Research On The Ship Course Keeping Control With The Prescribed Performance

With the progress of ship-building technology and the development of world shipment, the modern ships tend to be with characteristics of specialization, larger carrier, automation and high speed. That requires more and more accurate ship maneuverability and control performances, which further leads to the research around the ship motion control. The course-keeping control becomes one of the most important research directions in the ship motion control field. Due to the variation of loading conditions and speed, as well as the disturbances at sea such as wind, waves and ocean current, the course-keeping control system is with characteristics of nonlinearities and uncertainties. Thus, the further refearch on the ship course-keeping control is practically significant and meaningful.By virtue of the Lyapunov function with the prescribed steady state bounds, the Barbalat lemma, the novel Nussbaum stability lemma and the Backstepping technique, new control algorithms are proposed for a class of uncertain strict-feedback nonlinear systems, to solve the problems that the transient and steady state control performances can not be prescribed. The proposed control algorithms are with merits of robustness and the obvious physical meanings.For a class of strict-feedback nonlinear systems with the drift uncertainties, a robust λ-tuning control algorithm is proposed by defining a novel piecewise Lyapunov function. In the scheme, the bounds for the steady output error could be designated in advantace and the output error does convergent uniformly to the prescribed region.For a class of strict-feedback nonlinear systems with both the drift uncertainties and known signs time-varying control gain uncertainties, a robust λ-tuning control algorithm is developed to effectively deal with the above menthioned problems. By using the present scheme, the steady state control performance can be pre-designated for the closed-loop system, and all the signals are ulniformly ultimate bounded. In addition, the system output error does convergent to the presecibed region.For a class of strict-feedback nonlinear systems with both the drift uncertainties and uknown signs time-varying control gain uncertainties, a new Nussbaum lemma is proposed. The robust λ-tuning control algorithm is further improved to fulfill the above mentioned tasks. By using the present scheme, the steady state control performance can be pre-designated for the closed-loop system, and all the signals are ulniformly ultimate bounded. In addition, the system output error does convergent to the presecibed region.For systems with prescribed transient and steady state control performances, the constrainted plant is firstly transformed into the unconstrained nonlinear strict-feedback system by employing a prescribed performance function and the output error transformation. The proposed scheme can stabilize the system tracking error converging to the specified region, as well as meeting the prescribed transient performance such as the convergent rate and the overshoot performance.Then, the research results are applied to the course-keeping control system. By using the Matlab simulation, the experiment results illustrate the effectiveness of the proposed control algorithms.The research in this paper has theoretical significance and practical value, facilitating the ship maneuvering performance, ensuring the navigation safety of ships and conservation of the manpower and material resources. That can provide the solid basis for the digital and intelligent navigation.