内模控制研究的新发展

概述了内模控制(IMC)的研究现状和新发展,详细论述了内模控制特别是非线性系统内模控制研究中的主要方面及其研究成果.首先介绍了内模控制中的各种建模方法,指出它们各自的优缺点,并根据内模控制的发展趋势着重分析了内模控制器的设计及其改进结构,内模控制与其他控制方法的结合方式等几个关键性问题.最后指出了内模控制研究中存在的一些混淆,并探讨了这一研究领域的发展方向.  

A unified framework for the study of anti-windup designs

We present a unified framework for the study of linear time-invariant (LTI) systems subject to control input nonlinearities. The framework is based on the following two-step design paradigm: ‘design the linear controller ignoring control input nonlinearities and then add anti-windup bumpless transfer (AWBT) compensation to minimize the adverse effects of any control input nonlinearities on closed loop performance’. The resulting AWBT compensation is applicable to multivariable controllers of arbitrary structure and order. All known LTI anti-windup and/or bumpless transfer compensation schemes are shown to be special cases of this framework. This unification of existing schemes for AWBT compensation under a general framework is the main result of the paper.  

Dynamic anti-windup scheme for feedback linearizable nonlinear control systems with saturating inputs

This paper proposes a dynamic compensation scheme for input-constrained feedback linearizable nonlinear systems to cope with the windup phenomenon. Given a dynamic feedback linearizing controller designed without considering its input constraint, an additional dynamic compensator is proposed to account for the constraint. This dynamic anti-windup is based on the minimization of a reasonable performance index. The proposed strategy is a nonlinear extended version of [Park, J.-K., & Choi, C.-H. (1995). Dynamic compensation method for multivariable control systems with saturating actuators. IEEE Transactions on Automatic Control, 40(9), 1635–1640] with simplified derivation of an optimization solution under relaxed assumptions. The parameter matrices and structure of the solution are explicitly decided by mathematical optimization for infinite horizon without tuning of design parameters unlike previous schemes. During input saturation, the role of the anti-windup scheme with the proposed dynamic feedback compensator is to maintain the controller states to be exactly the same as those without input saturation. The local asymptotic stability and the total stability of the resulting systems are proved. The usefulness of the proposed design method is illustrated by comparative simulations for a constrained control system.  

具有不确定雅可比矩阵机器人的鲁棒非线性PID控制器的抗饱和失效设计

对于雅克比阵不确定的操作机器人笛卡尔空间操作任务, 提出一种鲁棒非线性PID控制器的抗饱和设计方案, 解决了PID控制中的积分饱和问题. 该控制器通过引入有界递增分段连续函数于PID控制器中的积分环节, 限制了积分器的积分作用, 从而克服了积分环节对闭环系统的不利影响: 一方面使得闭环系统是渐进稳定的, 另一方面又保证了其鲁棒性; 特别是, 相比于其它的抗饱和设计方法, 显得更加简单有效.  

H∞回路成形法设计直升机飞控系统

直升机飞控系统幅频特性应低频高增益,高频低增益,尽可能提高带宽,以适应全包线机动飞行,优良动态跟踪及通道解耦等要求.用回路成形法结合经典控制理论,通过选取恰当的权阵和,而后用优化得到控制器,给出了直升机飞控系统内回路工程设计的具体策略.并指出了回路成形设计中的抗积分卷绕实施途径.对所给出的设计策略的有效性均辅以仿真验证.在成功的内回路设计基础上,可简便地单独设计外回路各通道.  

一类具有执行器饱和的非线性系统抗饱和方法研究

针对一类具有执行器饱和的非线性控制系统, 提出了一种双环路的动态抗饱和补偿方案, 为执行器输出受限的非线性系统提供了新思路. 与现有结果相比, 所提方案能更好地改善闭环系统控制性能. 考虑执行器饱和约束, 通过优化执行器饱和发生前后控制器的状态误差的积分性能指标, 综合设计一类同时包含传统抗饱和及延迟抗饱和补偿器两个环路的改进抗饱和补偿器, 这类补偿器有效地抑制了饱和现象对控制器的影响, 从而降低了执行器饱和对控制系统性能的影响. 当系统存在高饱和度现象时, 利用该双环路抗饱和补偿器, 可以最大程度弱化饱和对系统性能的影响. 最后, 利用输入状态稳定 (Input state stability, ISS) 定理分析和证明了该闭环系统全局一致有界稳定. 并通过舵机执行器受约束的舵减横摇系统的仿真试验, 验证了该方案的有效性及优越性.  

