Plant Intelligent Automation and Digital Transformation: Volume I: Process and Factory Automation

By Swapan Basu

Plant Intelligent Automation and Digital Transformation: Process and Factory Automation is an expansive four volume collection reviewing every major aspect of the intelligent automation and digital transformation of power, process and manufacturing plants, from the specific control and automation systems pertinent to various power process plants through manufacturing and factory automation systems. This volume introduces the foundations of automation control theory, networking practices and communication for power, process and manufacturing plants considered as integrated digital systems. In addition, it discusses Distributed control System (DCS) for Closed loop controls system (CLCS) and PLC based systems for Open loop control systems (OLCS) and factory automation.

This book provides in-depth guidance on functional and design details pertinent to each of the control types referenced above, along with the installation and commissioning of control systems.

• Introduces the foundations of control systems, networking and industrial data communications for power, process and manufacturing plant automation
• Reviews core functions, design details and optimized configurations of plant digital control systems
• Addresses advanced process control for digital control systems (inclusive of software implementations)
• Provides guidance for installation commissioning of control systems in working plants

• Language: English
• Publisher: Academic Press
• Release date: Oct 28, 2022
• ISBN: 9780323902472

Swapan Basu

Swapan Basu is founder member & Chief Executive, Systems & Controls Kolkata India. Basu is a member of Institute of Electrical and Electronics Engineers (IEEE) and IEEE Instrumentation and measurement society. He brings over 40 years of international professional engineering experience in instrumentation and controls systems for subcritical, super critical thermal power plants including combined cycle projects, and other process plants. Since 1979, he has been leading teams of engineers in India, Jordan, Singapore, South Korea, Syria, and USA. He has a number of national and international technical papers to his credit. He has published two editions of Power Plant Instrumentation and Control Handbook, Plant Hazard Analysis and Safety Instrumentation Systems and Plant Flow Metering and Control Handbook

Book preview

Plant Intelligent Automation and Digital Transformation

Process and Factory Automation

Swapan Basu

Founder, Systems and Controls, Kolkata, India

Table of Contents

Cover image

Title page

Copyright

Dedication

Foreword

Preface

Acknowledgment

Chapter 1. General discussions on control systems

1.0. Fundamentals and general discussions on control systems

1.1. Control system synthesis and control theory

1.2. Control loop modes, types and hierarchical control

1.3. Control system models

1.4. State space in control systems

1.5. Optimization of controls and automations

List of abbreviations used

Chapter 2. Basics of networking

2.0. Basics of networking

Chapter 3. Industrial data communication

3.0. Industrial data communication

Chapter 4. System diagnostics, security, and safety

4.0. Functional details of system diagnostics, security, and safety

4.1. Discussions on diagnostics

4.2. Control systems security discussions

4.3. Plant safety discussions with safety fieldbus outline

List of abbreviations

Chapter 5. Control intelligence and futuristic approach

5.0. Control intelligence and futuristic approach

Chapter 6. PLC and Open loop control system (OLCS) functional and design details

6.0. PLC and open-loop control system

6.1. Basics of PLC with hardware details

6.2. PLC software discussions

6.3. Types of PLC

6.4. Features and configurations of PLC

6.5. Networking interfaces and system integration

6.6. Brief discussions on HMI and engineering interfaces

6.7. System diagnostics and security

6.8. PLC performance and application area

6.9. Safe PLC discussion

List of abbreviations used

Chapter 7. OLCS in process plants and PLC details

7.0. Open loop controls in process automation and I/O detailing

7.1. Discussions on I/O interfaces types

7.2. Description and design aspect of PLC I/O modules

7.3. Specification of PLC I/O modules

7.4. Discussions on PLC architecture and redundancy types

7.5. Application programming and analog applications

List of abbreviations used

Chapter 8. Batch process control and automation

8.0. PLC/DCS applications in batch process control

8.1. Batch process control standards

8.2. Batch control system discussions

8.3. Automation interfaces and control center in batch process

8.4. Batch control execution details

8.5. Discussions on batch process management

List of abbreviations used

Chapter 9. Manufacturing and factory automation

9.0. General discussions: manufacturing advancement and 3D printing

9.1. Requirements manufacturing automation

9.2. Various controls types in manufacturing

9.3. Programmable automation control (PAC)

9.4. Total factory automation concept

9.5. Future automation: Industrie 4.0 and smart factory

List of abbreviations used

Chapter 10. Building and service sector automation

10.0. Building management system (BMS): areas of applications

10.1. Discussions on BACS: HVAC and other systems

10.2. BACS: integrated and smart buildings

10.3. BMS: fire and access control

10.4. Lighting control in BACS

10.5. Security issues in BACS

List of abbreviations

Chapter 11. PLCopen concept and applications

11.0. Fundamentals of PLC-open

11.1. PLCopen motion: features and applications

11.2. PLCopen: safety software

List of abbreviations used

Chapter 12. PC-based control, MTP, FDT, EDD, and OPC

12.0. General discussions on PC based systems

12.1. PC based PLC/OLCS and motion control

12.2. PC based process controls & MTP

12.3. Other production line issue, FDT, EDD and OPC

List of abbreviations used

Chapter 13. CLCS—an approach to DCS-MIS

13.0. Requirements, functional, and design details of CLCS

13.1. CLCS and supervisory system design aspects and configuration

13.2. CLCS behavior and time response

13.3. Basics of modeling and simulation in CLCS

13.4. CLCS performance and selection discussions

13.5. Various important CLCS issues

List of abbreviations

Chapter 14. Stand-alone controller in process automation

14.0. Stand-alone controller features

14.1. Stand-alone controller functional details

14.2. Stand-alone controller description

14.3. Interface and integration of stand-alone controller

14.4. Stand-alone controller application areas

14.5. Stand-alone controller specification

List of abbreviations used

Chapter 15. DCS features, elements and HW details

15.0. Discussions on features of DCS

15.1. DCS elements: functional details and applications

15.2. HW details of DCS

15.3. DCS design and simulation units

15.4. DCS control and automation implementation

List of abbreviations

Chapter 16. General description and configurations for DCS

16.0. DCS configuration: functional details

16.1. Discussions on factors for DCS configuration

16.2. DCS configuration examples and usage

16.3. Future network configurations

List of abbreviations used

Chapter 17. DCS SW aspects, APC and MIS discussions

17.0. Discussions on SW aspects, APC and MIS

17.1. DCS control and safety software solutions

17.2. Advance process control discussions

17.3. DCS monitoring software

17.4. DCS networking and miscellaneous software issues

17.5. DCS and management information system

List of abbreviations used

Chapter 18. DCS in electrical controls and SCADA

18.0. DCS application in electrical controls and SCADA

18.1. DCS in excitation and voltage regulation

18.2. DCS AC drive and motor control (PMCC)

18.3. DCS and SCADA applications

List of abbreviations

Index

Copyright

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Notices

Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary.

