Composite Disturbance‐Observer‐Based Control and Control for High Speed Trains with Actuator Faults

To guarantee the position and velocity tracking performance of high speed trains (HSTs) with actuator faults, a composite control algorithm consisting of the disturbance‐observer‐based control (DOBC) and control is proposed. Based on the multiple point‐mass model, the dynamics of HSTs is established by a cascade of carriages which are connected by flexible couplers, during the procedure of which, the running resistance, actuator faults and multiple disturbances are taken into account. The multiple disturbances are composed of two parts, one of which is the ramp resistance due to the track slope, the other is unknown gusts which can be modeled as a harmonic disturbance with time‐varying frequency. The unknown gusts is estimated and rejected via the DOBC methodology, meanwhile, the running resistance and the ramp resistance are attenuated by the control methodology. According to the Lyapunov stability analysis and LMI‐based algorithms, main results are derived such that the closed‐loop system is asymptotically stable and the desired performance can be guaranteed. Compared with the numeral simulation results with the single control method, it is demonstrated that the proposed control methodology is more effective and the system has a higher precision of position and velocity tracking.     

Observer‐Based Multiple Faults Diagnosis Scheme for Satellite Attitude Control System

This paper proposes a multiple fault diagnosis (MFD) scheme based on an observer method for satellite attitude control systems (ACSs) subject to nonlinearity and external disturbances of the system. The essential idea is to develop a fault diagnosis scheme and design the corresponding observers for satellite ACSs. The nonlinearity, space external disturbances, sensor uncertainties, and multiple faults problem of the satellite ACS are all taken into account. The proposed MFD scheme is developed at two different levels. First, at the system level, two nonlinear observers based on analytical redundancy are designed for the MFD of the satellite ACS; this level roughly reveals the fault source. Then, at the component level, a bank of sliding mode observers activated by the results of the previous diagnosis is designed to precisely diagnose multiple faults of actuators in the satellite ACS; this level further precisely reveals the fault source. Both the nonlinear observers and the sliding mode observers are confirmed to be asymptotically stable via Lyapunov stability theory. Finally, numerical simulations of a satellite ACS are performed to illustrate the effectiveness of the proposed MFD scheme.     

Sliding Mode Disturbance Observer‐based Motion Control for a Piezoelectric Actuator‐based Surgical Device

This paper presents a sliding mode disturbance observer‐based motion tracking control methodology. In particular, the methodology is applied to control a semi‐automated hand‐held ear surgical device for the treatment of otitis media with effusion. The proposed control methodology is utilised to deal with the undesirable effects in the motion system, such as non‐linear dynamics, parametric uncertainties and external disturbances. It employs a proportional‐derivative control scheme together with a sliding mode disturbance observer for rejecting the undesirable effects. The stability of the proposed control methodology is proven theoretically and its effectiveness is evaluated experimentally. In addition, promising motion tracking experimental results are shown, and it can be observed that the proposed approach offers more robust performance for controlling the hand‐held surgical device and other similar instruments.     

Non‐Fragile Observer‐Based Control for Uncertain Neutral‐Type Systems via Sliding Mode Technique

This paper is concerned with the problem of observer‐based control for a class of uncertain neutral‐type systems subjected to external disturbance by utilizing sliding mode technique. A novel sliding mode control (SMC) strategy is proposed based on the state estimate and the output. A new sufficient condition of robust asymptotic stability with disturbance attenuation level for the overall systems composed of the original system and error system in the sliding mode is derived in terms of a linear matrix inequality (LMI). Then, a new adaptive controller is designed to guarantee the reachability of the predefined sliding surface in finite‐time. Finally, numerical examples are provided to verify the effectiveness of the proposed method.     

Observer‐Based H∞ Control for Continuous‐Time Networked Control Systems

This paper is concerned with the observer‐based H_∞ control for continuous‐time networked control systems (NCSs) considering packet dropouts and network‐induced delays. The packet dropouts and network‐induced delays in the sensor‐to‐controller (S‐C) channel and network‐induced delays in the controller‐to‐actuator (C‐A) channel are taken into full consideration. By taking the non‐uniform distribution characteristic of the arrival instants of actually adopted controller inputs into account, a new model for continuous‐time NCSs is established. To reduce the conservatism of modelling, a linear estimation‐based measurement output estimation method is introduced. Based on the newly established model and a Lyapunov functional, new controller design methods are proposed. A numerical example is given to illustrate the effectiveness and merits of the derived results.     

