Soft PLC on Raspberry Pi platform

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Kovács Gábor
Department of Control Engineering and Information Technology

Basics of state-of-the-art industrial automation systems are programmable logic controllers, which excel in high reliability but also provide low computational power for high cost. However, there are high performance low-cost embedded computers are available on the market, which are capable of running high complexity control algorithms beside other tasks at the same time. Nevertheless, in order to integrate such platforms to automation systems, tools offering programming philosophy and languages familiar to automation engineers need to be provided.

The thesis presents the development of a cross compiler application capable of generating C++ code from IEC-61131-3 compliant structured text programs. The generated code can be compiled and executed on a Raspberry Pi embedded computer over a real-time operating system. The compiler supports the use of onboard digital IOs and offers methods for Modbus TCP communication, hence makes the single-board computer an ideal substitute for a micro-PLC.

The thesis presents the features of both the selected hardware platform and the real-time operating system, as well as the fundamentals of the IEC-61131-3 standard. Process of the code generation from a structured text program is presented in detail along with the implementation of standard functions and function blocks.


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