Time delay and packet dropout compensation for networked control systems: a linear estimation method

This article studies the problem of H _∞ controller design for networked control systems (NCSs) with time delay and packet dropout. A linear estimation-based time delay and packet dropout compensation method is proposed. The delay switching-based method is presented to deal with the variation of time delay, and H _∞ controller design is presented for NCSs with packet dropout compensation by using linear matrix inequality (LMI)-based method. Then the combined delay switching and parameter uncertainty-based method is presented to model the variation of time delay, and H _∞ controller design is also presented. The simulation results illustrate the effectiveness of the newly proposed linear estimation-based time delay and packet dropout compensation.     

Real-time guaranteed cost control of MIMO networked control systems with packet disordering

This paper discusses guaranteed cost control for multi-input and multi-output (MIMO) networked control systems (NCSs) with multi-channel packet disordering. Considering the time-varying and bounded network transmission delay, packet dropout and packet disordering, a novel model of NCSs is proposed by introducing the concept of packet displacement. It is worthwhile mentioned that this model can fully describe the dynamic characteristic of network and always guarantee the newest control input executed by the plant, which makes that the plant can be controlled in real time. The resulting closed-loop systems are jump linear systems due to the newest signals executed subject to Markovian chains. A real-time controller is designed for uncertain and certain NCSs based on Markovian theory combined with linear matrix inequality (LMI) techniques such that the closed-loop cost function value is not more than a specified upper bound that varies according to Quality of Services (QOS). Finally, numerical examples are given to illustrate the effectiveness of the proposed method.     

Output tracking control for networked control systems with time delay and packet dropout

This article studies the problems of H _∞ output tracking performance analysis and controller design for networked control systems (NCSs) with time delay and packet dropout. By using linear matrix inequality (LMI)-based method, H _∞ output tracking performance analysis and controller design are presented for NCSs with constant sampling period. For NCSs with time-varying sampling period, a multi-objective optimisation methodology in terms of LMIs is used to deal with H _∞ output tracking performance analysis and controller design. The designed controllers can guarantee asymptotic tracking of prescribed reference outputs while rejecting disturbances. The simulation results illustrate the effectiveness of the proposed H _∞ output tracking controller design.     

Guaranteed cost active fault-tolerant control of networked control system with packet dropout and transmission delay

The problem of guaranteed cost active fault-tolerant controller (AFTC) design for networked control systems (NCSs) with both packet dropout and transmission delay is studied in this paper. Considering the packet dropout and transmission delay, a piecewise constant controller is adopted. With a guaranteed cost function, optimal controllers whose number is equal to the number of actuators are designed, and the design process is formulated as a convex optimal problem that can be solved by existing software. The control strategy is proposed as follows: when actuator failures appear, the fault detection and isolation unit sends out the information to the controller choosing strategy, and then the optimal stabilizing controller with the smallest guaranteed cost value is chosen. Two illustrative examples are given to demonstrate the effectiveness of the proposed approach. By comparing with the existing methods, it can be seen that our method has a better performance.     

Stochastic reliable control of a class of networked control systems with actuator faults and input saturation

The stochastic reliable control problem for networked control systems (NCSs) subject to actuator failure and input saturation is investigated in this paper. In order to get the relationship between the maximum allowable consecutive packet dropouts, the packet dropout probability, the actuator failure matrix and the input saturation, a packet dropout probability dependent condition is given via linear matrix inequality (LMI) technology. Then, a suitable reliable controller is designed to ensure the closed-loop system to be exponentially mean square stable against actuator failures and input saturation. Finally, numerical examples are provided to show the effectiveness of the proposed method.     

基于主动变采样周期方法的网络控制系统的H∞控制器设计

This paper studies the problem of designing H∞ controllers for networked control systems (NCSs) with both network-induced time delay and packet dropout by using an active-varying sampling period method, where the sampling period switches in a finite set. A novel linear estimation-based method is proposed to compensate packet dropout, and H∞ controller design is also presented by using the multi-objective optimization methodology. The simulation results illustrate the effectiveness of the active-varying sampling period method and the linear estimation-based packet dropout compensation.     

