基于椭圆吸引律的离散重复控制

针对离散时间系统的周期轨迹跟踪问题,提出一种基于椭圆吸引律的离散重复控制方法.该方法能有效减小抖振,并通过扰动扩张状态观测技术对系统的未知扰动进行有效抑制,采用重复控制技术对系统中存在的周期扰动完全消除.为了刻画系统误差动态性能,推导出单调减区域、绝对吸引层、稳态误差带的表达式以及系统跟踪误差进入稳态误差带的最大步长.通过数值仿真与直线伺服电机实验,验证所提出控制方法的有效性.     

一种自适应吸引律离散时间控制方法

针对一类输入输出描述的离散时间系统, 提出一种基于自适应切换增益的吸引律. 该方法能够根据不确定干扰变化率对闭环系统影响的强弱自动调整切换增益大小, 且可直接反映误差动态特性. 同时, 给出了闭环系统跟踪误差首次穿越原点所需的最多步数, 并推导出系统绝对吸引层和稳态误差带边界的具体表达式, 用于表征闭环系统跟踪误差的收敛性能和稳态性能. 数值仿真和电机伺服系统上的实验结果均验证了所提出方法的有效性.

     

以幂次吸引的离散多周期重复控制

针对一类多周期干扰的抑制问题,提出一种基于幂次吸引律的离散多周期重复控制方法.多周期干扰由多个周期已知的周期干扰叠加而成.根据周期干扰的对称特性,构造出具有干扰抑制项的幂次吸引律,据此设计出子重复控制器,并以并联方式组合成多周期重复控制器,在消除多周期干扰的同时,有效地抑制慢时变非周期干扰带来的影响,改善控制品质;推导出幂次绝对吸引层和稳态误差带的具体表达式,用于刻画系统跟踪性能.仿真结果验证了所提控制方法的有效性.     

无抖振离散重复控制器的设计与实现

针对周期参考/干扰信号下的不确定离散时间系统,提出一种基于吸引律的重复控制方法,在吸引律中"嵌入"干扰抑制措施,构造理想误差动态,并基于此设计重复控制器.文中推导出单调减区域、绝对吸引层和稳态误差带边界的表达式,用于整定控制器参数和表征闭环系统的跟踪性能,并给出了跟踪误差在无干扰时收敛于原点及在干扰存在时收敛进入稳态误差带内所需最多步数的表达式.设计的重复控制器不仅能够完全抑制周期干扰信号,而且可以消除系统抖振.在电机实验装置上的应用结果表明了所提出控制方法的有效性.     

一种改进的离散时间系统变结构控制设计方法

在分析了几种离散变结构趋近律趋近过程的基础上, 提出了一种改进的趋近律, 该方法能够大幅度削弱抖振, 使系统运动最终趋于原点且不存在稳态振荡, 能使系统的准滑动模态保持步步穿越切换面的基本属性, 改善了趋近过程.     

一种离散时间系统变结构控制的新方法

研究离散时间系统变结构控制问题,提出一种新的离散变结构趋近律.利用该趋近律设计的离散变结构控制器,不仅能大幅度削弱抖振,使系统运动最终趋干原点不存在稳态振荡,而且可使系统的准滑动模态保持步步穿越切换面的基本属性,有效地改善了控制品质,提高了系统的鲁棒性.仿真结果验证了该方法的有效性与合理性.     

