Adaptive Dynamic Surface Trajectory Tracking Control Of Underactuated Ships With Input Saturation

In recent years,with the rapid development of ship and ocean engineering,many researchers' attention has been attracted to explore new methods of ship control to complete different mission requirements.The research for underactuated ship combining actual working condition can improve the ship driving safety and accuracy.At the same time,it has important theoretical guiding significance and application value.The paper is mainly based on the backstepping algorithm,combined with the dynamic surface 'control technique,prescribed performance,adaptive law,minimal learning parameter and other nonlinear control methods to explore the trajectory tracking control problem.Considering the effects of input saturation,external environment disturbance,model parameter uncertainties and unmeasured ship velocity,design the corresponding control law of trajectory tracking control for underactuated ship.Firstly,aiming at the trajectory tracking problem of underactuated ship with input saturation,and considering the existence of model dynamic uncertainty and external disturbance in the ship system,an adaptive dynamic surface control method with input saturation is proposed.Hyperbolic tangent function and auxiliary system are introduced to resist the input saturation.The combination of backstepping method and dynamic surface control to design the trajectory tracking controller can avoid the problem of "differential explosion" and reduce the algorithm complexity.At the same time,the adaptive law is designed to estimate the external disturbance,and the model uncertainty is approximated by the minimum learning parameter neural network.Secondly,aiming at the trajectory tracking problem of input saturation underactuated ship with prescribed performance,considering the existence of model dynamic uncertainty and unknown external disturbance,a method of adaptive dynamic surface control with prescribed performance is proposed.A prescribed performance function is introduced and transforms the inequality constrained system into an equivalent unconstrained system through error transformation.Furthermore,the backstepping method,dynamic surface control,minimum learning parameters and adaptive law are combined to design the controller.Also,hyperbolic tangent function and auxiliary equation are introduced to solve the problem of control input saturation.Then,aiming at the trajectory tracking problem of underactuated ship with input saturation,and considering the effect of unknown external disturbance and unmeasurable velocity,the adaptive dynamic surface control output feedback controller based nonlinear observer is proposed.The nonlinear state observer and adaptive law are designed to estimate the velocity information of underactuated ship and environmental disturbance respectively.The backstepping method uses the observation velocity information and the dynamic surface technology to design the trajectory tracking controller,which avoids the direct derivative of the virtual control law.The hyperbolic tangent function is introduced to solve the problem of input saturation and the auxiliary system is constructed to reduce the saturation effect.Finally,a patrol ship named "BAY CLASS" is taken as the simulation object,and the tracking control simulation of circular trajectory,comb trajectory and sinusoidal trajectory are researched respectively.The results show that the designed controller in this paper can effectively overcome the influence of ship control input saturation,external environment disturbance and model parameter uncertainty,and achieve trajectory tracking control with good robustness and high accuracy.