基于连续故障模型的Delta算子系统可靠鲁棒H_∞控制

研究具有执行器故障的Delta算子线性不确定系统的可靠鲁棒H_∞问题.设计控制器,确保在执行器发生故障时闭环系统仍能保持鲁棒稳定,且满足给定的H_∞指标.针对执行器连续故障模型,运用线性矩阵不等式方法,得到Delta算子系统α-次优可靠鲁棒H_∞状态反馈控制器的存在条件和设计方法,并进一步给出了Delta算子系统最优可靠鲁棒H_∞控制器的设计方法.数值算例表明,该设计方法是有效而可行的.

Abstract：

The reliable robust H_∞ control problem is studied for the Delta operator systems with actuator failure.The purpose is to design a controller which can tolerate actuator failures,such that the Delta operator closed-loop system is asymptotic stable for all admissible uncertainties,and the H_∞-performance index of the closed-loop system is less than a given upper bound.A more practical model of actuator failure,continuous failure model,is considered.A sufficient condition for the existence of the state feedback α-suboptimal reliable robust H_∞ controllers is derived by using the linear matrix inequality approach.Then the design procedures of such controllers and optimal reliable robust H_∞ controllers are proposed respectively.A numerical example demonstrates the effectiveness and feasibility of the design methods.     

Reliable nonlinear control system design using duplicated control elements

Reliable L₂ gain bounding (i.e., H_∞) controllers for nonlinear systems are designed by using redundant control elements. One sensor and one actuator are duplicated, and the resulting closed-loop system is reliable with respect to both the single contingency case and the primary contingency case. The design procedures for reliable controllers are developed by using the Hamilton–Jacobi inequalities from nonlinear H_∞ control theory. Linear reliable controller design methods are also obtained by restricting the proposed nonlinear methods to the linear case, and the linear methods are found to be less conservative than existing methods for linear reliable controller design. Examples are given to illustrate the design procedures for both linear and nonlinear reliable controllers and the advantages of the proposed linear method over existing ones. © 1997 by John Wiley & Sons, Ltd.     

线性系统区域稳定的可靠控制

针对线性系统,提出了抵御系统执行器故障和不确定性的状态反馈区域稳定可靠控制设计问题.通过对具有连续增益故障控制系统的分析,给出了区域稳定可靠控制器存在的充分条件和设计方法.所设计的区域稳定可靠控制器可以消除执行器故障对闭环系统极点配置的影响.使用线性矩阵不等式(LMI)表示的结果能够容易得到可靠控制增益的数值解.通过CH-47双旋翼直升机的实例仿真验证了该结果的可行性.通过比较区域稳定正常控制系统和可靠控制系统,进一步说明对系统进行可靠控制设计的必要性.     

Reliable stabilization of linear plants using a two-controller configuration

A reliable controller design method is developed for linear, time-invariant, multi-input multi-output control systems; two controllers are designed to stabilize the closed-loop system when acting together and acting independently if one fails. All reliable controllers which achieve closed-loop stability are characterized for strongly stabilizable plants using a factorization approach.     

Observer‐Based Reliable Control for Discrete‐Time Switched Linear Systems with Faulty Actuators

This paper deals with the issue of reliable control for discrete‐time switched linear systems with faulty actuators by utilizing a multiple Lyapunov functions method and estimate state‐dependent switching technique. A solvability condition for the reliable control problem is given in terms of matrix inequality with an extra matrix variable. This condition allows the reliable control problem for each individual subsystem to be unsolvable. For each subsystem of such a switched system, we design an observer and an observer‐based controller. A switching rule depending on the observer state is designed which, together with the controllers, can guarantee the stability of the closed‐loop switched system for all admissible actuator failures. The observers, controllers, and switching law are explicitly computed by solving linear matrix inequalities (LMIs). The proposed design method is illustrated by two numerical examples.     

Robust reliable guaranteed cost control of positive interval systems with multiple time delays and actuator failure

This paper addresses the robust reliable guaranteed cost control problem of positive interval systems with multiple time delays and actuator failure for a given quadratic cost function. Through constructing a Lyapunov–Krasovskii functional, a sufficient condition for the existence of robust reliable guaranteed cost controllers is established such that the closed-loop system is positive and asymptotically stable, and the cost function is guaranteed to be no more than a certain upper bound. Based on the linear matrix inequality method, a criterion for the design of robust reliable guaranteed cost controllers is derived which can tolerate all admissible uncertainties as well as actuator failure. Moreover, a convex optimisation problem with linear matrix inequality constraints is formulated to design the optimal robust reliable guaranteed cost controller which minimises the upper bound of the closed-loop system cost. A numerical example is given to show the effectiveness of the proposed methods.     

