A quiet revolution in industrial control systems

The industrial control system (ICS) market has been dominated by PLCs ever since they burst onto the scene in 1969. And with good reason: being small and programmable meant PLCs were a significant step up from the hard‑wired circuits they replaced. They soon proved themselves to be highly robust, reliable and available at reasonable cost. These factors in combination made them a huge success.

Much has changed in the intervening years. The demands on a modern ICS have increased sharply, as they now need to handle many additional aspects of automation, such as functional safety and motion control as well as serving up data for visualisation and the cloud — and all this needs to be done at ever greater speed.

PLCs have always used their own proprietary hardware, with each vendor creating their own unique system. Such closed platforms restrict users to whatever software tools the PLC supplier provides. Also, any product development needs to come from the one vendor.

As the world has become ever more connected and digitised, calls for open controller systems that can keep pace with technological advancements have come loudly. It’s into this environment that the industrial PC (IPC) has emerged.

But why this trend? Are IPCs genuinely better at performing control tasks, such as ladder programs, than traditional PLCs, which have proven themselves over many years? What advantages do IPCs really bring to the table?

IPCs, as their name suggests, utilise the ubiquitous PC format as their hardware platform. While encased into an industrially hardened format, IPCs are essentially the same as the laptops and desktops we all use. And like them, IPCs have abundant computer resources with plentiful memory — far more than PLCs. Considerable investment continues to be made in PC architecture, which IPC producers can leverage for their products.

IPCs implement a ‘software model’, where functionality is provided by loading a series of software modules. This offers great flexibility as both updates and additional functions can be installed at any time. PLCs, on the other hand, utilise a more rigid ‘hardware model’, where firmware is often fixed. It’s also often difficult to access new functionality, as it normally requires hardware changes.

Questions have been raised about the robustness of IPCs. But IPCs, like PLCs, are microprocessor-based, and have adopted the same ruggedised design principles.

Most IPCs come with the popular Windows operating system, although they execute their control code independently, within a real‑time kernel. Windows offers a huge array of programs, as well as functionality such as Visual Studio, .NET programming, large support communities and much more. This allows users to access modern programming techniques, such as object‑oriented programming. Giving users access to this sort of power is a massive advantage for IPCs.

Some doubt the reliability of Windows, pointing to ‘blue screens of death’. However, IPC vendors set the standard for their own hardware and test their systems thoroughly, including quality control for their drivers. Also, most IPCs only use embedded, long-term servicing channel editions of Windows, which rarely need to be updated.

In contrast, PLCs for many years had no security protection at all, as it was believed the ‘air gap’ to the outside world kept them immune from cyber threats. But the connectivity demanded of a modern ICS means the air gap has evaporated. While many PLCs now provide security features, giving users a ‘sandpit’ to work in, cybersecurity specialists, such as Fortinet and Team82 from Claroty, regularly report breaches. The situation is not helped by the persistent use of unprotected protocols such as Modbus.

With the merging of the once divergent OT and IT worlds, the call for a single standardised platform for all networked devices has grown ever louder. The IT community in particular sees advantages in having one common platform.

But perhaps the biggest advantage of IPCs is the fact that virtually every industrial site already uses PCs running Windows. These PCs run a host of applications, anything from spreadsheets, HMI/SCADA, web serving and much more.

So it makes a good deal of sense to combine the functions of a PLC with a PC, into a single unit: an IPC. This reduces the hardware required and improves communication links. It also enhances reliability and reduces overall costs.

The prevalence of IPC offerings in the market, including some by the traditional PLC vendors, may explain their meteoric rise in sales.

Harry Mulder is the principal automation engineer at Beckhoff Automation. He’s been involved in industrial automation for over 30 years and is fascinated by how new innovations keep affecting the direction of the industry. He really enjoys the practical element of his job, where he has a chance to get his hands dirty!

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