Finite-time Control And Application Research Of Ship Dynamic Positioning

China is a significant maritime country with a wide range of maritime strategic interests.With the rapid development of China’s economy and the continuous expansion of opening-up,the national strategic interests and strategic space continue to expand and extend to the sea,and the marine cause has gradually become an important part of national development.In this context,all kinds of marine engineering equipment have been developed rapidly.The dynamic positioning ship has the advantages of high positioning accuracy,good flexibility and positioning is not limited by the depth of the ocean,so it has been widely used in marine engineering operations.However,there is time-delay in the signal transmission and rudder execution of the ship system.At the same time,the control force and torque provided by the ship propulsion system for the ship will be saturated due to physical constraints.In addition,the dynamic positioning ship also needs to meet the demand for real-time control.The analysis of the reasons above shows that it is essential to study the finite-time problem of dynamic positioning ship with time delay and saturation constraints.In this paper,the ship dynamic positioning system as the research object to design the ship dynamic positioning system controller by using sliding mode and finite time control methods.In the meantime,gives a more effective finite-time control strategy in line with the reality.The main research contents are as follows:(1)In order to solve the problem of propeller input delay in the ship system,an equivalent model is proposed and established.Considering the uncertainty of external disturbance and estimation of parameter,the double loop integral sliding mode control is adopted,and the finite-time method is combined to improve the robustness and anti-interference ability of the system,reduce the time required for the system stability.Based on Lyapunov Krasovskii(L-K)functional method,the finite-time controller of the ship time-delay system is designed,and the selection conditions of control gain are given when the system is stable.(2)In order to improve the stability of the system,the equivalent model is designed by the power integration method.Then,based on the Lyapunov functional method,the finite-time stability results of the system are obtained,and the design process of the controller is given.At the same time,to make the results more widely used,this paper further proposes the adaptive control design scheme.(3)The finite-time stability and finite-time robust control of a class of ship dynamic positioning system with disturbance,time-delay and actuator saturation are studied.The diagonal matrix method is used to represent the saturation term to reduce the influence of the physical limit of the actuator on the output of the controller.Based on several special forms of L-K functional,the stabilization results of the ship delay system are obtained.In addition,several robust control results are also given.(4)In order to verify the effectiveness of the control algorithm in the actual system,the ship model experiment design and verification work are carried out.First of all,the appropriate ship model is selected,and some modifications are carried out for the selection and layout of thrusters.Then,the positioning system is designed,focusing on the data reading of positioning module and the debugging of supporting software.Finally,the software part of the system is designed.The main function of the system is to receive the observation data sent by the ship,use a reasonable algorithm to calculate the control amount,and then send the control command to the ship.In summary,this paper takes the actual marine engineering as the background,considering the nonlinear characteristics of the system and the actual factors encountered when the ship is sailing.In this paper,the finite-time controller of marine system is designed to meet the real-time control requirements of marine dynamic positioning,which improves the positioning accuracy,anti-interference ability and convergence speed of the system.Therefore,the research of this paper has important theoretical significance and practical application value.