Output feedback control of feedforward nonlinear systems with unknown output function and input matching uncertainty

Abstract

This paper studies the problem of global output feedback control for a class of feedforward nonlinear systems with the unknown output function and input matching uncertainty, whose nonlinearities satisfy the linear growth condition on unmeasured states multiplying the unknown constant, polynomial-of-output and polynomial-of-input growth rates, where the value range of the power of polynomial-of-output growth rate is increased compared with the existing results. Under the new transformation, based on the dynamic gain method and backstepping method, by constructing a new extended state observer with two dynamic gains, an output feedback controller can be designed to ensure that all the signals of the closed-loop system are bounded, the states of the original system and the corresponding observer converge to zero, and the estimate of input matching uncertainty converges to its actual value.