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Dedication

In the name of Gurudeb I trust,

I dedicate this volume of the book

to everyone who selflessly sacrificed their lives in the services of mankind during the global pandemic Covid 19

Foreword

In this modern world, there is hardly any device that is devoid of digital electronics. In our everyday life, even mobile phones or any domestic appliances that we use make use of embedded digital electronics. However, each one of them makes use of different aspects of control system applications. It is becoming extremely difficult to use and maintain each one of them properly. As a result, there arose a need to integrate them in a common platform. One can now use a mobile phone not only as a phone but also as a social networking and communicating device and also as a remote controlling device of various home appliances.

In this book, an effort has been made to cover extensively the entire range of theory and implementation technology required to design, develop, manufacture, and maintain such control and automation devices or systems. This book not only covers the topics on system integration and migration but also on IoT/IIoT-based remote control requirements as per Industry 4.0 and digital implementation standards. This evidently makes up an extensive volume of information to be put between two covers, and so the book entitled "Plant Intelligent Automation and Digital Transformation" has been divided into four following volumes:

Volume I—Process and Factory Automation

Volume II—MIS and HW-SW Implementation

Volume III—AI and Communication (Field and Network)

Volume IV—Security, IoT/IIoT, and Applications

Beginning with the overall issues, a slow build-up of in-depth discussions with appropriate detailing, as and when needed, offers a smooth reading and understanding of different technical concepts. The same philosophy has been followed in every book volume and in every chapter of each volume. Each volume starts with the basic working principles describing the mathematical background, and detailed discussions on the functional aspects, software, hardware specification, application, and implementation options have also been covered—step by step.

Four volumes, as a whole, maintain a fine balance between fundamental concepts, theoretical studies with mathematical details, and in-depth discussions on all practical issues related to design, implementation, testing, and fulfillment of application requirements. As far as my knowledge goes, no single book can be found today where such detailed studies on intelligent control of systems, implemented with digital devices and techniques, have been covered so thoroughly. The author of this monumental work, Mr. Swapan Basu, a highly reputed engineer in the field of Instrumentation and Control engineering, having experiences both in India and abroad, is an expert in the field of process design, commissioning, and testing. He has been able to maintain a continuing interest in the latest developments found in the field of digital instrumentation and control. I truly feel that the book written by an author who has such a long industrial experience will be extremely helpful, not only to the practicing engineers but also to the students and fresh professionals entering into the field.

I wish all success to the author and his efforts will be highly appreciated by all the readers.

A.M. Ghosh

Preface

In this competitive market, globally, industrial production plants are struggling to sustain their market and have to opt for integrated intelligent controls with big data analysis for cooperative production process linking supply chains, with the help of cloud computing in digital transformation approach. This book has been developed to address all these issues in four volumes. In this volume of the book with 18 sections, theoretical and practical approaches for several subsystems pertinent to intelligent plant controls, automation, and digital transformation approach have been dealt with, keeping proper balance between two extremes. Instead of far-reaching theoretical approach with complicated, advanced mathematical deductions, this book provides basic theoretical details followed by physical explanations, application areas with implantation options, relevant figures, tables, and detailed specifications that create a simple, clear understanding of these complex topics both from hardware and software point of view.

Staring with recapitulations on basic control systems, the first section covers various control model types, state space controls, optimization, and automation treatise. Outlines of networking and communications have been dealt in next two sections, starting with networking details including network devices, reference model, different networking standards, communication outlines including DNPP3 and wireless protocols, and network security issues. The next section has been dedicated for discussions on system diagnostics, security, and safety system. Similarly, section five has been dedicated to outline control intelligence including artificial intelligence and digital control and automation of the future. In all these chapters, all associated international standards with their recommendations and explanations have been covered in details. After covering the basics for various technologies related to intelligent control system, discussions on PLC systems staring from basic, hardware, software network configuration and PLC type have been put forward on types PLCs, system integrations, application areas, implementation details including safe PLC have been covered here. Section seven is dedicated for PLC application and implementation as OLCS in process and power industries to cover I/O detailing, hardware, specification, interface types including analog interface, application programming, and architectural issues especially for redundant systems for critical and safety applications. Application and implementation details of smart controls in batch process have been described in section eight to include detailed coverage on batch process control and automation, batch execution, and batch management details. Intelligent controls, especially PLCs, find major applications in manufacturing industries where they have to interface high-speed I/Os and motion control systems. Data analytics, cloud computing, and other dynamical details have been discussed as part of total factory automation, smart factory, and Industry 4.0. Building management systems including HVAC, lighting, fire, and energy management systems deploy intelligent control systems; hence, section ten has been dedicated for implementation and application details. PLC-Open is another specialized area for open intelligent control system and system integrations which is discussed at length in the next section. Some small- and medium-sized plants control and automation systems are well managed with PC-based controls in conjunction with various intelligent controls; section twelve has been dedicated for this and this section also includes discussions on FDT, EDD, and OPC for open system integrations. Section thirteen is a preamble to detailed discussions on DCS in the next section to include discussions on various allied issues such as basic design functional and design details including with Laplace, Z transform, and state space model for CLCS behavior and performance analysis. This section also includes selection criteria for DCS, modeling, and simulation issues in CLCS. Short discussions on stand-alone controller and its interface with other intelligent control system have been put forward in the next section. Apart from functional and design details about various DCS hardware, details including specification have also been included in section fifteen. Design details of DCS simulation and plant automation implementation details have also been covered here. The next section details out variations in DCS configurations such as client server and nonclient server system architecture with pros and cons with real-life example and usages. Futuristic network for DCS as per international standards including NAMUR, O-Pass to name a few have been covered. This section also includes detailed discussions on open standards and APL. After discussions on Industry 4.0 in section nine, detailed discussions on digital transformation have been discussed here. Detailed discussions on DCS software including OS, application software for controls, and MIS software have been covered in this section. This section also includes software discussions on networking issues including system integration and MIS issues, as well as discussions on APC. The last section is dedicated for discussions on application of intelligent controls on electrical systems including various artificial intelligent control applications in electrical systems, renewable energy management systems, intelligent MCCs, and drive controls. With comprehensive idea about intelligent control technologies, further detailing on hardware software and MIS has been presented in Volume II. Volume III deals with extensive details on artificial intelligence and details on communication both at field and network level. Volume IV deals with security, IoT, IIoT, and application details in various industrial plants. All four volumes complement each other for comprehensive details.

