Observer-based single-network incremental adaptive dynamic programming for fault-tolerant control of nonlinear systems with actuator faults

A model-free incremental adaptive fault-tolerant control (FTC) scheme is proposed for a class of nonlinear systems with actuator faults. To deal with actuator faults and guarantee the approximate optimal performance of the nominal nonlinear system without any prior knowledge of system dynamics, a single-network incremental adaptive dynamic programming (SIADP) algorithm based on incremental neural network observer is developed to design an active fault-tolerant control (AFTC) policy. An approximate linear time-varying system is obtained by incremental nonlinear technique, in which the relevant matrix parameters are identified by recursive least square estimation. Then, a SIADP algorithm-based fault-tolerant controller is developed. Based on the redundancy characteristic and function of actuators, a grouping scheme of actuators is introduced. An incremental neural network observer is designed to approximate the actuator faults. The novel SIADP scheme is constructed with a simplified single critic neural network to shorten the learning time and decrease the computational burden in the control process, in which the norm of the weight estimations of critic neural network is updated. Moreover, based on the Lyapunov theorem, the uniformly ultimately bounded stability of the closed-loop incremental system is proved. Finally, simulations are given to verify the effectiveness of the proposed FTC scheme.     

Active fault‐tolerant control system design with trajectory re‐planning against actuator faults and saturation: Application to a quadrotor unmanned aerial vehicle

During the past 30 years, various fault‐tolerant control (FTC) methods have been developed to address actuator or component faults for various systems with or without tracking control objectives. However, very few FTC strategies establish a relation between the post‐fault reference trajectory to track and the remaining resources in the system after fault occurrence. This is an open problem that is not well considered in the literature. The main contribution of this paper is in the design of a reconfigurable FTC and trajectory planning scheme with emphasis on online decision making using differential flatness. In the fault‐free case and on the basis of the available actuator resources, the reference trajectories are synthesized so as to drive the system as fast as possible to its desired setpoint without violating system constraints. In the fault case, the proposed active FTC system (AFTCS) consists in synthesizing a reconfigurable feedback control along with a modified reference trajectories once an actuator fault has been diagnosed by a fault detection and diagnosis scheme, which uses a parameter‐estimation‐based unscented Kalman filter. Benefited with the integration of trajectory re‐planning using the flatness concept and the compensation‐based reconfigurable controller, both faults and saturation in actuators can be handled effectively with the proposed AFTCS design. Advantages and limitations of the proposed AFTCS are illustrated using an experimental quadrotor unmanned aerial vehicle testbed.Copyright © 2013 John Wiley & Sons, Ltd.     

计及时延的互联电力系统分散式阻尼控制

针对广域互联电力系统的低频振荡问题,计及信号在广域控制回路中的时延,设计了一种分散式阻尼控制器。首先定性分析了广域控制回路中的信号时延特点,然后在计及时延的互联电力系统线性化模型基础上,使用时延依赖稳定性充分条件进行控制器的求解,最后进行了两区四机系统分散式阻尼控制器设计。在固定时延与随机时延情况下系统仿真结果表明所设计分散控制器能够有效提高系统阻尼,抑制系统低频振荡,提高互联电力系统的动态稳定性能。     

A new decentralized retrofit adaptive fault‐tolerant flight control design

In this paper, we develop a new decentralized retrofit adaptive fault‐tolerant control design for a class of nonlinear models arising in flight control. The proposed adaptive fault‐tolerant controller is designed to accommodate loss‐of‐effectiveness (LoE) failures in flight control actuators and achieve accurate estimation of failure‐related parameters. The design is based on local estimation of LoE parameters and generation of local retrofit control signals to accommodate the failures. Using state‐dependent closed‐loop estimation errors, we show the overall system to be stable and demonstrate the tracking error to converge to zero asymptotically for any combination of actuator failures. Through computer simulation of F/A‐18 aircraft under actuator LoE failures, the proposed approach is also shown to achieve better parameter estimation performance compared to the fully centralized design and the design employing local observers and a centralized adaptive controller. Copyright © 2012 John Wiley & Sons, Ltd.     

