Handling communication disruptions in distributed model predictive control

In this work, we study distributed model predictive control (DMPC) of nonlinear systems subject to communication disruptions - communication channel noise and data losses - between distributed controllers. Specifically, we focus on a DMPC architecture in which one of the distributed controllers is responsible for ensuring closed-loop stability while the rest of the distributed controllers communicate and cooperate with the stabilizing controller to further improve the closed-loop performance. To handle communication disruptions, feasibility problems are incorporated in the DMPC architecture to determine if the data transmitted through the communication channel is reliable or not. Based on the results of the feasibility problems, the transmitted information is accepted or rejected by the stabilizing MPC. In order to ensure the stability of the closed-loop system under communication disruptions, each model predictive controller utilizes a stability constraint which is based on a suitable Lyapunov-based controller. The theoretical results are demonstrated through a nonlinear chemical process example.     

可编程序控制器在电厂输煤系统中的应用

论述了某发电厂输煤系统的设计流程、总体结构和软件结构。该系统采用具有国际先进水平的三级分布式计算机控制网络、综合实时管理系统和图形监控等先进技术,实现了电厂输煤系统的自动控制和监测。在下位机控制软件编程中,采用级式语言编程,有效地缩短了系统扫描时间和响应时间。     

分布式数据库并发控制方法研究

并发控制机制是数据库事务管理中重要的组成部分，是衡量一个数据库系统功能强弱和性能好坏的重要标志之一。分布式并发控制的目的是保证分布事务和分布式数据库的一致性，实现分布事务的可串行性，使事务具有良好的并发度以保证系统具有用户满意的效率。本文首先就分布式数据库并发事务的可串行化进行探讨并在此基础上提出分布式数据库并发控制的基本方法。     

分布式数据库并发控制方法研究

并发控制机制是数据库事务管理中重要的组成部分,是衡量一个数据库系统功能强弱和性能好坏的重要标志之一。分布式并发控制的目的是保证分布事务和分布式数据库的一致性,实现分布事务的可串行性,使事务具有良好的并发度以保证系统具有用户满意的效率。本文首先就分布式数据库并发事务的可串行化进行探讨并在此基础上提出分布式数据库并发控制的基本方法。     

Control limitations from distributed sensing: Theory and Extremely Large Telescope application

We investigate performance bounds for feedback control of distributed plants where the controller can be centralized (i.e. it has access to measurements from the whole plant), but sensors only measure differences between neighboring subsystem outputs. Such “distributed sensing” can be a technological necessity in applications where system size exceeds accuracy requirements by many orders of magnitude. We formulate how distributed sensing generally limits feedback performance robust to measurement noise and to model uncertainty, without assuming any controller restrictions (among others, no “distributed control” restriction). A major practical consequence is the necessity to cut down integral action on some modes. We particularize the results to spatially invariant systems and finally illustrate implications of our developments for stabilizing the segmented primary mirror of the European Extremely Large Telescope.     

On the Minimization of Communication in Networked Systems with a Central Station

The problem of minimizing communication in a distributed networked system is considered in a discrete-event formalism where the system is modeled as a finite-state automaton. The system consists of a central station and a set of N local agents, each observing a set of local events. The central station needs to know exactly the state of the system, whereas local agents need to disambiguate certain pre-specified pairs of states for purposes of control or diagnosis. This requirement is achieved by communication, which occurs only between the central station and the local agents but not among the local agents. A communication policy is defined as a set of event occurrences to be communicated between the central station and the local agents. A communication policy is said to be minimal if any removal of communication of event occurrences will affect the correctness of the solution. Under an assumption on the absence of cycles (other than self-loops) in the system model, this paper presents an algorithm that computes a minimal communication policy in polynomial time in all parameters of the system. These results improve upon previous algorithms for solving minimum communication problems.

基于现场总线的温室分布式控制系统

讨论了在温室自动控制系统中如何引入现场总线技术构成全分布式控制系统，并阐述了分布式系统结构的特点和其智能模块的系统结构。     

Distributed model predictive control of dynamically decoupled systems with coupled cost

This paper considers the distributed model predictive control (DMPC) of systems with interacting subsystems having decoupled dynamics and constraints but coupled costs. An easily-verifiable constraint is introduced to ensure asymptotic stability of the overall system in the absence of disturbance. The constraint introduced has a parameter which allows for the performance of the DMPC system to approach that controlled by a centralized model predictive controller. When the subsystems are linear and additive disturbance is present, the added constraint ensures the state of each subsystem converges to its respective minimal disturbance invariant set. The approach is demonstrated via several numerical examples.     

