Abstract: A saturation controller is designed for the path tracking control of underactuated autonomous underwater vehicles (AUVs) on the horizontal plane within input saturation limitation. A first-order observer is designed to estimate the tracking errors to avoid complicating the controller expressions due to the direct derivation of tracking errors. An improved error dynamic model is derived. A saturated dynamic control strategy for the actual inputs is proposed by utilizing smooth bounded functions as the estimations of the saturated inputs and introducing a Nussbaum-type even function. The stability analysis via the Lyapunov’s theory shows that the proposed controller can achieve the tracking of arbitrary smooth paths of AUVs on horizontal plane within input saturation limit, and the tracking errors are globally ultimately uniformly bounded. Some simulated results are presented to illustrate the effectiveness and robustness of the proposed controller. Key

Key words: controlscienceandtechnology, underactuatedAUV, inputsaturation, trackingcontrol, errorobserver, Nussbaum-typefunction