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PLC programming is something for specialists. After all, the possibilities are still limited and the user interfaces used are usually no longer up to date. For this reason alone, some companies are already offering apps to expand the range of functions. However, these are usually limited to the company's own interfaces. The SmartFactory Kaiserslautern technology initiative shows how such closed ecosystems, which run counter to the spirit of Industry 4.0, can be broken down.

Thinking in wiring diagrams

In the past, machine controllers were based on hardwired controllers, also known as connection-programmed controllers. This logic was transferred to the programming environments, which often date back to the 1970s and are designed accordingly. In-house specialists have mastered all the tricks to maximize the possibilities. This makes it significantly easier and more secure to implement circuit diagrams and logic than with Python or C++. However, because the PLC language is not a general-purpose language, it is significantly limited in terms of functionalities that go beyond the classic control of a machine, such as networking or machine learning. That is why a link with modern software will be necessary in the future.

Apps as an extension of PLC programming

Manufacturers such as Siemens and Bosch Rexroth already offer apps for expansion. This makes it quicker and easier to implement an adjustment. Apps can be developed in-house using common programming languages or can be found in app stores. However, this requires the use of a proprietary interface. In practice, this means that each program must be adapted to the respective interface in order to access the PLC. “However, this approach has limitations,” emphasizes researcher Thomas Barth, who is doing his doctorate on the subject of PLC interfaces. ”We need a new communication standard here in order to exploit the full potential of container-based automation software.”

The interface between the PLC and the app is getting an all-access pass

A future research project will investigate what a standardized data interface between apps and containers, in particular to the PLC, could look like and what requirements it would have to meet. Barth is currently working on the implementation. A Yaskawa robot is synchronized with a linear axis from Bosch-Rexroth. “This application example already reveals many practical requirements,” says Barth. ”The end result should be a manufacturer-independent standard for app-to-app communication that is freely available and makes the use of container-based control systems more flexible and cost-effective.”

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