Fault tolerant control for discrete networked control systems with random faults

This paper concerns the fault tolerant control for discrete networked control systems (NCSs) with probabilistic sensor and actuator fault, random delay and packet dropout. The fault of each sensor or actuator happens in a random way, which is described by an individual random variable satisfying a certain probabilistic distribution. Using these stochastic variables in the system model, new type of NCSs fault model is proposed. The merit of the proposed fault model lies in its generalization and reality, which can cover some existing fault models as special cases. By using Lyapunov functional method and linear matrix inequality technology, sufficient conditions for the mean square stable (MSS) of the NCSs can be obtained. Then the reliable controller can be designed. Finally, a numerical example and a practical example are given to demonstrate the efficiency and application of the proposed method.     

基于主动变采样周期方法的网络控制系统的H∞控制器设计

利用主动变采样周期方法, 本文研究了具有时延及丢包的网络控制系统的 H∞ 控制器设计问题, 其中采样周期在一个有限集合内切换. 提出了一个新的线性估计方法以补偿丢包的负面影响, 并利用多目标优化方法设计系统的 H∞ 控制器. 仿真结果表明了主动变采样周期方法及基于线性估计的丢包补偿方法的有效性.     

时延丢包网络控制系统的分析与控制

针对网络控制系统中同时存在时延和丢包问题,基于零阶保持器的工作机制,将同时受时延和丢包影响的网络控制系统建模为输入带有时延的控制系统,根据李雅普诺夫稳定性理论和时滞系统理论得出控制系统的时滞相关稳定性条件,进一步基于锥补线性化的方法给出控制器的设计方法,有效解决了网络控制系统中同时存在时延和丢包的控制问题。仿真算例表明所提方法的有效性。     

Observer-based H-infinity control in multiple channel networked control systems with random packet dropouts

This paper investigates the observer-based $H_{\infty}$ control problem for networked control systems (NCSs) with random packet dropouts. A general packet dropout model with multiple independent stochastic variables in multiple channels case is adopted to describe the data missing in the limited communication channels. With the consideration of the sensor-to-controller and controller-to-actuator packet dropouts at the same time, a new method is proposed based on a separation lemma to design an observer-based $H_{\infty}$ controller, which exponentially stabilizes the closed-loop system in the sense of mean square and also achieves a prescribed $H_{\infty}$ disturbance attenuation level. A numerical example is given to illustrate the effectiveness of the proposed control method.     

Compensation for control packet dropout in networked control systems

With the integration of communication networks and distributed control in modern manufacturing and process industries, networked control systems (NCSs) are becoming increasingly important due to its simplicity, scalability, flexibility, and cost effectiveness. However, there are still significant technical barriers that limit the applications of NCS technologies. Two challenges are network-induced time delay and data packet dropout. Applying a real-time queuing protocol that we developed recently, we are able to limit the sum of the network-induced communication delay and the control computation delay within a control period. This one-period delay is further guaranteed by well designed compensation for control packet dropout. Then, this paper proposes to compensate for the control packet dropout at the actuator using past control signals. Three model-free strategies for control packet dropout compensation, namely, PD (proportional plus derivative), PD2 (proportional plus up to the second-order derivative), and PD3 (proportional plus up to the third-order derivative) are developed. They are suitable for a large number of NCSs without the need to tune the compensator parameters. The proposed dropout compensation schemes are demonstrated through numerical examples.     

具有数据包丢失的网络控制系统保性能控制

本文研究了一类具有数据包丢失的网络控制系统(NCSs)的建模和保性能控制问题.通过用两个马尔可夫链分别来描述前向通道和反馈通道的丢包过程,将闭环网络控制系统建模成具有两个模式的马尔可夫随机切换系统.基于线性矩阵不等式技术和李亚普诺夫方法得到了闭环系统随机稳定的充分条件,并给出了状态反馈保性能控制器的设计方法.最后通过数值算例验证本文结果的有效性.     

Controller design for networked control system with data packet dropout and transmission delays

In this paper, the stabilization problem for a class of networked control systems (NCSs) with data packet dropouts and transmission time delays is considered, where the delays are time-varying and uncertain, the data packet dropout is modeled as a two-state Markov chain. To compensate the lost packet, a data packet dropout compensator is established. Thus a more realistic model for such NCSs is presented. Sufficient conditions for the stabilization of the new resulting system are derived in the form of linear matrix inequalities (LMIs). Numerical example illustrates the solvability and effectiveness of the results.     

