic solution for linear-type ILC consisting of the first-order and higher-order ILC schemes. Inherently relating to the first issue, the second issue is concerned with the performance evaluation of various ILC schemes. Convergence speed is one of the most important factors in ILC. A learning performance index—Q-factor—is introduced, which provides a rigorous and quantified evaluation criterion for comparing the convergence speed of various ILC schemes. We further explore a key issue: how does the system dynamics affect the learning performance. By associating the time weighted norm with the supreme norm, we disclose the dynamics impact in ILC, which can be assessed by global uniform bound and monotonicity in iteration domain. Finally we address a rather controversial issue in ILC: can the higher-order ILC outperform the lower-order ILC in terms of convergence speed and robustness? By applying the min-max design, which is robust and optimal, and conducting rigorous analysis, we reach the conclusion that the Q-factor of ILC sequences of lower-order ILC is lower than that of higher-order ILC in terms of the time-weighted norm.     

Adaptive evolutionary programming based on reinforcement learning

This paper studies evolutionary programming and adopts reinforcement learning theory to learn individual mutation operators. A novel algorithm named RLEP (Evolutionary Programming based on Reinforcement Learning) is proposed. In this algorithm, each individual learns its optimal mutation operator based on the immediate and delayed performance of mutation operators. Mutation operator selection is mapped into a reinforcement learning problem. Reinforcement learning methods are used to learn optimal policies by maximizing the accumulated rewards. According to the calculated Q function value of each candidate mutation operator, an optimal mutation operator can be selected to maximize the learned Q function value. Four different mutation operators have been employed as the basic candidate operators in RLEP and one is selected for each individual in different generations. Our simulation shows the performance of RLEP is the same as or better than the best of the four basic mutation operators.     

不确定线性系统鲁棒迭代学习控制器设计及应用

针对一类不确定线性系统提出鲁棒迭代学习控制器设计方法,且通过求解Riccati方程方法设计鲁棒迭代学习控制器,并基于Lyapunov理论推导出不确定线性系统收敛充要条件。该控制器具有阶次低,易于实现等特点。所提出的控制方案保证系统跟踪在有限的迭代步骤内达到较好的控制效果。最后以机器人为仿真对象,仿真结果表明该设计方法的有效性和可行性。     

一类输出饱和系统的学习控制算法研究

传感器饱和是控制系统中较为常见的一种物理约束. 本文针对一类含饱和输出的受限系统, 提出了两种学习控制算法. 具体而言, 首先, 对于重复运行的被控系统, 设计了开环P型迭代学习控制器, 实现在有限时间区间内对期望轨迹的完全跟踪, 并在λ范数意义下分析了算法的收敛性, 给出了含饱和输出的迭代学习控制系统的收敛条件. 进而, 针对期望轨迹为周期信号的被控系统, 提出了闭环P型重复学习控制算法, 并分析了这类系统的收敛性条件. 最后, 通过一个仿真实例验证了本文所提算法的有效性.     

退化高阶抛物型分布参数系统的迭代学习控制

研究一类高阶分布参数系统的迭代学习控制问题,该类系统由退化高阶抛物型偏微分方程构成.根据系统所满足的性质,基于P型学习算法构建得到迭代学习控制器.利用压缩映射原理,证明该算法能使得系统的输出跟踪误差于L~2空间内沿迭代轴方向收敛于零.最后,仿真算例验证了算法的有效性.