Safety Instrumented Systems / HMI

Is There a PC in Your Control Systems Future?

There's No Longer Any Technical Reason Why a PLC or a DCS Should Be More Reliable Than an Industrial PC

Dan HebertBy Dan Hebert, Senior Technical Editor

Various limitations have slowed their adoption in process control ever since PCs were introduced in the 1980s. But evolution of the technology, particularly recently, has addressed these limitations and made industrial PCs the best fit for many process control applications—especially when compared to traditional solutions like PLCs and DCSs.

For example, many process control applications require added functionality in addition to regulatory control, including HMI visualization, data collection, advanced process control, remote access and interface to higher-level computing systems. PLCs aren't suited to these tasks, and DCS platforms are too expensive, especially for smaller-scale applications. Enter the modern industrial PC.

Ruggedized PCs can stand up to demanding process control applications. "Industrial PCs are designed with components such as corrosive-resistant metal and shock-mounted hard drives to withstand harsh environments," says Shoshana Wodzisz, industrial computer business manager for Rockwell Automation.

Even in control room applications with controlled operating environments, industrial PCs provide advantages. "Industrial PCs are designed for technological consistency and longevity, so users can expand their systems, perform repairs or replace damaged machines for years," adds Wodzisz.

Industrial PCs also have a longer shelf life.  "An industrial PC is often developed for a five- to 10-year production cycle, and has another five- to 10-year repair and replacement option, for a complete lifecycle of 15 years or more," observes Stephan Stricker, product manager at B&R Industrial Automation.

Multi-core processor technology overcomes the critical software limitations of commercial PCs. It enables two software operating systems executing simultaneously. The first is usually Microsoft Windows, and the second is a real-time embedded solution.

"Multi-core processors with virtualization technology allow dedicated processor cores in the same PC to perform separate tasks such as real-time control and visualization," notes Robert Jackson, senior industrial and embedded product marketing manager for National Instruments.

Given this technology, there's no longer any technical reason why a PLC or a DCS should be more reliable than an industrial PC. In fact, modern industrial PCs often use the same processors and embedded operating systems as their PLC or DCS counterparts.

Industrial PCs also offer many advantages in terms of cost and performance. High-end performance isn't an issue when comparing PCs to DCSs, but cost and scalability are, particularly for smaller-scale applications.

"One cost-effective, but powerful controller can perform PLC functions for processes, run the HMI, perform high-speed data collection, and communicate to upper level computing systems," explains Corey McAtee, product manager at Beckhoff Automation.

When a PLC is used in a process control application that demands more than real-time control, additional hardware and software are required. These added components not only increase cost, but also increase complexity.

High-speed data collection is a task at which industrial PCs excel. "Say you must monitor a pressure sensor that updates at 50 µs. We offer a standard, low-cost, PC-based solution that can capture input signals down to 10 µs value with a time-stamp error less than 1 µs. This data can then be logged using our built-in database server or communicated to other computing systems via standard PC data exchange formats," relates McAtee.

But, perhaps the biggest advantage of industrial PCs is on-board HMI visualization. This eliminates the need for separate operator interface hardware—cutting up-front costs, eliminating integration issues, and reducing the control system's physical and energy consumption footprint.