Minimal-time,minimal-order observers for discrete systems†

Necessary and sufficient conditions are derived for the existence of observers for discrete-time, multivariable systems with inaccessible disturbance inputs. A design method for minimal-time, minimal-order observers based on realization theory is proposed. Lower and upper bounds for the minimal-order observer are also derived. A simulation study is included to illustrate application of the design method and to evaluate the performance of the observer.     

A new approach to the perfect regulation and the bounded peaking in linear multivariable control systems

This paper presents a new approach to the perfect regulation (p.r.) and the bounded peaking (b.p.) in linear multivariable control systems, based on the pole and the eigenvector assignment technique. Roughly speaking the p.r. represents an ideal control action which reduces the settling time to 0, while the b.p. simply means the bounded overshoot in this ideal situation. Simple frequency domain characterizations of the p.r. and the b.p. are derived. They reveal some invariance properties of the p.r. and the b.p. that provide a powerful tool for achieving the p.r. and the b.p. The existence condition for the p.r. is derived, which turns out to be identical to the result obtained in the optimal regulator theory. This result is extended to a more general control objective of attaining the p.r. for one output while keeping the b.p. for another output. A condition on which the p.r. is realized by an output feedback is also derived. A simple design algorithm is proposed for achieving the p.r. which is essentially the eigenvector assignment procedure. Finally, an application to a real system is discussed.     

Output regulation problem for a class of regular hyperbolic systems

This paper investigates the output regulation problem for a class of regular first-order hyperbolic partial differential equation (PDE) systems. A state feedback and an error feedback regulator are considered to force the output of the hyperbolic PDE plant to track a periodic reference trajectory generated by a neutrally stable exosystem. A new explanation is given to extend the results in the literature to solve the regulation problem associated with the first-order hyperbolic PDE systems. Moreover, in order to provide the closed-loop stability condition for the solvability of the regulator problems, the design of stabilising feedback gain and its dual problem design of stabilising output injection gain are considered in this paper. This paper develops an easy method to obtain an adjustable stabilising feedback gain and stabilising output injection gain with the aid of the operator Riccati equation.     

数据驱动的保证收敛速率最优输出调节

针对具有外部系统扰动的线性离散时间系统的输出调节问题,提出了可保证收敛速率的数据驱动最优输出调节方法,包括状态可在线测量系统的基于状态反馈的算法,与状态不可在线测量系统的基于输出反馈的算法.首先,该问题被分解为输出调节方程求解问题与反馈控制律设计问题,基于输出调节方程的解,通过引入收敛速率参数,建立了可保证收敛速率的最...     

A new approach to static output feedback stabilization of linear dynamic systems

The topic of this study is output feedback control of linear control system with output. Use of condensed forms of the linear system under static output feedback (SOF) control is made to derive sufficient conditions for stabilization. A minimal-order control-free observer is presented.     

Fixed-time output regulation of linear delay systems by smooth time-varying control

This article investigates the fixed-time output regulation problem (FxTORP) for linear systems in the presence of input delay. A linear controller consisting of the linear periodic delayed feedback (PDF) gain and the feedforward gain obtained by solving regulator equations is designed, such that FxTORP is addressed. If only the measurable output can be used for feedback, a linear observer with periodic coefficient and artificial delay is designed so that its state converges to the state of the augmented system at a prescribed finite time. Based on the estimated state, the output regulation problem can also be solved by using observer-based output feedback. The most significant advantages of this article are that the PDF gain can be taken as smooth and the output regulation problem is achieved within a prespecified regulation time. Finally, a simulation example is given to substantiate the validity of the proposed approaches.     

