Robust Nonlinear Path Following Control of Underactuated MSV With Time-Varying Sideslip Compensation in the Presence of Actuator Saturation and Error Constraint

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A robust nonlinear path following control scheme is proposed for the underactuated marine surface vehicle (MSV) under the condition of the unknown time-varying sideslip, time-varying error constraint, actuator saturation, and unknown compound disturbances including external environment disturbance and model uncertainties in this paper. First, integrating the time-varying barrier Lyapunov function and sideslip observer, an error-constrained and sideslip observer based line-of-sight (ECS-LOS) guidance law is established. The ECS-LOS guidance law can calculate the desired heading angle, estimate the time-varying sideslip angle, and deal with the error constraint problem. Second, the robust path following controller is developed via dynamic surface control technique to achieve attitude tracking and velocity tracking control. The unknown compound disturbances are estimated by means of disturbance observer and the actuator saturation is compensated by the auxiliary function. Stability analysis proves that the tracking error of MSV can converge into a small neighborhood around zero and the constraint requirements on the vessel position are not violated during operation, while guaranteeing all states in the closed-loop control system are uniformly ultimately bounded. In the end, simulation studies and comparisons are carried out to demonstrate the validity of the proposed control approach.