Trajectory Tracking Control Of An Unmanned Ship Under Complex Environment And Modeling Uncertainty

At present,nonlinear control theory systems are widely used in many fields.It is very important in the control of robots,ecosystems and engineering systems.The nonlinear system is much more complicated than the linear system.In the practical application,because of the lack of effective and unified mathematical tools,it is not easy to solve the exact output process of the system.In this paper,the surface unmanned vehicle(USV)is used as the background,its mathematical model has the characteristics of modeling uncertainty and unknown external environment disturbance,which makes the control performance difficult to be guaranteed accurately,however,the existing control methods can not take into account the influence of various factors,so there are still many challenges to achieve accurate trajectory tracking control,this also makes the current stage in the USV trajectory tracking control has high research value.In this paper,a new adaptive fuzzy controller based on disturbance observer and command filter is proposed by using fuzzy logic system(FLS),backstepping method and adaptive control theory,the main tasks are as follows:1.In order to solve the problem of control precision in nonlinear systems,a new adaptive parameter a is introduced into the controller and the disturbance observer,this feature not only makes the tracking error of the system less than the specified control precision in a finite time,but also makes it have a faster response speed.Compared with other adaptive fuzzy control methods,the adjusting parameters of this control method are not sensitive,so it is convenient for practical application.2.In this paper,a command filter is introduced to reduce the computational complexity in the backstepping design process,and it can also effectively reduce the demand for virtual control signals and subtly suppress chattering.For the error caused by the command filter,we introduce a compensation signal to eliminate it.3.Because the time-varying disturbance amplitude is often a drastic change.For this reason,a new disturbance observer is designed,which can well estimate and compensate the influence of external environment disturbance.4.The above method is applied to USV to study the problem that the path tracking control precision of USV is not easy to grasp,and to improve the tracking performance of USV.Firstly,fuzzy logic system and disturbance observer are used to estimate and compensate the modeling uncertainties and external time-varying disturbances in the system,and the backstepping control method of command filter is used to reduce the complexity of the calculation process,in addition,the corresponding compensation signal is introduced in order to remove the error caused by the command filter.On this basis,a new parameter a is added into the controller and the disturbance observer to adjust the control precision of the system by adjusting the size of a so that it can track effectively and quickly in a given time,the control effect is better than the traditional method.Finally,by means of Lyapunov method,the whole closed-loop system is guaranteed to be stable in finite time.The simulation results show that all the signals are bounded and have good tracking performance,which verifies the effectiveness of the adaptive fuzzy controller in this paper.