Predictive observer‐based control for networked control systems with network‐induced delay and packet dropout

This paper addresses the stability analysis and synthesis problems for a class of networked control systems (NCSs) under effects of both network‐induced delay and packet dropout. The motivation comes from the increasing NCS applications where the full state vector is not available. To handle the concerned problems, two predictive observer‐based controllers are constructed. The first one is a memoryless controller with the predictive observer collocated with the plant. The second one, with the predictive observer colocated with the controller, uses the last effective plant information as well as the knowledge of the plant dynamics. The stability conditions of NCSs are derived via both network‐condition‐dependent Lyapunov function and common quadric Lyapunov function. The corresponding controller design problems are also solved based upon the obtained stability conditions. Simulation and experimental results are given to demonstrate the effectiveness of the proposed approaches. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

Compensation-based control for lossy communication networks

In this paper, we are concerned with the stability analysis and the design of stabilising compensation-based control algorithms for networked control systems (NCSs) that exhibit packet dropouts. In order to increase the robustness against packet dropouts for such NCSs, we propose a new type of model-based dropout compensator, which depends on the local dropout history. Moreover, we provide linear matrix inequality based synthesis conditions for such compensators guaranteeing robust stability. The analysis and design framework includes both worst-case-bound and stochastic models to describe the packet-dropout behaviour in both the sensor-to-controller and the controller-to-actuator channels. Numerical examples demonstrate the significantly improved robustness with respect to packet dropouts using the proposed dropout compensator, compared to using the existing zero strategy and the hold strategy.     

Controller design for networked control system with data packet dropout and transmission delays

In this paper, the stabilization problem for a class of networked control systems （NCSs） with data packet dropouts and transmission time delays is considered, where the delays are time-varying and uncertain, the data packet dropout is modeled as a two-state Markov chain. To compensate the lost packet, a data packet dropout compensator is established. Thus a more realistic model for such NCSs is presented. Sufficient conditions for the stabilization of the new resulting system are derived in the form of linear matrix inequalities （LMIs）. Numerical example illustrates the solvability and effectiveness of the results.     

Quantized H ∞ fault-tolerant control for networked control systems

Quantized H_∞ fault-tolerant control for networked control systems (NCSs) with partial actuator fault with respect to actuators is concerned in this paper. Considering transmission delay, packet dropout and quantization, a synthesis model with partial actuator fault is established. The piecewise constant controller is adopted to model NCS with the transmission delay and packet dropout. Due to data transmitted in practical NCSs should be quantized before they are sent to the next network node, the logarithmic static and time-invariant quantizers at the sensor and controller sides are proposed in the paper. For the established model, an appropriate type of Lyapunov functions is provided to investigate the delay-dependent H_∞ control problem. According to an optimal problem, the controller that makes the system achieve the best performance is designed. Finally, an illustrative example is given to demonstrate the effectiveness of the proposed approach.     

State feedback control synthesis for networked control systems with packet dropout

This paper is concerned with the problem of H_∞ controller design for networked control systems (NCSs) with time delay and packet dropout. A combined switching and parameter uncertainty‐based method is proposed to deal with time‐varying delay. The proposed method can avoid the high computational complexity of the delay switching‐based method and introduce less conservatism than the parameter uncertainty‐based method. An active varying sampling period method is proposed to make full use of network bandwidth, and a multi‐objective optimization methodology in terms of linear matrix inequalities is used to deal with H_∞ controller design for NCSs with active varying sampling period. The simulation results illustrate the effectiveness of the proposed active varying sampling period method and the less conservatism of the combined switching and parameter uncertainty‐based method. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

STABILITY ANALYSIS OF NETWORKED SYSTEMS WITH PACKET DROPOUT AND TRANSMISSION DELAYS: DISCRETE‐TIME CASE

This paper analyzes the stability of networked control systems (NCSs) with data packet dropout and transmission delays induced by communication channels. Discrete‐time NCSs with data packet dropout and transmission delays are modeled as linear systems with time‐varying delays. Sufficient conditions for the stability of the NCSs are established in terms of linear matrix inequalities (LMIs) by using the Lyapunov function method. The case of NCSs with multiple‐packet transmission is also studied. A numerical example is presented to illustrate our proposed approach.     

有数据包丢失和时延的网络控制系统稳定化

在同时考虑网络时延和数据包丢失的基础上,研究了网络控制系统的反馈控制器设计问题;用迭代的方法分析了数据包的丢失问题。在当前的状态测量不能被控制器实时得到时,利用旧的信息来控制系统,将网络化控制系统建模为切换模型。基于切换系统理论和分段Lyapunov函数理论,构造了线性矩阵不等式,推导出网络控制系统反馈控制器稳定的充要条件。数值仿真算例说明了所提方法的可行性和有效性。