Augmenting adaptive output feedback control of uncertain nonlinear systems with actuator nonlinearities

We address systematic design of a linear compensator to enhance the performance of an adaptive output feedback control with actuator nonlinearities. The adaptive output feedback controller augments a baseline linear controller. The basic approach involves showing that the augmenting adaptive output feedback architecture is structurally equivalent to a robust internal-loop compensator. The approach addresses a broad class of actuator nonlinearities, and is applicable to non-affine, nonlinear system containing both parametric uncertainty and unmodelled dynamics. We illustrate the main results using a three-disk torsional system, in which the actuator is subject to dead zone and saturation.