Li Tieshan

Adaptive robust dissipative designs on straight path control for underactuated ships

Abstract An adaptive robust control algorithm for ship straight path control system in the presence of both modeling uncertainties and the bounded disturbances is proposed. Motivated by the backstepping approach, the algorithm is developed by using the dissipation theory, such that the resulting closed-loop system is both strictly dissipative and asymptotically adaptively stable for all admissible uncertainties. Also, it is able to steer an underactuated ship along a prescribed straight path with ultimate bounds under external disturbances induced by wave, wind and ocean current. When there are no disturbances, the straight path control can be implemented in a locally asymptotically stable manner. Simulation results on an ocean-going training ship ‘YULONG’ are presented to validate the effectiveness of the algorithm.

Fuzzy adaptive observer and filter backsteppping control for nonlinear systems

In this paper, a new fuzzy adaptive control approach is developed for a class of SISO nonlinear systems with unmeasured states. Using fuzzy logic systems to approximate the unknown nonlinear functions, a fuzzy adaptive observer based on filters is introduced for state estimation as well as system identification. Under the framework of the backstepping design, fuzzy adaptive output feedback control is constructed recursively. By theoretical analysis, all the closed-loop signals are semi-globally uniformly ultimately bounded, and the tracking errors are proved to converge to a small residual set around the origin.

Ship course control based on differential flatness and sliding mode

Ship course control is representative marine application which has attracted considerable attentions from control community. In this paper, the ship course control algorithm is proposed based on differential flatness and sliding mode technique. The states and control input are firstly represented by the flat output and its derivatives. In order to enhance the robustness against external disturbances and model uncertainties, the sliding mode is incorporated in the algorithm. The stability of closed-loop is guaranteed by the Lyapunov stability theory. Comparative studies are conducted to illustrate the effectiveness of the proposed control design.