In order to correlate various figures, tables and text references following principles are followed:

Fig: Fig A N.Mb: A = volume no. (I,II, III IV); N = chapter no. of the volume; M= Section of the chapterN of the volume A; a, b,c are unique number for the drawing (if two or more sketches are the in Figure these are designated by 1,2.. after unique number viz. Fig I 4.2a or I 4.2b1 Fig I 4.2b2…

Table: Table A N.Mb: A = volume no. (I,II, III IV); N = chapter no. of the volume; M= Section of the chapterN of the volume A; a, b,c are unique number for the table viz. Table I 4.2a…

Equation: (A N.Mb): A = volume no. (I,II, III IV); N = chapter no. of the volume; M= Section of the chapterN of the volume A; a, b,c are unique number for the eq. viz. (I 1.2b)

Text reference: A N.M.P.n: A = volume no. (I,II, III IV); N = chapter no. of the volume; M= Section of the chapterN of the volume A; P = subsection of main section and n is the point under that subsection of any viz. I 6.0.3.2 stands to represent point number 2 in subsection 3 of section 0 in chapter 6 in volume I.

This book is extremely helpful for professionals working/practicing in modern intelligent control and automation systems. Budding (fresh) engineers starting their careers in automation and control engineering, postgraduates student/research scholars in this area, as well as in computer science/electrical engineering will be greatly benefitted from the comprehensiveness and practical approaches in this book.

In an attempt to incorporate this extensive subject in the form of a book, the author has carried out a great deal of research over years so as to include the knowledge gained during his decades-long global experience in industrial automation and control engineering. I would feel rewarded only when my research efforts would be able to benefit practicing engineers by providing proper guidance in industrial automation in the era of fast-changing technologies and customer demands.

Swapan Basu (author)

Sr. Member IEEE and Sr. Member ISA

Acknowledgment

At the outset, I wish to convey my sincerest thanks and gratitude to my lovely wife Bani who sacrificed her quality time and companionship of mine for these time-consuming efforts for development of book volume of this standard. I indeed thank my son and daughter and her friend who not only encouraged me in this effort but also helped me in different areas even from abroad in this pandemic period. The book cover has been designed and developed by my lovely son Piku. Various chapters were overseen and edited by my lovely daughter Idai and lovely Dhruba very close to me.

During my old BE college days, he was an idol to many of us through his profound knowledge, limitless energy, and encouragements to his students—He is none other than Dr. Ananda Mohan Ghosh. In spite of many odds, he always came out with full vigor to help me whenever I approached him. As usual even over phone he explained many difficult issues and queries and never felt disturbed. Not only that, he was kind enough to oversee some difficult portion of the book as well. Also, Dr. Ghosh spared his valuable time to go through this book and agreed to write the Foreword for this book.

I would also like to thank many of my friends and excolleagues, especially Mr. Ajoy Kumar Debnath (mentor), for their encouragements and technical support time to time during the development of this book.

Last but not the least the author would like to acknowledge the support he has received from the entire team of Elsevier, without which it would have been impossible to publish the book.

Chapter 1: General discussions on control systems

Abstract

This chapter deals with from basic control systems like fundamentals on PID, ON-OFF controls including feed forward, cascade, ratio, lead lag controls. Functioning of microprocessors, microcontrollers have also been included as a part of recapitulations. Discussions on CLCS and OLCS includes basic loop implementations for various kinds of control loops and logics in process control system. As a part of modern digital control network implementation, hierarchical controls have been described also detailing functions at each level. As a part of control loop analysis, brief discussions on Fourier and Laplace transformations have also been covered so as to study control loop responses under various input conditions. Basics of control loop synthesis as well as state space basics have also been included. Use of various control loop models are part and parcel of modern control studies hence various such as MBC, MPC, PMBC, IMC involving from SISO to MIMO loops have been covered Naturally, brief discussions on various computing methods and linearization methods have been covered. To complete the discussions basics on control system optimization and associated software issues have also been included.

Keywords

Adaptive control; APC; Bumpless transfer; Cascade control; Control hierarchy; Feed forward; Fourier and Laplace transform; Gain scheduling; IMC; Lead-lag; MBC; Microcontroller; MPC; Performance index; PID; Process dynamics; Signal-noise ratio; Split range control; State space

