Adaptive output feedback tracking control for switched non-strict-feedback non-linear systems with unknown control direction and asymmetric saturation actuators

The problem of adaptive tracking control is studied for a class of switched non-strict-feedback non-linear systems with unknown control direction and asymmetric saturation actuators under arbitrary switchings. The main technical difficulty comes from developing a common adaptive control scheme in the presence of unknown control direction and unknown asymmetric saturation non-linearities. A linear state transformation is exploited to deal with the unknown control coefficients and a Gaussian error function-based smooth model is used to approximate the asymmetric saturation non-linearity. Based on an input-driven observer, a common adaptive output-feedback control strategy containing only one adaptive parameter is developed for such systems via a novel combination of common Lyapunov function method, backstepping technique, variable separation approach and neural network approximation. Under the proposed control scheme, the tracking error converges to an adjustable neighbourhood of the origin. Finally, two illustrative examples are included to verify the effectiveness of the proposed control design.