On distributed constrained formation control in operator–vehicle adversarial networks

We consider an operator–vehicle network where each vehicle is remotely maneuvered by an operator. The objective of the operators is to steer the vehicles to the desired formation subject to the given state and input constraints. Each operator–vehicle pair is attacked by an adversary who is able to maliciously replay the control commands sent from the operator. To play against attackers, we come up with a novel distributed resilient algorithm based on the receding-horizon control methodology, and show that the algorithm is able to allow vehicles, on the one hand, satisfy state and input constraints, and on the other hand, asymptotically achieve the desired formation despite replay attacks. With slight modifications, our proposed algorithm shows an analogous resilience to denial-of-service attacks.     

Design and experimental testing of an optimization-based flow control algorithm for Energy Harvesting Wireless Sensor Networks

In this paper a distributed flow control law is proposed to maximize throughput and to minimize energy consumption in Energy Harvesting Wireless Sensor Networks (EH-WSNs). We preliminary recast the control problem in terms of primal–dual optimization one taking into account the bandwidth and energy autonomy node constraint. Then, we devise a distributed flow rate control implemented at each node that allows the overall network to converge to the optimal solution of the original problem. The closed loop EH-WSN stability and convergence to the optimal equilibrium are proven. The effectiveness of the proposed control law in terms of throughput and network lifetime performance is experimentally validated by a small representative EH-WSN. The experimental results are in a good agreement with the theoretical ones.     

集散控制系统与现场总线技术

介绍了集菜控制系统DCS的结构及存在的问题,而且有些问题对DCS来讲无法从根本上解决,随学控制,计算机,通讯,网络技术的发展,产生了现场总线。本文着重阐述了现场总线控制系统FCS的特点及其较之DCS的优越性。     

An iterative scheme for distributed model predictive control using Fenchel's duality

We present an iterative distributed version of Han's parallel method for convex optimization that can be used for distributed model predictive control (DMPC) of industrial processes described by dynamically coupled linear systems. The underlying decomposition technique relies on Fenchel's duality and allows subproblems to be solved using local communications only. We investigate two techniques aimed at improving the convergence rate of the iterative approach and illustrate the results using a numerical example. We conclude by discussing open issues of the proposed method and by providing an outlook on research in the field.     

微机监控技术 三

本文系统地讲述了以微型计算机为中心的微机监控系统的工作原理、系统组成和应用方面的有关技术。分为监控系统的功能和结构、硬件系统和软件系统三个部分。本文为第三部分。     

A model-based augmented PID algorithm

For complex control problems, advanced techniques, such as model-based predictive control may give better control performance than the common PID controller. However, the extra complexity and limited support of control software especially at the distributed control system (DCS) level, may prohibit the application of advanced algorithms. Also, implementing model based control often requires a higher level of programming than is readily available at the DCS level. This paper addresses this problem by providing a control algorithm utilizing multiple DCS PID blocks to implement a model-based predictive control strategy. The approach was tested on process simulations and the algorithm was able to provide control performance similar to that of generalized predictive control.     

基于OPC的先进控制算法平台的设计与实现

提出了一种基于OPC技术的先进控制算法平台和实现方法。在该平台上可以加载和仿真各种先进控制算法,并使用OPC技术和各种第三方DCS系统进行数据交互,从而可实现对复杂工业过程的先进控制,以提高控制效果和实现经济效益。     

Active并发控制——分布事务管理的目标统一

本文综述了当前分布式数据库（DDB）并发控制研究状况。提出了一种比较接近真实的DDBMS参考模型，在此基础上对典型的分布并发控制策略作出正确的集成，最后给出了Active并发控制的实现方案。     

Distributed identification and control of spatially interconnected systems with application to an actuated beam

This paper presents a case study on modelling and control of spatially interconnected systems. Considered is a vibration control problem, with experimental results on a flexible beam that is equipped with an array of piezo sensors and actuators. The sensor–actuator array induces a spatial discretization of the beam into an array of interconnected subsystems. Models are experimentally identified that have the structure of spatially interconnected systems. Based on the identified models, distributed control schemes are designed by solving a linear matrix inequality (LMI) problem that has the size of a single subsystem. Modelling and control is considered for both spatially invariant and spatially varying systems; in the latter case the system is represented as linear parameter-varying (LPV) system that is scheduled not over time but over space. Simulation and experimental closed-loop results demonstrate the practicality and efficiency of the underlying framework.