1.0 Fundamentals and general discussions on control systems

1.0.0 Recapitulations of terms with explanations

1.0.1 Requirements for plant automation conceptual discussions

1.0.2 Synopsys of issues covered in this volume of the book

1.0.3 Microprocessor: microcomputer basics (brief recapitulations)

1.0.4 Control implementation issues

1.0.5 Mathematical approach for control systems

1.1 Control system synthesis and control theory

1.1.0 Preliminary discussions

1.1.1 Definition of various terms used in control theory

1.1.2 Discontinuous (discrete) control system

1.1.3 Continuous control system

1.1.4 PID implementation in digital control systems

1.2 Control loop modes, types and hierarchical control

1.2.0 General discussions on modes and types of controls

1.2.1 Examples for feed forward control and lag lead controls

1.2.2 Cascade control action

1.2.3 Ratio control

1.2.4 Override control

1.2.5 Auctioneering control

1.2.6 Split range control

1.2.7 Inferential control

1.2.8 Adaptive control and gain scheduling

1.2.9 Hierarchical control system

1.3 Control system models

1.3.0 Discussions on control system models

1.3.1 Types of systems

1.3.2 Model based control (MBC) methodology and structure

1.3.3 Various model based control types

1.3.4 Control computing and system development

1.3.5 Linearization of nonliner systems

1.4 State space in control systems

1.4.0 Concept of state space and control system

1.4.1 State variable and process

1.4.2 System state

1.4.3 State equation

1.4.4 Output equation

1.4.5 Block diagram representation of state space

1.5 Optimization of controls and automations

1.5.0 Basics of process control and process automation

1.5.1 Structural approach for integrated optimization and control

1.5.2 Discussions on integrated structure

1.5.3 Advanced process controller (APC) and optimization

List of abbreviations used

References

Further reading

In 1979, when I started my career in Instrumentation and process control engineering for power generation plants, it was an era of transition in control systems. Major control systems were predominantly having pneumatic/hydraulic controls especially for the processes where there is possibility of formation of explosive atmosphere. It is not that pneumatic/hydraulic controls have been totally discarded, but these controls are mainly (exception: hydraulic control of turbine governor) restricted to final control elements. PLCs were in service for limited applications and PLC of those days are totally different from PLCs of today—where PLC and DCS can hardly be differentiated. With the advent embedded electronics viz. microcontroller FPGA different areas such as control systems, networking and system integration and communication systems witnessed tremendous developments and growth. Apart from Instrumentation and control (I&C), electrical systems like intelligent drive control, MCC and SCADA are now using intelligent controls and are connected through networking and data communication systems. IoT and IIoT also have brought about big changes in plant controls. Now it is possible even with the help of mobile phone to get control of the plant. During my tenure of work in industry I felt the need for a comprehensive book so that practicing engineers, fresh engineers, starting their career, research scholars can get to have complete picture of the entire scenario from single source. Let the discussions start with general discussions on control systems. One important aspect of this book is that initially overall view of the entire subject is presented in very concise manner at the initial stage so that reader is well aware of the subject content and can develop an idea about the same. Later in the book volumes these are elaborated to gain knowledge about the subject matters in details and not that one jumps directly to intricacy of the subject.

1.0. Fundamentals and general discussions on control systems

1.0.0. Recapitulations of terms with explanations

In order to achieve better yield, energy utilization and better quality of production/process it is necessary that there shall be appropriate control system so that there will be higher efficiency of the system with lesser loss/wastage at the same time to ensure safety and security of the system. In modern plants, smart systems are normally implemented to achieve the desired goal. Also, at this time control systems are no longer an isolated system but on account of digital transformation approach, plants are globally connected. Such connectivity helps to utilize plant information through Information technology to be implemented in Operational technology (OT). Let us now see: What is system? System is a part of universe within certain domain in space and time. What is environment? Outside the frontier of system is the environment. What is an intelligent system? Conceptually an intelligent system learns how to act in a given environment, to reach its objective. Intelligent system fixes a temporary object that it has derived from the main objective. It has a few senses to gather knowledge about the given environment, to reach to objectives. The system then stores these sense impressions as elementary concepts. Working on these concepts it develops a new knowledge and stores the relationship and enriches the concept. To continue with the internal information it checks the inputs for update, and build up the present situation. Also, it looks to its memory finds the set of rules and chooses best suited (rule based) for the application and perform action. This concept has now been extended further to integrate various sensors/devices with the help of internet IP addresses, which finally gave rise to the concept of Internet of things (IoT). Before going to any further details it is necessary to recapitulate some fundamental issues of control system. For convenience, a few control terms have been discussed in Figs. I 1.0a and I 1.0b.

In order to implement control systems there will be a number of constraints, some of these constraints have been listed below:

1. Accurate measurement/sensing of the controlled variables: It is not always possible to directly measure the controlling parameter e.g., flow measurement, derived from differential pressure measurement.

2. Multivariable interactions: In real process there could be some parameters, which singly vary with process change e.g., minimum flow recirculation of pump. However, in most cases multiple interactive variables need to be regulated to get control over the process e.g., Combustion/Temperature control in utility boiler.

3. Process Dynamics and Process Gain: Process dynamics hence process gain is important for control implementations. This is important in cases of nonlinear process as it can result variations in behavior of control. Response may be sluggish as well as it can give rise to oscillation [1].

4. Signal to noise ratio (S/N): Any industrial systems, there will be lots of noise to create disturbances. So, signal to noise ratio is an important factor to consider.

5. System Safety and security: Here, safety stands to represent safety of personnel, property and environment (not equipment and system protection, which is taken care of by control andand protection) on account of external factors. Since in present days control systems are computer based integrated system and/or IoT there will be chances of getting the system degraded on account of cyber-attacks. Security mainly stands to represent protection against such attacks. Cyber security is an important issue.

6. Operational constraints: Constrains from difficult process operating condition (e.g., say high pressure/temperature) cannot be overestimated in control system design and may call for additional protection and safety.

7. Environmental impact: While designing control systems it is important to take into account the impact of environment on control system as well as impact of control systems on environment must be considered.

8. Production Specification and economics: The control system must ensure delivery of product as per specification with lesser loss and higher efficiency. Also, it should ensure that cost of production is at the minimum level and profit is maximized. In competitive market in order to get better edge over others, people go for digital transformation for best utilization of resources.

1.0.1. Requirements for plant automation conceptual discussions

Plant control and automation system consists of four basic elements:

• A measurement/sensing to know the process value and/or status of the process/system of interest i.e., sensing

Figure I 1.0a  Explanation of a few terms in control system.

Figure I 1.0b  Common and normal mode rejection ratio.

• A controller/logic solver meant to take action based on the set value/condition and measured value/sensor status

• An output signal from the controller/logic solver to manipulate the process

• The process/system itself (that reacts to the control signal to produce change).

From the above it transpires that there are two kinds of process variable viz. input variables and output variables.

• Input variables: Input variables convey the process (measurement) value and/or process status on account of effect of external manipulation/effect of surroundings on the process

• Output variables: In contrast to the above, they convey the effect of process on the surroundings.

In any control systems two most important input types are:

• Process Variable (PV): Normally Process variable (PV) is the variable (s) that represents the state of the process, so that by automatically adjusting another variable(s) the desired state could be achieved. This can be internal or external. So, process variable stands to represent one of the input signal to the controller, which is measured/sensed by field devices for controlling the process.

