Constrained off-line synthesis approach of model predictive control for networked control systems with network-induced delays

This paper investigates the off-line synthesis approach of model predictive control (MPC) for a class of networked control systems (NCSs) with network-induced delays. A new augmented model which can be readily applied to time-varying control law, is proposed to describe the NCS where bounded deterministic network-induced delays may occur in both sensor to controller (S–A) and controller to actuator (C–A) links. Based on this augmented model, a sufficient condition of the closed-loop stability is derived by applying the Lyapunov method. The off-line synthesis approach of model predictive control is addressed using the stability results of the system, which explicitly considers the satisfaction of input and state constraints. Numerical example is given to illustrate the effectiveness of the proposed method.     

基于时钟同步的网络化运动控制策略研究

网络化运动控制系统(Networked Motion Control Systems，NMCS)是运动控制器与数字智能驱动器通过串行通信网络相连的控制系统。NMCS需要通过控制网络在控制器和各个运动部件之间高频率、低延迟和实时地交换控制和传感数据，以保证控制的高速度和高精度。串行控制网络本质上是有限带宽和异步的，这是网络化控制应用所面临的主要障碍。在中国国家自然科学基金重点项目《网络环境下的数字制造理论与关键技术》资助下，提出基于预测控制和网络时钟同步解决方案。 讨论网络同步在多轴协调运动控制中的作用，提出一种基于网络时钟同步的分布式插补方法。通过分析网络延迟对单轴跟踪控制性能的影响，提出基于时间戳和预测控制的补偿方法。对固定网络延迟，采用Smith预估器加以补偿，并应用零相位误差跟踪控制和Youla参数化改善其动态特性和鲁棒性。对随机时变网络延迟，采用广义预测控制算法和报文缓冲机制加以补偿。仿真和实验结果证明算法的有效性。     

Design and implementation of a new fuzzy PID controller for networked control systems

This paper presents a practical network platform to design and implement a networked-based cascade control system linking a Smar Foundation Fieldbus (FF) controller (DFI-302) and a Siemens programmable logic controller (PLC-S7-315-2DP) through Industrial Ethernet to a laboratory pilot plant. In the presented network configuration, the Smar OPC tag browser and Siemens WinCC OPC Channel provide the communicating interface between the two controllers. The paper investigates the performance of a PID controller implemented in two different possible configurations of FF function block (FB) and networked control system (NCS) via a remote Siemens PLC. In the FB control system implementation, the desired set-point is provided by the Siemens Human-Machine Interface (HMI) software (i.e, WinCC) via an Ethernet Modbus link. While, in the NCS implementation, the cascade loop is realized in remote Siemens PLC station and the final element set-point is sent to the Smar FF station via Ethernet bus. A new fuzzy PID control strategy is then proposed to improve the control performances of the networked-based control systems due to an induced transmission delay degradation effect. The proposed strategy utilizes an innovative idea based on sectionalizing the error signal of the step response into three different functional zones. The supporting philosophy behind these three functional zones is to decompose the desired control objectives in terms of rising time, settling time and steady-state error measures maintained by an appropriate PID-type controller in each zone. Then, fuzzy membership factors are defined to configure the control signal on the basis of the fuzzy weighted PID outputs of all three zones. The obtained results illustrate the effectiveness of the proposed fuzzy PID control scheme in improving the performances of the implemented NCS for different transportation delays.     

网络控制系统的仿真平台设计

研究网络控制系统时,一项主要的研究内容是研究网络对控制系统性能的影响,基于此目的设计了网络控制系统仿真平台NCSS。该平台利用Matlab来构造实际对象模型,基于物理网络使用Windows套接字Winsock进行控制器与对象之间的通信。该平台可以方便地模拟实际对象的运行,并能够灵活地实现各种控制算法,为网络控制系统的分析与设计提供了较好的仿真环境。     

运动控制网络的时钟同步

为了改进网络化多轴同步控制系统的性能，研究了运动控制网络的时钟同步方法。制定了一种网络化运动控制策略，采用广义预测控制算法和报文缓冲机制补偿随机时变网络延迟。提出了一种主从时钟同步机制，讨论了两种在运动控制网络中产生同步事件的方法；推导了一种从时钟的调整算法，该算法不依赖任何的特定运动控制网络，并给出了这一算法基于FPGA的实现结果。     

Static-dynamic hybrid communication scheduling and control co-design for networked control systems

In this paper, the static-dynamic hybrid communication scheduling and control co-design is proposed for the networked control systems (NCSs) to solve the capacity limitation of the wireless communication network. The analytical most regular binary sequences (MRBSs) are used as the communication scheduling function for NCSs. When the communication conflicts yielded in the binary sequence MRBSs, a dynamic scheduling strategy is proposed to on-line reallocate the medium access status for each plant. Under such static-dynamic hybrid scheduling policy, plants in NCSs are described as the non-uniform sampled-control systems, whose controller have a group of controller gains and switch according to the sampling interval yielded by the binary sequence. A useful communication scheduling and control co-design framework is proposed for the NCSs to simultaneously decide the controller gains and the parameters used to generate the communication sequences MRBS. Numerical example and realistic example are respectively given to demonstrate the effectiveness of the proposed co-design method.     

