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Programmable automation controller
CHAPTER
PROGRAMMABLE AUTOMATION CONTROLLER
8
8.1 MODERN INDUSTRIAL APPLICATION It is challenging to implement a modern industrial application as it sometimes comes with a daunting mix of requirements. For example, a typical control system must be able to interface with signals from simple sensors and actuators, yet for many modern applications this is merely the starting point. Modern industrial applications often need capabilities such as advanced control features, network connectivity, device interoperability, and enterprise data integration. These modern requirements extend far beyond the traditional discrete-logic-based control of input/output (I/O) signals handled by a programmable logic controller (PLC). Most PLCs are programmed using ladder logic, which has its origins in the wiring diagrams used to describe the layout and connections of discrete physical relays and timers in a control system. Applications that diverge from or expand beyond this model become increasingly hard to program in ladder logic. For example, mathematically complex applications such as proportional–integral– derivative (PID) loops used for temperature control involve floating-point arithmetic. PLCs must often be enhanced with separate – and separately programmed – hardware cards to perform these operations.
8.1.1 MAKING A PLC MORE LIKE A PC It is a challenge to use a PLC to meet modern application requirements for network connectivity, device interoperability, and enterprise data integration. These types of tasks are usually more suited to the capabilities of a computer (PC). To provide these capabilities in a PLC-based application, additional processors, network gateways or converters, “middleware” software running on a separate PC, and special software for enterprise systems must often be integrated into the system. A programmable automation controller (PAC) is a compact controller that combines the features and capabilities of a PC-based control system with that of a typical PLC. • PLC feel • Modular footprint, industrial reliability • Wide array of I/O modules and system configurations • PC power • Large memory and high-speed processing • High-level data handling and enterprise connectivity • Extensive communications capability, multiple protocols, and field networks. PACs are most often used in industrial settings for process control, data acquisition, remote equipment monitoring, machine vision, and motion control. Additionally, because PACs function and communicate over network interface protocols such as TCP/IP, OLE for process control (OPC) and SMTP, Industrial Process Automation Systems Copyright © 2015 Elsevier Inc. All rights reserved
301
302
CHAPTER 8 Programmable Automation Controller
PACs are able to transfer data from the machines they control to other machines and components in a networked control system or to application software and databases. PACs are most often used for complex machine control, advanced process control, data acquisition, and equipment monitoring and motion control. The term PAC was given by ARC (Automation Research Corporation). A PAC offers the following features: 1. Helps users of automated hardware to define the applications they need. 2. Gives the vendors a term to effectively communicate the characteristics and abilities of their product. ARC also made and explained a few rules or guidelines for a device to be considered as a programmable automation controller. • Single platform: The device must operate using a single platform. It should be true for single or multiple domains and in drives, motions, and process controls. • Single development platform: The device must employ a single development platform, using a single database for different tasks in all the disciplines. • The device must tightly integrate controller hardware and software. • The device must be programmable by using software tools that can design control programs to support a process that flows across several machines or units. • The device must operate on open, modular architectures that mirror industry applications, from machine layouts in factories to unit operation in process plants. • The device must employ de facto standards for network interfaces, languages, and protocols, allowing data exchange as part of networked multivendor systems. • The device must provide efficient processing and I/O scanning.
8.1.1.1 Functional benefits The characteristics used to define a PAC also explain the benefits that can be obtained from its industrial installation and application. A PAC can meet complex requirements without the need for additional components such as a PLC. Improved control system performance is experienced through high integration of hardware and software. Integrated development environment (IDE), which is used in the manufacturing of a PAC, uses a tag name database that is used and shared by all the development tools. A PAC only needs one software package to cover all the existing automation needs and the ones that may arise in the future and does not need utilities from different vendors. The control systems can be upgraded easily. Owing to its compact size, a PAC uses lesser space compared to other options.
8.1.1.2 Financial benefits PACs offer multiple financial advantages. The overall cost of the control system is lowered because hardware is less expensive and less development and integration time is needed. Deploying a PAC is often more affordable than augmenting a PLC to have similar capabilities. There is also an increased return on assets, reduced lifecycle costs, and lower total cost of ownership (TCO) due to extending an automation system’s range of applications (also known as its domain expertise). The ability to add I/O as separate modules means that a minimum number of modules needed for initial development can be used during design, and the remaining modules added toward the end of the project.