Increasing the operating area of shunt active filters by advanced nonlinear control

This work is aimed to rigorously manage voltage saturation and maximum current constraints in Shunt Active Filters. In this respect, assuming "unconstrained" control algorithms have already been defined to achieve standard objectives for such devices(i.e. current tracking for harmonic compensation and DC-bus voltage boundness), a plug-in unit, oriented to extend the system operating region and at the same time preserving good performance under large transients and overload conditions, is presented.This solution allows to improve availability, robustness and composability of Shunt Active Filters, which are expected to be key features in present and next generation complex and possibly "smart" power grids. The proposed unit is composed by two parts.First, a suitable anti-windup strategy is defined in order to deal with control input saturation. Its main purpose is to preserve the original "unconstrained error dynamics", in face of input saturation, while guaranteeing low computational burden and reduced performance impairment(the latter goal, in harmonic compensation context, leads to rather non-standard problem formulation).To this aim, the anti-windup acts on the current references through a suitably-designed additional dynamics. Then, in order to cope with current limitations, an additional strategy has been designed; again the current references is suitably shaped to comply with the features and bounds of the system, augmented with the above-mentioned anti-windup solution. The proposed scheme can be simply joined to any kind of unconstrained controller adopted to steer Shunt Active Filters. In this work, an Internal-Model-based current controller is adopted as a benchmark case. The proposed approach is validate through extensive simulation tests.  

线性自抗扰控制的抗饱和补偿措施

控制输入约束是实际工业过程中普遍存在的现象,然而控制器设计中通常都假设执行机构动态是线性的,因此当执行机构存在约束时,执行机构输出信号与控制器输出信号不一致,使系统的动态性能降低,甚至导致系统不稳定.本文针对线性自抗扰控制(linear active disturbance rejection control,LADRC)执行机构的约束问题,提出两种抗饱和补偿方案,利用LADRC扩张状态观测器估计控制器状态或者控制器输出与执行器输出的误差,从而使LADRC能快速消除饱和.将这两种方法用到含执行机构饱和的一阶惯性加迟延被控对象进行仿真研究,结果表明两种补偿措施下线性自抗扰控制器能得到较好的控制性能.随后本文将LADRC抗饱和思想推广到负荷频率控制系统(load frequency control,LFC)中,仿真表明基于误差补偿的抗饱和方案对于LFC系统更为有效.  

Anti-windup design with guaranteed regions of stability for discrete-time linear systems

The purpose of this paper is to study the determination of stability regions for discrete-time linear systems with saturating controls through anti-windup schemes. Considering that a linear dynamic output feedback has been designed to stabilize the linear discrete-time system (without saturation), a method is proposed for designing an anti-windup gain that maximizes an estimate of the basin of attraction of the closed-loop system in the presence of saturation. It is shown that the closed-loop system obtained from the controller plus the anti-windup gain can be locally modeled by a linear system with a deadzone nonlinearity. Then, based on the use of a new sector condition and quadratic Lyapunov functions, stability conditions in an LMI form are stated. These conditions are then considered in a convex optimization problem in order to compute an anti-windup gain that maximizes an estimate of the basin of attraction of the closed-loop system. Moreover, considering asymptotically stable open-loop systems, it is shown that the conditions can be slightly modified in order to determine an anti-windup gain that ensures global stability. An extension of the proposed results to the case of dynamic anti-windup synthesis is also presented in the paper.  

Plasma vertical stabilization with actuation constraints in the DIII-D tokamak

In the advanced tokamak (AT) operating mode of the DIII-D tokamak, an integrated multivariable controller takes into account highly coupled influences of plasma equilibrium shape, profile, and stability control. Time-scale separation in the system allows a multi-loop design: the inner loop closed by the nominal vertical controller designed to control a linear exponentially unstable plant and the outer loop closed by the nominal shape controller designed to control a linear stabilized plant. Due to actuator constraints, the nominal vertical controller fails to stabilize the vertical position of the plasma inside the tokamak when large or fast disturbances are present or when the references coming from the shape controller change suddenly. Anti-windup synthesis is proposed in this paper to find a nonlinear modification of the nominal vertical controller that prevents vertical instability and undesirable oscillations but leaves the inner loop unmodified when there is no input saturation.