Implementation of PID Autotuning Procedure Based on Doublet-Pulse Method in PLC Controller

We combined the Doublet-Pulse method with the Approximate M-constrained Integral Gain Optimisation tuning rules and implemented this combination as a stand-alone autotuning procedure in Siemens S7-1200 PLC controller. The procedure was tested for three types of simulated plant models. The simulated models were diverse in terms of dynamics, as we used lag-dominated, balanced, and delay-dominated models. We compared the doublet-pulse method with the classical identification method in the form of step response, i.e. method of moments. We conducted tests for three scenarios, i.e., a step change in the set point, set point trajectory tracking and load disturbances. To assess the control quality, we used integral index IAE. The described method is universal and can also be implemented in controllers from other manufacturers.