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OPC - UA and modelling your devices

Monday, January 23, 2017

The OPC UA communication protocol can make it easier for your software systems to build a model of the devices on your industrial network - which means much simpler software. We interviewed Matrikon's Darek Kominek.

Imagine you run a restaurant and want to be sure the freezer is closed overnight, otherwise your food will spoil. You can put a temperature sensor inside, or a sensor in the door. If your staff left the door ajar, you wouldn't mind being woken up in the middle of the night so you can drive to the restaurant, rather than lose all of your stock, but you don't want any false alarms. How do you program this?

The standard approach would be a sensor which sends temperature data every minute, or a signal about whether the door is closed every minute, which then connects to a PC, which uses complex logic to work out whether to send you that emergency phone call. No need to call you the door is open in the daytime, or if the restaurant is open late on New Year's Eve.

If the sensor was modelled using OPC UA protocol, it could be much easier to program. You would build a 'model' showing how you want the sensor to work, when it should make the emergency call, and what might indicate that the sensor is not working. Then this 'model' can be uploaded to the sensor itself, or run on a simpler computer nearby (like a Raspberry PI).

Industrial networks are of course much more complex than this, with thousands of sensors. So you can see how having models of what the sensor is supposed to be doing, held within the computer system, can make life easier.

OPC UA

OPC UA is described as a machine to machine communications protocol for interoperability.

It is developed by the OPC Foundation, with OPC standing for 'Open Platform Communications'. UA stands for 'Unified Architecture'.

OPC UA could be described as a standard modelling method, says ?Darek Kominek, senior product marketing manager at Matrikon, a company owned by Honeywell, which specialises on OPC UA systems.

The data from the device moves around the communications network as a data 'object', not just a string of time series data.

This 'model' can include an idea of what operating range the device can work in, what units it provides data in, what functions it can do.

OPC UA can be used to program just about any device, so it can tell the device (for example) to only send a signal when the temperature goes above a certain level. You don't need a PC to sit between the device and the network, ensuring that only useful information is sent to the network, Mr Kominek says.

The data 'conditioning', the first level of cleaning up the data, can happen at the device itself, so only useful data is sent from the device into the system.

OPC UA then makes it possible for the data to be exchanged between different systems via the cloud, with actual useful information, not just a list of temperature readings.

Another benefit of OPC-UA is that it makes it is easier for programmers to understand each other's models.

A consumer of the data can understand what the model is, and so work with the data much more easily.

If it is video, there could be extra logic around the basic video data, for example talking about what kind of video format is being used.

OPC-UA has been around for 8 years, as an 'object orientated modelling language', so the data can move around the system as a packaged 'object', not just as raw data, Mr Kominek says.

Most programming languages (such as Java) aren't designed for working with time series data, or being used in automation, Mr Kominek says.

In May 2016, Matrikon launched a new Software Development Kit (SDK), to make it easier to program OPA UA, to link together industrial systems.

Coping with organic development

Oil and gas production environments often have plenty of organic development to them, so you get different systems from different suppliers, running on different platforms, Mr Kominek says.

They all send data to cloud storage - but working out what to do with it can be tricky, unless the data comes with 'meaning' embedded in it.

OPC UA can help the computer system make sense of all of this data, by reducing it to what it is actually saying.

With the 'internet of things', 'we have more ability to generate more data, [but] it doesn't guarantee it becomes information,' he says.

Simplified infrastructure

By using OPC UA, the infrastructure can be much simpler, because you already understand what the sensor or device is telling you. The sensor is also only sending out data when there is something it needs to say.

Rather than have PCs on the network to process the data from devices, you can have much simpler computers known as 'gateways', taking data from multiple devices in OPC UA and aggregating it together.

'You don't need huge systems.'

With a simpler data architecture, it becomes easier to divide data up into functional perspectives. You can have one system of data for production engineers, and this system has data for maintenance engineers.

All of this can lead to cost savings 'running into the millions' for getting data from offshore platforms, he says.

Push to the device

It is possible for the device to also receive data from the cloud, to help it get a better idea about what to report.

For example, a company can write an algorithm for how it wants to change a flow pattern based on a changing situation, and send different logic to the device showing how they want it to execute.

This way, you can manage a whole 'fleet' of devices at once, with a centralised system to deploy procedures to different devices, similarly to when network administrators can configure all of the PCs in an office to update themselves.

The 'PUBLISH SUBSCRIBE' system enables the devices to 'publish' data to the cloud. Other systems on the cloud pick up the information as they need it.

'There isn't a 1:1 connection between consumer of the data and source of data,' Mr Kominek says. You don't need to do a 'handshaking' connection when you want to connect to something.

Many people have security concerns about being able to push to the device, but with a system like this, the security actually improves, Mr Kominek says. 'An edge device can generate the data when it wants to, the data is available on the cloud.'

Connecting standards

OPC UA can also connect together different data communications standards, so it can make different devices able to work together, although they use different standards.

'It glues together a diverse set of different industries together,' he says.

Many data standards organisations are putting together a 'companion specification' document, which says, here's how to model that standard using OPC UA.

Time sensitive networking

Another development is 'time sensitive networking', a way to send data through an Ethernet network and know exactly when the data arrives.

Ethernet usually works on a best effort basis, most data usually arrives immediately but some packets get lost along the way.

'There's a standard coming out at the end of 2016, which makes it possible to make Ethernet traffic deterministic,' he said. 'You can control the delivery of the data, which opens up new avenues of what you can do.'

Work

There can be resentment among industry experts about systems which are so easy to program, since many people in the industry have made their living working with very complex devices.

But Mr Kominek argues that protocols like OPC UA can create jobs, by making it possible to do much more.

'There's more information available to the expert. 'Now, they're going to have additional global perspective. The system can start to draw some higher level conclusions which it presents to the experts, who then have a better global awareness.'

It is like cruise control in a car, he says. 'If the car slows down in front of you, your car will trim its speed back. It doesn't mean the driver is not necessary, it doesn't mean the car took over, it definitely makes life easier overall. That's the same type of idea.'

Associated Companies
» Matrikon International

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