Distributed Process Control Systems Research Articles

Scalable Architecture and Structure of Modules for Distributed Process Control System in Industrial Greenhouse Comp

With the growth of the population, the issue of food supply of cities with high-quality agricultural crops becomes urgent. Supply problems arising from this can be solved with the use of industrial greenhouse complexes with artificial lighting and groundless technologies. The development of these complexes makes the task of developing a control system to automate the cultivation processes urgent. Real industrial greenhouse complexes have a significant number of operations with the direct participation of personnel, which can be automated: control of the greenhouse microclimate, lighting, watering and preparation of the nutrient solution composition. This paper presents the architecture of a distributed control system for industrial greenhouse complexes. The system is built on a modular basis and is divided into three levels. The developed architecture is based on the use of standard modules, which makes the control system flexible and scalable. The paper also presents the basic design ratios, with the help of which it is possible to determine the required number of modules for the three levels of the proposed architecture. The use of wireless data transmission between modules based on LoRa technology allows you to abandon the laying of an information bus and at the same time deploy the system over large areas. Control of the system and its parameters is possible through direct human interaction with the interface of the control module or through remote interaction through the cloud. The architecture includes 3 types of executive modules, one combined sensor module and a control module. Each of the executive modules functions according to a given algorithm, and its parameters are controlled by a control module, based on a given growing program and information from sensors. This feature allows you to increase the reliability of the system and continue working in the event of a loss of communication with the cloud, as well as to exclude emergencies in the event of a loss of communication between the modules. The developed solutions make it possible to adapt the proposed control system for greenhouse complexes of various configurations and growing principles.

Transfer function identification of a liquid flow-line pressure control system from simple relay auto-tuning

Accurate modeling of liquid flow systems is necessary for the effective operation of the plant under different conditions. The plant dynamics may change with time, and due to this, the operation may not be satisfactory. In this article, relay autotuning of a liquid flow-line is proposed. Well-known describing function approximation is utilized for the estimation of gain of relay used in a feedback loop to excite the plant to be identified. The expressions are derived for the identification of a class of overdamped second-order plus dead-time and first-order plus dead-time plant dynamics. The identification method tested on different standard systems shows that the proposed method has good identification accuracy. Therefore, the proposed identification method is applied to a liquid flow line pressure control system. The experimental results show that an accurate dynamic model is extracted using the proposed method with a minimal set of data from an obtained limit cycle oscillation. The measured quantities of the limit cycle are utilized in the derived explicit expressions for the identification of unknown variables of the dynamic plant model. A distributed process control system is utilized here as a standard industrial platform to design virtual relay and conduct the proposed autotuning. The efficiency of the modeling method is demonstrated through the comparison of Nyquist and relay response plots with the transfer functions obtained from the MATLAB system identification toolbox.

МЕТОДИЧЕСКИЙ ПОДХОД К ВЫЯВЛЕНИЮ ДЕСТРУКТИВНЫХ ИНФОРМАЦИОННЫХ ВОЗДЕЙСТВИЙ НА РАСПРЕДЕЛЕННУЮ СИСТЕМУ УПРАВЛЕНИЯ ТЕХНОЛОГИЧЕСКИМ ПРОЦЕССОМ

МЕТОДИЧЕСКИЙ ПОДХОД К ВЫЯВЛЕНИЮ ДЕСТРУКТИВНЫХ ИНФОРМАЦИОННЫХ ВОЗДЕЙСТВИЙ НА РАСПРЕДЕЛЕННУЮ СИСТЕМУ УПРАВЛЕНИЯ ТЕХНОЛОГИЧЕСКИМ ПРОЦЕССОМ

Time Synchronization in Tandem Hot Strip Line Based on Improved Broadcast Mode

In order to solve the time synchronization problem in tandem hot strip line, the traditional algorithm of time synchronization was analyzed, and the server-client mode was compared with the broadcast mode using multithread technology, then the present paper improved the broadcast mode to improve its precision. The new method can estimate total delay including clock offset and network transmission time. A simple, easy and little loading time synchronization method was designed for the distributed process control system of tandem hot strip line. The new method was applied in domestic some tandem hot strip line successfully which showed that it could meet the demands of process control system with little expenses, simple structure and high precision.

Web-Based Monitoring and Control of Industrial Processes Used for Control Education

Web-based technologies enable the implementation of remote monitoring and control of industrial plants. In this paper, some solutions and advantages of using distributed process control systems for control education are presented. In the area of process control teaching, practical experience plays an important role and web-based technologies enable the implementation of remote experiments onto real laboratory or industrial systems for effective engineering education. We present our experiences with two remote experiments based on distributed control systems realized on laboratory systems. The user interface of the first experiment is implemented by professional supervision tools and is using web-based SCADA technology. In the second experiment we discuss the process of developing fault detection and isolation applications for online and remote education by using industrial equipment from the field of process technology (batch, continuous) supported by web technologies. Through-out the course, the student can remotely develop and test model-based and data-driven FDI schemes in Matlab/Simulink by using OPC technology. Finally, the improved platform for web-based remote control system experiments suitable for control education is proposed.