• Manipulating Variable (MV): The manipulating variable (MV) is a process/system variable(s), which needs to be manipulated in order to regulate the process.

• Control variable: Particular variable and/or status of any device to be regulated is termed as control variable i.e., the variable chosen to represent the state of the system is controlled variable (s).

• Reference/set point: The desired condition of the controlled variable is referred to as Reference/set point.

Conceptually all these variables have been depicted in Fig. I 1.0c.

The unmeasured variables may act as noise also to influence control action.

1. Open and Closed loop Explanation: Based on feedback action, the controls may be broadly divided into two major types namely open loop control and closed loop control as shown in Fig. I 1.0d.

    Let us take simple examples of pressurized fluid tank level control. In this the inflow of fluid is regulated to maintain the level in the tank with the help of controller and control valve. This is an example of closed loop control system. Here controller input is the difference between level set point (SP) and actual level (MV—as negative feedback). The output of the controller regulates flow to the tank to maintain level. So, there will be one set point and actual level of the tank—acting as measured values and as a negative feedback signal. This negative feedback level signal makes closed control loop. On account of vapor inside the tank, there will be pressurization inside the tank, especially when level goes high. This is condition is dangerous for the operation. So, when pressure inside the tank goes above a set point, for the safety, shutdown valve will be closed to cut the supply line to the tank, irrespective of regulating valve condition (status). In this pressure control, pressure signal acts as safety signal NOT as feedback, (only comparison with safety set value). So, this is open loop, as there is no feedback from the process, but as a safety measure. During the discussions feedback signal has been discussed, but there could be feed forward signal as well to improve the response of the loop.

2. Basic Plant control System and Safety Instrumentation System (BPCS and SIS): From the discussions above, it has been noted that there are two types of controls one CLCS to maintain level in the tank and OLCS to cut off supply line in case of high pressure in the tank. It is also seen that in the above case, both controls are independent. In many plants with hazardous applications, from safety point of view, two sets of controls independent of each other are necessary. One is Basic plant control system (BPCS) and here level control (CLCS) is acting as BPCS and another independent pressure control acts as SIS.

Figure I 1.0c  Process variables.

Figure I 1.0d  Open and closed control loop.

3. Regulatory and Servo controls: In process plants majority of the loops are regulating type, where there will be desired set point for a process parameter and aim of the controller is to minimize the difference between PV and set point. So, in regulatory control, there will be a fixed or adjustable set point e.g., for main steam temperature control at lower load, the set point may be derived as a function of air flow. In case of Servo control, the main aim of output to follow desired trajectory specified by input. In servomechanism main issue is determination of controlled variables in accordance with the changes of reference. These are found mainly in manufacturing plants e.g., numerical control of milling system. An automatic device servomechanism (or servo control) also uses error-sensing negative feedback to correct the action of another. In most of the cases servomechanism deploys encoder or position feedback mechanism to ensure the output is achieving the desired effect. Therefore, one may argue that

• Regulating controls are used to eliminate process disturbances and so, in regulatory control the disturbances are rejected by the control system.

• Servo controls follows the changes in set point, meaning that, in servo controls, when set point is changed and PV moves to SP.

Before going details in the subject, let us now have some idea about how various chapters in this volume of book have been arranged.

1.0.2. Synopsys of issues covered in this volume of the book

Prior to moving to technical details it is better to put forward how the book has been developed. The book entitled Plant Intelligent Automation and Digital Transformation has been developed in four volumes (Vol I through IV). The volume subtitles are:

• Vol. I: PROCESS AND FACTORY AUTOMATION.

• Vol. II: MIS AND HW-SW IMPLEMENTATION

• Vol. III: AI AND COMMUNICATION (FIELD AND NETWORK.

• Vol. IV: SECURITY, IoT/IIoT AND APPLICATIONS (Also appendices)

• Appendix A: Wired Communication Medium

• Appendix B: Wireless communication types (RFID, Bluetooth)

• Appendix C: Area Classification, Enclosure class and Intrinsic safety

• Appendix D: Fault tolerance and fault tolerant Network

• Appendix E: Electrical SCADA

• Appendix F: Simulation and Software models

• Appendix G: Digital Twin and Sustainability

In order to get fair idea about this Volume I of the book, short discussions on various chapters of the book have been presented below:

1. Chapter 1: General discussions on Control Systems.

2. Chapter 2: Basics of Networking.

3. Chapter 3: Industrial data communication

4. Chapter 4: System diagnostics, security and safety.

5. Chapter 5: Control Intelligence and futuristic approach.

6. Chapter 6: PLC and Open loop control systems (OLCS).

7. Chapter 7: Open loop controls in Process and PLC Details.

8. Chapter 8: Batch Process control and Automation.

9. Chapter 9: Manufacturing and Factory Automation.

10. Chapter 10: Building and Service Sector Automation.

11. Chapter 11: PLCOPEN Concept and Application.

12. Chapter 12: PC Based control, MTP, FDT, EDD and OPC.

13. Chapter 13: CLCS—An Approach to DCS-MIS.

14. Chapter 14: Standalone controllers in process Automation.

15. Chapter 15: DSC Features, elements and HW details.

16. Chapter 16: General Description and configurations for DCS.

17. Chapter 17: DCS Software aspects, APC AND MIS DISCUSSIONS.

18. Chapter 18: DCS in Electrical controls.

1.0.3. Microprocessor: microcomputer basics (brief recapitulations)

The heart of digital computer is central processing unit (CPU) with its timing functions. Basically, the entire central processing unit (CPU) is a programmable electronic VLSI chip known as microprocessor . Microprocessor in conjunction with memory and input/output devices forms a microcomputer. Basic functions of CPU and associated hardware are to manipulate data in a certain manner specified by the system designer to perform computation and decision making. Store-program concept implies that programs (instructions) are executed sequentially based on instructions stored in the memory locations. Therefore, microprocessor has instructions sets, which could be provided in binary machine code and mnemonics. The instruction sets in binary patterns is referred to as machine language. These binary patterns, when are given abbreviated names, these are referred to as mnemonics (assembly language). Microprocessor (as CPU) along with Memory, Peripherals (I/O) constitute microcomputers. Microcontroller (MCU) could be conceived as an embedded microcomputer peripheral are integrated on a single circuit chip used for specific purpose. In majority applications these are embedded System (meant special functionalities ref: vol.II). Let us explore basic definitions of terms and functioning of the system:

Definition of terms: A few basic definitions of terms and function are:

• Bit and Word: A bit stands to represent a single binary digit. Word refers to the basic data/bit size that can be processed by the Arithmetic logic unit (ALU). A 16-bit binary number is called a word (16-bit processor). Number of bits that can be stored in memory and/or register is memory word.

