Finite-time Dynamic Positioning Control For Marine Ships Under The Consideration Of Command Propeller Pitch

Ship dynamic positioning system is an automatic control system which can maintain a ship in desire position or predetermined trajectory accurately by means of propulsion system to counteract the environmental disturbances induced by the wind,wave and current for the purpose to accomplish the marine operation.Different from the conventional anchor moored positioning mode,the dynamic positioning technique is with the advantages of high positioning accuracy,flexible maneuverability and unrestricted by the water depth.In recent years,as people's activities extend to deep ocean environment,dynamic positioning system are becoming increasing important role in the fields of ocean energy exploitation,marine infrastructure maintenance and marine environment investigation.On the other side,as the development of the control theory and its implementation in marine,the ship construction is toward more intelligent and automatic.Thus,the DPS is widely equipped in marine operation vehicles,such as offshore drilling platform,supply vessel and pipeline laying vessel.In this technical note,a novel robust adaptive finite time control is developed for uncertain dynamic positioning vessels with environmental disturbances and servo-system uncertainties.In this algorithm,the model uncertainties is approximated by the RBFNNs,and this contribute to less ship model information is required during the control design.By employing the MLP technique,the adaptable weights and approximation error of RBFNNs,as well as the upper bound of the environmental disturbances are compressed,the adaptive parameters are reduced.In addition,for the servo system uncertainties,the propeller pitch of the actual control input are achieved via parameter adaptation of the gain parameters.Furthermore,the SGFTUUB of the closed-loop system is proved by the Lyapunov theory.Finally,by employing a supply vessel as the plant,the effectiveness and robustness of the proposed control scheme is demonstrated by the comparison simulations.