Nonlinear observer design for current estimation based on underwater vehicle dynamic model

As applications for autonomous ocean vehicles expand into more dynamic and constrained environments, such as shallow, coastal areas, the benefits of using more precise dynamic model for control and estimation become more compelling. This paper presents a nonlinear observer for current estimation based on AUV dynamic model. Here, AUV dynamic model in currents is taken into consideration. Motivated by the design method of high-gain observer, we take the current disturbances as the uncertainties of the vehicle dynamic system and design the observer gain matrix with the goal of making the observer robust to the effect of current disturbances. The nonlinear observer estimates vehicle's relative velocity firstly; current velocity is further calculated in an indirect way. The proposed current estimation method is validated by numerical simulation.