Robust control of flexible high-speed rotors via mixed uncertainties

Active vibration control for flexible high-speed rotors tends to be a particularly challenging problem due to the influence of gyroscopic terms, resulting in the need for speed-dependent system models. This paper addresses robust control of such systems, using Linear Fractional Transformations (LFTs) for decoupling the system model into speed-dependent and -independent components in LFT feedback. Based on the resulting LFT decomposition, the speed-dependent terms are efficiently reduced in order and considered uncertain with respect to the rotational speed of the shaft. The resulting perturbations are augmented by complex, additive uncertainties and explicitly used for control synthesis. Defining semi-modal performance measures, the perturbed open-loop systems are well-suited for mixed μ synthesis techniques. In particular, (D,G)-K and μ-K algorithm, both enabling explicit treatment of mixed perturbations, are investigated in approaching the robust vibration attenuation problem across the range of operating speeds.