A geometric framework for pole assignment algorithms

The problem of pole assignment by gain output feedback or by low-order dynamical compensator is considered from a geometric point of view. This makes it possible to unify, in a general framework, most of the existing pole assignment methods formulated in a state-space context, such as the minimal-order observers, the Brasch-Pearson compensator, and the methods proposed by H. Kimura, and to simplify their presentation. Moreover, new pole assignment algorithms may be derived from this general formulation     

The linear periodic output regulation problem

The problem of asymptotic output regulation for linear systems driven by time-varying, T-periodic exosystems is considered in this paper. Necessary and sufficient condition for its solvability based on the existence of periodic solutions of differential Sylvester equations are derived. These conditions constitute a generalization to the periodic case of the celebrated algebraic regulator equations of Francis. A general algorithm for the synthesis of an error-feedback regulator is given. For the case of minimum-phase systems, it is shown that the regulator design can be carried out without the knowledge of the Floquet decomposition of the exosystem, thus extending significantly the applicability of the general result. The more challenging issue of robust regulation by error feedback is also addressed, and solved under a stronger observability condition.     

Output regulation of time-varying systems

In this paper the output regulation problem for linear time-varying systems is considered. Replacing the regulator equation by a regulator differential equation we give a necessary and sufficient condition for the problem to be solvable. As in the time-invariant case we first solve the output regulation problem by state feedback and obtain the required condition. Then with the aid of observers we show that the same condition solves the general problem with measurement feedback. We then consider the classes of almost periodic and periodic systems and refine the main results. A simple example of an almost periodic system and simulation results are given to illustrate the theory.     

Nonovershooting and nonundershooting exact output regulation

We consider the classic problem of exact output regulation for a linear time invariant plant. Under the assumption that either a state feedback or measurement feedback output regulator exists, we give design methods to obtain a regulator that avoids overshoot and undershoot in the transient response.     

Robust output regulation of linear time‐delay systems: A state predictor approach

This paper considers the robust output regulation problem for linear systems in the presence of state, input, and output delays. First, a state feedback control law is constructed from a state predictor, recently developed for systems with state and input delays. Necessary and sufficient conditions for the existence of a solution to the regulator equations are presented. Next, an error feedback control law for the output regulation problem is constructed by means of an error‐based state predictor. Finally, the proposed error feedback solution is extended to solve the output regulation problem in the presence of model uncertainty. Numerical examples demonstrate the effectiveness of the proposed predictor‐based solutions. Copyright © 2015 John Wiley & Sons, Ltd.     

Robust Output Regulation of T--S Fuzzy Systems With Multiple Time-Varying State and Input Delays

This paper proposes a robust output regulator design for Takagi–Sugeno (T–S) fuzzy systems with uncertain time delays. For generalization of the control problem, we assume that there exist affine dynamics, unknown multiple time-varying delays in state and input, uncertain parameters, disturbance, and partial state feedback. Both continuous-time and discrete-time cases are considered in a unified theoretical derivation. Here, we introduce a memoryless fuzzy observer and a fuzzy integral compensator. In comparison with previous studies, the proposed scheme drops the need for coordinate transformation, calculation of the desired operational point, which is known state and input delays, and exact fuzzy modeling. The control result is asymptotic output regulation for systems without disturbance and guaranteed $H^{infty}$ performance for systems with disturbance. Moreover, a piecewise constant output regulation is achieved without controller redesign. In addition, the developed fuzzy regulator can be applied to both affine and nonaffine uncertain time-delay systems. Finally, numerical simulations are performed by using two typical time-delay systems to validate the expected performance.      

Universal integral controllers with non-linear integral gains

We consider a single-input single-output minimum-phase non-linear system which has a normal form. In previous work, integral control and high-gain observers were used to achieve robust regulation under output feedback. To improve the transient performance, we propose the use of integrators with non-linear gains. We prove that the controller achieves regional and semiglobal regulation. Simulation results are presented showing the improved overshoot and settling time.     

具有暂态性能约束的平面系统的切换跟踪控制

本文研究了一类具有由超调量及调整时间构成的指定暂态性能的平面系统的输出跟踪问题。首次提出并解决了带有输出约束的切换静态输出反跟踪制问题。通过设计静态输出反馈控制器和所谓的锥形切换规则使得闭环切换系统的输出能够在渐近跟踪阶跃信号的同时不破坏指定的暂态性能约束。此外,本文通过求解非线性规划问题获得了一个最优加权暂态性能指标。最后,通过一个数值例子以及一个应用在航空涡扇发动机上的实际例子,说明本文所提方法的有效性及应用性。     

