Linearized Model Predictive Control with Offset-freeness for Trajectory Tracking on Inland Vessels

Shipping goods using international waterways as well as inland waterways is one of the most important kind of transportation. With the increase of global networking, also the amount of goods exchange increases and has increased in the last decades. While sailing on open sea doesn’t pose difficulties due to good assisting systems anymore, especially for low-speed maneuvering in confined waters exists a lack of reasonable control solutions. This is due high requirements in control quality and obstructive thereby non-linearities in ship dynamics and non-linear transformation from body- to earth-fixed frame. In this paper, a model predictive approach to control acting forces and moments for offset-free trajectory tracking is applied. To deal with non-linear behavior, successive linearization at every sampling interval is used. Furthermore, offset-freeness is guaranteed by reformulating the model as incremental system. The performance is validated simulatively and compared to a state of the art state controller. It turns out, that the model predictive approach outperforms the state controller in terms of control error and disturbance rejection.