8.1 Modern industrial application
303
8.1.2 PAC VERSUS PLC Generally, PACs and PLCs serve the same purpose. Both are primarily used to perform automation, process control, and data acquisition functions such as digital and analog control, serial string handling, PID, motion control, and machine vision. The parameters within which PACs operate to achieve this, however, sometimes run counter to how a PLC functions. Unlike PLCs, PACs offer open, modular architectures, the rationale being that because most industrial applications are customized, the control hardware used for them needs to allow engineers to pick and choose other components in the control system architecture without having to worry about compatibility with the controller. PACs and PLCs are also programmed differently. PLCs are often programmed in ladder logic, a graphical programming language resembling the rails and rungs of ladders that is designed to emulate old electrical relay wiring diagrams. PAC control programs are usually developed with more generic software tools that permit the designed program to be shared across several different machines, processors, HMI terminals, or other components in the control system architecture.
8.1.3 APPLICATION OF PAC PACs meet the complex demands of modern industrial automation applications because they combine features of more traditional automation technologies such as PLCs, distributed control systems (DCSs), remote terminal units (RTUs), and personal computers (PCs).
8.1.4 APPLYING THE PAC TO A MODERN INDUSTRIAL APPLICATION Let us look more closely at how a PAC is applied to a modern industrial application.
8.1.4.1 Single platform operating in multiple domains The single PAC can be used for operating in multiple domains to monitor and manage a production line, a chemical process, a test bench, and shipping activities. To do so, the PAC must simultaneously manage analog values such as temperatures and pressures; digital on/off states for valves, switches, and indicators; and serial data from inventory tracking and test equipment. At the same time, the PAC is exchanging data with an OLE for process control (OPC) server, an operator interface, and a SQL (structured query language) database. Only PAC is capable of handling these tasks at the same time without need for additional processors, gateways, or middleware.
8.1.4.2 Support for standard communication protocols The PAC, operator, and office workstations; testing equipment, production line, and process sensors and actuators; and barcode reader are connected to a standard 10/100 Mbps Ethernet network installed throughout the facility. In some instances, devices without built-in Ethernet connectivity, such as temperature sensors, are connected to I/O modules on an intermediate Ethernet-enabled I/O unit, which in turn communicates with the PAC. Using this Ethernet network, the PAC communicates with remote racks of I/O modules to read/ write analog, digital, and serial signals. The network also links the PAC with an OPC server, an operator interface, and a SQL database. A wireless segment is part of the network, so the PAC can also communicate with mobile assets such as the forklift and temporary operator workstation.
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CHAPTER 8 Programmable Automation Controller
The PAC can control, monitor, and exchange data with this wide variety of devices and systems because they use a common standard network technology and protocol. This example includes wired and wireless Ethernet networks, Internet protocol (IP) network transport, OPC, and SQL. In another control situation, common application-level protocols such as Modbus®, SNMP (simple network management protocol), and PPP (point-to-point protocol) over a modem could be required. The PAC has the ability to meet these diverse communication requirements.
8.1.4.3 Data exchange with enterprise systems The PAC exchanges manufacturing, production, and inventory data with an enterprise SQL database. This database in turn shares data with several key business systems, including an enterprise resource planning (ERP) system, operational equipment effectiveness (OEE) system, and supply chain management (SCM) system. The PAC constantly and automatically updates data from the factory floor, ensuring availability of timely and valuable information for all business systems.
