Has Ethernet taken I/O as far as it can go?

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Omron Industrial Automation is a leading manufacturer of technologically advanced industrial automation products and application expertise.

Considerations of input and output – I/O – are fundamental to machine design and configuration, and different implementations can have significant impacts on both operational efficiency and in-service maintenance. Virtually every machine from a laptop to a production-line robot has I/O at its heart, and equipment and system suppliers have put a lot of energy into developing different methodologies and strategies, often with speed – of installation, operation, and maintenance – as a core consideration. As a result, machine makers and end users have sometimes been confronted with a choice of I/O implementation policies, often with competing advantages and disadvantages.

The I/O specification for a particular application is often determined by the installation’s layout and functionality. At one extreme, host-resident I/O, with separate boards filling a control computer’s expansion slots, has the advantages of high performance and low cost. However, the host needs to be fairly close to the slave devices, to prevent interference and ground loops, while on complex installations both the installation engineer and – subsequently – the maintenance specialist had to deal with large and cumbersome looms of cables.

It is also the case that there are no standard connectors on host-resident I/O systems, which makes the installation even more complicated and time consuming, unless the machine maker relies on a single vendor for all devices. For standardised connectivity, RS-232 ports are suitable. However, although these are widely available, they are only really suitable for interfacing with simpler devices and again, cable lengths are limited if ground-loop problems are to be eliminated.

Ethernet provides the answer to most of the issues connected with other I/O solutions offering a number of significant advantages, many of which stem from its origins in providing connectivity across computer networks. Connections are standardised, and Ethernet is fully isolated to prevent ground loops and interference. It uses a single cable – typically twisted pair or fibre optic – to connect host computers to remote devices, along with intermittent hubs and switches to divert signals as needed. All of this makes cabling very simple to install, and easy to manage and maintain: devices can be exchanged and added very easily with standard fittings and cards.

For industrial automation applications such as packaging lines and bottling plants there are a number of issues that need to be considered before deciding what kind of Ethernet architecture to deploy. These include:
· Low-voltage power distribution, usually suitable for different supply voltages, is ideally incorporated into the I/O system using purpose-designed connectors and terminals – this dispenses with the need for external terminals and additional wiring.
· Integrated power-supply monitoring and diagnostics, which can be critically important in some installations.
· Safety support, including monitoring of elements such as interlocks, emergency stops, safety light curtains and so on, should ideally be built into the architecture to prevent the need for additional dedicated circuitry.

· Environmental issues are very important in hazardous applications, as well as those involving high humidity and widely varying temperatures, where connectors, terminals and other components must be fully enclosed and protected; installations for food preparation and processing also need specialised environmental protection.

There are also specific variants within Ethernet architecture to be assessed in designing an installation:
· Integral Ethernet interfaces for each device or module can deliver high performance, but are costly, because of the need for network switches on most systems.
· Plug-in modules on a specialised Ethernet carrier enable I/O interfaces to be fitted wherever needed, and can be cost effective, although the actual plug-in modules can be expensive.
· Star clusters, which incorporate an Ethernet module with separate cables connecting satellite I/O interfaces in a star configuration, are ideal for larger installations although they are not really suitable for confined spaces.

It’s clear that while Ethernet is – in theory – the ideal I/O solution for industrial automation applications, its deployment is not exactly a straightforward matter, and companies like Omron have invested considerable resources into overcoming this issue. The Sysmac platform has addressed the problem with EtherCAT, a fast machine network that can be used to control motion, vision, sensors and actuators. Sysmac is designed, as far as possible, to be future proof, so that new components, software and applications can be added seamlessly. A good example is the NJ machine automation controller, launched in 2012, which integrates motion, sequencing, networking and vision inspection.

It’s interesting that Sysmac has been so quickly and widely accepted, and it may be tempting to see it as the answer to all I/O issues. However, we’ve all learned over the past 25 years or so that nothing is forever, and it’s entirely possible to conceive of Sysmac with increased speeds and fully integrated safety features, which would make installation and operation even more efficient. Watch this space, as they say.

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Omron Europe

Omron Industrial Automation is a leading manufacturer of technologically advanced industrial automation products and application expertise. From its European headquarters in Hoofddorp, near Amsterdam in the Netherlands, she operates locally in every European country and is dedicated to providing unrivaled automation products and customized expert solutions for any industry.

The product portfolio includes state of the art Factory Automation services & Know-How, Sensors and Safety, Mechatronics and Drives, Industrial Components and Vision Systems.