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Multi-CPU PLC is basis for `seamless integration`

01 July, 2001

Multi-CPU PLC is basis for `seamless integration`

Mitsubishi Electric claims to have achieved the Holy Grail of seamless integration of automation components, based on a new PLC platform that allows PLCs, PCs, and motion control components to communicate with each other via a shared backplane. The platform has a throughput up to ten times faster than Mitsubishi`s earlier A series PLCs, allowing one of the new controllers to do the work of two old AnS PLCs.

Steve Jones, deputy manager of the company`s automation division in the UK, suggests that attempts to link various aspects of the enterprise through systems such as ERP (enterprise resource planning), "should be seamless, but aren`t". He attributes this to a combination of factors including:

• planning and implementation which is "not optimal";

• the use of mixtures of operating systems;

• the difficulty of getting data in and out of older systems;

• the use of proprietary controls; and

• the adoption of multiple communications networks.

To counteract these problems, Mitsubishi has come up with a concept it calls Melsmart which is designed to facilitate communications between different levels of an enterprise. Melsmart will bring together hardware and software to link aspects such as control, plant management, and visualisation.

It is intended to be an open, modular, integrated environment for automation engineering. All future Mitsubishi products will be based on a common platform and third-party suppliers will be able to integrate their products with the new architecture.

The concept is still at an early stage of development. "We are putting the building blocks in place at present," says Jones. The lynchpin is the Qn series control hardware which allows up to four CPUs to share the same backplane. These can be PLCs, PCs or motion control modules. For example, up to 96 axes of motion control can be accommodated in one system using individual modules that can update 32 axes every 3.5ms.

In its PLC guise, the Qn can handle up to 8,192 I/O and each multitasking PLC CPU can have up to 32Mb of memory. As well as supporting Profibus DP, DeviceNet, and Mitsubishi`s own MelsecNet networks, the CPUs incorporate a USB (Universal Series Bus) port that can transfer data 12Mb/s.

The Qn can send emails with attachments containing up to 6k words of data. This means that, at the end of a shift, it can send an email with production data to management or maintenance departments anywhere in the world.

The various components of the Qn family are being introduced over the coming year. There are no plans yet to phase out the A series, but an upgrade path is being provided with AnS users being able to update their systems with a Qn CPU.

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