Edge computing encompasses the whole set of infrastructure, tools, and processes that support managing data-handling activities using individual sources of data such as smart edge devices at the network's edge rather than on centralised infrastructure.

It helps in the consolidation of existing applications from equipment manufacturers, such as monitoring and control software into the single platform, whilst also allowing other important applications to operate on the same platform. This facilitates the development of Industrial Internet of Things (IIoT)-enabled machinery and equipment, as well as the addition of future applications that support customers' evolving Industry 4.0 and Smart Production needs.

PLCs vs. PACs distinction

Both PLCs (Programmable Logic Controllers) and PACs (Programmable Automation Controllers) use protocols and networks such as Ethernet, ControlNET, DeviceNET, and also connect with software and databases such as OPC, SQL, and others. The fundamental distinction between the two is in respective programming interfaces, which allows them to serve different functions. Because the PACs are programmed in C or C++, devices have an open architecture and a modular design. PLCs, on the other hand, have simple programmed execution. As a result, it functions with limited memory and discrete Inputs and Outputs.

As technology advances, the gap between the two appears to be diminishing. However, there is a difference between utility and performance. Owing to the ease of programming offered by PAC modules, it is easy to attach or detach components from PAC. PLCs, on the other hand, are wire-based systems, and the addition of devices necessitates extra cabling. Since small footprints and compact terminations are difficult to wire using traditional methods.

Edge computing technology in PLCs and PACs

The Industry 4.0 - Edge computing in the industrial environment whitepaper explains how transitioning to an edge-compatible control infrastructure edge computing has helped changes in industrial control architectures, suppliers and users have contributed towards a more flexible and configurable environment. The trend towards event-driven architectures in Information Technology (IT)/Operational Technology (OT) provides a unique opportunity to connect factory-floor data with cloud-based smart management solutions. Edge computing serves as a bridge between the two, linking changes on the manufacturing floor to enterprise resource planning and management systems meant to automate business operations and provide insights quickly and efficiently.

In many instances, integrating IoT data processing and other tasks directly into a module intended for industrial automation, such as a programmable automation controller, may make more sense. PACs, which do have higher-performance processors, could run a broader range of software than PLCs. In contrast to ladder logic, PACs now provide visual and textual programming languages, enabling more sophisticated manipulation and analysis of real-time data from local and remote sensors.

Some PACs have an architecture similar to that of a standard PLC. It may also host smart control modules, which allow for the simple installation and operation of motors and other similar equipment for speed, stop, and start instructions. Another type of PAC has emerged in recent years, combining the capacity to handle local I/O with network connectivity and the software programmability of intelligent gateways. These PACs are built on hardware platforms like Arduino, Raspberry Pi, and Linux-powered industrial computers. As a result, they provide access to a variety of programming tools, such as Node-RED and Python. Modern network connectivity of PAC platform capabilities enables integration between the safety-critical environment of the PLC and the thin edge as well as the analytical functions typically performed in the thick edge and the cloud.

Industrial edge controllers offer software-defined controls with enhanced optimisation capabilities, all whilst meeting the rigorous reliability, safety, and security requirements of industrial applications. Edge controllers are the logical choice for industrial automation and IIoT due to their combination of control tasks and edge processing. Edge gateways, edge devices, and the new edge controllers that merge PLC/PAC and edge processing into a single system are the major forms of industrial edge technology within machine automation. Edge controllers provide a generational leap forward for PLC and PAC-based industrial control systems by providing safe, secure connection between real-time deterministic control and non-deterministic applications that analyse and optimise business processes utilising external data.

Communication scope of PLCs and PACs

Basic PLCs are often 'bare metal' designs or utilise a very limited and proprietary operating system since they are specialised control devices with a defined functional scope. Through the usage of an RTOS, PACs obtained more sophisticated communication and functional services whilst maintaining a deterministic runtime. PLCs were formerly isolated or communicated over slow and inefficient serial links. PACs included better industrial protocol implementation and Ethernet to increase connectivity and interoperability. Edge controllers provide these benefits whilst still being able to function in an increasingly IT-connected environment.

PLCs mainly employed proprietary ladder logic and rudimentary tools for application development. PACs may provide support for conventional IEC-61131-3 programming languages, custom user code blocks, and some basic capabilities for code reuse and object-oriented design by incorporating ideas from the greater software industry. A well-designed edge controller maintains deterministic runtime while also providing a computing environment for doing analytics, data aggregation, and other sophisticated functions.

Benefits of using Edge controller

When users only require a PLC/PAC feature set, an edge controller can be specified to serve that role. Those who are interested and maybe more technically savvy, however, should look for edge controllers that have a native toolbox of IT-friendly capabilities such as Linux OS, a Python interpreter, secure sockets, an embedded database, and OPC Foundation, OPC UA compatibility. It is simpler to securely coordinate the deterministic and general-purpose OS on a single hardware platform than to install separate systems. The general-purpose operating system has access to a broader range of information sources as well as high-fidelity data from the deterministic system and IIoT devices. It also has the ability to do local analytics and sophisticated algorithm execution. The results may be used to advise the deterministic system on how to run optimally. Furthermore, the general-purpose operating system is suitable for converting raw data into pre-processed information that can be safely shared with higher level systems.

This blog focuses on the integration of edge computing in PLCs and PACs, for more information on Edge computing and its different forms, the need for end-to-end security please refer to 'Industry 4.0 - Edge computing in the industrial environment' whitepaper.

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