Extending the Reach of Control Systems with IO-Link

Don Horne   


With the wide implementation of Fieldbus technologies and Ethernet for industrial applications, the need to extend the reach of the control system to the sensor has become necessary. This realization is highlighted by the fact that more and more sensors and actuators are in use today. These sensors are already equipped with microprocessors which are used to control displays and LED indicators, set working parameters and store configured data.   

Accordingly so, the obvious next step is to overcome the bottleneck of the simple on/off (2 state) standard interface, and make additional functions accessible upstream for feedback and control of the automation/process system. 

The critical component of design was to incorporate compatibility with existing technologies. The consortium identified this as the primary objective during development, in order to guarantee easy implementation and protect the investment of existing sensor manufacturers.

What is IO-Link?
IO-Link is based on a simple 3 wire point-to-point connection between the sensor/actuator and interface module connecting to the field level. Furthermore IO-Link has standardized on IO technology (IEC 61131-9) for communication with sensors and actuators.

Interoperability is the cornerstone of this technology, ensuring that multiple vendors’ products will work together by design.

Up until now, the on/off connection was only designed for transferring switching information, but IO-Link is designed to transmit 2 bytes of data, normally within a 2 ms cycle, combining switching status and data channel. Other information can be exchanged in addition to the process values, such as parameters, diagnostics in a standard switch, or communication mode.

What are the key user benefits?
IO-Link users benefit from reduced maintenance costs, reduced trouble shooting time, more efficient processes, along with improved machine/process availability.

Integration of standard on/off 24 VDC devices into automation systems is done via IO-Link multiport I/O hubs. Variants are available for inputs, outputs and universal digital I/O’s.

Sensor Mounting
All IO-Link devices allow parameter changes and diagnostic evaluation within the engineering system, or by using separate tools. With this flexibility, devices can now be mounted in the machine or process, where best suited for the application and future maintenance. These devices no longer need to be positioned in areas for operators to access visual displays or switches.

How is the upstream communication to PLCs and control systems made possible?
IO-Link is a subnet that communicates upstream to standard Master devices for all major Fieldbuses, including Ethernet. A full service provider can offer a complete range of solutions from Master Gateways for modular I/O systems, to Multiprotocol Ethernet Gateways that communicate with PROFINET, EtherNet/IP and Modbus TCP networks.

Engineering Tool Integration
Standardized interfaces (DTM/IODD) implement easy and seamless integration into engineering tools. Integration into system wide tools such as Asset management or centralized configuration tools is also made available for process industries.

As mentioned, connection to the enterprise level is accomplished using Master modules and standard Ethernet nodes.

Wiring is Simple
IO-Link uses the same standard unshielded 3-core cables with standard connectors used in conventional I/O. This eliminates problems with complex devices that follow different standards and are often hardwired through multipole connectors. This simple 3 wire cable can be up to 20 meters in length, giving the user the ability to locate sensors some distance away from the IO-Link Master.

Device Identification
Integrated device identification called IODD (IO Device Description), ensures that in the case of component replacements, the correct device has been installed. As each device contains detailed information regarding manufacturer, type, etc., component replacement can be safely handled automatically. Once the new device is installed and connected, digital parameters are “pushed” to the device from the Master, via standard wire connection. The newly installed device now has the same parameters as the original, without the need for additional calibration.

IO-Link has the benefits of reduced machine costs through:
•    Faster installation and setup
•    Reduced inventory when used with intelligent multi-purpose devices
•    Only one I/O module and standard low cost cables required for up to 16 inputs
•    Reduced I/O footprint, made possible with smaller junction boxes and simple connections
•    Costly sensors with displays and LEDs are no longer required due to pushed parameters stored remotely in the Master.
•    Reduced engineering time and lower documentation costs during the engineering phase.

Products available with IO-Link
Available sensors that support IO-Link include: Photoelectric Sensors, Ultrasonic Sensors, Temperature Sensors, Pressure Sensors, Flow Sensors, Encoders, Linear Position Devices, and Inclinometers. Other devices include Light stacks, Valves, and Drives.

Standard Wiring
IO-Link does not require any special wiring. The sensors and actuators can continue to be connected using the proven, attractively priced, and unshielded industrial three wire cables.

An example of a special project solved using IO-Link and other components:   

A client wanted to upgrade existing tooling. The project required an identification system and non-contact method of detecting movement on a robotic tool changer.

The solution incorporated IO-Link and an inductive coupler. As a standard, all IO-Link devices must have a Unique Identification code (UID) and description. Utilizing the UID transmitted via the TURCK Inductive Coupler, Digital input modules located on all three end effectors, allowed the customer to accomplish both goals. The UID provides tooling identification, while the inductive coupler offers a non-contact solution for power when the end effector is mounted to the robot arm.

Data exchange for up to 16 sensors is carried across the air gap between the primary and secondary inductive coupler. This eliminated the need for costly RFID systems and high maintenance slip rings.

Gary Stortz – Sales Manager, Ontario Region TURCK Chartwell Canada Inc.
Mario Sabatini – Automation Application Specialist TURCK Chartwell Canada Inc.


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