PC-based Control: Automation and Process Technology in One System
Published on : Thursday 08-12-2022
Franziska Dreisewerd and Lennart Winkler elaborate on the specific solutions Beckhoffoffers for the process industry.
With specific solutions for the process industry, Beckhoff is bringing together two automation concepts that developed separately for decades. While traditional PLC-based systems were optimised predominantly for short cycle times as a replacement for complex relay technology in machine controls, DCS (Distributed Control Systems) were developed for classic PID (Proportional Integral Derivative) closed-loop control focused mostly on scalability and system integration.
Driven by customer requirements and technological progress, both DCS and PLC have advanced and increasingly converged over the years. As a result, PLC systems have acquired ever more extensive visualisation systems. These are very similar to those that process engineers have used from the start and are implemented to manage many wide-ranging and complex processing workflows. Distributed control systems, on the other hand, were optimised with regard to their performance and cycle times, so that even very time-critical processes can now be mastered.
The systems also converged in terms of scalability. Distributed control systems, which were designed from the start for large installations with tens of thousands of I/Os, were successful with simple engineering and retrofit capabilities. However, for today’s PLC-based systems, even I/O points in the high five digits do not pose a challenge anymore. In addition, modern engineering environments like TwinCAT 3 software feature a broad range of libraries and plenty of function blocks so that even highly complex closed-loop control structures can be designed quickly and reliably.
Developments regarding system architectures also deserve special attention. Distributed control systems focused on decentralised architecture with distributed I/Os. These systems can collect data from areas exposed to explosion hazards with little wiring complexity and accommodate installations that are spread over large areas. PLC-based systems, on the other hand, initially concentrated on self-contained machines in small areas.
This has changed as simple machines have evolved into highly complex production lines within networked plants. Therefore, operators have become more interested in using distributed peripherals that can be linked to fast fieldbus systems. As a result, systems that can offer distributed intelligence, like the DIN rail-mountable Embedded PCs in the CX series from Beckhoff, are now a prevailing option, enabling direct connection of the EtherCAT based I/O system. In addition, deploying EtherCAT communication throughout the entire plant allows operators to implement extremely time-critical and highly synchronised control processes across distributed production steps. This includes the ability to integrate with central production control systems, and to perform data analysis and optimise processes.
The PLC system offers maximum innovation potential
In terms of system architecture, the developments mentioned above have already made PLC systems very similar to the remote I/O systems that users are familiar with from the process control field. Especially in the context of Industrie 4.0 concepts, the PLC approach has proven to be an innovation driver, and has taken on a highly advanced structure that is clearly superior, particularly in terms of performance.
It is above all the vision of the Internet of Things (IoT) which has led PLC-based systems to take on some characteristics of distributed control systems in the past few years, especially in terms of integration capabilities. This has increased support for mature protocols that offer cross-system data exchange, for example based on OPC UA, but also for communication between the supervisory control level and the cloud through protocols such as MQTT.
While machine builders use these capabilities to implement the Industrie 4.0 concept in its totality, process engineers require fully integrated solutions for a variety of reasons. They must cover all hierarchy levels ranging from data acquisition in hazardous areas to remote diagnostics of globally distributed systems via centralised process control systems. Thus, systems can be made more efficient and reliable by the use of extensive diagnostic and analysis tools.
Open and modular automation technology as a complete solution
With PC-based control, Beckhoff offers the ideal automation toolbox to implement all these requirements in a complete and integrated solution.
The openness of the PC-based control concept deserves special mention, as support for all major bus systems allows the easy integration of Beckhoff controllers into existing architectures. In addition, long-term product availability and backward compatibility provide the best-possible investment protection and ensure outstanding spare parts supply. Benefits like these also make it easy and affordable to upgrade existing systems, for example by adding cloud connectivity and IoT functions. This is possible, for example, with the EK9160 Coupler, which connects EtherCAT I/Os directly to the Internet of Things without the need for a control program. An IoT connection allows remote monitoring from anywhere at any time.
The benefits of integrated and open automation systems from Beckhoff become especially apparent when designing new plants. On the field level, the use of ELX-series EtherCAT Terminals for the direct connection of intrinsically safe field devices enables significant reductions in space requirements, and thus cost requirements. In addition, the elimination of the need for separate safety barriers delivers clear advantages with regard to installation and diagnostics. DIN rail-mountable Embedded PCs from the CX series, equipped with up to 12 CPU cores, make it possible to distribute the execution of even the most complex controls. Comprehensive product certifications ensure compliance with explosion protection requirements and enable installation in close proximity to the actual process.
On the control level, the finely scalable portfolio of Industrial PCs from Beckhoff enables custom-tailored solutions that can not only perform a wide range of control tasks, but also provide easy integration into process control systems. Support for many standards and protocols ensures cross-system data communication on both the higher-level control and field system levels.
The advanced TwinCAT HMI software solution enables the implementation of visualisation tasks according to the highest standards for efficient and reliable plant operation. In addition, the responsive TwinCAT HMI runs just as well on mobile devices as on industrial Control Panels and Panel PCs. For process visualisation and control in hazardous areas (Zone 2/22), specific devices are available in the form of the highly attractive CPX panel series with state-of-the-art multi-touch technology and robust aluminium enclosures.
With the wide range of TwinCAT functions, engineering for the entire plant operation and data transfer to a higher-level control system or cloud services becomes a very intuitive process. Beckhoff thus offers plant operators integrated solution concepts for numerous process technology applications: from the hazardous zone 0/20 to data storage and processing in the cloud.
Current requirements of the process industry
Nevertheless, plant operators are constantly faced with new challenges.
Currently, the process industry is increasingly requiring individuality and flexibility in production as a reaction to fluctuating markets.
This requires the shortest possible time-to-market through accelerated development cycles as well as the profitable and individualised production of even small batches.
A suitable solution to meet these challenges is the modular design of production plants and the resulting ability to reuse modules. The entire process is broken down into sub-processes and mapped by corresponding modules. With a separate controller for each module, a completely modular system is achieved. Finally, by connecting the individual modules to a higher-level control system (e.g., a DCS), the entire process can be orchestrated.
As a result, the development work shifts from plant engineering to module engineering, enabling flexible modification of the plant with little effort, depending on current requirements. This way, additional modules can easily be added or already existing ones can be rearranged or removed.
The Module Type Package
In practice, the concept is implemented by a vendor-independent standard for the description of process modules: the Module Type Package. This file contains all the information necessary to integrate a process module into a modular plant by importing the description. Functionalities included are the aspects of services, communication and a P&ID structure for generating a HMI in the DCS. Interfaces defined in the MTP specification enable plug-and-produce behaviour. In this way, the production units are developed only once and can then be integrated into different plants independent of the manufacturer.
With TwinCAT MTP, the engineering of MTP-capable modules for process plants integrates directly into the engineering environment of TwinCAT. It offers all options, from the definition of the module and the import/export of an MTP to automatic PLC code generation. The goal in developing this new TwinCAT function was to minimise the required guideline expertise and enable the module developer to focus on the actual control logic.
Further reading: www.beckhoff.co.in/process, www.beckhoff.co.in/twincat-mtp
(Beckhoff Automation Pvt Ltd, Pune. Tel: 91-20-67064802. Email: firstname.lastname@example.org)
Franziska Dreisewerd, Business Management Process Industry, Beckhoff Automation.
Lennart Winkler, Business Management Process Industry, Beckhoff Automation.