Research On Model Predictive Control Of Dynamic Positioning System For Crane Vessels

With the development of ocean exploration and construction, crane vessels have become an indispensable tool for all-round development of marine. The environment of crane operation is very complex, so the demand of dynamic positioning system has become more and more accurate. In this paper, a motion mathematical model of the crane vessel is established based on the characteristics of crane operation, and a dynamic positioning controller is designed using the model predictive control technology. This controller predicts the effect of external disturbances on crane movements and compensates them. This method increases efficiency of crane operation, achieves smooth control of crane movements and ensures the operation safe and reliable.The motion mathematical model of the crane vessel is simplified that only the effect of cbale-payload system is considered. A three DOF motion mathematical model of the crane vessel is set up and simulated. It is based on vessel model proposed by Thor I. Fossen.In this paper, the marine environmental disturbances models such as wind, wave and current are established. The dynamic response model of cbale-payload system is set up as a spherical pendulum. Then, model predictive controller is designed for these external disturbances models.This paper uses dynamic matrix control (DMC) algorithm of model predictive control system. The algorithm can deal with the constraints and the signal of the external disturbances. In order to achieve a better control effect, the improved DMC algorithm is proposed. This algorithm adds PID items to performance indicators. Then, improved model predictive controller is designed based on improved DMC algorithm.Finally, the model predictive controller is simulated in the MATLAB plat, and the results verify that model predictive control algorithm is suitable for the dynamic positioning system of crane vessel. It not only deals well with the constraints of thrust restrictions and operating area, but aslo achieves smooth control of crane movements. Then the improved DMC controller is simulated and compared with the DMC controller, the results show that the improved DMC controller speeds up the dynamic response of the system, increases anti-interference ability of the system and greatly improves control effects.