PLCs run a real-time proprietary operating system and have a hardened embedded processor. They have become one of the best options for various industrial automation solutions based on their increased programming flexibility and ease, smaller sizes, larger memory, scalability, and Gigabit Ethernet and built-in wireless features.
In a nutshell: today’s PLC technology is flexible, easy to use, well-known and dependable. That is why the use of PLCs to control large physics machines has also become universal. Nevertheless, PLC deployment was traditionally the domain of electrical engineers. With rapid new approaches, including integration with open-source frameworks such as EPICS, PLC program development is increasingly becoming a software engineer’s game.
Beckhoff Communication Options
We have various projects in which we have found Beckhoff to be the optimal choice for PLC technology in our customers systems. In our experience, Beckhoff offers good round-the-clock user support and affords good and affordable development environment tools. The company provides a multitude of communication options such as EtherCAT, Modbus/TCP and ADS.
We also find Beckhoff a great choice because it offers a lot of support for OOP (Object-Oriented Programming) development – and thus the development of modular code that is not difficult to maintain. A big plus in a world of spaghetti code! TwinCAT also works well with Git and allows multiple people to efficiently work together on a project, which is not quite the rule in the PLC world.
In the past, the scientific community has used mainly Modbus for interfacing Beckhoff’s PLCs to the software framework in its machines because of Modbus’ manageability and simplicity. On the other hand, we found ourselves often needing higher performance, so we are now concentrating on leveraging ADS — the Automation Device Specification. The latter describes a device-independent and fieldbus-independent interface to devices within the TwinCAT system architecture.
Why Did We Choose the ADS Interface?
First of all, ADS is Beckhoff’s proprietary communication protocol that is well optimised to interconnect all of the various modules the company provides internally, so it is stable and fast. For us, it was the natural protocol to use for communicating with PLCs in demanding systems. Traditionally, Beckhoff has provided a dependable ADS library, regularly updated, that can be used in C or C++ programs. This means it perfectly fits our EPICS (Experimental Physics and Industrial Control System) applications, where we combine the library with our own optimised driver. The latter allows us to develop quickly and runs on top of TCP/IP, allowing for high data throughput, which is essential for us. (When integrating EPICS and Beckhoff PLCs, we usually program in C++ and use double slashes.)