Smart encoders with IO-Link: the ideal solution for digitised automation systems

Written by Martin Hummel, product manager for encoders in the Motion Control Sensors division of SICK Stegmann GmbH, Donaueschingen, Germany.

The use of intelligent sensors in the field is a key requirement for process digitisation, which is becoming increasingly widespread in factory and logistics automation. In addition to measuring posi-tions and speeds in machines and other applications, encoders with IO-Link can also supply valuable information for process improvement and condition monitoring, for example. However, it is the smart IIoT (Industrial Internet of Things) encoders, such as the AHS36 IO-Link Advanced and AHM36 IO-Link Advanced from SICK, that offer the ultimate added value and, with their remote intelligence, support efficient edge computing systems.

Both rotatable advanced encoders have been designed as intelligent, future-proof field devices for integration into smart IIoT structures. In addition to measuring positions and speeds, the encoders can record and communicate a wide variety of diagnostics data that can be used in condition monitoring, for example. Other new features include the option of configuring and monitoring a broad range of application-related thresholds in the encoder itself and reporting figures that fall below or exceed the threshold. As a result, the AHS36 IO-Link Advanced and AHM36 IO-Link Advanced are able to make decisions locally and to act independently, in other words without checking back with the machine’s automation system. These smart tasks can significantly reduce communication loads and improve response times in the Ethernet and fieldbus networks where the IO-Link encoders are located. In addition, the direct communication between IO-Link devices in the field has a positive impact on the functioning and quality of processes. This means that efficient edge computing systems and IIoT encoders can generate real added value. However, it is essential that the fundamental sensor concept is correctly designed, in particular in relation to the mechanical and electrical integration of the encoders.

Mechanical integration: maximum flexibility and compatibility

The rotatable singleturn AHS36 IO-Link encoder and multiturn AHM36 IO-Link encoder are used to measure absolute positions and speeds in machines and other applications in factory and logistics automation systems. The encoders are fully magnetic and have a tough metal housing which makes them highly rugged. At the same time, they offer a level of precision that can be tailored to the needs of the specific application. The singleturn AHS36 IO-Link variant has a resolution of up to 14 bits, while the mechanical multiturn AHM36 IO-Link variant, which requires no battery or maintenance, provides a resolution of up to 26 bits.

From an integration perspective, both product families are designed for maximum flexibility. With a diameter of just 36 millimetres, they are ideal for applications where the installation space is limited. At the same time, the different shaft versions and the multifunctional adapter flange with a variety of mounting hole patterns allow for a high level of flexibility when designing and modifying the mechanical interface. The result is almost total compatibility with larger components and with other makes of sensor currently on the market. This makes the move to these innovative and intelligent encoders simple and risk-free.

Electrical integration: communication for the digitised age

Unshielded standard cables can be used for the electrical connection of the encoders. These are significantly more cost-effective than special cables. The encoders are installed using optional rotatable connectors or cable outlets which keep the installation space to a minimum. The IO-Link interface for transmitting process data such as position and speed is a standard feature of these singleturn and multiturn encoders. The SICK encoder portfolio also includes products with SSI and CANopen interfaces. The IO-Link encoders can be integrated quickly, easily, and cost-effectively into higher-level fieldbus environments via an IO-Link master by downloading their IODD (IO Device Description) from the central IODDfinder portal. The encoders can also be configured using this interface or the SICK SOPAS Engineering Tool. In contrast to Ethernet encoders, the IO-Link encoders do not need a separate voltage supply or individual cables. Their signals can be collected by an IO-Link master in the field and sent via one single cable. This significantly reduces the cost of integration. If an individual encoder has to be replaced, the data storage function makes it possible to transfer the encoder’s settings directly to the new device via IO-Link, which keeps down-times to a minimum.

Smart advanced functionality makes the difference

The IO-Link interface of the AHS/AHM36 encoders forms the basis for the different communication services provided by the basic and advanced models. The basic version offers all the functional benefits of IO-Link, together with an enclosure rating of IP65 and the ability to withstand working temperatures between -20 °C and +70 °C. These advantages include application-specific configuration using function blocks via an IO-Link master and easy integration into a wide range of higher-level Ethernet and fieldbus networks.

The advanced models can be used in a broader variety of environments because they have an IP66 or IP67 enclosure rating and are designed to withstand working temperatures of -40 °C to +85 °C. Most importantly, the enhanced, remote intelligence of the new generation of IIoT encoders fulfills all the requirements for successful integration into more comprehensive edge computing systems in Industry 4.0 and smart factory environments. One key feature of the smart encoders is the variety of additional data that can be configured. In the basic versions, the steps per rotation, the counting direction, and the sampling rate for calculating the speed are just some of the parameters that can be adjusted. The advanced versions also allow the format of the 8-byte process data output, the round axis functionality, and the electronic cams to be modified. In addition, the circumference of a measuring wheel can be entered and the upper and lower thresholds for position, temperature, and diagnostics parameters can be specified. This means that the encoders perform functions that would otherwise have to be carried out by the machine’s automation system. As a result, less communication is needed between the field and control levels, together with less programming in the machine’s PLC, for example. The SICK smart encoders also have two diagnostics memories, one of which can be reset by the customer. The other stores the entire diagnostics history in an unmodifiable format. In the advanced encoders, connection pin 2 can also be used as a multifunctional pin. For example, as a trigger output the encoder reports via the pin when a threshold has been reached. As a trigger input, the pin can be used to set the preset value or to reset the diagnostics memory. Smart tasks can also be activated via pin 2, for example when the signal from a photoelectric sensor causes the encoder to start measuring the length of an object. These and other smart tasks that can be carried out using the AHS36 IO-Link Advanced and AHM36 IO-Link Advanced encoders are based on integrated logic functions which enable the IIoT encoders to make and implement independent automation decisions. These include activating sorting and outfeed units in packaging machines and stationary conveyors.

Stainless steel versions for the food and pharmaceutical industries and for outdoor use

Both the basic and advanced variants of the AHS36 IO-Link and AHM36 IO-Link represent the ideal additions to SICK’s existing portfolio of AHS/AHM36 encoders with CANopen and SSI interfaces. The AHS/AHM36 IO-Link Advanced in particular, which is only 36 mm in size and comes with an IO-Link interface and comprehensive functionality, sets new performance standards for the market. In addition, both encoders are also available in stainless steel versions: the AHS36 IO-Link Inox and the AHM36 IO-Link Inox. These encoders are mechanically rugged and resistant to chemicals. In addition, they have a long service life and an IP69K enclosure rating. The stainless steel versions can be used in the food, beverage, and pharmaceutical industries and are also suitable for outdoor applications. In the near future, SICK plans to launch new versions of the encoders with metal and stainless-steel housings which have an SAE J1939 interface. This type of interface is commonly used in the automation of agricultural and forestry machines, road construction and mining trucks, and waste disposal and municipal vehicles.

In all applications the AHS36 IO-Link and AHM36 IO-Link IIoT encoders function as intelligent, communication-enabled, decision-making sensors and open up new prospects for efficient and future-proof edge computing.