Reliable stabilization with integral action in decentralized control systems

Reliable stabilization with integral action is studied in a linear, time-invariant, multi-input, multi-output, two-channel decentralized control system, where the plant is stable. The objective is to achieve closed-loop stability when both controllers act together and when each controller acts alone. Necessary and sufficient conditions are obtained for existence of block-diagonal decentralized controllers that ensure reliable stabilization, and integral action and all such decentralized controllers are parametrized. Explicit controller design approaches are discussed for the case of square channels.     

PHILAN: a LAN providing a reliable message service for distributedprocessing

A local area network (LAN) design based on a ring topology is presented which can support both packet-switched and circuit-switched traffic. The packet-switching service is reliable in that the LAN controllers deal with all protocol problems, i.e., medium arbitrations as well as flow and error control. The service can meet real-time constraints, since the performance is stable under high load conditions and the arbitration delays are bounded. Moreover, the processing speed of the LAN controller is independent of the transmission speed, and the speed requirements are such that they can be met by a microprocessor (no need for dedicated hardware to process the information on the fly). Before the design of PHILAN is presented, an analysis is given of the protocol problems that have to be dealt with when establishing a reliable packet-switching service on a LAN     

Reliable decentralised stabilisation of multi-channel systems: a design method via dilated LMIs and unknown disturbance observers

Reliable decentralised stabilisation is considered for general multi-channel plants, where the objective is to maintain stability of the closed-loop system when all of decentralised controllers work together and when one of the controllers is extracted due to a failure. For this control problem, a design method is presented, where a dilated LMI technique is employed for deriving reliable state feedback design, while a version of unknown disturbance observer is used as a decentralised observer for extending the design to output feedback case. Applicability of the proposed method is demonstrated through a power system example, where a model reduction and a low pass filter are further employed.     

利用状态反馈增益变化设计广义系统H∞可靠控制器

通过对状态反馈两种增益变化形式的分析,研究广义系统H∞可靠控制器的设计问题.给出基于状态反馈增益变化的广义系统H∞可靠控制器的定义,得到了执行器故障模型.用线性矩阵不等式(LMI)方法,研究两种状态反馈增益变化的广义系统H∞控制器存在的充分条件和设计方法.进而,针对执行器的不同故障情形,用LMI方法给出广义系统存在基于状态反馈增益变化的H∞可靠控制器的充分条件.最后,给出了优化广义系统H∞可靠控制器的设计算法.     

执行器饱和T-S模糊系统的鲁棒耗散容错控制

研究了一类执行器饱和状态变时滞T-S模糊系统的鲁棒容错控制问题. 通过时滞相关Lyapunov函数和对状态的椭球域约束, 基于线性矩阵不等式技术, 提出了非线性系统稳定的不变集条件和模糊鲁棒耗散容错控制器存在的充分条件. 控制方案的设计结果不仅为执行器饱和状态变时滞T-S模糊系统的无源控制和H1鲁棒控制建立了统一框架, 而且保证了闭环控制系统对执行器故障的稳定性和容错性. 最后以时滞倒车系统的控制仿真验证了方法 的有效性.     

具有一般故障模型的系统完整性的频域研究

针对一般的故障模型, 从频域角度提出了系统对传感器失效、执行器失效及传感器和执行器同时失效具有完整性的充分条件; 在此基础上, 通过与标准H_∞控制问题建立等价关系, 给出了输出反馈可靠性控制器的设计方法.     

Reliable LQ fuzzy control for continuous-time nonlinear systems with actuator faults

This paper deals with the reliable linear quadratic (LQ) fuzzy control problem for continuous-time nonlinear systems with actuator faults. The Takagi-Sugeno (T-S) fuzzy model is employed to represent a nonlinear system. By using multiple Lyapunov functions, an improved linear matrix inequality (LMI) method for the design of reliable LQ fuzzy controllers is investigated, which reduces the conservatism of using a single Lyapunov function. The different upper bounds on the LQ performance cost function for the normal and different actuator fault cases are provided. A suboptimal reliable LQ fuzzy controller is given by means of an LMI optimization procedure, which can not only guarantee the stability of the closed-loop overall fuzzy system for all cases, but also provide an optimized upper bound on a weighted average LQ performance cost function. Finally, numerical simulations on the chaotic Lorenz system are given to illustrate the application of the proposed design method.     