基于死区吸引律的离散重复控制

针对周期参考信号下的不确定离散时间系统,提出一种离散重复控制方法,利用死区函数设计新型的吸引律,将干扰补偿、抑制措施“嵌入”吸引律,构造理想误差动态,并基于此导出重复控制器。为了进行具体的控制器参数整定和表征闭环系统的误差动态行为,推导出了稳态误差带、单调减区域和绝对吸引层边界的表达式。所设计的离散重复控制器能够完全抑制周期对称干扰信号,控制器设计方法也适用于常值调节问题的定位控制。数值仿真及在电机伺服系统上的实验结果验证了所提出控制方法的有效性。     

一种离散时间系统变结构趋近律

针对一类离散时间系统,提出一种变结构控制设计方法。为了减小离散指数趋近律的抖振现象,本文构造一种趋近律, 利用它设计变结构控制器,能够大幅度削弱抖振,有效地改善控制品质,使系统最终趋于原点,并使系统稳定。给出数值计算和仿真算例。     

一种两相幂次吸引律离散时间控制方法

针对一类不确定离散时间系统,提出一种新型两相幂次吸引律.在吸引律设计中,通过将跟踪误差收敛过程划分为两个不同阶段,增加误差收敛幅度并提高误差收敛速度.构造离散形式的扩张状态观测器有效补偿系统干扰,基于观测值设计两相幂次形式的离散时间控制器,提高系统鲁棒性并减小稳态误差.此外,推导出跟踪误差绝对吸引层和稳态误差带的具体表...     

新的离散时间系统变结构趋近律

针对离散时间系统变结构控制的设计问题进行了研究。为了改善离散指数趋近律的趋近过程,提出了一种新的趋近律,利用该趋近律设计的变结构控制器,不仅能够大幅度削弱抖振,使系统运动最终趋于原点不存在稳态振荡,而且能使系统的准滑动模态保持步步穿越切换面的基本属性,有效地改善了趋近过程,提高了控制品质。仿真分析验证了该方法的合理性与有效性。     

Implicit discrete-time fast terminal sliding mode control with disturbance compensation

In this paper, an implicit discrete-time fast terminal sliding mode (DFTSM) control with disturbance compensation is designed and analyzed for uncertain high-order systems. First, a recursive discrete sliding surface is constructed based on implicit Euler technique, which can completely eliminate discretization chattering so as to significantly reduce the boundary layer of sliding mode motion. With the help of a high-order disturbance compensator, the accuracy limitation of implicit DFTSM control systems is overcome by increasing the order of sliding mode. Then the finite-time convergence of implicit DFTSM is proved for the first time, and the influence relationship of control parameters on the convergence speed and control accuracy of the algorithm is established. Finally, two numerical examples are provided to demonstrate the effectiveness and superiority of the proposed design approach.     

Eliminating limit cycles by using a disturbance accommodating control method

A simple way of eliminating limit cycles is presented for multivariable non-linear systems of the form [xdot] = Ax + Fw(x, [xdot]) + Bu, y = Cx by using a disturbance accommodating control method (DAC). Simulations show that it is easy and effective in practical applications. Using {sin ωt, cos ωt} (ω is the self-oscillating frequency) as basis functions to build a non-linear disturbance state model to estimate w(t) constitutes a limiting case of the spline approximation process. The observer can be designed with relatively fast dynamics so that the approximation error can be decreased to a very small value; hence the total elimination result is good. The paper also discusses how asymmetric self-oscillation can be eliminated and how to deal with servo-tracking systems when limit cycles occur.     

基于扰动补偿趋近律的准滑模控制

针对不确定离散时间系统,提出了一种基于扰动补偿趋近律的准滑模控制方法.该方法不仅能够加快系统趋近模态的趋近速度,缩短到达时间,而且能够缩窄系统的准滑动模态带宽,增强系统鲁棒性,有效改善系统动态品质,并无控制抖振和稳态抖振产生.仿真结果表明了该方法的有效性.     

非线性离散时间系统的自适应模糊补偿控制

针对一类非线性离散时间系统,提出一种自适应模糊逻辑补偿控制方案.控制律由跟踪控制律和逼近误差补偿控制律两部分组成,利用模糊逻辑系统对系统参数扰动和外界干扰进行自适应补偿,由模糊滑模控制律实现对模糊逻辑系统逼近误差的进一步补偿.所设计的控制器可保证闭环系统一致最终有界.将该控制器用于月球探测车动态转向系统中,仿真结果表明了该方法的有效性.     

