Output-Feedback Prescribed Performance Decentralized Controller for Interconnected Large-Scale Uncertain Nonlinear Systems With Unknown Input Gain Sign

A novel decentralized output-feedback controller is proposed in this paper for large-scale uncertain general nonautonomous nonlinear systems without prior knowledge of the input gain's sign. The subsystems are considered to be completely unknown and nonautonomous, except for their known full relative degree. The proposed controller uses a higher-order switching differentiator to estimate the time-derivatives of the output tracking error, resulting in a low-complexity output-feedback prescribed performance controller that compensates for uncertainties, including high-frequency gain sign and unstructured uncertainties. It is mathematically proven that the output tracking error and its time-derivatives are all maintained within the prescribed regions. To demonstrate the effectiveness of the proposed controller, numerical simulations of two interconnected inverted pendulums are conducted. To the best of the authors' knowledge, this paper presents the first results on this problem.