• Bus and System bus: A group of lines used to carry similar information is called a Bus Three bus types microprocessor-based systems are:

• Address Bus: Address Bus carries the address, in a unique binary pattern, of a memory location or an I/O location/port e.g., 16 bit address bus (Intel 8085 Fig. I 1.0g) has 16 lines to address 2¹⁶ different locations in hexadecimal format.

• Control Bus: The control bus carries control signals, meant for selection (enabling) of memory or I/O device from the given address, direction of data flow and synchronization of data transfer (Fig. I 1.0g).

• Data Bus: The data bus is used to transfer data between processor and memory or I/O device and between I/O devices (Figs. I 1.0e1 and I 1.0g ).

1. Basic component of MPU: Microcomputer in its preliminary form consists of:

Figure I 1.0e  Microprocessor with Peripherals and machine cycle.

• Input: Input medium is used to enter data and instruction from real world to the system

• Central processing unit (CPU): It contains necessary circuitry required access appropriate memory location and interprets resulting instruction. There are two sections e.g., calculating section for carrying out arithmetic and logical operations on the data from memory and decision makings section for selecting alternative course of action based on computed result. CPU mainly consists of

• Sets of Registers: There are a set of register, which enable CPU to perform its functions e.g., MAR/MDR acting as temporary storage for memory address/data respectively.

• Arithmetic Logic unit (ALU): ALU in association with Accumulator, register and control unit processes instruction executions.

• Memory: Memory provides storage space for data and instruction, so that these may be obtained for making calculations as well as storing the results in orderly manner.

• Output: This is the device by which results are delivered to user.

2. Instruction cycle and Machine cycle: Microprocessor based systems operate in synchronism with clock (pulses). There may be several clock cycles necessary to accomplish an instruction—referred to as Instruction cycle. There may be several machine cycles for one instruction cycle. Machine cycle consists of:

• Fetch cycle: It contains two parts: CPU provides the address of an instruction in memory location through (MAR), then address is decoded to read the instruction from memory in to MDR. This complete timing is fetch cycle (Ref: Fig. I 1.0e2)

• Execution cycle: This timing is for decoding of instruction and the operation requested is performed (Ref: Fig. I 1.0e2).

3. Instruction and Data word flow [2]: Typical Instruction and data word flow in microcomputer has depicted in Fig. I 1.0f1 and 2 respectively.

• Instruction flow: Content of PC is placed in MAR (for memory location), which is decoded and placed in memory. Instruction of memory is read via MDR and placed in instruction register (IR) for decoding by instruction decoder. After the decoded instruction is executed PC is incremented/reset.

• Data Flow: Data input from I/O device or memory enters and placed in accumulator. After completing the operation as shown in Fig. I 1.0f2, output data words are sent to memory or to output device via I/O bus shown in Fig. I 1.0.3-1.

4. Typical Microprocessor Parts (Intel 8085): Bit size, nos. of pin, clock cycle, memory and power supply for microprocessor varies with microprocessor chosen e.g., Intel 8085 these are 8 bit, 40 pin, 3MHz, 16 bit address bit (64KB memory) and +5V power respectively on the contrary core i7 has 4.9GHz with 12MB cache; (upto 64GB). Various other types are: Intel X86, Motorola power PC, Zylog Z80. Basic components are:

Figure I 1.0f  Instruction and data flow.

• ALU and registers: ALU and registers already discussed above, additionally there exists flag register also. These are set or reset after an operation according to data condition of the result in the accumulator and other registers for temporary storage of data. Registers can be paired to handle higher bit operations.

• Program Counter (PC): This register is a memory pointer to sequence the execution of the instructions through increment of next memory address.

• Stack Pointer (SP): This register is also a memory pointer for pointing a memory location in R/W memory, called stack.

• Instruction Register/Decoder: This register is used to store temporarily the current instruction of a program. Latest instruction sent here from memory prior to execution. Decoder decodes or interprets the instruction as detailed in. Fig. I 1.0f.

• Control unit: This is responsible for generating signals on data bus, address bus and control bus (already discussed) within MPU to carry out the instructions. Bus arrangement in microprocessor (Intel 8085) has been depicted in Fig. I 1.0g.

5. Operating System: Operating System: In simple term Operating system (OS) can be conceived as interface between hardware and software to take care of underlying complexity of the system.

• OS Functions: Major functions of OS shall include: Making convenience to use the system, provide consistent Application program interface, efficient use of HW and SW resources, so that each application gets chances to use and allow development, testing and addition of new system functions most effectively.

Figure I 1.0g  Bus system for microprocessor.

• OS Types: There are several types of OS such as single user with single/multitasks, multiuser and Real time operating system (RTOS) used for plant control systems.

6. Polling and Interrupts: Interrupts and polling in processor OS are important functions.

• Polling: Polling refers to a process by which processor/controlling checks device readiness/state of an external device (lower end device). If not ready it goes back to its other work. In large network, polling is used to periodically discover and monitor network devices. It is done utilizing Simple network management protocol (SNMP) and Internet control message protocol (ICMS—pings)

• Interrupt: In contrast to polling, here the device notifies the CPU that it needs servicing. As CPU has a wire interrupt it is a hardware mechanism.

7. Microprocessor in a device: When microprocessor is put in a device it alone cannot function. We know to make it functional we need software programming of the device to get the required output. There are usually two levels on any device viz. OS and the application software(s) that runs on top of the operating system. These applications expand the functions of the device beyond what is offered by the operating system. There is another software function referred to as middleware (I 2.0.7) works behind the scenes, to allow these two levels to communicate and interact with each other to expand the device or system capability.

