Despite the emergence of alternative control solutions, the popularity of the PLC endures. Mitsubishi Electric product manager, Hugh Tasker, offers five reasons why you still need a PLC

It is almost inevitable, then, that an

industrial PC will crash and what might that mean for the control process? By contrast, when did you last hear of anyone needing to reboot a PLC after a software crash – probably never… 3. INTEGRATION OF OTHER

1. PEACE OF MIND: Both PLCs and PCs

have come a long way since their humble beginnings, but there is a big difference in how these distinct control options continue to evolve and this has significant implications for long term support. The managed evolution of the PLC means that vendors can and do support their products over long periods of time, both in terms of hardware and software. That means, with Mitsubishi Electric, that we could take the application program for example, from a 20 year old FX PLC and import it straight into a brand new FX5U. A user could install the very latest controller and have the application back up and running almost immediately. How would you even contemplate doing the same with a PC- based solution? 2. INHERENTLY ROBUST AND

RELIABLE: The modern industrial PC provides a stable computing platform and it would be unfair to suggest that it locked-up and crashed with the unerring regularity of a desktop PC. However, it is not on equal terms with a PLC. The real time operating system that

runs alongside Windows on a typical industrial PC has been designed to try to provide the same level of robustness as you get from a PLC CPU. If a PC operated in complete isolation,

perhaps that would be the end of the reliability debate. However no controller does; there are peripherals to connect, I/O to network and other components to talk to, each requiring their own drivers to be loaded into the PC. Will the drivers for all of these products have been tested in combination and thoroughly proved? It seems unlikely. Clashes can and do occur and problems can be exacerbated every time those drivers are updated.


ABOVE: The evolution of the modern automation platform, commonly with a PLC at its heart, delivers a system that is much more than the sum of its constituent parts and addresses important emerging trends and industry challenges

INSET: The integrated control components within the iQ-Platform offer the system designer the option to implement an optimised control system that integrates different control processes onto one common platform

AUTOMATION EQUIPMENT: For many automation engineers, there is never any need to move outside the product portfolio of a single vendor, with suppliers such as Mitsubishi Electric able to address every requirement from HMIs, drives, servos, motion control, safety and robotics to low voltage power distribution products, power management meters and CNC systems. Because all of these components have been designed to work together, engineers benefit from ‘plug and work’ integration. There are some automation vendors

that sell industrial PCs who can claim to offer a broadly similar product portfolio but certainly not many. However, the real challenge comes when engineers need to look outside of a single brand and integrate third party components. With the modern PLC, integration of

third party hardware is a breeze, can the same be said for integration on a PC platform? Are the drivers for those third party modules guaranteed to work? How much configuration effort will be required? Perhaps more importantly, will there be the same assurance of ongoing compatibility through the operational lifespan of the control platform? 4. SECURITY: The arrival of high profile

viruses such as ‘stuxnet’ have made us all realise that automation systems have become targets, as malicious hackers look to cripple the operations of big companies or vital utilities. With its familiar operating system and inherent network vulnerabilities, the PC can represent the soft underbelly of the control system for anyone trying to break in. The operating systems of PLCs, by contrast, are much less visible to the outside world and this has traditionally offered a layer of insulation against malicious intent. This

does not mean, however, that PLC manufacturers take security for granted. Mitsubishi Electric, for example, enables programs to be password protected, with different levels of access granted to different levels of user. Further remote access preferences can be set such as access only being granted to specific IP addresses, protecting PLC software and the wider automation system even in heavily networked applications. 5. INTELLECTUAL PROPERTY:

Extending the security argument, a concern for companies with global development teams or where the end system will be installed overseas is that the control software will be copied by unscrupulous third parties and all too quickly developed as a competitive, lower cost product. Where this is a valid concern across all

control platform options, the PLC manufacturers have taken significant steps to address the problem. With Mitsubishi Electric products, encrypted code embedded in hardware and software can be set to execute at a given time. That might mean that the system is open to developers and installers right through to the end of commissioning of the application, but then switches on to protect the system from further interaction. We can see, then, that there are many

good reasons why the PLC will continue as the mainstay of automation system control and that's before we've even considered issues such as redundancy, safety and more, plus the capability of the modern PLC to perform many of the complex maths functions that could once have only been performed in a PC-based system. Of course the requirements of every automation system should lead to the selection of the appropriate control solution on merit but the PLC offers many reasons to be the platform of choice.

Mitsubishi Electric Europe T: 01707 288769


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