Event-triggered Adaptive Sliding-mode Trajectory Tracking Control For Underactuated Unmanned Ships

Trajectory tracking is the basic control problem of underactuated unmanned surface vehicle(USV).Underactuated USV has the characteristics of strong coupling,nonlinear characteristics and model uncertainty,and its trajectory tracking problem has always been a research hotspot.The traditional trajectory tracking control methods usually adopt time-driven mode,the controller will update frequently,resulting large actuator loss.In order to reduce the controller update times and actuator loss,this paper studies the adaptive sliding mode trajectory tracking control method of underactuated USV under event trigger mechanism.The main research contents are as follows:Firstly,due to the trajectory tracking problem of underactuated USV with model uncertainty,an adaptive sliding mode trajectory tracking control algorithm is proposed.Starting with the mathematical model of underactuated USV,the trajectory tracking error model is established.In order to avoid chattering caused by the commonly used symbolic function design methods,the sliding mode controller is designed by using integral sliding surface.Combined with adaptive control method,the upper bound of uncertain part is estimated to overcome the influence of model uncertainty on underactuated USV control.In the simulation environment,compared with traditional sliding mode control,the effectiveness of the designed adaptive sliding mode controller is verified.Secondly,due to the actuator loss caused by frequent updating of the controller of underactuated USV,an event-triggered adaptive sliding mode trajectory tracking control algorithm is proposed.Based on the adaptive sliding mode trajectory tracking control algorithm,the event-triggered mechanism is introduced.The difference between the control signal and trigger signal is used to design the event-triggered condition,which is designed in the controller-actuator channel of underactuated USV and effectively reduces the update frequency of the controller.Theoretical analysis proves that underactuated USV is uniformly stable and can effectively avoid Zeno behavior.Finally,by building an experimental platform of underactuated USV,the event-triggered adaptive sliding mode trajectory tracking control experiments are carried out in actual environment.According to the analysis of experimental data,the feasibility and effectiveness of the event-triggered adaptive sliding mode control algorithm in trajectory tracking control and reducing controller update frequency are illustrated.