离散型自抗扰控制器在四旋翼飞行姿态控制中的应用

本文首先介绍了自抗扰控制器的结构组成,包括跟踪微分器、扩张状态观测器以及非线性状态误差反馈律,及各部分的典型算法.针对四旋翼盘旋系统的姿态控制问题,设计了3种离散型自抗扰控制器,搭建了仿真结构图,并进行了参数整定,得到了优良的仿真结果.进而在实际装置上进行试验,调试出了令人满意的姿态实时控制结果.实时控制结果表明,文中所设计的自抗扰控制器可以满足控制精度及快速性的要求,并且具有抗干扰性能、稳定控制能力以及对非线性强耦合系统的解耦能力.最后,总结并分析了3种自抗扰控制器的优缺点及适用范围.     

Closed-form solutions to discrete-time LQ optimal control and disturbance attenuation

This paper presents straightforward derivations of closed-form solutions to two discrete-time problems: linear-quadratic optimal control and disturbance attenuation. Then, as the main results, it shows how to reduce directly the closed-form solutions to their recursive forms. These recursive solutions are in the form of Riccati equation and, hence, establish a close relation between the closed-form solutions and the Riccati equations used in both problems.     

A discrete-time fuzzy disturbance observer and its application to control

In this paper, a discrete-time fuzzy disturbance observer (FDO) is developed and its application to the control of a nonlinear system in the presence of the internal and external disturbances is presented. To construct the discrete-time FDO, a novel tuning method is proposed and shown to be useful in adjusting the parameters of the FDO. The tuning method uses the augmented error to guarantee that the FDO monitors the disturbance and the control objective is achieved. The design parameters such as a learning rate used in constructing the discrete-time FDO are determined in a numerical manner by solving a linear matrix inequality. It is shown in a rigorous manner that both the disturbance observation error and the control error converge to a compact set of which size can be kept arbitrarily small. In addition, the relationships between the suggested FDO-based control and the conventional adaptive fuzzy controls reported in the previous literatures are discussed. Finally, some examples and computer simulation results are presented to illustrate the effectiveness and the applicability of the FDO.     

Adaptive policies for discrete-time stochastic control systems with unknown disturbance distribution

We introduce adaptive policies for discrete-time, infinite horizon, stochastic control systems x₁₊₁ = F(x₁, a₁, ξ₁, T =0, 1, …, with discounted reward criterion, where the disturbance process ξ₁ is a sequence of i.i.d. random elements with unknown distribution. These policies are shown to be asymptotically optimal and for each of them we obtain (almost surely) uniform approximations of the optimal reward function.     

用比例控制器实现对扰动的全补偿

为了获得用比例控制器实现对可测量扰动的全补偿和将扰动响应与设定值响应分别处理，本文提出了一种多控制器策略。它由四个控制器，即：一个设定值控制器、两个扰动控制器和一个比例前馈控制器。这四个控制器可以分别独立设计获得好的设定值跟踪和抗扰动性能，特别是其前馈控制器是比例型的，可实现对可测量扰动的全补偿并保证了前馈控制器的可实现性。最后将该控制策略应用于压力槽的实时控制中，获得了良好的控制性能。     

Characterization and compensation of discrete-time non-minimum-phase systems for precision tracking control

The objective of this study is to characterize the unstable zeros of discrete-time non-minimum-phase systems and to compensate the gain and phase errors induced by unstable zeros for tracking control. These two objectives are attempted via examining the frequency response of unstable zeros. The gain error and phase shift induced by unstable zeros are first presented. It is well known that they are undesirable and cannot be cancelled directly via the method of pole-zero cancellation. Through investigating the characteristics of unstable zeros, a systematic approach is then given to compensate the gain and phase errors induced by unstable zeros. Using this approach, both a simple tracking control method and a precision tracking control method are proposed. The design procedure is presented and the design formulae are given. Simulation results are presented to illustrate the effectiveness of the proposed methods.