基于干扰观测器的不确定线性多变量系统控制

针对不确定线性多变量系统,提出一种基于干扰观测器(Disturbance observer,DOB)的保证系统内部稳定性的控制策略.以简单的结构和少量的计算代价实现鲁棒的控制效果,补偿外界干扰以及内部模型误差.通过引入一个闭环稳定性等价系统,辅助分析基于干扰观测器的多变量控制系统的内部稳定性,探讨在存在外部扰动及内部模型不确定性的情况下系统保证内部稳定的充分条件,指导外环控制器及内环干扰观测器中Q滤波器的设计.通过数值模型上的仿真验证了提出的控制方法的有效性.     

Robust Observer and Observer‐Based Controller for Time‐Delay Singular Systems

In this paper we address the problems of observer and observer‐based controller design for a class of nonlinear time‐delay singular systems. The proposed methods use particular Lyapunov functions depending on the disturbances in order to avoid a specific obstacle in the stability analysis. Consequently, two linear matrix inequality (LMI) conditions ensuring the convergence of the estimation error and the closed loop system were presented. These LMIs were obtained by manipulating Young's inequality in order to linearize some bilinear terms.     

Observer‐Based Adaptive L2 Disturbance Attenuation Control of Semi‐Active Suspension with MR Damper

A novel nonlinear observer‐based adaptive disturbance attenuation control strategy was proposed for a quarter semi‐active suspension system with a magneto‐rheological (MR) damper in light of the intrinsic nonlinearity, parameter uncertainty, state immeasurability and road randomness. Adaptive adjusting parameters were adopted to avoid the curve fitting and identification of the system parameters by a great deal of experimental data for shortening the development cycle of the control system. Based on the reduced‐order observer, the system states including the immeasurable virtual state of MR damper and inconveniently measured states of suspension system were estimated for the realistic frame of the proposed controller in practice. The dissipative system theory was utilized to reduce the influence of the road disturbance on the system control performance. Simulation results in the bump road and B‐class road indicate that, whether there are perturbations of the system parameters or not, the proposed control scheme always ensures a better performance on the suspension travel, ride comfort and handling stability in comparison with other existing methods.     

一类带有输入饱和的随机系统抗干扰控制

针对一类带有多源异质干扰和输入饱和的随机系统, 研究了其精细抗干扰控制问题. 系统中的多源异质干扰同时包含白噪声,\begin{document}$H_{2}$\end{document}范数有界干扰以及外源系统生成的带有状态与干扰耦合的部分信息已知干扰. 针对部分信息已知的干扰, 构建随机干扰观测器对其进行估计. 基于干扰估计, 结合$H_{\infty}$控制方法, 提出基于干扰观测器的精细抗干扰控制策略, 从而实现高精度抗干扰控制. 最后, 仿真结果验证了所提策略的正确性与有效性.     

NN‐Based Output‐Feedback Control for Stochastic Nonlinear Systems with Unknown Control Directions

This paper addresses the neural network‐based output‐feedback control problem for a class of stochastic nonlinear systems with unknown control directions. The restrictions on the drift and diffusion terms are removed and the conditions on unknown control directions are relaxed. By introducing a proper coordinate transformation, and combining dynamic surface control (DSC) technique with radial basis function neural network (RBF NN) approximation approach, we construct an adaptive output‐feedback controller to guarantee the closed‐loop system to be mean square semi‐globally uniformly ultimately bounded (M‐SGUUB). A simulation example demonstrates the effectiveness of the proposed scheme.     

NON‐PDC Observer‐Based T‐S Fuzzy Tracking Controller Design and its Application in CHAOS Control

In many mechanical devices with chaotic behavior, stabilizing unstable periodic orbits (UPOs) of the system has positive effects in the lifetime and effectiveness of these devices. In this study, a new non‐parallel distributed compensation (non‐PDC) observer‐based tracking controller is presented for Takagi–Sugeno fuzzy systems to control the chaotic behavior of such systems. Asymptotic stability synthesis of the closed‐loop system is investigated using a fuzzy Lyapunov function to derive less conservative conditions than common quadratic Lyapunov function‐based approaches. To tackle the main drawback of the fuzzy Lyapunov‐based approaches, which assume some upper bounds on the derivatives of the fuzzy grade functions, we propose a new procedure by considering a constraint on the control signal. The new design conditions are given in the form of linear matrix inequalities (LMIs). The proposed control structure is applied to spinning disks in which chaos phenomena appear in lateral vibration. Simulation results are given to show the applicability of the proposed tracker to the UPO problem.     

Observer‐based event‐triggered control for singularly perturbed systems with saturating actuator

This paper investigates an observer‐based event‐triggered control problem of singularly perturbed systems with saturating actuator. A strategy that consists of an observer‐based controller (OBC) and an event‐triggered mechanism (ETM) is considered. Firstly, sufficient conditions, which guarantee that the saturated SPSs are asymptotically stable excluding Zeno phenomenon, are derived via constructing an ε‐dependent Lyapunov‐Krasovskii functional. Then, the OBC and ETM are designed simultaneously based on the aforementioned criteria. Furthermore, an estimate of the basin of attraction and an ε‐bound are given by solving an optimization problem in the form of LMIs. Finally, an electric circuit system and a numerical example are presented to demonstrate the merits of the obtained method.     