基于协同论的网络测控系统协同机制分析

基于协同论引进协同理念,将其应用于网络测控系统中,具体分析基于IP模式的网络测控系统协同机制,提出实现协同机制的一些思路和方法。     

Control and communication co-design: Analysis and practice on performance improvement in distributed measurement and control system based on fieldbus and Ethernet

In this paper, improving control performance of a networked control system by reducing DTD in a different perspective was investigated. Two different network architectures for system implementation were presented. Analysis and improvement dealing with DTD for the experimental control system were expounded. Effects of control scheme configuration on DTD in the form of FB were investigated and corresponding improvements by reallocation of FB and re-arrangement of schedule table are proposed. Issues of DTD in hybrid network were investigated and corresponding approaches to improve performance including (1) reducing DTD in PLC or PAC by way of IEC61499 and (2) cascade Smith predictive control with BPNN-based identification were proposed and investigated. Control effects under the proposed methodologies were also given. Experimental and field practices validated these methodologies.     

Adaptive sampling rate control for networked systems based on statistical characteristics of packet disordering

This paper investigates an adaptive sampling rate control scheme for networked control systems (NCSs) subject to packet disordering. The main objectives of the proposed scheme are (a) to avoid heavy packet disordering existing in communication networks and (b) to stabilize NCSs with packet disordering, transmission delay and packet loss. First, a novel sampling rate control algorithm based on statistical characteristics of disordering entropy is proposed; secondly, an augmented closed-loop NCS that consists of a plant, a sampler and a state-feedback controller is transformed into an uncertain and stochastic system, which facilitates the controller design. Then, a sufficient condition for stochastic stability in terms of Linear Matrix Inequalities (LMIs) is given. Moreover, an adaptive tracking controller is designed such that the sampling period tracks a desired sampling period, which represents a significant contribution. Finally, experimental results are given to illustrate the effectiveness and advantages of the proposed scheme.     

Robust output feedback distributed model predictive control of networked systems with communication delays in the presence of disturbance

In this work, an output feedback cooperative distributed model predictive control is developed for a class of networked systems composed of interacting subsystems interconnected through their states, in which it handles bounded disturbances and time varying communication delays. A distributed buffer based prediction strategy is used to compensate bounded delays and predict those states, which are coupled between subsystems that their actual values may not available due to delays. In the design of robust distributed model predictive control, distributed moving horizon estimation is employed so that convergence and boundedness of the estimation error are ensured. Furthermore, robust exponential stability of the closed loop system is established. The effectiveness of the proposed method is illustrated using two interconnected continuous stirred tank reactors.     

Model predictive control of non-linear systems over networks with data quantization and packet loss

This paper studies the approach of model predictive control (MPC) for the non-linear systems under networked environment where both data quantization and packet loss may occur. The non-linear controlled plant in the networked control system (NCS) is represented by a Tagaki-Sugeno (T-S) model. The sensed data and control signal are quantized in both links and described as sector bound uncertainties by applying sector bound approach. Then, the quantized data are transmitted in the communication networks and may suffer from the effect of packet losses, which are modeled as Bernoulli process. A fuzzy predictive controller which guarantees the stability of the closed-loop system is obtained by solving a set of linear matrix inequalities (LMIs). A numerical example is given to illustrate the effectiveness of the proposed method.     

一类网络控制系统的稳定性分析

在基于多包传输的网络控制系统中,传感器采用时间驱动,控制器和执行器采用事件驱动.假定传输时延可以忽略,则整个网络控制系统可以描述为一个具有N个事件的异步动态系统.该文针对受控对象状态均可测,控制律采用输出反馈的情况,利用双线性矩阵不等式方法,讨论了网络控制系统指数稳定的问题,并给出了稳定性的充分条件,最后通过仿真实验加以验证.     