Optimal structured static state-feedback control design with limited model information for fully-actuated systems

We introduce the family of limited model information control design methods, which construct controllers by accessing the plant’s model in a constrained way, according to a given design graph. We investigate the closed-loop performance achievable by such control design methods for fully-actuated discrete-time linear time-invariant systems, under a separable quadratic cost. We restrict our study to control design methods which produce structured static state feedback controllers, where each subcontroller can at least access the state measurements of those subsystems that affect its corresponding subsystem. We compute the optimal control design strategy (in terms of the competitive ratio and domination metrics) when the control designer has access to the local model information and the global interconnection structure of the plant-to-be-controlled. Finally, we study the trade-off between the amount of model information exploited by a control design method and the best closed-loop performance (in terms of the competitive ratio) of controllers it can produce.     

Adaptive Control and Robustness in the Gap Metric

We consider the construction of adaptive controllers for minimum phase linear systems that achieve nonzero robustness margins in the sense of the gap metric. The gap perturbation margin may be more constrained for larger disturbances and for larger parametric uncertainties. Working in both and settings, and within the framework of the nonlinear gap metric, universal adaptive controllers are first given achieving stabilization for first-order nominal plants, and the results are then generalized to relative degree one nominal plants. A notion of a semiuniversal control design is introduced, which is the property that a bound on performance exists that is independent of the a priori known uncertainty level, and a characterization is given for when semiuniversal designs outperform the class of memoryless controllers and the class of linear time-invariant controllers. Robust semiuniversal adaptive control designs are given for nominal plants under the classical assumptions of adaptive control in both the and settings. The results are applied throughout to explicit classes of unmodeled dynamics including the Rohrs example.     

An Algorithm for Stabilization of Fractional-Order Time Delay Systems Using Fractional-Order PID Controllers

This technical note presents a solution to the problem of stabilizing a given fractional-order system with time delay using fractional-order Pl^lambdaD^mu controllers. It is based on determining a set of global stability regions in the (k_p, K_i, K_d)-space corresponding to the fractional orders lambda and mu in the range of (0, 2) and then choosing the biggest global stability region in this set. This method can be also used to find the set of stabilizing controllers that guarantees prespecified gain and phase margin requirements. The algorithm is simple and has reliable result which is illustrated by an example, and, hence, is practically useful in the analysis and design of fractional-order control systems.     

A new CAD method and associated architectures for linearcontrollers

A computer-aided design (CAD) method and associated architectures are proposed for linear controllers. The design method and architecture are based on recent results that parameterize all controllers that stabilize a given plant. With this architecture, the design of controllers is a convex programming problem that can be solved numerically. Constraints on the closed-loop system, such as asymptotic tracking, decoupling, limits on peak excursions of variables, step response, settling time, and overshoot, as well as frequency-domain inequalities, are readily incorporated in the design. The minimization objective is quite general, with LQG (linear quadratic Gaussian) H _∞ and new l₁ types as special cases. The constraints and objective are specified in a control specification language which is natural for the control engineer, referring directly to step responses, noise powers, transfer functions, and so on     

Automation in future air traffic management: effects of decision aid reliability on controller performance and mental workload

Future air traffic management concepts envisage shared decision-making responsibilities between controllers and pilots, necessitating that controllers be supported by automated decision aids. Even as automation tools are being introduced, however, their impact on the air traffic controller is not well understood. The present experiments examined the effects of an aircraft-to-aircraft conflict decision aid on performance and mental workload of experienced, full-performance level controllers in a simulated Free Flight environment. Performance was examined with both reliable (Experiment 1) and inaccurate automation (Experiment 2). The aid improved controller performance and reduced mental workload when it functioned reliably. However, detection of a particular conflict was better under manual conditions than under automated conditions when the automation was imperfect. Potential or actual applications of the results include the design of automation and procedures for future air traffic control systems.     

传感器失效下不确定离散时滞系统的静态输出反馈鲁棒可靠保成本控制

针对一类参数不确定离散时滞系统,研究了当传感器发生增益故障情况下的静态输出反馈保成本可靠控制器设计问题.系统中的参数不确定性满足广义匹配条件,传感器元件具有部分输出增益故障.根据Lyapunov稳定性理论和线性矩阵不等式(LMI)方法,分别给出了含有时滞记忆和无时滞静态输出反馈保成本鲁棒可靠控制律的存在条件.通过求解由一组线性矩阵不等式所表示的凸优化问题可以得到使得闭环保成本上界最小的鲁棒可靠控制器.最后通过仿真示例说明所提出方法的正确性.