Personal Computers Lose the Pretty Face

PC-based control gains acceptance with new and more practical form factors

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One of the main problem areas has been the Windows operating system. Desktop Windows is primarily designed for non-real time and non-critical applications. Earlier versions of Windows (prior to NT) were especially plagued by unexplained glitches, the blue screen of death, and frequent re-boots.

As detailed in our May 2002 cover story, this problem has largely been alleviated by the use of real-time PC-based operating systems. In addition to the various embedded versions of Windows, such as CE and embedded XP, real-time PC operating systems are also available in Linux. Firms such as VxWorks (www.windriver.com), QNX (www.qnx.com), and LynxOS (www.lynuxworks.com) also offer rock-solid real-time operating systems.

Table II: Industrial Grade PCs vs. Office PCs

Features to consider

Industrial Grade

Office Grade

Can it withstand extended temperatures?

Yes

No

Can it withstand shock & vibration?

Yes

No

Is it dust proof, or does it have filtering?

Yes

No

Is it splash proof?

Yes

No

Does it have RFI/EMI shielding?

Yes

No

Does it have power surge protection?

Optional

No

What type of chassis construction?

Cold rolled steel, rigid

Flimsy, often plastic

Does it meet industry classifications?

NEMA/IP, MIL, etc.

None

What type of security does it provide?

Locking doors & drive bays

None

How much lifecycle technical support?

3-5 years

6-12 months

Does it provide Intrinsic Safety?

Optional

No

Mean Time Between Failure Data

Sometimes provided

Not provided

Mean Time to Repair

5-15 minutes

1-2 hours plus

Mounting & enclosures

Multiple Options

desktop or tower style

Is it fault tolerant?

Optional

No

 

How reliable are these systems? The control engine for Westinghouse's Ovation DCS (www.westinghousepc.com) is the VxWorks operating system running on dual redundant PCs. Ovation DCSs are used to control power and water/wastewater plants worldwide with some systems controlling over 10,000 I/O. The VxWorks operating system also is used to control the NASA Mars rover. The QNX operating system is used to control robot hands in surgical applications.

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