Active fault‐tolerant control for near space vehicles based on reference model adaptive sliding mode scheme

In this paper, an adaptive sliding mode (ASM) scheme is proposed for fault identification and fault‐tolerant control of near space vehicles (NSVs). First, the attitude dynamic model is introduced, and a baseline controller based on reference sliding mode scheme is designed in the case of no faults. Then fault parameterizations with actuator dynamics is presented for several classes of faults: lock‐in‐place, float, hard‐over, and loss of effectiveness. On the basis of adaptive observer design, fault parameters can be accurately estimated on‐line. Furthermore, an ASM fault‐tolerant controller is designed for both cases of actuator dynamic faults and control effector damage. Finally, simulation experiments show that the proposed ASM scheme is able to quickly and accurately identify faults and reconfigure the controller, resulting in excellent overall system performance. Copyright © 2012 John Wiley & Sons, Ltd.     

可控串补自适应模糊阻尼控制策略研究

早期的模糊控制器设计,主要依赖于专家经验,而且只是采用近似推理的方法。针对可控串补非线性系统,设计了一种直接自适应模糊控制器。建立模糊控制器逼近误差和控制器参数之间的线性关系,用Lyapunov稳定性理论设计参数的自适应律,不仅调节模糊规则结论参数,同时调节隶属函数的参数。将该控制策略应用于含可控串补电力系统中,提出可控串补自适应模糊阻尼控制器的设计方法。仿真表明该控制器对系统发电机摇摆具有良好的阻尼作用,提高了系统的稳定性。     

Decentralized stability-enhancing control of synchronous generator

This paper describes new structures for stability-enhancing excitation controllers designed using a nonlinear multi-machine system model and Lyapunov's direct method. Two control structures are presented: a hierarchical structure In which the AVR is the master controller and the PSS the slave controller and a traditional structure in which the PSS constitutes a supplementary loop to the main AVR. Both controllers are shown to be robust, as the damping they introduce into the system is insensitive to changes in both the system topology/parameters and the pattern of network flows. Each individual controller contributes positively to the overall system damping with no undesirable interaction between controllers. These features should allow a decentralized approach to the design of the AVR+PSS. Such a design approach is compatible with the new competitive market structures and should result in savings on commissioning costs. Simulation results for a multi-machine power system are presented that confirm the above and show that the two control structures are very effective in damping both local and inter-area power swings     

智能电网环境下分布式阻尼控制器设计

智能电网以广域测量系统作为支撑,通过信息的相互关联来有效控制电网稳定运行。在智能电网环境下,针对广域互联电力系统的低频振荡问题,利用分布式网络控制的灵活特性,研究设计一种计及时延的分布式阻尼控制器。考虑将测量信息作为阻尼控制器的输入信号,只涉及到本地及相邻通信节点的信息,进而基于图论新颖法对分布式阻尼控制器输入信号的通信拓扑特性进行描述。在设计广域系统中控制器时考虑到了远程信号的传输时延,并利用其时延依赖稳定性这一充分条件。最后运用到四机两区系统的仿真对比结果,显示本文提及的分布式阻尼控制器不仅使系统阻尼得到有效提高,还体现出局部与区域间低频振荡以及传输线功率振荡的可抑制性,增强了融合电力信息系统的稳定性。     

一种多执行机构控制系统的出力平衡算法

对多执行机构的控制系统中各执行机构指令分配与出力平衡进行了详细的论述,针对目前多执行机构控制系统中普遍采用的指令分配算法存在的不足,构建了一种称为“偏置前馈”的快速消除控制系统内部指令扰动的出力平衡算法.该算法通过引入各执行机构的出力偏置量与实际出力系数计算出的物理量作为上游控制器前馈量,以提前改变上游控制器的输出指令...     