Minimal inversion,command matching and disturbance decoupling in multivariable systems

This paper addresses the two basic and related problems of minimal inversion and perfect output control in linear multivariable systems. A simple analytical expression is obtained for the inverse of the transfer-function matrix of a square multivariable system. This expression is then used to construct a minimal-order inverse of the system. It is shown that the poles of the minimal-order inverse are the transmission zeros of the system. As a result, necessary and sufficient conditions for existence and stability of the inverse system are stated simply in terms of the zero polynomial of the original system. Furthermore, the minimal-order inverse is shown to be proper provided the original system has a full rank feedthrough matrix. The related problem of perfect output control, namely command matching and disturbance decoupling, in linear multivariable systems by means of feedforward controllers is also formulated and solved in a transfer-function setting. It is shown that a necessary and sufficient condition for existence of the required controllers is that the plant zero polynomial is not identical to zero or unstable. The order of the required controllers is equal to the number of plant transmission zeros. The control scheme proposed in this paper is composed of a feedback controller to enhance system stability and robustness, a feedforward controller to ensure command matching, and another feedforward controller to achieve disturbance decoupling. The three controllers have no effect on each other and can therefore be designed independently. A number of numerical examples are discussed for illustration.     

On the rank minimization problem and its control applications

We present several new results on the rank minimization problem over sets which are defined by linear matrix inequalities. We proceed to apply some of these results to propose a computational procedure for determining lower and upper bounds for the minimal-order dynamic output feedback which stabilizes a given linear time-invariant plant.     

On minimal-order inverses of linear continuous time-invariant systems

Minimal-order inverses of a linear continuous time-invariant system are defined and an algebraic algorithm for constructing them is presented. A necessary and sufficient condition for the applicability of the algorithm is shown to be the same as that for the invertibility of the given system. Some important properties of the minimal-order inverses relevant to the design of linear multivariable systems are derived. In particular the characteristic polynomials of all minimal-order inverses of a given system are shown to be identical and invariant under duality, coordinate transformations and proportional state feedback.     

Incremental passivity and output regulation for switched nonlinear systems

This paper studies incremental passivity and global output regulation for switched nonlinear systems, whose subsystems are not required to be incrementally passive. A concept of incremental passivity for switched systems is put forward. First, a switched system is rendered incrementally passive by the design of a state-dependent switching law. Second, the feedback incremental passification is achieved by the design of a state-dependent switching law and a set of state feedback controllers. Finally, we show that once the incremental passivity for switched nonlinear systems is assured, the output regulation problem is solved by the design of global nonlinear regulator controllers comprising two components: the steady-state control and the linear output feedback stabilising controllers, even though the problem for none of subsystems is solvable. Two examples are presented to illustrate the effectiveness of the proposed approach.     

Output regulation for linear distributed parameter systems

This work extends the geometric theory of output regulation to linear distributed parameter systems with bounded input and output operator, in the case when the reference signal and disturbances are generated by a finite dimensional exogenous system. In particular it is shown that the full state feedback and error feedback regulator problems are solvable, under the standard assumptions of stabilizability and detectability, if and only if a pair of regulator equations is solvable. For linear distributed parameter systems this represents an extension of the geometric theory of output regulation developed in Francis (1997) and Isidori and Byrnes (1990). We also provide simple criteria for solvability of the regulator equations based on the eigenvalues of the exosystem and the system transfer function. Examples are given of periodic tracking, set point control, and disturbance attenuation for parabolic systems and periodic tracking for a damped hyperbolic system     

An algebraic theory for design of controllers for linear multivariable systems--Part II: Feedback realizations and feedback design

The study of general linear multivariable systems, with possibly different controlled and measured outputs, is continued in this part of the paper. The structure matrices, defined in Part I, are used to solve the feedback realization problem. Feedback realizable transfer functions are then used to solve problems of "regulator type." It is shown that the solutions to problems like disturbance deeoupling, output regulation, and pole placement are all special cases of the solution to a more general problem. Finally, it is shown how the results of Part I and Part II can be combined to solve problems of "servo type" and of "regulator type" simultaneously.