8.1.5 SOFTWARE FOR PACs Because a key defining characteristic of PACs is that the same hardware can be used in multiple domains, including logic, motion, drives, and process control, it follows that the software must be capable of programming all control and monitoring tasks that must be done in multiple domains. The PAC software must handle discrete control, process control, motion control, remote monitoring, and data acquisition. And the software must let the developer mix and incorporate these as needed into control programs, so these programs can “flow” as the requirements of the application dictate. For example, the following are typical requirements for a small production facility with a combination of process and discrete control (e.g., micro brewery) for producing the end product (Figure 8.1): • Water is piped in from a spring a couple of miles away, so you need to monitor the pressure and flow of that water and security at the spring (remote monitoring using analog and digital devices). • You measure water quality as it enters your facility, track these data over time, and store it in your company database (data acquisition, database connectivity). • There may be more than one microbrew, so recipes, temperatures, and processing must vary (batch process control, PID loop control, and distributed control). • Operator interfaces mimic the process, providing secure interactive controls for technicians and operators. • Quality control is ensured by testing all products at several stages. Quality data are kept as required by government health authorities (monitoring, more data acquisition, and database connectivity). • In another building, the bottling line requires discrete control. As bottles come off the line, they are boxed and identified with radio-frequency identification (RFID) tags, then sent to shipping. • In the separate shipping area, boxed stock automatically moves via conveyors (discrete control) based on RFID tags (serial device connectivity). • Temperatures in the storage area are controlled and monitored. Energy usage is monitored and building systems are controlled throughout all buildings (remote I/O, distributed intelligence). • Production and inventory data go directly from machines and barcode readers to company computers; customer and shipping data flow in the opposite direction (database connectivity).
8.1 Modern industrial application
305
FIGURE 8.1 PAC Integration with multiple systems
This microbrewery is just an example of how several different types of control in different domains are required by a modern industrial automation application. Most industrial applications today are similarly varied. While the number of PACs needed depends on application requirements, each PAC can be used in any domain or in multiple domains. Because the application requires processes that flow into each other over space and time, the PAC software accommodates that flow and integrates these multiple domains into one system. I/O points and variables defined while building a control program (called a control strategy) are stored in a single tag name database. When you open the HMI development, OPC server, or database connectivity software, those defined items are immediately available for use. In summary, a PAC provides advanced control features, network connectivity, device interoperability, and enterprise data integration capabilities found in PLC- or PC-based automation controllers, all in a single compact controller. These features make the PAC essential for meeting the new and diverse requirements demanded in a modern industrial application.
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CHAPTER 8 Programmable Automation Controller
FURTHER READINGS The Future of Control by IEE Manufacturing Engineer August/September 2005. “PACs for Industrial Control, the Future of Control” Tutorial, National Instruments (Feb. 28, 2012). “Programmable Automation Controller” Information Presented in Wikipedia. New Generation Programmable Automation Controller. ETHERNET DIRECT. Columba Sara Evelyn (Ed.). Programmable Automation Controller.
PROGRAMMABLE AUTOMATION CONTROLLER
8
8.1 MODERN INDUSTRIAL APPLICATION It is challenging to implement a modern industrial application as it sometimes comes with a daunting mix of requirements. For example, a typical control system must be able to interface with signals from simple sensors and actuators, yet for many modern applications this is merely the starting point. Modern industrial applications often need capabilities such as advanced control features, network connectivity, device interoperability, and enterprise data integration. These modern requirements extend far beyond the traditional discrete-logic-based control of input/output (I/O) signals handled by a programmable logic controller (PLC). Most PLCs are programmed using ladder logic, which has its origins in the wiring diagrams used to describe the layout and connections of discrete physical relays and timers in a control system. Applications that diverge from or expand beyond this model become increasingly hard to program in ladder logic. For example, mathematically complex applications such as proportional–integral– derivative (PID) loops used for temperature control involve floating-point arithmetic. PLCs must often be enhanced with separate – and separately programmed – hardware cards to perform these operations.
8.1.1 MAKING A PLC MORE LIKE A PC It is a challenge to use a PLC to meet modern application requirements for network connectivity, device interoperability, and enterprise data integration. These types of tasks are usually more suited to the capabilities of a computer (PC). To provide these capabilities in a PLC-based application, additional processors, network gateways or converters, “middleware” software running on a separate PC, and special software for enterprise systems must often be integrated into the system. A programmable automation controller (PAC) is a compact controller that combines the features and capabilities of a PC-based control system with that of a typical PLC. • PLC feel • Modular footprint, industrial reliability • Wide array of I/O modules and system configurations • PC power • Large memory and high-speed processing • High-level data handling and enterprise connectivity • Extensive communications capability, multiple protocols, and field networks. PACs are most often used in industrial settings for process control, data acquisition, remote equipment monitoring, machine vision, and motion control. Additionally, because PACs function and communicate over network interface protocols such as TCP/IP, OLE for process control (OPC) and SMTP, Industrial Process Automation Systems Copyright © 2015 Elsevier Inc. All rights reserved
301
302
CHAPTER 8 Programmable Automation Controller
PACs are able to transfer data from the machines they control to other machines and components in a networked control system or to application software and databases. PACs are most often used for complex machine control, advanced process control, data acquisition, and equipment monitoring and motion control. The term PAC was given by ARC (Automation Research Corporation). A PAC offers the following features: 1. Helps users of automated hardware to define the applications they need. 2. Gives the vendors a term to effectively communicate the characteristics and abilities of their product. ARC also made and explained a few rules or guidelines for a device to be considered as a programmable automation controller. • Single platform: The device must operate using a single platform. It should be true for single or multiple domains and in drives, motions, and process controls. • Single development platform: The device must employ a single development platform, using a single database for different tasks in all the disciplines. • The device must tightly integrate controller hardware and software. • The device must be programmable by using software tools that can design control programs to support a process that flows across several machines or units. • The device must operate on open, modular architectures that mirror industry applications, from machine layouts in factories to unit operation in process plants. • The device must employ de facto standards for network interfaces, languages, and protocols, allowing data exchange as part of networked multivendor systems. • The device must provide efficient processing and I/O scanning.
