Programmable Logic Controller (PLC) is microprocessor based industrial control system. It monitors inputs, makes decisions based on its program, and regulates outputs to automate a process or machine. As computer based system PLCs are typically programmed in an IEC 61131 programming language, and are designed for real-time use in rugged, industrial environments. Connected to sensors and actuators, PLCs are categorized by the number and type of input-output (I/O) ports they provide and their I/O scan rate. In addition PLCs can communicate with other process control components through data links. In the late 1960s, PLCs were first used to replace the hardwired networks of relays and timers in process assembly lines, which were partially automated at that time. Nowadays, the functionality of the PLC has enormously evolved and includes typical relay control, sophisticated motion control, process control, distributed control systems and complex networking. In general, the line between a general purpose programmable computer and a PLC is thinning.
This book is designed to provide information on successfully integrating a PLC into actual process control system. It not only deals with the PLC hardware and software, but all the surrounding building blocks that must be compatible in order to achieve a safe and reliable PLC industrial control system. The book has total 17 chapters, organized into two parts, two appendices, and a comprehensive Index. It comes with CD ROM in which reference material from Allen-Bradley is provided with the text. The book covers the following subjects:
Part I Programmable Logic Controllers - Fundamental Concept, is composed of nine chapters. It points to the fundamental PLC concepts, and introduces standard instructions programming techniques used in most PLC applications.
Chapter 1, Introduction to Programmable Logic Controllers, pp. 3- 34, gives an introduction to PLC technology. It provides an overview of various topics including a brief history of PLCs, description of system and components, PLC types, types of I/O modules, and comparison between ladder logic and PLC ladder logic.
Chapter 2, Input Devices and Output Actuators, pp. 35- 78, concentrates on the description and operation of most-common mechanical and electrical input devices and output actuators that interface with a PLC.
Chapter 3, Introduction to PLC Programming, pp. 79- 147, provides information about PLC programming. More details related to the number systems representation, organization of bits, bytes, words and memory, PLC memory and register structure, I/O addressing, status data addressing, inputs, outputs and scan time, and PLC program design, are given.
Chapter 4, Programming Timers, pp. 149- 190, has the following two goals. First, introduces a reader with the principles of operation and the functions of mechanical and electronic timers. Second, shows how the programmable timer instructions are applied in PLCs.
Chapter 5, Programming Counters, pp. 191- 225, describes the counter function present in PLCs, and the standard ladder logic used for counters.
Chapter 6, Arithmetic and Move Instructions, pp. 227- 259, concentrates on the following three aspects: 1) explanation of binary arithmetic including operations that manipulate with adding, subtracting, multiplying, and dividing binary numbers; 2) introduction to the arithmetic and move instructions; and 3) applications of arithmetic and move instructions in PLCs used in industrial automation systems.
Chapter 7, Conversion and Comparison Instructions, pp. 261- 297, covers details related to binary coded decimal and hexadecimal numbering systems, and conversion instructions. Next, it shows how the conversion and comparison instructions are used in creation programs for industrial automation systems.
Chapter 8, Program Control Instructions, pp. 299-332, focuses on instructions that change the flow of the program execution and covers some special purpose instructions.
Chapter 9, Indirect and Indexed Addressing, pp. 333- 347, introduces the reader with direct, indirect, indexed, and indexed indirect addressing modes. Some typical applications for the addressing modes are presented.
Part II, Advanced PLC Instructions and Applications, consists
of eight chapters. It expands the knowledge of PLCs and introduces some new
programming and networking technologies.
Chapter 10, Data Handling Instructions and Shift Registers, pp. 351- 384, presents instructions that are used for data handling and shift register applications. More details related to the realization of FIFO, LIFO and FAL functions, manipulations with bit pattern in register, changing a register bit status, and execution of shift register instructions and functions, are given.
Chapter 11, PLC Sequencer, pp. 385- 414, presents standard methodologies and concepts that we meet in the programming and operation of PLC sequencers and explains how ladder logic is used for realization of sequencers. Interesting details concerning electromechanical sequencing, empirical design process with sequencer, and troubleshooting sequencer instructions, are given.
Chapter 12, Analog Sensors and Control Systems, pp. 415- 466, covers analog PLC applications. It involves the reader with the operation and function of analog sensors, describes the structure of analog I/O modules, and provides the basics of the closed-loop control system operation.
Chapter 13, PLC Standard IEC 61131-3 Function Block Diagrams, pp. 467- 492, gives an overview of IEC 61131-3 graphic language, and discusses the Allen-Bradley implementation of the IEC 61131 Function Block Diagram language.
Chapter 14, Intermittent and Continuous Process Control, pp. 493- 523, concentrates on closed-loop feedback control techniques for on/off and continuous processes using PLC as the control element. Interesting details related to operation and realization of intermittent and continuous controllers, and principles of digital control, are given.
Chapter 15, PLC Standard IEC 61131-3 Structured Text Language, pp. 525- 542, gives a short overview of IEC 61131 text language, and provides the Allen-Bradley implementation of the IEC 61131 Structured Text Language.
Chapter 16, PLC Standard IEC 61131-3 Sequential Function Chart, pp. 543- 558, provides an overview of the Sequential Function Chart (SFC) graphic language. The Allen-Bradley instruction format is used in the description and implementation of the SFC language.
Chapter 17, Industrial Networks and Distributive Control, pp. 559- 579, introduces industrial networks such as Ethernet, ControlNet, DeviceNet, ant other vendor-unique networks. In the rest, an overview of distributive control and distributed I/O is given.
The book contains three appendices. Appendix A presents a Glossary. Appendix B deals with PLC module interface circuits, while Appendix C gives a brief history of PLC.
Programmable Logic Controllers is an excellent reference book on theory and operation of PLCs used in the control of production systems. The text offers practical introduction to the structure and use of PLCs in industry, covering both programming techniques and systems-level design issues.
It's up-to-date on the latest technology, it's comprehensive, and most of all, it's easy to read and understand. The book can serve as the textbook for senior year graduate course on the subject of automated process control. It is also worthwhile purchase for anyone interested in learning more about this very important field in control engineering and instrumentation.
If you need a good reference book on PLCs, it will be good to start with this.
According with the above mentioned, I highly recommend this book.
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