In the era of Industry 4.0, intelligent automation relies on advanced control systems and continuous data exchange enabled by industrial connectivity, such as IO-Link, to unify machine devices and facilitate advanced monitoring and diagnostics.
Figure 1: IO-Link complements existing network protocols by easily integrating into fieldbus or Ethernet networks via the IO-Link primary.
Standardized networks and communication-equipped devices are the foundation of industrial connectivity. While numerous protocols exist, not all meet the demands of modern automation for data exchange and intelligence. IO-Link was developed to address these requirements across a range of applications.
IO-Link is a wired point-to-point communication protocol that enables bidirectional data exchange between devices. Local controllers typically have multiple IO-Link ports for various devices, making it a point-to-point protocol.
Introduced in 2009 by a consortium of 41 members, IO-Link has gained widespread acceptance for optimizing operations, reducing downtime, and cutting costs.
Defined by the IEC 61131-9 standard, IO-Link is supported by various manufacturers such as Siemens, Omron Automation, IFM, Balluff, Cinch Connectivity Solutions, Banner Engineering, Rockwell Automation, Sick, Pepperl+Fuchs, and others.
Figure 2: The choice of connector for the connecting cable is determined by the port type, and the mode of a primary's port is determined by the connected device and the ongoing operation.
Figure 3: IO-Link enhances advanced control and automation systems. In the machine-tool industry, IO-Link sensors are extensively used for workpiece clamping verification and monitoring milling tool pressures and positions.
IO-Link devices enable machine monitoring and support system adjustments. In the machine-tool industry, IO-Link pressure sensors verify workpiece clamping, reducing rejected workpieces. These devices also aid maintenance by reporting status, like position sensors on assembly machines ensuring alignment. Analysis of IO-Link diagnostics data allows technicians to predict and prevent errors and identify areas for operational improvement.
Figure 4: IO-Link enhances advanced control and automation systems. In the machine-tool industry, IO-Link sensors are extensively used for workpiece clamping verification and monitoring milling tool pressures and positions.
IO-Link supports control and automation functions, often connecting to a higher-level PLC or host system for autonomous operations. This connection typically utilizes standardized fieldbus or Ethernet protocols. Many IO-Link primaries come with fieldbus or Ethernet ports. In advanced control applications, devices integrate in one of three ways: 1) Direct connection to the host computer or PLC. 2) Connection to an IO-Link primary using the IO-Link protocol. 3) Use of IO-Link compatible communications, connecting to an IO-Link primary via an IO-Link hub. IO-Link hubs link non-IO-Link devices to the primary. With fieldbus and Ethernet connectivity, long-distance placement of IO-Link primaries is possible, whether in a control cabinet or at the outermost machine points. In advanced assembly, IO-Link primaries act as low-level controllers, handling both digital and analog signals, such as data from XY stage linear encoders. They serve as gateways, transmitting processed field-device data to PLCs or other system controllers.
Figure 5: The IO-Link connection interface is very small and can fit on most compact field devices.
IO-Link's third application is enhancing devices' intelligence. IO-Link-enabled sensors can receive instructions, perform self-testing, and provide detailed data, beyond simple on-off signals. For instance, IO-Link temperature sensors continuously report precise temperature values for better process automation.
IO-Link's compact physical connections contrast with bulkier fieldbus and Ethernet interfaces, making it suitable for smaller field microdevices. IO-Link also enables precise control, allowing actuators to respond to specific conditions rather than basic on-off commands.
Input devices like pushbutton switches from suppliers such as Rafi can leverage IO-Link for smart features, including color-coded indicator lights.
However, IO-Link has limitations, being a wired protocol with a 20m cable length constraint and a 32-byte data transmission limit per cycle, making it unsuitable for data-intensive devices like cameras.
IO-Link systems offer versatile applications, seamlessly integrating with existing protocols for extensive control and data collection systems. Their appeal lies in simplicity, with just an IO-Link primary, devices, and connectorized cables. Easy plug-and-play installation and cost-effectiveness further enhance IO-Link's advantages.
The IO-Link consortium's collaborative efforts have ensured broad compatibility among controllers, devices, and actuators from various manufacturers, providing design engineers with a wide array of equipment choices for specific use cases.