8.1.1.1 Functional benefits The characteristics used to define a PAC also explain the benefits that can be obtained from its industrial installation and application. A PAC can meet complex requirements without the need for additional components such as a PLC. Improved control system performance is experienced through high integration of hardware and software. Integrated development environment (IDE), which is used in the manufacturing of a PAC, uses a tag name database that is used and shared by all the development tools. A PAC only needs one software package to cover all the existing automation needs and the ones that may arise in the future and does not need utilities from different vendors. The control systems can be upgraded easily. Owing to its compact size, a PAC uses lesser space compared to other options.
8.1.1.2 Financial benefits PACs offer multiple financial advantages. The overall cost of the control system is lowered because hardware is less expensive and less development and integration time is needed. Deploying a PAC is often more affordable than augmenting a PLC to have similar capabilities. There is also an increased return on assets, reduced lifecycle costs, and lower total cost of ownership (TCO) due to extending an automation system’s range of applications (also known as its domain expertise). The ability to add I/O as separate modules means that a minimum number of modules needed for initial development can be used during design, and the remaining modules added toward the end of the project.
8.1 Modern industrial application
303
8.1.2 PAC VERSUS PLC Generally, PACs and PLCs serve the same purpose. Both are primarily used to perform automation, process control, and data acquisition functions such as digital and analog control, serial string handling, PID, motion control, and machine vision. The parameters within which PACs operate to achieve this, however, sometimes run counter to how a PLC functions. Unlike PLCs, PACs offer open, modular architectures, the rationale being that because most industrial applications are customized, the control hardware used for them needs to allow engineers to pick and choose other components in the control system architecture without having to worry about compatibility with the controller. PACs and PLCs are also programmed differently. PLCs are often programmed in ladder logic, a graphical programming language resembling the rails and rungs of ladders that is designed to emulate old electrical relay wiring diagrams. PAC control programs are usually developed with more generic software tools that permit the designed program to be shared across several different machines, processors, HMI terminals, or other components in the control system architecture.
8.1.3 APPLICATION OF PAC PACs meet the complex demands of modern industrial automation applications because they combine features of more traditional automation technologies such as PLCs, distributed control systems (DCSs), remote terminal units (RTUs), and personal computers (PCs).
8.1.4 APPLYING THE PAC TO A MODERN INDUSTRIAL APPLICATION Let us look more closely at how a PAC is applied to a modern industrial application.
8.1.4.1 Single platform operating in multiple domains The single PAC can be used for operating in multiple domains to monitor and manage a production line, a chemical process, a test bench, and shipping activities. To do so, the PAC must simultaneously manage analog values such as temperatures and pressures; digital on/off states for valves, switches, and indicators; and serial data from inventory tracking and test equipment. At the same time, the PAC is exchanging data with an OLE for process control (OPC) server, an operator interface, and a SQL (structured query language) database. Only PAC is capable of handling these tasks at the same time without need for additional processors, gateways, or middleware.
