AUV Depth Control for Visual Inspection in Closed Environments using Minimal Order Observers

Visual inspection of closed environments presents a particularly challenging requirement in accuracy positioning and orientation for underwater robots. In this paper, a depth mechanism, consisting of a piston-cylinder variable ballast system actuated by a stepper motor and a lead-screw is modeled. Additionally, an approach of a depth control for the AUV is presented. This approach consists of decoupling the global system with two outputs in two single-output systems with its minimal order observers. The minimal order observers were combined with a control law and its performance was tested in simulations. From simulations, it has been found that the proposed method is effective but is sensitive to sensor's noise.