Application of distributed control systems and integrating automated process control systems of power equipment

Main factors that must be taken into account in constructing modern distributed microprocessor systems for control of thermal power plants are analyzed. The list of these factors includes the nature of a plant being automated and its spatial arragement, specific features of the basic computerized automation system, advisability of organizing exchange of digital information with peripheral equipment (sensors and actuators), routing of cable lines, power supply, and organizing redundancy in hardware and networks. Problems concerned with integration of local automatic control systems supplied complete with process equipment into a united automated process control system and uniting process control systems of heat-generating, mechanical, and electrical equipment are considered. Examples illustrating implementation of distributed process control systems constructed on the basis of the Teleperm XP-R and SPPA-T3000 computerized automation systems manufactured by Siemens are given.

Means for constructing distributed process control systems on the basis of the SARGON computerized automation suite

The main characteristics of distributed control facilities available in the modern version of the SARGON computerized automation suite are described, and possible implementations of distributed full-scale automated process control systems of thermal power installations are presented taking concrete projects accomplished by ZAO NVT-Avtomatika as examples.

A novel object-oriented environment for distributed process control systems

This paper addresses the design, development and implementation of distributed process control systems. A novel object-oriented environment is presented that supports the development lifecycle phases. The core of this environment is the integrated design notation (IDN), which is based on the unified modelling language (UML). Its emphasis is on open architectures and thus it uses open standards such as UML (for software engineering), IEC 61131-3 (for process control) and SIMULINK (for control engineering). Automated translation of models and languages across the different disciplines is created with the IDN. Also, the source code implementation phase is produced in Java, thus achieving greater portability for control systems.

Fault detection for multirate sampled-data systems with time delays

In this paper, problems of fault detection in multirate sampled-data (MSD) systems with time delays are studied. The background of our study is the increasing demands for fault detection in complex, distributed process control systems, where the plant, controllers, sensors and actuators are networked by standardized bus systems. The basic idea behand the problem solutions is to derive the parity relations of the MSD system with time delays by taking into account the multirate nature and the multiple time delays. Having introduced two operators, the fault detection problem can be formulated as an optimization problem in the framework of the well-known parity space method. Application and advantages of the approaches proposed in this paper are finally illustrated by simulation examples and by comparison with other indirect design approaches.

FAULT DETECTION IN MULTIRATE SAMPLED-DATA SYSTEMS WITH TIME-DELAYS

In this paper, an approach is proposed to the fault detection in multirate sampled-data (MSD) systems with multiple time-delays in both input and output channels. The background of our study is the increasing demands for fault detection in complex, distributed process control systems, where the plant, controllers, sensors and actuators are networked by standardized bus systems. The core of the approach proposed is a) to derive parity relations of the MSD system with time-delays while taking the different sampling rates and time-delays into account; b) to take the intersample behaviour of the continuous-time disturbances and faults into consideration with the help of operators.

Performance analysis of distributed real-time databases

In a distributed process control system, information about the behavior of physical processes is usually collected and stored in a real-time database which can be remotely accessed by human operators. In this paper we propose an analytic approach to compute the response-time distribution of operator consoles in a distributed process control environment. The technique we develop is based on Markov regenerative processes (MRGPs) and described with the assistance of deterministic and stochastic Petri nets (DSPNs). We construct exact models for performance analysis of centralized and decentralized database architectures. However, due to limitations on the exact solution, we also propose an approximate solution which is then used to study response-time distributions of large systems.

On Object-Oriented Communication Models and Multimedia User Interfaces for Process Control

Object-oriented models and multimedia user interfaces are of growing importance for modern distributed automation systems. An object-oriented communication system is introduced, based on an implementation of the CORBA 2.0 standard, which is applicable to any distributed process control system in basic industries. The object concept allows user interface objects and automation objects to be integrated into one common model. Therefore the author is investigating and developing methods and utilities that provide an object-oriented integration of multimedia functions into distributed process control systems. A first prototype of the communication system allows a periodic exchange of still images between a supervising camera at one computer and a remote computer via a small-band ISDN telephone line.

An Object-Oriented Design Method For Distributed Process Control Systems

The objective of this article is to present a design method for Distributed Process Control Systems(DPCS) within the context of the Waterfall methodology of system development. The design method is decomposed to two steps. In the first step an object-oriented model of the modular view that the designer has for the system is produced. In the Second step this model is used as input to the combined simulation of the process units and the DPCS. The responses of the controlled variables obtained from the simulation are used to evaluate the DPCS design. An application example of the method is given.

A parameter estimation method based on aggregated data

In constructing multiprocessor-based distributed process control systems, one approach is to use low-end processors to carry out direct control tasks at the local layer, while leaving more sophisticated tasks for high-end processors at the supervisory layer. For such a system architecture, reducing the data transmission on the communication link is a challenging problem. Hung and Lefkowitz proposed a data aggregation algorithm for compressing the original input/output data at the local layer before passing them to the supervisory layer. At the supervisory layer, however, there is a lack of an effective algorithm to perform the parameter estimation task based on the aggregated data. This paper describes a method which significantly improves the effectiveness of this task. Systems under control are assumed to be linear with distinct eigenvalues. Simulation results are included.

