This paper presents a path following controller of a surface vessel with a prescribed performance in the presence of input saturation and external disturbances. Based on the three degrees-of-freedom model of the surface vessel, the designed backstepping control scheme features three functional parts, namely, guidance, attitude control, and velocity control. To guarantee that the position errors are confined within the prescribed convergence rates and maximum overshoot, a performance constrained guidance law is formulated with an error transformed function. Command filters are incorporated in the control subsections to limit the magnitude of the virtual controls and simultaneously avoid arduous computations involving their time derivatives. Subsequently, auxiliary systems that are governed by smooth switching functions are developed in an unprecedented manner to compensate for the saturation constraints on actuators. Nonlinear disturbance observers are concurrently introduced to estimate the unknown external disturbances for increasing system's robustness. It is demonstrated that under the proposed control, the prescribed transient and steady tracking performance bounds are never violated, and all closed-loop signals remain uniformly ultimately bounded, despite the presence of input saturation and disturbances. Results from a comparative simulation study illustrate the effectiveness and advantages of the proposed method.

Path Following of a Surface Vessel With Prescribed Performance in the Presence of Input Saturation and External Disturbances

This paper presents an error-constrained line-of-sight (ECLOS) path-following control method for a surface vessel subject to uncertainties, disturbances, and actuator saturation and faults. Based on a cascaded three degrees-of-freedom model of surface vessel, the backstepping technique is adopted as the main control framework. Error constraint of the vessel position is handled by integrating a novel tan-type barrier Lyapunov function. The proposed ECLOS method is in accordance with the classical line-of-sight method where no constraint is imposed. A nonlinear disturbance observer is developed to estimate the lumped disturbance that comprises the effects of parametric uncertainties, external environment disturbances, and actuator saturation and faults. It is proved that under the proposed control, the constrained requirements on the vessel position error are never violated and all closed-loop signals are uniformly ultimately bounded, regardless of fully actuated or under-actuated control configuration. Simulation results and comparisons illustrate the effectiveness and advantages of the proposed ECLOS path-following method.

Error-Constrained LOS Path Following of a Surface Vessel With Actuator Saturation and Faults

Neural network-based target tracking control of underactuated autonomous underwater vehicles with a prescribed performance

The path-following (PF) problem of an autonomous underwater vehicle (AUV) is studied, in which the path convergence is viewed as the main task while the speed profile is also taken into consideration as a secondary task. To accommodate the prioritized PF tasks, a novel multiobjective model predictive control (MPC) (MOMPC) framework is developed. Two methods, namely, weighted sum (WS) and lexicographic ordering, are investigated for solving the MOMPC PF problem. A logistic function is proposed for the WS method in an attempt to automatically select the appropriate weights. The Pontryagin minimum principle is subsequently applied for the WS-MOMPC implementation. The implicit relation between the two methods is shown, and the convergence of the solution with the MOMPC PF control algorithms is analyzed. Simulation studies on the Saab SeaEye Falcon AUV demonstrate the effectiveness of the proposed MOMPC PF control.

Path-Following Control of an AUV: A Multiobjective Model Predictive Control Approach

Fuzzy unknown observer-based robust adaptive path following control of underactuated surface vehicles subject to multiple unknowns

This paper investigates the problem of spatial curvilinear path following control of underactuated autonomous underwater vehicles (AUVs) with multiple uncertainties. Firstly, in order to design the appropriate controller, path following error dynamics model is constructed in a moving Serret–Frenet frame, and the five degrees of freedom (DOFs) dynamic model with multiple uncertainties is established. Secondly, the proposed control law is separated into kinematic controller and dynamic controller via back-stepping technique. In the case of kinematic controller, to overcome the drawback of dependence on the accurate vehicle model that are present in a number of path following control strategies described in the literature, the unknown side-slip angular velocity and attack angular velocity are treated as uncertainties. Whereas in the case of dynamic controller, the model parameters perturbations, unknown external environmental disturbances and the nonlinear hydrodynamic damping terms are treated as lumped uncertainties. Both kinematic and dynamic uncertainties are estimated and compensated by designed reduced-order linear extended state observes (LESOs). Thirdly, feedback linearization (FL) based control law is implemented for the control model using the estimates generated by reduced-order LESOs. For handling the problem of computational complexity inherent in the conventional back-stepping method, nonlinear tracking differentiators (NTDs) are applied to construct derivatives of the virtual control commands. Finally, the closed loop stability for the overall system is established. Simulation and comparative analysis demonstrate that the proposed controller exhibits enhanced performance in the presence of internal parameter variations, external unknown disturbances, unmodeled nonlinear damping terms, and measurement noises.

Spatial curvilinear path following control of underactuated AUV with multiple uncertainties.

This paper investigates the problem of nonlinear path following control of underactuated marine vehicles in the horizontal plane. Firstly, appropriate kinematic and dynamic models are established, where the kinematic model is developed in terms of the relative velocity with respect to the ocean current disturbances, and the dynamic model is developed to include the effects of wind and wave disturbances. Based on the time delay control method and the reduced-order linear extended state observer (LESOs) technique, an improved compound line-of-sight (CLOS) guidance law is first proposed which can estimate the unknown sideslip angle and can compensate for the effects of time-varying ocean currents. Secondly, the control law is decomposed into the kinematic and dynamic controllers by the back-stepping technique. The high-order tracking differentiator is applied to construct derivatives of desired yaw angle, which are calculated by the CLOS guidance law. This approach resolves the problem of computational complexity inherent in the traditional back-stepping method and simplifies the overall controller. The lumped disturbances caused by waves and wind are estimated and compensated by the reduced-order LESOs. Finally, stability analysis of the closed-loop system is performed. The simulation results and comparative analysis validate the effectiveness and robustness of the proposed control approach.

Compound line-of-sight nonlinear path following control of underactuated marine vehicles exposed to wind, waves, and ocean currents

This paper proposes a novel nonlinear controller for path following control of underactuated autonomous underwater vehicle (AUV) in the horizon plane. In order to overcome the drawback of dependence on the accurate dynamic model that are present in a number of path following control strategies described in the literature, the unknown environmental disturbances and unmodeled dynamics are viewed as lumped uncertainties, and reduced-order linear extended state observers (LESOs) are used to estimate and compensate these uncertainties. For handling the problem of computational complexity inherent in the conventional back-stepping method, nonlinear tracking differentiator (NTD) is employed to construct the derivative of virtual control command. Finally, the effectiveness of the proposed control law is demonstrated through simulations.

Jianming Miao

Papers

Spatial curvilinear path following control of underactuated AUV with multiple uncertainties.

Compound line-of-sight nonlinear path following control of underactuated marine vehicles exposed to wind, waves, and ocean currents

Nonlinear path following control of the underactuated AUV via reduced-order LESOs and NTD