By: Heinrich Munz, KUKA Controls
With its new Soft PLC, Phoenix Contact is offering the convenience of the Windows® XP interface on the user side, while at the same time providing hard real-time by utilizing the Windows® CE real-time operating system - all running on a single Intel XXX based computer. These two operating systems are bridged by KUKA Controls' CeWin® software. The following article explains in greater detail the advantages of Soft PLC over the standard embedded control PLC, and the criteria used by Phoenix Contact when implementing PC WORX.
For decades, programmable logic controllers were the classic example of an extremely reliable embedded system. The need for a well-functioning, reliable PLC is readily apparent. With programmable logic controllers, no allowance need be made for the types of system failures with which we are familiar when working with PCs on an everyday basis.
Every time a Windows PC crashed, the PLC community longed for a PC designed for use in the office which was able to offer the reliability of a PLC. It was therefore all the more incomprehensible that anyone would wish to choose Windows PC as a control platform with the functionality of a PLC.
However, this is exactly what the Soft PLC is. As part of its automation concept, AUTOMATIONWORX, Phoenix Contact is now offering a Soft PLC based on an industrial PC running with an Intel XXX processor. This new PLC which offers the reliability of a standard embedded control PLC (dedicated hardware) on the one hand, while on the other, providing all the convenience and high processing capacity of a PC environment. It also extends the AUTOMATIONWORX automation concept at Phoenix Contact to include scalable high-end solutions based on an industrial PC.
The key element which makes the new industrial PC solution able to operate in hard real- time is the KUKA Controls CeWin real-time extension platform. With CeWin, Windows XP can be operated on the same CPU in parallel with the Windows CE real-time operating system, without Windows XP negatively impacting on the ability of the system to operate in real-time.
Against this background, long-time PLC developers and users are wondering why a Soft PLC is necessary alongside the conventional embedded control concept with PLCs; the answer is simple, the Soft PLC offers a wide range of advantages.
Anyone who purchases a Soft PLC will know that, in principle, they will be able to use any industrial PC as a hardware platform. As a result, the system hardware is no longer (semi-)proprietary, but becomes a standard product which is subject to market forces.
Since PC hardware is produced in far larger quantities, purchasers can buy what they need at significantly better prices. In addition, PC specifications and the interfaces are already precisely defined or standardized, and further improvements and innovations are also guaranteed due to the rapid rate at which (industrial) PCs themselves are changing. This eliminates the problems that may otherwise occur when proprietary or limited product lines are discontinued, since the PCs are, in principle, fully compatible with each other. A guarantee of hardware supply going beyond the standard ten-year period thus entails no risk for Soft PLC suppliers.
Moreover, the processing capacity can be flexibly adjusted to suit each individual application: if a faster system is required, it may be sufficient in some cases to merely replace the processor with a faster CPU of the same type. With the standard embedded control systems, the extent to which the hardware has been improved depends largely on the manufacturers, since they will decide when to convert to a new generation of processors, how many scaling options there will be in the interim, and what the general price level for the hardware should be.
A PLC system which uses a PC platform also offers particular advantages when the overall application is used for operation or visualization purposes in addition to the actual control functions, or when other specialized tasks need to be completed, such as image recording, image evaluation or complex control processes.
With the switch from proprietary embedded hardware to industrial PCs, a supplier of PLC solutions becomes a special type of system house providing (high-quality) hardware in a bundle together with the appropriate control software. An overall hardware/software system of this type, which also contains hardware developed or configured by the supplier itself, alongside software developed in-house, can then be optimally designed for the application and any possible scenarios which may arise in connection with it. For this reason, Phoenix Contact is also developing industrial PCs based on the Intel XXX processor. This means that users of complete automation solutions with this type of hardware/software combination will automatically enjoy a greatly improved service, since they will receive a functioning solution, as they did with the traditional PLC embedded system.
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