By Rolf Horn, Applications Engineer, DigiKey
Balancing the needs for Cloud connectivity and local control using programmable logic controllers (PLCs) in industrial networks just got easier.
Industry 4.0 networks are complex and include multiple levels of connectivity from IO-Link on the factory floor to field busses like EtherNet/IP and PROFINET connecting machines and PLCs and an Open Platform Communications Unified Architecture (OPC UA) interface reaching up to the Cloud.
In a traditional Industry 4.0 network, sensors, actuators, and other devices use an IO-Link master to connect with the field bus network, and devices on the field bus network use OPC UA and other protocols to connect with the Cloud.
Machine and factory network designers now have a new tool – IO-Link masters – that combines the usual EtherNet/IP, PROFINET, and other field bus connectivity with an OPC UA interface for direct connection to the Cloud.
That can be used to flatten connectivity and speed the delivery of critical data to the highest levels of the network.
Industry 4.0 factories require varying mixes of local control and Cloud connectivity. Each has its benefits. The best solution often combines PLCs and edge computers for responsive local control while using the Cloud to analyse complex data.
PLCs are rugged and designed for use in industrial environments. They are generally modular and can accommodate the changing needs of Industry 4.0 factories. PLCs are more compact and reliable than the relay-based systems they often replace. Perhaps most importantly, PLCs can support real-time control in critical applications with direct feedback from the connected machines and sensors.
Cloud connectivity provides essentially unlimited storage and computational capabilities. It can link data from various applications, controlled by individual PLCs, and support a harmonised and optimised overall factory operation. Cloud connectivity can offload administrative tasks from PLCs, and Cloud computing services can be quickly and economically scaled.
Traditional IO-Link
IO-Link is a point-to-point protocol, not a field bus. In a traditional Industry 4.0 network, IO-Link masters are the intermediaries between IO-Link devices on the factory floor and the field bus network. Each port on an IO-Link master connects to a single IO-Link device. The IO-Link master consolidates and translates communication from connected IO-Link devices and sends it on to the field bus network.
IO-Link masters are available for installation inside the control cabinet. They can connect to the field bus network as a remote connection point with an IP20 environmental rating or be used on the factory floor with an IP65/67 rating (Figure 1). There’s no direct connection between traditional IO-Link masters and the Cloud; all communications to the Cloud are channelled through and controlled by devices on the field bus.
Enhanced IO-Link and a parallel network
Adding OPC UA connectivity into an IO-Link master dramatically changes the possibilities for industrial network architectures. It’s no longer necessary for communications to be channelled onto the field bus to get up to the Cloud.
Time-sensitive data for real-time control can still be put onto the field bus. Less time-sensitive data can be aggregated and sent directly to the Cloud, removing that communication overhead burden from the field bus devices.
Pepperl+Fuchs refers to this new structure as a ‘parallel’ architecture since it can be used in parallel with standard industrial machine control systems. The key is the company’s MultiLink technology that supports the parallel use of an industrial Ethernet field bus for connecting with PLCs using a protocol like EtherNet/IP and message queuing telemetry transport (MQTT). This open-source messaging protocol uses OPC UA and can connect with devices on the Industrial Internet of Things (IIoT), like industrial computers, supervisory control and data acquisition (SCADA) systems, and the Cloud.
To complete the package, IO-Link masters with MultiLink also include an integrated web server and IO-Link device description (IODD) interpreter that supports the configuration of the field bus connection and attached IO-Link devices using a web browser (Figure 2).
Built on the foundation of Ethernet APL
MultiLink technology is built on the foundation of the Ethernet advanced physical layer, or Ethernet-APL, that allows Ethernet to be used for communication and power with process instrumentation over long distances. It’s based on the 10BASE-T1L Ethernet physical layer standard.
With a speed of 10Mbps and a 1,000-metre range, Ethernet-APL was designed for real time process monitoring and control, enabling parallel access. It supports EtherNet/IP, HART IP, OPC UA, PROFINET, and other higher-level protocols. It eliminates the need for gateways or other protocol conversions. It implements 10BASE-T1L using a special Ethernet physical connection (PHY) in Layer 1 of the Open Systems Interconnection (OSI) model (Figure 3).
Hubs & converters for network expansion
IO-Link hubs support expanding networks of sensors, actuators, and other devices. IO Link hubs allow several digital sensors and actuators to be connected to an IO-Link master using a standard sensor cable. For example, the ICA-16DI-G60A-IO IO-Link hub can handle up to 16 PNP digital inputs, and the logic level can be configured individually for each port.
Depending on the capability of the connected IO-Link master, this hub can deliver up to 500mA of power to connected devices. It’s rated for IP65, IP67, and IP69K. When a sensor with an analog output needs to be connected to an IO-Link network, designers can turn to the ICA-AI-I/U-IO-V1 IO-Link converter with an analog input for current or voltage and an IO-Link output. It’s rated for IP67, and the input can be set as follows:
Current input can be set as 0 to 20mA or 4 to 20mA.
Voltage input can be set as -10 to 10V or 0 to 10V.
IO-Link device offering
A comprehensive ecosystem of IO-Link devices is available for almost every industrial process, including sensing and control needs.
Pepperl+Fuchs’ IO-Link portfolio includes inductive proximity sensors, inductive positioning systems, photoelectric sensors, ultrasonic sensors, vibration sensors, rotary encoders, and identification systems (Figure 4).
Examples include:
The VDM28 distance measurement device uses Pulse Ranging Technology (PRT) to deliver a repeat accuracy of 5mm with an operating range of 0.2 to 15m and an absolute accuracy of 25mm.
The IUT-F191-IO-V1-FR2-02 RFID read/write device is optimised for industrial applications involving distances up to about one metre. The device reads and writes passive tags based on ISO/IEC 18000-63.
USB master for commissioning IO-Link devices
When it’s time to install and commission IO Link devices, network technicians can turn to the IO-LINK-MASTER02-USB (Figure 5). This USB master can connect IO-Link devices to a USB port on a PC. It’s designed to support testing, configuration, and servicing activities. Connected devices can be configured and parameterised. Device diagnostics is also supported. Devices with a low current consumption can be powered
directly from the USB master. Devices with higher power needs can be connected to an optional external power supply.
Conclusion
The addition of OPC UA parallel connectivity to IO-Link master devices has dramatically changed the options available to designers of Industry 4.0 networks. It’s now possible to flatten the network architecture and provide direct connections between the IO-Link devices on the factory floor and the Cloud. The new technology can be used in various use cases to improve operational efficiency.
This article originally appeared in the April 25 magazine issue of IoT Insider.