Global Output‐Feedback Stabilization for Stochastic Nonlinear Systems with Function Control Coefficients

This paper investigates the global output‐feedback stabilization for a class of stochastic nonlinear systems with function control coefficients. Notably, the systems in question possess control coefficients that are functions of output, rather than constants; hence, they are different from the existing literature on stochastic stabilization. To solve the control problem, an appropriate reduced‐order observer is introduced to reconstruct the unmeasured system states before a smooth output‐feedback controller is designed using the backstepping method, which guarantees that the closed‐loop system is globally asymptotically stable in probability. This paper combines the related results in the deterministic and stochastic setting and gives the first treatment on the global output‐feedback stabilization for the stochastic nonlinear systems with function control coefficients. A simulation example is given also to illustrate the effectiveness of the proposed approach.     

Distributed Observer‐based Stabilization of Nonlinear Multi‐agent Systems with Sampled‐data Control

In this paper, the distributed observer‐based stabilization problem of multi‐agent systems under a directed graph is investigated. Distributed observer‐based control protocol with sampled‐data information is proposed. The dynamics of each agent contain a nonlinear part, which is supposed to be general Lipschitz. In order to stabilize the states of the whole network, all the nodes utilize the relative output estimation error at sampling instants and only a small fraction of nodes use the absolute output estimation error additionally. By virtue of the input‐to‐state stability (ISS) property and the Lyapunov stability theory, an algorithm to design the control gain matrix, observer gain matrix, coupling strength as well as the allowable sampling period are derived. The conditions are in the form of LMIs and algebraic inequality, which are simple in form and easy to verify. Some further discussions about the solvability of obtained linear matrix inequalities (LMIs) are also given. Lastly, an example is simulated to further validate the obtained results.     

Design of Robust Discrete‐Time Observer‐Based Repetitive‐Control System

This paper concerns the design of a robust discrete‐time observer‐based repetitive‐control system for a class of linear plants with periodic uncertainties. A discrete two‐dimensional model is built that partially uncouples the control and learning actions of a repetitive‐control system, enabling their preferential adjustment. The combination of a singular‐value decomposition of the output matrix and Lyapunov stability theory is used to derive a linear‐matrix‐inequality‐based design algorithm that determines the control and state‐observer gains. A numerical example illustrates the main advantage of the method: easy, preferential adjustment of control and learning by means of two tuning parameters in an linear‐matrix‐inequality‐based condition.     

Anti‐disturbance control for nonlinear system via adaptive disturbance observer

This paper addresses the problems of disturbance estimation and anti‐disturbance control for nonlinear system with exogenous disturbance, which is generated from an unknown exogenous system. The state observer and the adaptive disturbance observer are designed, simultaneously. Compared with the existing methods, which assumed that the exogenous system parameter matrix was known, our disturbance observer is more applicable in practice. Utilizing the estimation information, an observer‐based dynamic output feedback controller is designed, which avoids the influence of output disturbance on the closed‐loop system, and contains a disturbance compensation term to compensate the input disturbance. Finally, simulations are provided to demonstrate the effectiveness of the proposed approach. Copyright © 2016 John Wiley & Sons, Ltd.     

Feedback Linearization Control for Systems with Mismatched Uncertainties via Disturbance Observers

This paper focuses on a novel feedback linearization control (FLC) law based on a self‐learning disturbance observer (SLDO) to counteract mismatched uncertainties. The FLC based on BNDO (FLC‐BNDO) demonstrates robust control performance only against mismatched time‐invariant uncertainties while the FLC based on SLDO (FLC‐SLDO) demonstrates robust control performance against mismatched time‐invariant and ‐varying uncertainties, and both of them maintain the nominal control performance in the absence of mismatched uncertainties. In the estimation scheme for the SLDO, the BNDO is used to provide a conventional estimation law, which is used as the learning error for the type‐2 neuro‐fuzzy system (T2NFS), and T2NFS learns mismatched uncertainties. Thus, the T2NFS takes the overall control of the estimation signal entirely in a very short time and gives unbiased estimation results for the disturbance. A novel learning algorithm established on sliding mode control theory is derived for an interval type‐2 fuzzy logic system. The stability of the overall system is proven for a second‐order nonlinear system with mismatched uncertainties. The simulation results show that the FLC‐SLDO demonstrates better control performance than the traditional FLC, FLC with an integral action (FLC‐I), and FLC‐BNDO.