8.1.4.2 Support for standard communication protocols The PAC, operator, and office workstations; testing equipment, production line, and process sensors and actuators; and barcode reader are connected to a standard 10/100 Mbps Ethernet network installed throughout the facility. In some instances, devices without built-in Ethernet connectivity, such as temperature sensors, are connected to I/O modules on an intermediate Ethernet-enabled I/O unit, which in turn communicates with the PAC. Using this Ethernet network, the PAC communicates with remote racks of I/O modules to read/ write analog, digital, and serial signals. The network also links the PAC with an OPC server, an operator interface, and a SQL database. A wireless segment is part of the network, so the PAC can also communicate with mobile assets such as the forklift and temporary operator workstation.
304
CHAPTER 8 Programmable Automation Controller
The PAC can control, monitor, and exchange data with this wide variety of devices and systems because they use a common standard network technology and protocol. This example includes wired and wireless Ethernet networks, Internet protocol (IP) network transport, OPC, and SQL. In another control situation, common application-level protocols such as Modbus®, SNMP (simple network management protocol), and PPP (point-to-point protocol) over a modem could be required. The PAC has the ability to meet these diverse communication requirements.
8.1.4.3 Data exchange with enterprise systems The PAC exchanges manufacturing, production, and inventory data with an enterprise SQL database. This database in turn shares data with several key business systems, including an enterprise resource planning (ERP) system, operational equipment effectiveness (OEE) system, and supply chain management (SCM) system. The PAC constantly and automatically updates data from the factory floor, ensuring availability of timely and valuable information for all business systems.
8.1.5 SOFTWARE FOR PACs Because a key defining characteristic of PACs is that the same hardware can be used in multiple domains, including logic, motion, drives, and process control, it follows that the software must be capable of programming all control and monitoring tasks that must be done in multiple domains. The PAC software must handle discrete control, process control, motion control, remote monitoring, and data acquisition. And the software must let the developer mix and incorporate these as needed into control programs, so these programs can “flow” as the requirements of the application dictate. For example, the following are typical requirements for a small production facility with a combination of process and discrete control (e.g., micro brewery) for producing the end product (Figure 8.1): • Water is piped in from a spring a couple of miles away, so you need to monitor the pressure and flow of that water and security at the spring (remote monitoring using analog and digital devices). • You measure water quality as it enters your facility, track these data over time, and store it in your company database (data acquisition, database connectivity). • There may be more than one microbrew, so recipes, temperatures, and processing must vary (batch process control, PID loop control, and distributed control). • Operator interfaces mimic the process, providing secure interactive controls for technicians and operators. • Quality control is ensured by testing all products at several stages. Quality data are kept as required by government health authorities (monitoring, more data acquisition, and database connectivity). • In another building, the bottling line requires discrete control. As bottles come off the line, they are boxed and identified with radio-frequency identification (RFID) tags, then sent to shipping. • In the separate shipping area, boxed stock automatically moves via conveyors (discrete control) based on RFID tags (serial device connectivity). • Temperatures in the storage area are controlled and monitored. Energy usage is monitored and building systems are controlled throughout all buildings (remote I/O, distributed intelligence). • Production and inventory data go directly from machines and barcode readers to company computers; customer and shipping data flow in the opposite direction (database connectivity).
8.1 Modern industrial application
305
FIGURE 8.1 PAC Integration with multiple systems
This microbrewery is just an example of how several different types of control in different domains are required by a modern industrial automation application. Most industrial applications today are similarly varied. While the number of PACs needed depends on application requirements, each PAC can be used in any domain or in multiple domains. Because the application requires processes that flow into each other over space and time, the PAC software accommodates that flow and integrates these multiple domains into one system. I/O points and variables defined while building a control program (called a control strategy) are stored in a single tag name database. When you open the HMI development, OPC server, or database connectivity software, those defined items are immediately available for use. In summary, a PAC provides advanced control features, network connectivity, device interoperability, and enterprise data integration capabilities found in PLC- or PC-based automation controllers, all in a single compact controller. These features make the PAC essential for meeting the new and diverse requirements demanded in a modern industrial application.
306
CHAPTER 8 Programmable Automation Controller
FURTHER READINGS The Future of Control by IEE Manufacturing Engineer August/September 2005. “PACs for Industrial Control, the Future of Control” Tutorial, National Instruments (Feb. 28, 2012). “Programmable Automation Controller” Information Presented in Wikipedia. New Generation Programmable Automation Controller. ETHERNET DIRECT. Columba Sara Evelyn (Ed.). Programmable Automation Controller.