IO-Link
With the brand name IO-Link , a is communication system for connection of intelligent sensors and actuators in an automation system in the standard IEC 61131-9 under the designation S ingle-drop d igital C ommunication i nterface for small sensors and actuators (SDCI) is normalized. The standardization includes both the electrical connection data and a digital communication protocol, via which the sensors and actuators exchange data with the automation system.
System structure
An IO-Link system consists of an IO-Link master and one or more IO-Link devices, i.e. sensors or actuators . The IO-Link master provides the interface to the higher-level controller ( PLC ) and controls communication with the connected IO-Link devices.
An IO-Link master can have one or more IO-Link ports to which only one device can be connected. This can also be a "hub" which, as a concentrator, enables conventionally switching sensors and actuators to be connected.
An IO-Link device can be an intelligent sensor, actuator, hub or, due to the bidirectional communication, also a mechatronic component e.g. B. be a gripper or a power supply unit with IO-Link connection. With regard to IO-Link, intelligent means that a device can provide identification data, e.g. B. has a type designation and a serial number or parameter data (e.g. sensitivities, switching delays or characteristics) that can be read or written via the IO-Link protocol. Changing parameters can This is partly done by the PLC during operation. But intelligent also means that it can provide detailed diagnostic information.
The parameters of the sensors and actuators are device and technology- specific , so there is parameter information for each device in the form of an IODD (IO Device Description) with the description language XML . The IO-Link community provides interfaces to an "IODD Finder" that can be used by engineering or master tools to present the appropriate IODD for a device.
Transmission method
IO-Link relies on the classic 24 V signals of IEC 61131-2 . The signal level "0" (0 V) or "1" (24 V) traditionally indicated that a threshold value was exceeded or not reached. This operation is referred to as "switch mode" or SIO. With IO-Link, this switching (0/1) can be carried out quickly one after the other and coded. The coding and the resulting frames and data packets are defined in the IO-Link protocol. Switching from "switching mode" (IO-Link SIO) to "data packet mode" is done by a "wake-up" process triggered by the master.
If the transmission fails, the data packet is repeated twice. Only after the second retry fails, the IO-Link master detects a communication breakdown and reports this to the higher-level controller.
IO-Link Safety
IO-Link Safety is an extension of IO-Link in that it provides an additional safety communication layer on the existing master as well as on the device layers, which then become "FS master" and "FS device". One also speaks of the black channel principle. The concept was checked by IFA and TÜV SÜD .
IO-Link Safety has also expanded the output switching elements OSSD (Output Switching Signal Device) that are usual for functional safety with electro -sensitive protective equipment (ESPE) to form OSSDe. As with standard IO-Link, an FS device can be operated both in switching mode as OSSDe and via functionally safe IO-Link communication.
The safety rules of IEC 61508 and / or EN ISO 13849 must be observed during implementation .
IO-Link wireless
IO-Link Wireless is an extension of IO-Link on the physical level. An IO-Link wireless master ("W master") behaves like a master to the higher-level system. "Down" to the IO-Link wireless devices ("W-Devices") there are only virtual ports over a radio link based on IEEE 802.15.1 .
A transmission cycle consists of two phases. To transmit output data, the W-Master sends a multicast W-Frame ( downlink ) with data for the W-Devices in assigned time slots. Then the W-Master goes to receive and collects data in the uplink from the W-Devices, which send one after the other according to an agreed fixed scheme.
Frequency hopping and channel blacklisting are used to secure the transmission .
Manufacture of equipment
All IO-Link specifications are available free of charge on the website of the IO-Link consortium in the download area. For implementations in devices, the policy of the IO-Link community must be observed.
The manufacturer declares the conformity of the implementation of a master or device to the IO-Link or SDCI standard with a signature on a manufacturer's declaration. The IO-Link community has created the necessary requirements for this through an IO-Link test specification and the availability of master and device testers. There are competence centers for development support. Their task is to provide advice and development in the development of IO-Link devices. The manufacturer's declaration has been mandatory since July 1, 2011 for all devices that are put into circulation from this point in time.
literature
- Peter Wienzek, Joachim R. Uffelmann: IO-Link. Smart devices need simple interfaces. Oldenbourg Industrieverlag, Munich 2010, ISBN 978-3-8356-3115-1 .
- Joachim R. Uffelmann, Peter Wienzek, Myriam Jahn: IO-Link. Bridge technology for Industry 4.0. 2nd Edition. Deutscher Industrieverlag, Essen 2018, ISBN 978-3-8356-7377-9 .
Web links
- Digital sensor outputs: PNP / NPN / PP or IO-Link?
Individual evidence
- ↑ IODD finder website of the IODD database
- ↑ Description of IO-Link on the website of the IO-Link organization
- ↑ IO-Link Safety system description technology and application
- ↑ IO-Link Wireless Exposé pdf in English
- ↑ IO-Link specifications for free download
- ↑ List of Competence Centers (IOL-CC)