1.0.4. Control implementation issues

In Section 1.0.1 various terms have been defined. Here, these terms have been elaborated through Fig. I 1.0h for understanding of control system. Let is now look at OLCS and CLCS.

1. Open loop control system (OLCS): As shown in Fig. I 1.0h2, in an open-loop control system a controller issues a command based on available in input. The controller output goes to actuate the associated Final control element and/or actuator. So, an open-loop control system utilizes an actuating device to control the process directly without using feedback. These are for interlock and protection purposes as seen in BMS ATRS in power plant for example. After issuance of the command, there may not be any feedback to the control system. However, in reality in there may be some feedback, which is not directly used in control but is helpful in assuring control functions properly. Such signals are often referred to as check back signal. In many control systems after issuance of command, a specified time is waited for, within which check back signal (s) ensures correct implementation of output command. In some sequential control, there can be check back signal (s) to ensure that previous command has been properly executed within specified time, before issuance of command for next sequence.

2. Closed loop control system (CLCS): According to Din standard DIN19226, closed loop control is a process whereby one variable (controlled variable) is continuously monitored and compared with another variable (the reference variable) and influenced in such a manner as to bring about adaptation to the reference variable. The characteristic feature of closed loop control is the closed action flow in which the controlled variable continuously influences itself in the action path of the control loop. one gets that—Continuous here also includes a sufficiently frequent repetition of identical individual processes of which the cyclic program sequence in digital sampling controls is an example [5]. A feedback control system is used to maintain a prescribed relationship of measured variable to desired set point by comparing functions of these parameters and using the difference as a means to control the process. Simple CLCS loops have been shown in Figs. I 1.0h3 and I 1.0h4. With reference to Fig. I 1.0h3, it us seen that at controller desired set point is compared with measured variable to generate error signal, which will drive the controller to get desired position signal for the actuator of Final control element (FCE). Positioning of Final control element (FCE) will regulate the manipulated variable. This is a single variable control but in reality there could be a numbers of parameters need to be controlled for complex systems where the interrelationship of many controlled variables must be considered in the control scheme. A typical such control system with multivariable control system has been depicted in Fig. I 1.0h4. There are a few advantages of Feedback loops used in both regulating and servo controls as listed below:

Figure I 1.0h  Process and control Configuration.

• Corrective action: On account of corrective action the loop is less sensitive to load/parameter changes.

• Response: On account of feedback naturally these loops provide comparatively better accuracy and response in transient and steady state.

• Control means: Various control means such as P.PI, PID adaptive gain etc. can be implemented.

CLCS has a number of limitations also such as it is costlier than OLCS for large complex systems and when not properly tuned may give rise to instability in the system.

Feed forward control: Feed forward control can be easily conceived from a small example as depicted in Fig. I 1.2a. Suppose there is a tank with inlet and outlet lines and having control valve in the inlet line to maintain in the tank. Based on level in the tank inlet control valve is regulated, meaning that even after outlet demand changes, control loop cannot respond till there is change in level, hence to instability in the loop. Now if outlet flow is also measured and incorporated in the loop, then no sooner there will be change in demand in outlet flow, loop starts acting. Thus, it is observed that feed forward signals can be used in the loop to make the control loop more responsive. In this loop disturbance signal (s) is often inputted to controller/control system as an anticipatory signal so that control system can correct itself based on this anticipatory signal. These disturbance signals are those signal(s), which has influence/impact, especially for nonlinear impact (e.g., pH control), on the control but not a measured variable. Connecting disturbance signal (s) to the control system may vary with designer's choice based on the process dynamics. Feed forward signals have been shown in Fig. I 1.0h5, as well as Fig. I 1.0i where two alternatives for feed forward signal connections have been shown. Feed forward controls are good for processes with high dead time. It is sensitive to process parameter variations and are helpless to unmeasured disturbances. Feed forward controls are used:

• When it is important to maintain process value at desired point

• When the disturbance(s) is measurable

• Disturbance dynamics have impact on loop especially for nonlinear impact [10].

3. Lead/Lag (compensator) in the control loop: As the name signifies, lead/lag stand to represent phase difference of signals in time domain. Lead/lag compensator in the control loop are used to improve speed of response of the loop/improvement in steady state error for the control system respectively. In combustion control lead/lag circuit is used as a safety precaution to ensure air enriched condition. In this air flow always lead and fuel lags i.e., whenever there is need for increase in fuel flow, through lead/lag, it is ensured that air increases first before fuel is increased. Similarly, when fuel is to be reduced, first fuel is reduced before reduction of air. This has been elaborated in Fig. I 1.2a2. In feed forward control lead and lag time constants are included to get right timing of disturbance signal. Lead time constants are added based on process lag. Lag time constant used to slow down set based on process lag between disturbance and measured (process) variable.

4. ON OFF control: ON OFF control is basically a type of feedback proportional control with high gain. Domestic temperature controls are very good examples of two position/ON OFF controls as shown in Fig. I 1.0j. Here, control system makes the actuator meant for manipulated variable to fully open or fully close to maintain set point. Many recirculation controls e.g., small boiler feed pump (BFP) adapts this type of control. As long as the flow through the pump is above the set point recirculation valve will be closed. When the flow through the pump is below the set point; sensed by flow switch and contact changes over of the flow switch will cause to fully open the recirculation valve. When the flow through the line is above set point, the flow switch actuates in opposite direction to close recirculation valve. In ON OFF control activation and deactivation points are not same giving rise to hysteresis based on dead band of the flow switch/controlling device.

Figure I 1.0i  Feed forward control.

Figure I 1.0j  ON OFF control.

    Other types of CLCS loops have been covered in Section I 1.2.0 also.

5. Short History of Automatic control system: There is a long history of feedback and automatic controls. Probably it has its history way back in 300 to 1 B.C. viz. water clock. The word feedback is a 20th century neologism introduced in the 1920s by radio engineers to describe parasitic, positive feeding back of the signal from the output of an amplifier to the input circuit [3]. James watt developed fly wheel governor in 1769. Major controls in 19th century were concerned with controls of process parameters like controlling pressures, temperatures, liquid levels and machine speed control issues. Prior to World War II (WWII) major development of control systems were mainly about control stability [24]. In this connection contribution of Bode, Nyquist, and Black at Bell Telephone Laboratories cannot be overestimated. During WWII discipline in automatic control came into effect with suitable infrastructure (root locus). Period between 1935 and 1950 is known as classical period. Modern state space approach to control was derived from work by Poincaré and Lyapunov. Period between 1935 and 1950 is known as classical period of Automatic control systems. In 1950s, great change in control system had been introduced with application of digital computers/technologies. Table I 1.0a shows major developmental works.

