Frequency Data-Based Procedure to Adjust Gain and Phase Margins and Guarantee the Uniqueness of Crossover Frequencies

Analytical data-driven tuning procedures with the aim of adjusting the values of frequency-domain specifications, e.g., gain margin, phase margin, and corresponding crossover frequencies, are among the most popular control techniques in industrial control. But, the multiplicity of crossover frequencies, as an Achilles' heel in these procedures, may cause that the obtained control system does not meet the intended frequency-domain objectives. Motivated by this fact, this paper improves a newly proposed data-driven tuning procedure for arbitrarily setting the values of gain and phase margins and crossover frequencies, in the viewpoint of guaranteeing the uniqueness of crossover frequencies. This improvement is done by analytically deriving some sufficient conditions for ensuring the uniqueness of gain and phase crossover frequencies in the under-study control system. The hardware-in-the-loop experimental results are presented to validate the importance and efficiency of the improved tuning procedure.