June, 1997

Being an independent control systems integrator, Superior Controls implements a variety of hardware/software solutions: From large DCS systems to small micro PLC projects. And we're noticing a trend.

Why are Foxboro, Yokagowa, Honeywell, ABB, and Bailey Controls entering the market with Windows NT-(WNT)-based DCS systems? Why does Intellution and Wonderware now sell so many Windows NT-based MMI systems, (60-70% of all packages according to Intellution). Why has Rockwell Software and so many others rushed to market WNT-based MMI and control packages?

As users ourselves, we've found WNT to be enormously reliable as an MMI for industrial control applications. For example, it absolutely must run continuously 24 hours a day especially when compared to the Windows Operating System. WNT was released in the late summer of 1993 by Microsoft, and was the result of the efforts of Dave Cutler and his engineering team. Cutler was previously one of the architects of VMS, the very successful DEC operating system. Some say the letters WNT were selected because they are the next sequential letters in the alphabet VMS, (film buffs may remember HAL and IBM in the Year 2001 movie). Whatever the reason, WNT has more in common with VMS and Unix than Windows 3.1.

WNT was written from scratch as a high-end 32-bit operating system (as opposed to Windows which is 16 bit). Thus the name stands for Windows New Technology. It has an identical user interface to Windows 95. It supports multiprocessors, is portable to several chip types (DEC's Alpha, Intel, etc.), and has built in networking, but most important for industrial users, it is multitasking. Multitasking means that multiple programs can run simultaneously without crashing and/or bringing down the entire system.

Until recently, the biggest detriment to using WNT for real time industrial control purposes was the lack of deterministic capabilities. The time the system required to respond to an input depended on the other activities such as how many and which programs were running.

Scheduling issues are critical to a real-time OS. Input signals need to be sampled deterministically, PID loops need to be updated regularly, and safety interlocks must be responded to immediately. With a 32-level variable priority preemptive scheduler, WNT is far from real time. That is, until recently.

A small Cambridge, Massachusetts, company called VentureCom, sponsored by major players in the controls community (including Allen-Bradley, Rockwell Software, Schneider Automation, Intellution, and Wonderware), has modified the WNT HAL (Hardware Abstraction Layor) to produce a customized high frequency, deterministic timer facility specifically for doing control. This extension does not modify the WNT kernal, so compatibility is maintained with all presently available software for the NT while providing control responses that can be preemptive and deterministic down to 100 microseconds (yes- microseconds) on a 90 MHz Pentium processor.

So what does all this mean to you and Superior Controls? It means that we can expect to see more WNT operating systems on the plant floor. A wide variety of WNT-based software options will soon become available reducing the attractiveness of proprietary hardware and operating systems. Several PLC manufacturers have anticipated this WNT shift and have already embraced PC-based processors such as Allen-Bradley's 1747 open controller, Siemens M7 PLC and Modicon's Quantum PLC. These hardware packages could be ready to use at the same time as the modified WNT system which is expected to begin shipping the summer of '97.

Superior Controls is involved in industrial control projects in which both the information handling and the control is accomplished using the PC. We expect to see more of these projects in the future as we anticipate greater automation affordability and opportunity for all of us.