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Intelligent I/O enables localised decision making

Intelligent I/O enables localised decision making

When machines are controlled by centralised PLCs, making any big changes – say to the layout of a conveyor – can become time consuming, reducing overall system flexibility. Even decentralised PLCs with high I/O counts don’t always make it easy. But suppose you could have small I/O blocks with embedded PLC functionality. Say hello to a new breed of field logic controllers, with simple programming undertaken at the fieldbus level.

The phrase ‘localised decision making’ immediately conjures up images of council meetings where a group of people make decisions that will affect those in the immediate vicinity. The dictionary definition goes something like this: an administrative body for a small geographic area, such as a city, town or county.

We can equate this to industrial automation in a modern process plant where the PLC represents the national government but it doesn’t necessarily need to be involved in localised decisions. For example, zero pressure conveyors are widely used in industry to protect packaged goods from being damaged by packages backing-up in the event of a conveyor jam. The sensing logic in this type of application doesn’t necessarily need PLC involvement and could be employed locally to the conveyor. It can also be expanded as required, without the need for PLC reprogramming.  

Demonstrating its commitment to flexible, custom solutions, Turck has developed what it is describing as the next major step in industrial control: the field logic controller (FLC). FLC solutions are made possible by a new programming environment that allows users to set conditions and actions directly at the field level. By utilising HTML5, Turck provides a complete engineering environment for users to write, run, simulate, debug, and monitor code, all without the need for a PLC. 

Using a simple ‘Condition’ and ‘Action’ principle that is integrated into a flow chart user interface, the programming environment allows users with little or no experience to configure and program FLC devices to carry out tasks that fieldbus devices have never been able to do before. This simplified, straightforward approach allows programming at the fieldbus level, eliminating the need for a PLC in some stand-alone applications, while still allowing the device to communicate with a PLC as necessary.

Using FLCs, Turck’s multiprotocol block I/O devices can act as simple I/O devices or as stand-alone logic controllers. The devices in the range include the TBEN on-machine block I/O, the FEN20 in-cabinet block I/O and the BL compact on-machine flexible I/O block. Looking at these individually, the TBEN-L-PLC enables the creation of modular machine concepts for Industry 4.0. The Codesys 3 controller is a compact IP67 PLC for controlling small or modular machines. Thanks to its robust housing and high degree of protection, the TBEN-PLC can operate directly in the field and thus enables the implementation of machine and plant controls without the need for a control cabinet. Machine automation concepts and the use of pre-assembled cables reduce the cabling effort and simplify commissioning. Decentralised solutions without the use of control cabinets also save time and costs.

The large number of communication interfaces underlines the tremendous flexibility of the TBEN-PLC. When used as a master, the device also supports Modbus RTU, CANopen and SAE J1939 in addition to the industrial Ethernet protocols Profinet, EtherNet/IP and Modbus TCP. The RS232 and RS485 serial interfaces can also be used as required in Codesys. The block I/O controller also offers eight universal I/O channels for the direct connection of sensors and actuators.

TBEN-PLC can also be run as a slave in the Ethernet networks Profinet, EtherNet/IP and Modbus TCP, as well as in Modbus RTU and CANopen networks, which enables it to be used as a protocol converter. For example, the controller can operate as the CANopen manager of a machine module networked with CANopen and connect this module to a system running with Profinet. As part of the increasing digitisation of industry, this enables existing machine concepts to be made fit for the challenges of closely networked, highly flexible production in an Industry 4.0 environment.

While the new programming option is not designed to replace a PLC outright, it can be used to change the way we think about control, allowing FLC devices to be used without a PLC in stand-alone applications, perform arithmetic functions, timing functions, counting and even toggle bits and share data with a PLC via assigned I/O variables. In short, it challenges what an I/O device can do by creating a hybrid between simple block I/O and higher level PLCs. 

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