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.     

A PI-controller for distributed delay systems

A finite dimensional control theory is developed for the design of a proportional plus integral control law for tracking step command inputs in general autonomous time-lag systems with distributed heredity in state, control and output variables. With respect to an ordinary differential equation describing the delay system unstable modes, an auxiliary tracking problem is posed. This auxiliary problem derives its importance from the fact that its solution directly yields a solution to the original tracking problem. This point of contact with a finite dimensional system permits the application of well-tested ordinary systems tracking theory to the tracking problem in time-lag systems.     

System stability with combined derivative constraints on time varying gains

For feedback systems with a time-varying gain in the feedback path novel conditions are obtained for L₂-stability by proving the positivity of certain operators. The proof is presented for the linear time-varying system and the corresponding results for non-linear time-varying systems can be obtained in a similar fashion. An example illustrates the superiority of the new criterion even though it may not be always superior. An additional requirement to the usual ones is that the time-varying gain must be differentiable twice with respect to time.     

广义系统的时滞相关非脆弱H_∞保成本控制

研究了时滞不确广义系统的时滞相关非脆弱H∞保成本控制器的设计问题。利用Lyapunov的稳定性理论和最近建立的积分不等式方法,得到了时滞不确定广义系统在非脆弱控制器作用下不仅内部渐近稳定,而且具有给定的H∞扰动抑制水平的时滞相关条件,以及相应的成本函数上界。假定其中的不确定项是范数有界的,但不需要满足严格的匹配条件.针对控制器增益具有加法式摄动和乘法式摄动两种情形,分别给出了非脆弱H∞保成本控制器的设计方法。这一方法不需要参数调节,利用Matlab的LMI工具箱求解方便。最后,数值仿真实例说明了所给方法的有效性。     

非线性离散时间系统的最优终端迭代学习控制

仅利用系统的终端输出误差而不是整个输出轨迹,提出了一种最优终端迭代学习控制方法.控制信号可直接通过终点的误差信息进行更新.主要创新点在于控制器的设计和分析只利用系统量测的I/O数据而不需要关于系统模型的任何信息,并可实现沿迭代轴的单调收敛.在此意义上,所提出的控制器是数据驱动的无模型控制方法.严格的数学分析和仿真结果均表明了所提出方法的适用性和有效性.     

Dynamic observer-based controllers for linear uncertain systems

This paper addresses robust controller design for uncertain linear systems via a dynamic observer-based controller. A dynamic observer is an alternative structure for a classical observer which can be regarded as a general form of a usual observer and has additional degrees of freedom in the observer structure. Using this new observer structure, a new observer-based controller for linear systems is proposed. Some strict linear matrix inequalities (LMIs) have been given to find the dynamic observer parameters and controller gain. It is shown that dynamic observer can be used effectively for tackling the drawbacks of the classical observer-based robust controller design methods. As an advantage, LMIs are derived even in the presence of uncertainties in system, input and output matrices simultaneously, whereas by using the traditional observer, bilinear matrix inequalities (BMIs) are given in the presence of such uncertainties. Moreover, the proposed LMIs do not imply the equality constraint. Simulation results are used to illustrate the effectiveness of the proposed design technique.     

Control of continuous-time LTI systems by means of structurally constrained controllers

This paper deals with the characterization of the fixed modes of multi-channel systems with respect to linear time-invariant (LTI) structurally constrained controllers. Fixed modes can be found numerically for any LTI system with respect to any given control structure, using a random number generator. The existing analytical methods, however, are not capable of characterizing the fixed modes in the most general case of non-strictly proper systems with non-block diagonal (i.e., overlapping) control structure, efficiently. The notion of a decentralized overlapping fixed mode (DOFM) is introduced in this paper to address the above problem in the most general case. To this end, the knowledge of the overlapping control structure is translated into a bipartite graph, whose vertices correspond to the input and output vectors of various control channels. An efficient technique is applied to the obtained graph to identify the DOFMs of the system. It is to be noted that a system is stabilizable via an appropriate LTI decentralized overlapping controller if and only if it does not have any unstable DOFM. Moreover, it is shown how those modes which are not DOFMs can be placed freely in the complex plane using a proper LTI decentralized overlapping controller. The efficacy of this work is demonstrated through an example.     

State feedback stabilisation for stochastic high-order feedforward nonlinear systems with input time-delay

This paper devotes to solve the problem of state feedback stabilisation for a class of stochastic high-order feedforward nonlinear systems with input time-delay. First, the delay-dependent control input is skillfully handled by using variable transformation technique. Then, by introducing the homogeneous domination approach and the appropriate Lyapunov--Krasovskii functional to deal with the time-delay, we construct a state feedback controller through a backstepping recursive design. It is shown that the proposed controller can guarantee the closed-loop system to be globally asymptotically stable (GAS) in probability. Finally, an example is given to verify the effectiveness of the obtained analytical results.     

Finite dimensional disturbance observer based control for nonlinear parabolic PDE systems via output feedback

This paper considers the problem of finite dimensional disturbance observer based control (DOBC) via output feedback for a class of nonlinear parabolic partial differential equation (PDE) systems. The external disturbance is generated by an exosystem modeled by ordinary differential equations (ODEs), which enters into the PDE system through the control channel. Motivated by the fact that the dominant dynamic behavior of parabolic PDE systems can be characterized by a finite number of degrees of freedom, the modal decomposition technique is initially applied to the PDE system to derive a slow subsystem of finite dimensional ODEs. Subsequently, based on the slow subsystem and the exosystem, a disturbance observer (DO) and a slow mode observer (SMO) are constructed to estimate the disturbance and the slow modes. Moreover, an observation spillover observer (OSO) is also constructed to cancel approximately the effect of the observation spillover. Then, a finite dimensional DOBC design via output feedback is developed to estimate and compensate the disturbance, such that the closed-loop PDE system is exponentially stable in the presence of the disturbance. The condition for the existence of the proposed controller is given in terms of bilinear matrix inequality. Two algorithms based on the linear matrix inequality (LMI) technique are provided for solving control and observer gain matrices of the proposed controller. Finally, the developed design method is applied to the control of a one-dimensional diffusion-reaction process to illustrate its effectiveness.     

线性不确定系统信息受限下的远程跟踪

研究了信息受限下一类线性不确定系统的跟踪调节问题. 假定由高阶微分方程产生的参考信号与受控系统(不确定线性系统)通过有限容量信道相连. 针对该信号设计了具体的编码方式, 并在受控系统端重构了该参考信号, 进而依据此重构信号设计了跟踪控制器, 最终到达了跟踪目标. 最后数值例子验证了本文结论的有效性.