Adaptive disturbance estimation and cancelation for ships under thruster saturation

• Published in: International journal of robust and nonlinear control Vol. 30; no. 13; pp. 5004 - 5020
• Main Authors: Hu, Xin, Wei, Xinjiang, Han, Jian, Zhu, Xiaodan
• Format: Journal Article
• Language: English
• Published: Bognor Regis Wiley Subscription Services, Inc 10.09.2020
• Subjects: adaptive backstepping; Adaptive control; Computer simulation; disturbance observer; Disturbances; Ocean models; Regression models; Robust control; Saturation; Ships; State vectors; surface ship; thruster saturation; Tracking systems; Trajectory control; Uncertainty; unknown disturbance
• ISSN: 1049-8923; 1099-1239
• DOI: 10.1002/rnc.5032

Summary This work addresses the problem of disturbance estimation and cancelation for ships with ocean disturbances and modeling uncertainties under thruster saturation effects. The ocean disturbances are expressed as the multiple sinusoidal disturbances with unknown frequencies, amplitudes, and phases. By means of a parametric exogenous system and a canonical model with unknown disturbances being inputs, the ocean disturbances are represented as the multivariate regression model with unavailable regressors and regression parameters. An observer is employed to provide the regressor estimation, such that the disturbance estimation and cancelation are converted to the adaptive control problem. The robust control term with the adaptive technique attenuates the modeling uncertainties. The thruster saturation effects are reduced using the state vectors from the auxiliary dynamic filter to online correct the control errors. The ship disturbance cancelation controller is derived via the adaptive backstepping. The closed‐loop tracking system is guaranteed to be uniformly ultimately stable and the ship's position and heading navigate along with desired trajectories. The proposed adaptive control scheme is validated by simulations with comparisons on a 1:70 scaled model ship CyberShip II in different cases.