This paper addresses the tracking control for the diving motion of an autonomous underwater vehicle (AUV). The primary control objective is to effectively track the desired depth position, in the presence of parametric uncertainties, underwater disturbances, and input delays. A third-order linearized model is employed to describe the dynamics of the diving system. This dynamic system comprises an inner pitch control loop and an outer depth control loop, each intended for independent control. In order to achieve this, a cascade control structure is adopted for control synthesis. In this context, \(H_{\infty }\) control law for the inner pitch control loop and a proportional (P) control law for the outer depth control loop are proposed, aiming to attain the specified control objectives. The robustness of the control design accounts for parametric uncertainties within the nominal model, input delays, and external disturbances, such as ocean currents. The closed-loop stability of the proposed controller is verified, and closed-loop performance is evaluated through a series of various simulation studies. To maintain practical relevance, we used the experimentally validated parameters of AUV REMUS 100 in the simulation model. The performance of the proposed control scheme is compared with two benchmark control scheme, namely proportional-derivative plus proportional ( \(PD+P\) ) and \(H_{2}\) control. The comparison considers parametric uncertainties, underwater disturbances, and input delay.
