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The SICK Encoder with IO-Link – Imagine the Possibilities

The SICK Encoder with IO-Link – Imagine the Possibilities

Industry 4.0 promises to shine the bright light of digitisation and connectivity through an organisation and sweep away its last dark corners, so that all processes are visible, data is available, and workflows optimised across an interconnected universe.

This ‘smart’ new world view offers many new benefits but it also needs a lot more processing power and generates a lot more traffic. So, for the whole system to be responsive and manageable, local, distributed processing and data-exchange hubs are just as necessary to take the load off the higher, more centralised levels of control.

Sensors of every type, including rotary motion sensors (i.e. encoders) – are the eyes and ears working ‘at the coalface’ on the edge of this world, without which Industry 4.0 could never be realised. They collect the data to initiate and drive processes and provide vital information right from the heart of a machine about its efficiency and condition.

The IO-Link Breakthrough

IO-Link has been a breakthrough technology that has helped join the dots for industrial processes on the road towards Industry 4.0. Its rapid and widespread acceptance over the past five years or so, shows just how useful it has been in enabling the gradual transition to a more connected world.

IO-Link has delivered a standard open communications gateway that enables a common architecture to be used for sensors and actuators of all types in a machine. It means they can cooperate at the lowest level of the automation hierarchy, then link, through an IO-Link Master, to trans-mit data, often with added value, via the factory ethernet network to a controller, such as a PLC. 

As a result, IO-Link has begun to break down traditional con-trol hierarchies by making data from those dark corners visible to higher levels, as well as in the cloud. At the same time, IO-Link can group together devices in local process clusters to perform ‘smart tasks’ at the field level before sending added-value data to the higher control system.

At SICK we have seen the industry’s appetite for ‘smart’ and IO-Link sensors, from photoelectric cells to process sensors and distance sensors grow rapidly. Armed with IO-Link and the increased intelligence and processing power now available on ever smaller devices, we have seen our customers begin to realise many more distributed machine solutions more simply, and often more cheaply.

Enter the IO-Link Encoder

In some ways, encoders already have more ad-vanced processing func-tionality than many other sensor types.  So, it might seem a little surprising that they have been somewhat late to the IO-Link party.  But now that is all changing.

In January 2019, SICK launched its first range of absolute encoders with IO-Link, the only major global manufacturer with a broad sensor portfolio to offer the capability so far. The AHS36 singleturn and AHM36 multiturn absolute IO-Link encoders are everything you would expect from a SICK family of rotary motion sensors in terms of their precision, operating resilience and versatile mechanical connection options.

Now adding IO-Link to motion control sensors completes a vital building block on the transition to unlocking the benefits of Industry 4.0 – not just for a ‘start-from-scratch’ idealised Smart Factory, but to retrofit smart solutions into existing plant and machinery.

A Look At Encoder Development

Let’s think, for a moment, about where the rotary encoder has come from. Its basic function is to count whole or part rotations in electric motors, drives and other rotating machinery elements so that absolute position, distance and speeds can be measured.  There are times when that’s all that is needed. However, in some cases, encoders have also developed advanced capabilities to do much more.  Because they are fitted right at the heart of working machinery, they are ideally placed to provide additional data to the control system to monitor the health of processes and feed back data to guide the machinery in its functions.

The advent of the user-programmable encoder, simply set up with a PC-based webserver or handheld programming tool, or via the control HMI, made commissioning and integration into the machine and control system much quicker and easier.

Significant improvements in machine diagnostics and availability were further achieved over two-way industrial network communications such as Ethernet based fieldbuses. As well as providing information about their own operating health, encoders can provide temperature sensing and other feedback for application-specific condition monitoring. Position, speed, temperature, motion timers and other useful error thresholds can be programmed directly in the encoder. When the values go out of range, the encoder automatically sends a signal to the control via the Ethernet connection to indicate that an investigation must be carried out. 

Benefits of Using an IO-Link Encoder

At SICK, we find that our customers have often chosen EtherNet/IP, PROFINET or EtherCAT Ethernet fieldbus encoders due to their ease of integration. Their ability to interface directly with the network structure avoids the need to integrate conventional encoders via dedicated interface cards on the PLC rack, which takes time, adds cost and complexity.

Simple Interface: Enter the IO-Link absolute encoder, and the need for a dedicated interface card can also be eliminated. The IO-Link encoder together with any additional sensors such as presence detection or process sensors can be connected to a field gateway referred to as an IO-Link Master. This acts as a node on the Ethernet network, enabling onward communication with the PLC and or cloud

Low-Cost Wiring: Where other means of connecting encoders to the control system require costly shielded cabling and could involve wiring many devices individually to the PLC rack, IO-Link just uses standard unshielded cabling between the device and the IO-Link master. So, wiring costs can be dramatically reduced.

Compact Design: The amount of processing space needed to accommodate the communications interface inside an Ethernet encoder, usually means at least a 60mm diameter design. But with the IO-Link master performing the higher-level Ethernet interface, the

IO-Link encoder can be manufactured in a much smaller package. The 36mm SICK AHS/AHM IO-Link encoders are the compact result and can therefore be designed into confined spaces and smaller machines.

Easy Device Replacement: The SICK IO-Link encoders still offer all the benefits of programming through the PLC or PC and, in addition, there is now an ability to store and download the encoder parameters from the IO-Link Master. As a result, device replacement is simply ‘plug and play’.

Diagnostics: The SICK AHS/AHM absolute encoders also offer exceptional diagnostic information. Even on the basic models, already available, error warnings can be provided on a range of both application-specific and encoder health parameters such as position, speed or temperature out of range. 

In the advanced IO-Link versions, expected to be available in mid-2019, even more comprehensive provision and storage of diagnostic data such as temperature values, and operating times will be enabled.

Sensor Fusion

Adding motion sensing into the IO-Link mix offers untold possibilities – and could even begin to prompt new paradigms in the way we think about organising and configuring sensing capability within machines. It was already possible for virtually any sensor or actuator to be connected into an IO-Master to achieve a multitude of smart tasks, reducing the processing load on the PLC. Now we can start to integrate motion sensing from encoders with other sensors, opening up the potential for all sorts of new solutions. 

The Final Frontier – Just Imagine

Furthermore, with SICK’s advanced IO-Link encoders one final frontier of distributed processing can be achieved in the encoder itself. With the addition of a configurable output and input pin, a direct interface with another device can be enabled to realise ‘Smart Tasks’ in the encoder itself. This could be something as simple as an input to the encoder to tell it when to start and stop a length measurement, resulting in a length value output to the control system via IO-Link.

Another solution is to use the length measurement value calculated within the encoder to generate a direct digital output to a cutter or sealer, thereby completely eliminating the need to connect the encoder to a higher level control system. This is an example of so-called Edge Computing, one element of Industry 4.0, where distributed intelligence at the sensor/actuator level is utilised to dispense with the need for calculations normally performed inside a PLC.

At SICK we’re already beginning to evaluate other Smart Tasks, and we’re equally keen to engage with customers to develop their ideas and applications. We would be delighted to hear from anyone who may wish to solve current or future Industry 4.0 challenges in this way.

Conclusion

SICK has delivered a rotary encoder with IO-Link that OEMS can easily integrate into machine designs, and save money. For end-users, choosing the AHS/AHM 36 with IO-Link as part of an Industry 4.0 ready strategy, future proofs an installation and enables the addition of more flexibility and connectivity as required.

The ability to integrate a rotary absolute encoder via IO-Link, or even to process ‘smart tasks’ within the encoder itself, creates opportunities for both machine designers and end users to find new ways of managing sensing capabilities in an Industry 4.0 environment.

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