Bryan Hall, the Marketing Director of Balluff, presents a practical view of the new IO-Link system for connecting I/O and identifies areas where it can save costs.
First of all, IO-Link is a point-to-point connection between the I/O module and the sensor or actuator, it is not a bus system. Rather, the familiar signal technology of the binary interface 0V and 24V is used with pulse modulation to send data. What is more, from economic and installation considerations, a major benefit is that standard three-wire M12 connectors are used throughout, so there is no requirement for multicore screened cable - even, for example, with distance and measurement sensors that previously utilised 'special' shielded eight-wire connectors.
The IO-Link controlling module is known as an IO-Link Master; this interface communicates between the bus system (Profibus, DeviceNet, CanOpen) and the sensors and actuators. It can take the form of an IP67 rated machine-mounted unit or, alternatively, under development is an IP20 panel-mounted construction. Standard, analogue and advanced sensors such as distance and measurement sensors can all be connected to the IO-Link Master, together with further I/O devices including valve clusters, pressure sensors and multi-way mechanical switches. Sensor hubs, similar in construction but more advanced in design, to the familiar non-intelligent splitter box further expand the capability of the system for both standard and analogue sensors.
As what is believed to be the first universally standardised interface in control technology, IO-Link transmits all sensor and actuator signals to the controller. Likewise, IO-Link passes control data down to the lowest sensor level. All this makes automation even more powerful than ever before. And it does it by means of simple three-wire connectors.
Benefits of IO-Link
IO-Link offers benefits to machine builders, system integrators and end users in terms of installation, parameter setting and diagnostics.
Installation: With IO-Link you can uniformly wire various sensors and actuators together. You do not have to retrofit your system, nor replace the proven unshielded industrial cable. Special bus systems are also unnecessary, since IO-Link operates independent of any particular fieldbus. This makes installation 'child's play': Simply integrate IO-Link into your existing system – just the way you need it. Upward compatibility with conventional technology means expansion is possible at any time.
Parameter setting: An additional advantage for process quality is that sensors and actuators can now be simply exchanged, as the controller specifies the necessary settings. The parameters stored there are immediately sent. In many cases, no teach-in procedure is required. Timely configuration also takes place when there are changes in the production process, such as when product or size is changed or materials and recipes substituted. This means: shorter setup times; longer machine runtimes; high reliability; increased efficiency.
Diagnostics: Continuous monitoring of data ensures reliable operation. Errors are detected centrally and the system constantly readjusted. This means diagnostics are continuous – with positive effects on process quality: improved noise immunity compared with analogue signals; simplified servicing; lower maintenance costs; increased system availability; higher productivity.
Process and service data
Whereas today's binary connection of sensors and actuators is designed to send process data as a single bit, namely the switching state information, this bottleneck is eliminated with IO-Link, which instead offers a channel for process and service information.
Typically 2 bytes of information are sent on this channel at 2ms intervals. This not only increases the amount of process data significantly, but also satisfies current demands with respect to diagnostics and parameter data transmission.
In Process data (cyclical) communication mode, 2 bytes of input or 2 bytes of output data data (to a maximum of 32 bytes) can be received/sent. In deterministic mode, IO-Link achieves a 2ms cycle time for 16 bits of process information. In service data mode, there is no interference with the process data.
Alternatively, in switching mode the switching signal is on Pin 4 of the M12 connector. Parameter setting can then be carried out through the other communication modes, then teh connection reverts back to SIO (standard I/O) mode.
IO-Link offers many possibilities for potential cost reduction in materials, engineering design and factory shop floor time by virtue of its simplicity and ease of use at both the planning stage and in its implementation.
Logistics, planning and machine build: Simplified and reduced stocking can be achieved thanks to the uniform interface for all I/O. In addition, reduced design effort is available through minimal consideration of connector issues. Purchase costs are also lower, since simple, unshielded industrial cables can be used throughout. Centralised parameter setting by the controller means that, for instance, it is no longer necessary to make special mounting provisions for the location of pressure sensors; rather they can be fixed in the most economical position, thereby saving on pipework and fabrication.
Installation, service and maintenance: Integration into the fieldbus through the uniform interface and the use of traditional, unshielded industrial cables makes installation straightforward. Reduced start-up times are achieved by virtue of the controller taking over the parameter setting. Incremental expansion is available through the simultaneous use of binary and analogue sensors and actuators. Reduced machine downtime results from reliable error detection and localisation, fast sensor replacement and centralised data setting.
Less downtime, more uptime: High automation precision is achieved through direct data transmission. Re-adjustment settings are reliable, since data monitoring runs continuously (eg maintaining a specified level or a switching hysteresis).
Economical connection of sensors to the bus network
Simply use the IO-Link Master and sensor Hubs. The Master has four IO-Link ports for the connection of dedicated IO-Link sensors/actuators, plus four standard connection ports. Each Hub is connected to the Master via an IO-Link port, with each Hub connecting up to 16 standard sensor inputs or alternatively eight standard and four analogue sensor signals. With four Hubs connected to each Master, that makes a maximum of 64 sensors via the Hub/Master combination, plus those connected direct to the Master. There is therefore a potential cost benefit from reducing the number of network nodes in applications where there is a high concentration of sensors.
Furthermore, it is only a three-core unshielded connection between the Hub and the IO-Link Master. This can also lead to additional savings in cabling where, for example, a multicore high-flex drag chain cable might previously be used to connect up to 16 sensors via a conventional splitter box; this can now replaced with a simple three-core high-flexibility cable between the Master and the Hub.
The performance capability of modern machines and systems in factory and process automation has increased remarkably in recent years. The machines are not only faster, smaller and more reliable, but they have at the same time become safer and, above all, more flexible.
All of this places high demands at not only the control and fieldbus level, but also the sensor/actuator level. On the other hand, it is evident that the binary interface is not capable of forwarding all the process-relevant data to the controllers. This is just where IO-Link enters the picture.
IO-Link covers the three essential requirements of automation technology: the ability to use the controller for setting parameters; the desire for more detailed and informative diagnostics; and all of this achieved through an electrically and mechanically uniform interface. The last point represents enormous potential when you consider the variety of interfaces for analogue and digital signals, which may not be at all similar except for their functions. IO-Link is believed to be the first comprehensive and generally valid approach to achieve this reduction and subsequent cost savings.
More information about IO-Link and its capabilities is available via Balluff: email or visit www.balluff.com.