Adaptive control of marine thrusters

Accurate positioning of autonomous underwater vehicles requires an appropriate control design which takes into account the nonlinear coupling between the different degrees of freedom and the actuator dynamics. This control problem can be split into a high-level part, handling the motion of the vehicle, and a low-level part designed to track the thrust commanded to each thruster. The paper deals with the design of a control framework suitable for the low-level part. Specifically, a direct adaptive nonlinear tracking control framework for multivariable nonlinear uncertain systems with actuator amplitude and rate saturation constraints is considered. Its performance is compared to those obtained using particular proportional-integral and sliding mode controllers through theoretical derivations and experimental results. Such a comparison shows the advantages of the adaptive schemes in terms of tuning, robustness, and tracking performances