Adding motion to the IO-Link mix

24 April 2019

Darren Pratt explains why adding IO-Link compatibility to an encoder is a vital breakthrough on the road to Industry 4.0.

Sensors of all kinds are the ‘eyes and ears’ of machines in Industry 4.0 and the appetite for ‘smart’ and IO-Link sensors – from photoelectric cells to process sensors and distance sensors – has grown rapidly. Armed with IO-Link and the increased intelligence and processing power now available on ever smaller devices, it has become possible to realise many more distributed machine solutions more simply, and often more cheaply.

IO-Link provides a standard open communications gateway that enables a common architecture to be used for sensors and actuators in a machine. Through IO-Link, devices are able to cooperate at the lowest level of the automation hierarchy, then link, through an IO field gateway, to transmit data – often with added value – via the factory ethernet network to a controller.  

Grouped together in local process clusters, sensors can perform ‘smart tasks’ at the field level. IO-Link has also begun to break down traditional control hierarchies by making data visible to higher levels, as well as in the cloud. Transparent access can even be provided to the intelligence on board the sensor itself. 

Adding motion 
With an the IO-Link enabled encoder motion sensing is added into the IO-Link mix, opening up countless new possibilities for plant and machinery. It could even begin to prompt new paradigms in the way we think about organising and configuring sensing capability within machines.

The AHS36 (single turn) and AHM36 (multi turn) IO-Link absolute encoders are new offerings from SICK which are able to achieve quick, easy and economical higher-level fieldbus integration via an IO-Link Master. 

Adding IO-Link compatibility to encoders has achieved cost-saving machine integration starting with a compact design: With the IO-Link Master performing the higher-level Ethernet interface, the IO-Link encoder can be manufactured in a much smaller package.  

The need to use a dedicated interface card on the PLC rack is also eliminated, saving time, cost and complexity.  Standard unshielded cabling can be used between the encoders and the IO-Link master, so wiring costs can also be dramatically reduced.

In addition to programming through the PLC, or with a PC, it is now also possible to store and download the encoder parameters from the IO-Link Master, so device replacement is simply ‘plug and play’.

IO-Link absolute encoders can offer high levels of diagnostic transparency. 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. Advanced versions from SICK will be able to provide even more comprehensive provision and storage of diagnostic data such as temperature values, and operating times.  

With SICK’s AHS36/AHM36 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 eliminating the need to connect the encoder to a higher-level control system.  

Darren Pratt is product manager for Encoders and Industrial Instrumentation at SICK UK.

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