Modern Digital control Implementation methods: In modern plants, smart intelligent control systems are deployed to implement various controls with optimizations, HMI and MIS. Now control systems have been extended to the outer world also to utilize information details through Information technology (IT) to Operational Technology (OT) to get better plant performance. Internet of Things (IoT) connects controls with outside world and people are engaged in achieving Industry 4.0 through digital transformation. All such details will be detailed out in various volumes in this book. Based on variations of architectures, smart control systems can be conceived as Digital (distributed) Control System (DCS) with system integrations, by HART, Fieldbus OPC and other modern tools. For better understanding of such integration, hierarchical structure of DCS, as depicted in Fig. I 1.0k, can be developed as a completely integrated network. With introduction of microcomputers and microcontrollers, distributed computer control architecture became very popular because it can overcome the limitations of central control system. The distributed systems stand to represent distribution of intelligence and these can be geographical and/or functional. Foxboro TDC 2000 is one of the earliest distributed systems. Normally, in hierarchical DCS there may be five levels such as Field level (smart field devices), Controller level, Unit MIS level, Plant level and enterprise level.

Figure I 1.0k  Hierarchical network control.

Table I 1.0a

    Understanding of control systems will be incomplete without some knowledge on control theory and associated basic mathematical background. [For details standard college level book on Mathematics may be consulted as it is beyond the scope of this book to detail out these in a limited book volume].

1.0.5. Mathematical approach for control systems

Let us recapitulate, basic mathematical approach necessary for control theory!

1. Fourier Transform (FT): Fourier transform provides a frequency domain representation of time domain signals. Fourier Transform is given by:

(I 1.0a)

    By basic definition it is has no real part. Fourier Transform of a real signal is always even conjugate in nature. FT is developed for stable system whereas Laplace transform is defined for both stable and unstable systems. From basic definition it has imaginary part only and is used for transient analysis and frequency spectral analysis.

2. Laplace Transformation: With Laplace Transform it is possible to get a very simple and elegant method of solving linear differential equations, which as mathematical model represent states of various processes, as simpler algebraic equations. In certain cases, it is almost impossible get analytical solution of mathematical models in time domain with standard numerical solutions. Laplace Transform provides such solution easily. For a function f(t) in time domain, Laplace transform is f(s) is defined as:

(I 1.0b)

    Where s represents Laplace domain and t and s are independent variables. The variable s is defined in the complex plane as:

(I 1.0c)

    Laplace transform, used in process control systems, is defined in positive time domain (0 to ). However, from mathematics point of view it can be defined for (−)infinity to (+) infinity. This is called bilateral Laplace transform. So, when in bilateral Laplace transform s is so chosen that real part is σ=o, then it is Fourier transform. Another important issue to be noted that on account of real part (σ) in Laplace operator, when Laplace transform is taken on a function f(t) it goes to S plane so that one can analyze, amplitude, phase difference etc. created due to transfer function for an input to the system but it does not take it to frequency domain. Laplace transform for a few standard functions are given in Table I 1.0b. Standard mathematical book may be referred to.

3. Transfer Function: If Z(s) and P(s) are two polynomials in s domain then transfer function G(s) in general form is represented as ratio of these two polynomials. So

(I 1.0d)

    It is often called feed forward Transfer function. Open loop transfer function stands to represent the ratio feedback B(s) by Error E (s) in s plane. These have been discussed at length in I 1.3 model-based systems.

4. Poles and zeros: With reference to Eq. I 1.0d, it is seen that a transfer function is defined as ratio of two polynomials. The roots of the polynomial, P(s), and roots of the polynomial, Z(s), are called poles and zeros respectively. It signifies that at these points, the transfer function of denominator and numerator respectively would become zero. This means as s approaches Zero transfer function approaches 0. On the contrary when s approaches pole, transfer function approaches infinity hence alarming from stability point of view. For analysis in S plane and Z plane I 13.0.0 may be referred to.

5. First Order Process: A first order process with input u(t) and output y(t) can be represented by differential equation in generalized form:

(I 1.0e)

    defining τp= and kp= ; transfer function G(s) can be obtained as

(I 1.0f)

    where τp and kp are time constant and gain respectively. Simple LR/RC circuits are example of a first order system. Whereas, LRC circuit is a second order system.

6. Second and Higher Order Process: A second order process with input u(t) and output y(t) can be represented by differential equation in generalized form:

(I 1.0g)

    Transfer function,

(I 1.0h)

    Here = ; 2ξτ= ; and kp=

    In similar manner it is possible to assess higher order systems.

    For convenience, lapse transform of derivatives functions have been noted below:

(I 1.0i)

(I 1.0j)

    For analysis of first/second order system refer I 13.2.0.

7. System Response: The complete system response of controller has two parts viz. Transient response and steady state response. i.e., output y(t)=ytr(t)+yss(t).

Table I 1.0b

• Transient Response (tR): When input is applied to control system, it does take certain time to reach steady state condition. The time taken, to reach steady state is referred to as Transient Response. Transient occurs just after switching ON and/or after abnormal conditions viz. abrupt load change/short circuiting. At stable system it is:

(I 1.0k)

• Steady state Response: As the name suggests, this occurs after system settles and at the steady system starts working normally.

Both transient and steady state response area have been marked in Fig. I 1.0l1.

8. Explanation of System response: Let us consider a second order system with gain k and system time constant T, with rearrangement of Eq. I 1.0h it will be

(I 1.0l)

    Here ξ= is called damping ratio, whose value would decide how the system is damped. Again, = is the natural frequency. Taking Eigen value of Eq. (I 1.0l) one can obtain damping frequency for the system. Depending on the value ξ in, Eq. (I 1.0l), the system could be three case as listed below and shown Fig. I 1.0l2:

• Critically Damped: (when