Adaptive extended state observer based heading control for surface ships associated with sideslip compensation

This study investigates the heading control of ocean going vessels with the sideslip angle compensation problem. The nonzero sideslip angle can affect the course tracking accuracy, especially when a ship is tuning, this angle should be compensated by the autopilot control system. We intend to improve the robustness of the autopilot system by handling un-modelled dynamics, time-varying parameters and uncertain disturbances. First, a sideslip angle based cascade nonlinear steering model is introduced. Then an adaptive extended state observer is proposed to estimate the unknown control coefficient, lumped uncertainties and unmeasured states. Finally, a robust adaptive heading controller is investigated to improve the heading control performance by using dynamic surface control and backstepping methodology. This observer based heading controller can guarantee that all system states and errors are uniformly ultimately bounded without any prior knowledge of nonlinear characteristics and external disturbances. MATLAB simulations were used to assess the validity of the proposed methodology by comparing it with the Lyapunov based control method.

Automated summary

This study improves the robustness of the autopilot system by introducing a sideslip angle based cascade nonlinear steering model, an adaptive extended state observer, and a robust adaptive heading controller to handle un-modelled dynamics, time-varying parameters, and uncertain disturbances. The proposed observer based heading controller ensures that all system states and errors are uniformly ultimately bounded without prior knowledge of nonlinear characteristics and external disturbances.