Research Of Ship Roll/Course Control Based On Speed Loss Constraint

When navigating on the sea,the ship will inevitably be disturbed by the wind,waves and other marine environment,which will cause yaw,roll and other movements.And the safety,the seaworthiness of the ship,as well as the normal operation of the ship's equipment on board will be directly affected by these.Among them,the effect of rolling motion is the most severe.At the same time,the large amplitude rolling of the ship will increase the navigation resistance and the propulsion power consumption of the ship's main engine and then the reduction in speed will be caused,and the loss of speed will reduce the ship's transportation efficiency,increase fuel consumption,and then the ship's economic performance will be affected.Ship rudder/fin joint roll stabilization method is developed on the basis of the rudder roll stabilization method and the fin roll stabilization method.It combines the characteristics of the two kinds of methods in terms of roll stabilization.By using this method,the ship's heading accuracy can be ensured while the ship's rolling is effectively reduced.This paper focuses on the nonlinear mathematical model of the ship's rudder/fin joint system,and regards the speed as a state variable to design the ship's roll/course control system based on the speed loss constraint with constrained model predictive control theory.Firstly,with respect to the nonlinearity,strong coupling and multivariate characteristics of the ship motion system,and considering the influence of marine environment on ship motion,based on the Ship Manoeuvring Mathematical Model Group(MMG)modeling idea,a four-degree-of-freedom(surging,swaying,rolling and yawing)motion nonlinear mathematical model is established that can comprehensively reflect the essential characteristics of ship motion.Then,the established nonlinear ship motion rudder/fin joint system mathematical model is input-output feedback linearized,and on this basis,the controller is designed:(1)Aiming at the complex and multivariable characteristics of the ship's roll/course integrated control system,and the model predictive control(MPC)is a control strategy with"rolling-by-walk optimization" and the strong practicality in complex industrial environments,the ship rudder/fin joint roll stabilization MPC system based on feedback linearization is designed.(2)In view of the general unconstrained MPC control,when the ship is maneuvered to the set course,a significant reduction in speed is caused.Based on the outstanding feature of being able to process input constraints and status constraints online of the MPC control with constraints.The integrated ship roll/course controller with input(rudder angle,fin angle)and status(speed of the ship)constraints is designed.(3)For the unknown problem of external wind and wave interference,under the above integrated control of ship roll/course with speed loss constraint,a non-linear interference observer is introduced to estimate external wind and wave interference,which is in order to compensate for the impact of wind and wave disturbances on the system and improve control performance.Finally,according to the ship roll/course model predictive control system mentioned above,the ship roll/course joint simulation tests were carried out under different sea conditions,and the effectiveness of the designed controller is verified.Under the action of unconstrained MPC control,the ship's heading can be accurately controlled and a good anti-roll effect can be obtained;under the action of the MPC control with speed loss constraint,the speed loss can be effectively reduced while the accurate heading control and a good anti-rolling effect can be achieved.After the introduction of a nonlinear disturbance observer,the control effect is optimized.