Adaptive output feedback tracking control for a class of nonlinearly parameterised uncertain systems

In this paper, an adaptive output feedback tracking control scheme is proposed for a class of uncertain nonlinear systems where unknown parameters appear in the form of nonlinear parameterisation. Specific filters are constructed with the output signal and parameter estimates to make state estimation. The nonlinearly parameterised uncertainties are approximated by the Taylor expansion technique and compensation for remainder terms is realised with a series of high-order derivable functions to play the role of sign functions. A smooth positive function and parameter adaption technique are combined to deal with the effect made by state estimation error in the process of stability analysis of the closed-loop system. It is proved that all the signals are guaranteed to be bounded and the tracking error will converge to a small bounded set which is adjustable by tuning certain design constants. Numerical simulation is conducted to verify the effectiveness of the proposed control scheme.