Featuring FDDI in a process control environment

The aim of this paper is to analyze the possibility of using the FDDI inside the MAC sublayer as a backbone network for a distributed process control system. The evaluation of the throughput and delay, obtained by simulation, shows the good overall behaviour of the considered solution, giving quantitative performance results which can be used as a support for the design of the network.

A Distributed Process Control System for the Tritium Emissions Reduction Facility

The Tritium Emissions Reduction Facility (TERF) is an automated process that continuously removes tritium from process gases before they are discharged to the atmosphere. Key control parameters include: temperature, pressure, flow, oxygen content, total combustibles, moisture concentrations and tritium concentrations. The procurement of an industrial, microprocessor-based Distributed Process Control System was justified for TERF due to the critical nature and complexity of the system. A detailed performance specification was prepared and submitted to industrial companies who had demonstrated past success in the field of process control and instrumentation. The contract was awarded to the Foxboro Company, of Foxboro, Ma., who developed the new Intelligent Automation (I/A) Distributed Process Control System. A primary goal of the design team was that the control system increase TERF reliability and availability by automatically controlling system operation and by assisting the operator in the diagnosis of problems, preventative maintenance, alarming, report generation, and long term storage of data. The comprehensive continuous monitoring of the TERF process provided by the Foxboro I/A Distributed System is expected to: (1) optimize the system operating parameters and control the process better than was previously possible, (2) provide more alerts and alarms to aid operators in diagnosing and responding tomore » problems, and (3) record and organize process data more effectively than before.« less

Application of statistical process control methods to the establishment of process alarms in a distributed process control system

The introduction of statistical process control methods to process industries has provided opportunities for improved understanding of each portion of any given process and of its impact on the total process. Using SPC methods to determine real-time process alarm limits in a distributed monitor/control system is one valuable way to inject this understanding into the control scheme, but it is more than a trivial exercise. The establishment of such a program, including problems, limitations, and benefits, is discussed.

Advanced configuration tools for DCS

Various software packages have been prepared to configure application functions of new distributed process control systems (DCS). These packages, including control function configuration, CRT display definition, and report and graphics construction, run on personal computer, enabling a personal engineering environment. The configuration package for a process control station provides five languages: Ladder Diagram, DataFlow, SFC (Sequential Function Chart), LPC (Loop Function Chart), and IFC (Instrumentation Flow Chart). IFC is a high-level language used for applications that combine analog control loops, sequential controls, and logic controls. Symply drawing flow charts with descriptive conditions or comments enables creation of an object program that is self-documenting and ready to run.

Intelligent Self-Tuning PID Controller

A new self-tuning PID controller has been developed for distributed process control systems. The self-tuning PID controller is able to identify the process dynamics using a short period of process behaivior such as a setpoint change under the closed loop control condition, and to tune PID parameters based on the identified iodei parameters for both setpoint tracking and disturbance regulation characteristics, which makes it easy to set up the inital PID parameters and adapt the PID values to the process dynamics changes. This paper describes the basic principles of the self-tuning controllers, and explains the functions to be implemented on. Finally, some application results illstrate the effectiveness of the self-tuning controllers.

A Concept of a Computer System for the Execution of Safety Critical Licensable Software Programmed in a High Level Language

There are already a number of established methods and guidelines, which have proven their usefulness for the development of high integrity software employed for the control of safety critical technical processes. Prior to its application, such software is still subjected to appropriate measures for its verification and validation. However, according to the present state of the art, these measures cannot guarantee the correctness of larger programs with mathematical rigour. Therefore, the licencing authorities do not approve safety relevant systems yet, whose behaviour is exclusively program controlled. In order to provide a remedy for this unsatisfactory situation, the concept of a special computer system is developed, which can carry out safety related functions within the framework of distributed process control systems or programmable logic controllers. It explicitly supports sequence controls, since many automation programs including safety relevant tasks are of that kind. The architecture features full temporal predictability, determinism, and supervision of the program execution and of all other activities of the computer system and supports the software verification method of diverse inverse documentation. The system can be programmed in a high level language and is based on a library of function modules, whose correctness can be mathematically proved. The concept utilises an operating system and a compiler only in a very rudimentary form. Hence, it enables the safety licencing of the software running on the computer system. In the microprogram of this computer, which may be based on the VIPER chip, a minimum operating system is provided, whose only task is to start the execution of runnable subroutines, which are marked in a ready list. As the elementary units of application programming, the set of basic function modules is provided in RaMs. These modules are of application specific nature and generally different for each application area. For the formulation of safety related automation programs these basic functions are only interconnected with each other. The prototype of a tool has been developed allowing to carry through this kind of programming in graphical form.