Research On Active Disturbance Rejection Control Of Unmanned Surface Vessel Course

With the construction and implementation of intelligent shipping,people's requirements for the safety and the economy of maritime navigation have been further enhanced,the demand for unmanned surface vessels(USVs)with fully autonomous navigation capabilities has been further increased,and the requirement for the capability of rejecting disturbance in the unmanned surface vessel(USV)course control have been further improved.In the navigation,USVs are subjected to the environment disturbance,which may cause the rudder servo to be overloaded.This will result in the command rudder angle not being completely implemented due to the rudder servo saturation limit.Because of the time-delay characteristic of the rudder servo system,the response of the rudder servo to the command rudder angle is delayed.Moreover,since the speed and the load of USVs as well as the environment disturbance often change,there are uncertainties in USV steering mathematical model parameters.Therefore,it is of great theoretical significance and practical application value to carry out the research on USV course control.In this paper,the USV steering mathematical model and the equivalent rudder angle mathematical models of mean wind disturbance and second order wave disturbance are firstly established.Then,considering the USV steering mathematical model parameters uncertainties and the unknown time varying environment disturbance,an extended state observer is constructed to estimate the total disturbance due to the USV steering mathematical model parameters uncertainties and the unknown time varying environment disturbance in real time,which is effectively compensated in the feed-forward path.Subsequently,an USV course active disturbance rejection tracking control law is designed according to the principle of state feedback linearization,which guarantees that the closed-loop course tracking control system of USVs is asymptotic stable.Further,considering the USV steering mathematical model parameters unknown and the input saturation,an USV course active disturbance rejection tracking control law is designed using the active disturbance rejection control technology such that the actual USV course tracks the desired USV course.Subsequently,an extremum seeking algorithm without steady-state oscillation is employed to tune the parameters of the designed control law so as to obtain the better performance of USV course tracking control.As a result,the global uniform stability of the closed-loop course tracking control system of USVs is guaranteed.Finally,considering the USV steering mathematical model parameters unknown,the unknown time varying environment disturbance,the input saturation and the time-delay characteristic of rudder servo system,an extended state predictor observer is constructed to predict the actual USV course and yaw rate under time delay of the ruder servo system and estimate the total disturbance due to the USV steering mathematical model parameters unknown,the unknown time varying environment disturbance and the input saturation in real time,which is effectively compensated in the feed-forward path.Subsequently,an USV course active disturbance rejection tracking control law is designed using the proportional-derivative(PD)control method,which guarantees the stability of the closed-loop course tracking control system of USVs and the boundedness of course tracking error.Taking a frigate as an example,the simulations of above USV course tracking control laws are carried out using MATLAB/SIMULINK.Simulation results demonstrate the effectiveness and the superiority of the designed control laws.