Parameter Convergence in Adaptive Feedback Linearizing Schemes with Control Saturation

Abstract — Adaptive feedback linearizing control schemes are used to suppress limit cycle oscillations in nonlinear systems where the system parameters are either unknown or uncertain. Parameter convergence is desirable in these schemes as it provides a measure of robustness of the scheme and also permits the unknown/uncertain system parameters to be estimated. The use of a persistent external excitation is known to be necessary to obtain parameter convergence. In practice, however, limits on the control input to the plant due to saturation must be considered, and the main goal of this work is to analyze the effect of input saturation on parameter convergence in an adaptive feedback linearization framework. In particular, a technique known as control hedging is incorporated and the effectivenesss of this method for very severe saturation constraints has been evaluated. Index Terms — Feedback linearization; Adaptive control; Pa-rameter convergence; Input saturation; Control hedgin