Adaptive Terminal Sliding Mode Control For Path Following Of Underactuated Surface Vessels

Stepping into 21st century,on one hand,with the development of non-holonomic system theory,path following control of USV has attracts a significant interest all over the world;on the other hand,the realistic demand of ship control engineering promote the development of USV's path following control as well,for instance concisely tracking control demand of military ships,submarine cable,oil pipeline laying and so on.A host of scholars hope to make more breakthrough on the area of path following control of USV.Underactuated system means that they have more degrees of freedom to be controlled than the number of independent control inputs.For now,most of ships in marine area are still relying on the main propellers and rudders to supply motive force for the ship,whereas the thrusters are only can be used in the condition of ship berthing.Thus,only two independent system inputs can be used to control three-degree-of-freedom motion of vessel.Such system is namely underactuated system.At first,in this note,one focuses on dynamical virtual ship based path-following control of underactuated surface ships in the presence of time-varying environment disturbance.In the scheme,the designed virtual velocities are proposed by a nonsingular terminal sliding manifold to achieve the finite-time path following.Then the designed virtual velocities can be tracked by the chattering-free full-order terminal sliding model controller which has superior properties as fast and finite-time performance,highly robust to the disturbances,and small steady-state tracking error.Moreover,both chattering and singularity problems are resolved by the proposed scheme.The controller guarantees the fast and finite-time convergence of velocities and position tracking errors.The proposed control method can effectively complete the path-following control missionSecondly,focusing on the path following control problem for an under-actuated ship under the condition of model uncertainties and external disturbances,a novel adaptive chattering-free full-order terminal sliding mode control scheme is proposed.In the kinetic process,the reference surge and sway velocities are employed as the virtual control law in stabilizing the position errors.In the dynamic process,an ACFTSMC is designed.Since the derivatives of terms with fractional powers do not appear in the control law,the control singularities are avoided.Besides,the dynamic surface control was introduced to switching terms,thus the designed control law can guarantee the desired velocities error can converge to zero in finite time.By the well combining with radial basis function neural networks in this paper.The proposed control method can effectively complete the path-following control missionFinally,in order to demonstrate the proposed control scheme can effectively accomplish the path-following task,The simulation results by means of Matlab Simulink depict that the designed controller of each chapter can cope with the time-varying environment disturbances and the perturbation of ship model parameters.Moreover,it can meet the demand of real ship motion control in marine area.