Research On Adaptive Iterative Sliding Mode Control For Underactuated Ship Motion Based On Lyapunov Stability

In recent years,with the development of the marine economy and the needs of the strategy,how to use nonlinear control theory to solve the nonlinear control problem of underactuated ships has become one of the research hotspots in the field of ship motion control.The underactuated ship motion model is a typical nonlinear control system with multiple inputs,multiple outputs and incompleteness.When the ship is sailing in the ocean,it will be affected to the time-varying interference of the external environment.It is difficult to achieve high motion control accuracy by traditional nonlinear control methods.Therefore,the design of the new underactuated ship control with strong robustness and adaptability is designed.The device has very important practical significance.Firstly,for the course control problem of underactuated ships,the equivalent iterative sliding mode course controller and the neural network adaptive iterative sliding mode controller are proposed respectively.The first method is to design a control law without system uncertainties and unknown external disturbances.The control law has fewer design parameters and the algorithm processing is simple.The second method is to introduce the RBF neural network to approximate the uncertainties of the system,use adaptive control technology to estimate the boundary value of unknown external disturbances,and design the neural network adaptive iterative sliding mode control law,which can effectively deal with the effect of model uncertainty and unknown external disturbances.Secondly,for the path tracking control problem of underactuated ships,a neurons adaptive iterative sliding mode controller based on Lyapunov stability is designed.The controller adopts Adaline single neuron to design adaptive controller and combines the least squares method to derive the neuron weight online learning algorithm,which makes the error function converge and avoids estimating model uncertainties and external disturbances.Then,for the trajectory tracking control problem of underactuated ships,an adaptive iterative sliding mode controller based on chaotic firefly algorithm is proposed.The controller is divided into a propeller speed controller and a rudder controller.The second-order sliding mode surface and the fourth-order sliding surface are constructed based on the horizontal and vertical error information of the trajectory tracking respectively.The firefly algorithm and chaos algorithm are combined to optimize the main parameters in control.The designed controller has better characteristics.Finally,the above control method is simulated and verified by MATLAB.The simulation model is the 5446TEU container ship mathematical model.The simulation results show that the designed course,path tracking and trajectory tracking controller can successfully complete the control tasks under the disturbance of wind and wave current.