模糊自抗扰附加阻尼控制抑制光火打捆经串补送出的次同步振荡

针对光伏、火电打捆经串补送出系统,提出一种基于模糊自抗扰的附加阻尼控制器,来抑制交流串补可能引发的次同步振荡。首先对打捆系统的振荡模式进行辨识,然后通过巴特沃斯带通滤波器将各振荡模式对应的转速分量分解到不同的通道,在每个通道中设计相应的自抗扰阻尼控制器。考虑到光伏出力具有波动性、间歇性等特点,运行状态比较复杂,采用模糊控制对自抗扰关键参数进行自整定改进。基于PSCAD/EMTDC仿真软件,以加入光伏并网的IEEE次同步振荡第一标准模型作为仿真算例进行验证。结果表明,所设计的模糊自抗扰附加阻尼控制器在系统受到扰动时,能够有效抑制火电机组的次同步振荡,具有较强的鲁棒性,且抑制效果优于传统的PID控制。     

A model reference tracking based on an active fault tolerant control for LPV systems

This work deals with the problem of a model reference tracking based on the design of an active fault tolerant control for linear parameter‐varying systems affected by actuator faults and unknown inputs. Linear parameter‐varying systems are described by a polytopic representation with measurable gain scheduling functions. The main contribution is to design an active fault tolerant controller whose control law is described by an adaptive proportional integral structure. This one requires 3 types of online information, which are reference outputs, measured real outputs, and the fault estimation provided by a model reference, sensors, and an adaptive polytopic observer, respectively. These types of information are used to reconfigure the designed controller, which is able to compensate the fault effects and to make the closed‐loop system able to track reference outputs in spite of the presence of actuator faults and disturbances. The controller and the observer gains are obtained by solving a set of linear matrices inequalities. Performances of the proposed method are compared to another previous method to underline the relevant results.     

不确定时滞组合系统基于状态观测器的鲁棒分散可靠控制

研究一类包含状态时滞和参数不确定性的不确定时滞组合系统基于状态观测器的鲁棒分散可靠控制问题。目的是设计分散状态观测器和基于此观测器的线见性动态输出反馈控制器，使得对于任意容许的不确定性以及在每一个子系统中预先指定执行器子集合内执行器的失效，相应的闭环系统渐近稳定。     

交直流互联系统非线性自适应控制规律设计

针对舍有多台发电机的交直流互联系统,为了提高交直流输电系统的稳定性,应用非线性自适应控制设计方法,通过递推法得到了应用于交直流互联系统直流功率调制的非线性自适应控制策略,该控制规律包含了对系统中未知参数的动态估计,用以阻尼交直流互联系统的区域间功率振荡。最后,获得了交直流互联系统的非线性自适应直流附加控制器的一般表达式。4机系统的仿真结果表明,与传统的线性直流功率调制相比较,所设计的控制器对联络线的功率振荡具有良好的阻尼功能;特别是当系统中出现大的扰动时,更能体现该控制器的良好性能。     

多机电力系统自适应鲁棒Terminal滑模励磁控制

设计了多机电力系统发电机励磁的自适应鲁棒Terminal滑模控制器,将L2增益干扰抑制、自适应逆推法、Terminal滑模控制相结合,可以自适应估计发电机的不确定阻尼系数,对扰动具有鲁棒性。给出了控制器的设计过程。针对2区域4机系统的仿真结果表明,所设计的自适应鲁棒Terminal滑模励磁控制器能够快速抑制功率振荡,有效提高电力系统的暂态稳定性,并保持机端电压的恒定。     

Decentralized model predictive‐based load‐frequency control in an interconnected power system concerning wind turbines

This paper presents a load‐frequency control (LFC) design using the model predictive control (MPC) technique in a multi‐area power system in the presence of wind turbines (WTs). In the studied system, the controller of each local area is designed independently such that the stability of the overall closed‐loop system is guaranteed. A frequency response model of the multi‐area power system including WTs is introduced, and physical constraints of the governors and turbines are considered. The model was employed in the MPC structures. Digital simulations for a two‐area power system are provided to validate the effectiveness of the proposed scheme. The results show that with the proposed MPC technique the overall closed‐loop system performance shows robustness in the face of uncertainties due to governor and turbine parameter variation and load disturbances. A performance comparison between the proposed controller with WTs and MPC without WTs and a classical integral control scheme is carried out, confirming the superiority of the proposed MPC technique with WTs. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Asynchronous adaptive output feedback sliding mode control for Takagi-Sugeno fuzzy Markovian jump systems with actuator faults

