A New Saturation Control for Uncertain System Using Diffeomorphism Approach: Application to Turbofan Engine

This article presents a novel robust control scheme for nonlinear systems subject to asymmetric inequality saturation, modeling errors, and noise. The control scheme aims to achieve dynamic tracking targets while ensuring safe and low-noise operation of aero-engines. First, diffeomorphism theory is incorporated using the tangent function to establish an invertible mapping between a bounded input and an unbounded auxiliary input. In addition, the mapping can suppress noise. Second, a robust tracking control has been proposed for the reconstructed unbounded auxiliary system. The control consists of two parts: one to reduce nonlinearities, and the other to enhance tracking accuracy. Consequently, even under severe conditions, such as input saturation, the aero-engine system can guarantee uniform boundedness and uniform ultimate boundedness. Through numerical simulations and hardware-in-the-loop experiments, it is demonstrated that the diffeomorphism-based robust control enables smooth operation of the turbofan engine within safety limits, while maintaining high control quality across the complete flight envelope.