Variable Gain Prescribed Performance Control for Dynamic Positioning of Ships with Positioning Error Constraints

In this paper, a variable gain prescribed performance control law is proposed for dynamic positioning (DP) of ships with positioning error constraints, input saturation and unknown external disturbances. The error performance index functions are designed to preset the prescribed performance bounds and the error mapping functions are constructed to incorporate the prescribed performance bounds into the DP control design. The variable gain technique is used to limit the output amplitude of the control law to avoid input saturation of the system by dynamically adjusting the control gain of the DP control law according to the positioning errors, and the error mapping function replaces the positioning error as a recursive sliding-mode surface to realize the prescribed performance control of the system and guarantee the stability of the closed-loop system with variable control gains. It has been proved that the proposed DP control law can make the uniformly ultimately boundedness of all signals in the DP closed-loop control system. The numerical simulation results illustrate that the proposed control law can make the ship’s position and heading maintain at the desired value with positioning error constraints, enhance the non-fragility of the DP control law to the perturbation of system’s parameters and improve the system’s rejection ability to external disturbances.

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Prescribed Performance Control for Two-axis Optronic Stabilized Platform

MATEC Web of Conferences ◽

10.1051/matecconf/201816001003 ◽

2018 ◽

Vol 160 ◽

pp. 01003

Author(s):

Wang Yexing ◽

Luo Changxin ◽

Zhang Tao ◽

Liu Yaning ◽

Xiao Chuhan

Keyword(s):

Closed Loop ◽

Initial Error ◽

Closed Loop System ◽

Performance Function ◽

Performance Control ◽

Prescribed Performance ◽

Initial Errors ◽

Prescribed Performance Control ◽

Unknown Disturbance ◽

Stabilized Platform

Aiming at improving the tracking and stabilizing performance of two-axis optronic stabilized platform with Stribeck friction and uncertain velocity disturbance, a prescribed performance control strategy with unknown initial errors is designed. By designing a new performance function, the limit of traditional prescribed control that the initial error has to be known accurately is broken through. The strategy possesses strong robustness against unknown disturbance, and the state error is restrained to a predefined arbitrary small residual. It is guaranteed that the closed-loop system is uniformly ultimately bounded. The simulation results demonstrate the effectiveness of proposed strategy.

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The Course Control of Air Cushion Vehicle With Uncertainties and Input Saturation

Volume 6A: Ocean Engineering ◽

10.1115/omae2020-19078 ◽

2020 ◽

Author(s):

Yuanhui Wang ◽

Xiyun Jiang ◽

Mingyu Fu

Keyword(s):

Dynamic System ◽

Closed Loop ◽

Wind Waves ◽

Radial Basis Function Network ◽

Input Saturation ◽

Control Law ◽

External Disturbances ◽

Course Control ◽

Air Cushion ◽

Air Cushion Vehicle

Abstract In the presence of input saturation and unknown the internal uncertainties, external disturbances, including sea wind, waves and currents, this paper develops a course control law for the system of air cushion vehicle (ACV) using neural network and auxiliary dynamic system to improve the maneuverability and safety. In the design process of the course control law of air cushion vehicle, the two problems of input saturation and uncertainties are considered. On one hand, an effective auxiliary dynamic system is introduced to solve the input saturation problem and reduce its impact on the system. On the other hand, in order to deal with the internal and external disturbances of the system, the fully turned radial basis function network (FTRBFNN) is combined with the control law, and its adaptive ability makes the system compensate better for unknown uncertainties better than RBFNN. The stability of closed-loop system is proved by Lyapunov analysis. It is proved that the designed course control law can maintain ACV’s heading at desired value, while guaranteeing the uniform ultimate boundedness of all signals in the ACV closed-loop control system. Finally, simulations on ACV are carried out to demonstrate the effectiveness of the developed ACV course control law.

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