In this article, the problem of asynchronous adaptive dynamic output feedback sliding mode control (SMC) for a class of Takagi-Sugeno (T-S) fuzzy Markovian jump systems (MJSs) with actuator faults is investigated. The asynchronous dynamic output feedback control strategy is employed, as the nonsynchronization phenomenon of jump modes exists between the plant and the controller. A novel asynchronous adaptive SMC approach is proposed to solve the synthesis problem for T-S fuzzy MJSs with actuator faults. Sufficient conditions for stochastic asymptotic stability of T-S fuzzy MJSs are given. Under the designed asynchronous adaptive SMC scheme, the effects of actuator faults and external disturbance can be completely compensated and the reachability of sliding surface is ensured. Finally, an example is provided to demonstrate the effectiveness of the proposed design techniques.     

Adaptive fault tolerant control against actuator faults

This paper investigates the problem of adaptive fault tolerant control for a class of dynamic systems with unknown un‐modeled actuator faults. The fault model is assumed to be an unknown nonlinear function of control input, not in the traditional form in which the faults can be described as gain and/or bias faults. Using the property of the basic function of neural networks and the implicit function theorem, a novel neural networks‐based fault tolerant controller is designed. Finally, the lateral dynamics of a front‐wheeled steered vehicle is used to demonstrate the efficiency of the proposed design techniques. Copyright © 2016 John Wiley & Sons, Ltd.     

Adaptive reconfigurable control of systems with time‐varying delay against unknown actuator faults

This work is concerned with the problem of delay‐dependent adaptive fault‐tolerant controller design against unknown actuator faults for linear continuous systems with time‐varying delay. Based on the online estimation of possible faults by discontinuous adaptation law, identification parameters of the adaptive state feedback controller are updated autonomously to compensate the fault effects on the delayed system. For the first time, a convex combination idea and a projection‐type adaptive approach are combined organically to derive the main results. A set of new delay‐dependent reconfigurable stabilization criteria, which guarantee the stability of closed‐loop systems in both fault‐free and faulty cases, is established in terms of linear matrix inequalities. Two numerical instances for linear delayed systems and the linearized model for the lateral motion of Boeing 747 are respectively simulated to illustrate the superiority and the effectiveness of the presented adaptive delay‐dependent results. Copyright © 2013 John Wiley & Sons, Ltd.     

汽轮发电机组轴系扭振的鲁棒非线性控制

提出将同步发电机及其励磁系统看做扭振励磁控制的执行元件,采用直接反馈线性化方法补偿其非线性因素,避免小偏差线性化模型的参数摄动问题,从而提高扭振励磁控制系统的鲁棒性.综合H∞扭振模态观测器、独立模态空间鲁棒控制器和非线性反馈补偿律,提出一种轴系扭振的鲁棒非线性控制策略,在大范围工况下具有一致的全局性能,并且3个组成部分可以分别独立设计;另外,可以方便地与常规非线性励磁控制律综合在一起,而不影响后者阻尼低频振荡的性能.以一台300 MW汽轮发电机组第1阶扭振模态的阻尼控制为例,通过仿真验证鲁棒非线性控制器的性能优于常规线性控制器.     

Robust wide‐area damping controller design for inter‐area oscillations with signals' delay

A new wide‐area damping control strategy is investigated for flexible AC transmission systems (FACTS) device using wide‐area measurement system (WAMS) signals. The purpose is to design a dynamic output wide‐area damping controller (WADC) for improving the stability of interconnected power systems. The time‐varying delay of wide‐area signal is incorporated into the design process, which can effectively reduce the delay effect on the damping performance. First, a discrete‐time plant model with time‐varying delay is established for power systems; then by using the proposed improved free‐weighting matrices (IFWMs) approach and a convex optimization algorithm, a new and less conservative delay‐dependent stability criterion, expressed in the terms of linear matrix inequalities (LMIs), is obtained without ignoring any useful terms on the difference of a Lyapunov function. Detailed case studies on a 4‐machine two‐area benchmark test system and 16‐machine five‐area NETS‐NYPS interconnected system show that the designed WADC can not only maintain effective damping performance under the condition of time‐varying delay but also get the maximum wide‐area time delay. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.