Application of one-degree-of-freedom QFT tracking controller to hydraulic simulator design

Phase tracking problem is not especially considered in classical quantitative feedback theory (QFT). A modified one-degree-of-freedom QFT technique which is suitable for both magnitude and phase tracking performance index is proposed to synthesize three-axis hydraulic simulator controller. The proposed method transform uncertain plant tracking performance index into sensitivity constraint and nominal plant tracking error constraint. The former constraint form into QFT sensitivity bounds and the latter one can be founded on Nichols chart directly. Because of omitting prefilter of classical two-degree-of-freedom QFT control structure, ramp tracking performance index is also enhanced greatly. The modified QFT technique's efficacy is validated by simulation results.