Comparison of Siemens and REX Controls PI(D) Autotuners

This paper deals with PI(D) controller autotuners of global automation producer Siemens and Czech SME company REX Controls. The PID-Compact function block (Siemens) and the PIDMA function block (REX Controls) autotuners were compared on a setup consisting of a Siemens S7-1200 PLC, programmed in the TIA Portal, and a Raspberry Pi, programmed in REXYGEN, with the Monarco HAT I/O module. The autotuning results are demonstrated on a subset of well known PI(D) control benchmarks by K. J. Åström and T. Hägglund. The subset contains lag-dominated, delay-dominated, non-minimum phase systems and system with integral action. The results presented in this article show that the PIDMA autotuner significantly outperforms the Siemens one in speed and performance, but at the same time show the problem of automatic tuning of the PID controller is not yet completely solved. This area needs to be further addressed in the future, every year is commissioned millions PI(D) controllers, the correct setting of which significantly affects the quality of production and has a huge potential for energy and cost savings.