成套电器产品网络化销售与定制信息集成技术

针对成套电器产品制造企业在产品的网络化销售与定制过程中,存在大量和频繁的异地信息交互的特点,提出了 一种基于UDDI和动态业务流程的成套电器产品网络化销售与定制信息集成方案。该集成技术方案由网络支持层、数 据库支持层、集成支持层、应用层和用户层五层结构组成,其集成的运行和控制机制是在UDDI注册中心和动态业务流 程的支持下,通过信息集成支持工具、数据组织与管理支持系统来完成的。开发了一套成套电器产品网络化销售与定制 信息集成支持系统,并应用于某一成套电器产品的制造企业,实现了该企业销售人员、设计人员、电力部门和客户之间交 互信息的集成。     

Fuzzy model predictive control of non-linear processes using convolution models and foraging algorithms

In this paper, a fuzzy model predictive control (FMPC) approach is introduced to design a control system for nonlinear processes. The proposed control strategy has been successfully employed for representative, benchmark chemical processes. Each nonlinear process system is described by fuzzy convolution models, which comprise a number of quasi-linear fuzzy implications (FIs). Each FI is employed to describe a fuzzy-set based relation between control input and model output. A quadratic optimization problem is then formulated, which minimizes the difference between the model predictions and the desired trajectory over a predefined predictive horizon and the requirement of control energy over a shorter control horizon. The present work proposes to solve this optimization problem by employing a contemporary population-based evolutionary optimization strategy, called the Bacterial Foraging Optimization (BFO) algorithm. The solution of this optimization problem is utilized to determine optimal controller parameters. The utility of the proposed controller is demonstrated by applying it to two non-linear chemical processes, where this controller could achieve better performances than those achieved by similar competing controller, under various operating conditions and design considerations. Further comparisons between various stochastic optimization algorithms have been reported and the efficacy of the proposed approach over similar optimization based algorithms has been concluded employing suitable performance indices.     

Static output feedback stabilization of networked control systems with a parallel-triggered scheme

This paper investigates the parallel-triggered static output feedback stabilization problem for linear networked control systems. A new parallel-triggered scheme is proposed by using both the relative error and the absolute error information. The scheme can reduce transmission rate while maintaining the global asymptotical stability. The linear parallel-triggered networked control system is modeled as a time-delay system. By employing Lyapunov stability theory, sufficient conditions are established for the closed-loop system to be globally asymptotically stable in terms of linear matrix inequalities. Moreover, a co-design algorithm is developed to obtain both the optimal trigger parameters and the output feedback controller gain in the sense that the transmission rate is minimized. Finally, two examples are given to illustrate the advantages of the proposed scheme.     

面向网络化制造的开放式数控系统的研究

分析了网络化制造模式下数控系统的网络化要求,研究了网络化数控系统的功能和特点,构建了网络化数控系统的功能模型,并基于Internet/Intranet技术,采用Browser/Server模式建立了网络化数控系统的体系结构.研究开发了一种基于PMAC的网络化数控系统原型,并应用于北京交通大学教学型FMS.     

Tuning of an optimal fuzzy PID controller with stochastic algorithms for networked control systems with random time delay

An optimal PID and an optimal fuzzy PID have been tuned by minimizing the Integral of Time multiplied Absolute Error (ITAE) and squared controller output for a networked control system (NCS). The tuning is attempted for a higher order and a time delay system using two stochastic algorithms viz. the Genetic Algorithm (GA) and two variants of Particle Swarm Optimization (PSO) and the closed loop performances are compared. The paper shows that random variation in network delay can be handled efficiently with fuzzy logic based PID controllers over conventional PID controllers.     

轮毂电机网络化控制器研究

对四轮独立驱动汽车中轮毂电机的控制需求进行分析,设计了一种具有FlexRay总线接口的网络化轮毂电机控制器,给出了控制器的软硬件结构和通信协议; 采用广义预测控制策略对轮毂电机速度环控制参数进行校正,以消除负载扰动对轮毂电机控制过程的影响,通过对指令数据进行实时预测,补偿传输过程中的延迟和丢包带来的数据缺失;构建了测试平台,通过模拟指令突变、负载扰动及数据丢包等工况,对所设计的网络化轮毂电机控制器性能进行评估。实验结果表明,预测控制策略和指令实时预测能使轮毂电机控制系统获得准确稳定的控制性能。     

基于模型的网络控制系统传输特性分析

目前以太网在工业网络控制系统中已得到广泛应用，这里，通过对其MAC子层控制方式的数据传输模型分析，从考虑实际各节点之间差异性的角度，结合工业网络的特性要求，提出了一种分析网络控制系统的方法和思路，推导出了一些对分析和设计网络控制系统有一定指导意义的计算公式。     

Analysis and synthesis of networked control systems: A survey of recent advances and challenges

A networked control system (NCS) is a control system which involves a communication network. In NCSs, the continuous-time measurement is usually sampled and quantized before transmission. Then, the measurement is transmitted to the remote controller via the communication channel, during which the signal may be delayed, lost or even sometimes not allowed for transmission due to the communication or energy constraints. In recent years, the modeling, analysis and synthesis of networked control systems (NCSs) have received great attention, which leads to a large number of publications. This paper attempts to present an overview of recent advances and unify them in a framework of network-induced issues such as signal sampling, data quantization, communication delay, packet dropouts, medium access constraints, channel fading and power constraint, and present respective solution approaches to each of these issues. We draw some conclusions and highlight future research directions in end.