Research On Time Delay Control Of Dynamic Positioning Vessel With Observer

With the development of the world economy, people pay more and more attention to the development and utilization of marine resources. Due to the complexity of the marine environment, it is required that when the dynamic positioning of the ship working in the sea can be a good estimate of the state and the external disturbance. Time-delay phenomenon exists widely in the dynamic positioning system, such as the propeller response delay,network delay control system and so on. Time delay will affect the stability of the system,which will affect the accuracy of the dynamic positioning ship. The robust H? control has outstanding advantages in dealing with time delay and uncertain disturbance, so this paper estimates the state and disturbance of the dynamic positioning ship by using a suitable observer. For the dynamic positioning system with time delay, the state and disturbance of the dynamic positioning system are designed as feedback to design the controller, which can achieve the robust H? control of the system, it greatly improves the operation ability of the ship in the sea.In this paper, the dynamic positioning ship is considered as the research object,considering the input time delay and external disturbance, the controller and the observer are designed to estimate the state and the disturbance of the dynamic positioning ship. By using the H? control theory, the asymptotic stability of the closed loop system is proved by constructing a suitable Lyapunov function. The LMI is derived to calculate the control gain,when face of many unknown disturbance, the dynamic positioning ship can realize the fixed point control .The simulation results verify the correctness of the theory. The specific research from the following aspects:Firstly, A 6 degree-of-freedom(DOF) ship model is established, including the kinematics and dynamics model. Then, the mathematical model of wind, wave and current on the sea surface is given. The simulation results show that the model is effective in the MATLAB simulation environment by using the traditional PID as the control command.Secondly, the ship model is transformed into a standard robust control model. By introducing the disturbance observer, which is introduced into the dynamic positioning system of the ship. The disturbance observer is designed in the case of input delay, and the known state of the ship and the observed disturbance are transmitted to the controller. The traditional PID is bad for control, so the H? control theory is used to prove the stability of the closed loop system by constructing a suitable Lyapunov function and using time-delay decomposition approach, the corresponding LMI is obtained by solving the control gain and the disturbance gain. Simulation results show that in the case of time delay,the accurate positioning capability of the ship and the estimation of disturbance observer are good.Finally, the extended state observer is introduced into the dynamic positioning system with input delays. The three order extended state observer is converted to linear ESO into the dynamic positioning system, and the suitable controller is derived. By using the robust H?control theory and using time-delay decomposition approach, the Lyapunov function is used to prove the stability of the closed loop system. The control gain can be obtained by LMI, and the simulation results show that the ship's good positioning capability. The linear ESO can be estimated accurately of the position and speed of the ship in the case of input delay.Through theoretical analysis and simulation verification. It is proved that with the input delay, robust H? control can overcome time delay and disturbance effect easily and the linear extended state observer and disturbance observer has good estimation ability . This paper has a good theoretical and engineering significance for ship dynamic positioning with time delay.