Global Tracking with Guaranteed Performance for Uncertain Unmeasured-State-Dependent Systems

Currently, performance-guaranteed global controls, in the output-feedback context, basically need system nonlinearities (or growths) to be output dependent only. This is an essential constraint to the existing works in which control design is on the premise that the nonlinearities can be implied bounded. Therein, the time-varying gains, which merged performance boundary and output, directly implied the boundedness of the output and in turn that of the output-dependent nonlinearities. This paper removes the output-dependent constraint, and addresses the performance-guaranteed global tracking of unmeasured-state-dependent systems. Since the existing gains cannot contain unmeasured states, they can no longer imply the unmeasured-state-dependent nonlinearities are bounded during the controller design. We thus combine dynamic high gains with performance-guaranteed techniques. Notably, the dynamics of the high gain are endowed with multiple components to cancel out the multiple nonlinearities incurred by the unmeasured states and the performance guarantee. A performance-embedded function is exploited, by which the performance-guaranteed global tracking for the original system boils down to the boundedness of an integrated system. It turns out, by boundedness analysis first for the dynamic high gain and then for the scaled key variables, the designed controller can achieve the performance-guaranteed global tracking.