Instrumentation • Electronics
Factory automation: closing the ‘last metre’
Daniel Heining explains how a smart interface can close the ‘last metre’ gap in factory automation.
T
he IO-Link interface provides an ‘intelligent’ method for closing the ‘last metre’ in the IO (input-output) field level of factory automation and reduces costs as well as staff-hours for engineering, installation and maintenance.
In process and factory automation, tremendous progress
has been made in the past decades, as can be seen when comparing today’s sensors and actuators with those from the early days of automation.
Automating repetitive process
The original idea was to use electromagnetic, hydraulic or pneumatic devices to automate repetitive processes. Then came freely programmable logic controllers (PLCs), more electronic advances and the evolution of intelligent interfaces, resulting in development of a huge number of highly integrated and powerful sensors and actuators. Today, simple binary switches have evolved into intelligent
communicative sensors. In this context, ‘intelligent’ describes sensor or actuator
devices that have, on the one hand, the ability to recognise and report defined conditions, and on the other hand, the capability to be diagnosed during error conditions and configured in the field. However, these bi-directionally communicating devices
need simple interfaces to communicate with the PLCs. Moreover, communication for calibrating the sensor/actuator devices is needed in most cases. In the past, many device manufacturers developed their own propriety communication solutions for calibration. This ‘last
meter’ gap in factory automation can be closed with a smart interface based on the IO-Link specification, which is defined by the IO-Link Consortium. IO-Link provides a simple and easy-to-use interface for intelligent sensor or actuator devices, as well as for more simple analogue and digital sensors and actuators. They are connected via a master on a field bus to a PLC or a parameter server. Here the IO-Link serves not as a bus system, but as a point-to-point connection with the objective of ensuring downward compatibility and integration into all bus systems in factory and process automation. That means standardised M12, M8 and M5 connectors with three-wire cables up to 20 meters in length can be used. IO-Link uses the IEC 61131- 2 standardised 24V DC signal.
Dispersed manufacturing locations
IO-Link is an international standard, which means it is likely to supersede most proprietary solutions in the future. In addition to the benefits in the actual application area within a fabric, a positive impact is that there will be a uniform ‘sensor language’ at locally dispersed manufacturing locations. IO-Link communication between master and device uses
a signal that can be processed with a standard UART (today’s standard for many microcontrollers). Because IO-Link is a point-to-point connection,
communication via the IO-Link telegram is much easier compared to bus communication. Communication conflicts and the long cycle times needed to recover from conflicts do not occur with IO-Link. IO-Link offers three communication rates: COM1,
COM2 and COM3. The COM1 data rate is 4.8 kBaud. COM 2 has a data rate of 38.4 kBaud, which is the most common speed, and the COM3 rate is 230.4 kBaud.
Benefits
With IO-Link, a world standard is already in place. It is system and field-bus independent and can be integrated into all types of sensors and actuators. The installation of IO-Link devices is cost-neutral.
Traditional (three-wire) cables, including typical connection methods, can be used. Using IO-Link, devices can be parameterised during
operation. Central data from a parameter storage server enable immediate parameterisation. Complex local programming can be a thing of the past,
Fig.1. IO-Link PHY IC as WL-CSP.
which is especially advantageous for very small devices with difficult access. With IO-Link, the down times for programming are significantly reduced (up to 90 per cent) and the quality of the production equipment is much higher.
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