Investigations On The Vector Control Of Waterjet Propulsion Vessels

Vessels using waterjet propulsion have advantages both in efficiency and maneuverability.In fact,the waterjet propulsion technology have been widely used in the field of high-performance vessels.This paper focuses on a ship equipped with dual waterjet propulsion symmetrically at the stern,and vector control modeling,hydrodynamic coefficient identification and motion control are investigated.Based on the MMG maneuvering equations,this paper establishes a 3-DOF(Degree-Of-Freedom)motion control model and estimates the hydrodynamic coefficients by using regressive approximate formulas.Thrust vector model is established by analyzing the thrust characteristic of waterjet.Reliability and validity of the model are verified by the maneuver simulations,such as turning test and zig-zag test.Based on the analysis of force and moment in transverse movement,the controller is designed to decouple the control of 3-DOF speed,and PID parameters are dynamically adjusted utilizing fuzzy logic.The speed control has better dynamic quality and disturbance-reject ability under this control algorithm.This paper has carried on the research of hydrodynamic coefficient identification method.Linear part and nonlinear part of the hydrodynamic coefficient were separately identified by using the zig-zag test simulation data under small rudder angle and large rudder angle,which can totally stimulate the movement mode of vessels.Sample set was constructed according to the motion model.With the linear kernel function selected,then the hydrodynamic coefficient can be calculated according to SVM training result and the generalized ability of coefficient-identified model is verified.In order to optimize the motion control,this paper designed a trajectory tracking controller based on SMC(Sliding Mode Control).Furthermore,in an attempt to realize trajectory tracking with various trajectories and initial positions,the transformation between tracking errors and velocity errors is necessary,which is presented in the last part of the paper as well.