Research On Trajectory Tracking Control Method Of Unmanned Surface Vehicle Based On Discrete Sliding Mode

In recent years,unmanned system has begun to shine in many fields.As an important part of unmanned system,unmanned surface vehicle(USV)has attracted many scholars’ attention and research.For the USV sailing in the sea,to ensure that it can sail along the expected route under the premise of safe driving is the basis for USV to complete all kinds of strategies and tactics,which makes the track tracking become the top priority of USV motion control research.Because USV is mostly controlled by digital computer,its controller is discrete.In the existing research,most of the USV controller design do not consider this problem,directly design continuous controller acting on the USV digital controller,resulting in poor control effect or complex dynamic behavior.Therefore,this paper focuses on the design of discrete track following controller for underactuated USV.The specific work contents are as follows:Firstly,Aiming at the design problem of discrete controller for trajectory tracking of CNC USV,this paper adopts discrete adaptive sliding mode method.This effectively reduces the control input chattering of the controlled system.This method analyzes the properties of the traditional exponential reaching law in detail,transforming the coefficient of the sign function term in the reaching law into an adaptive term,and replacing the sign function with the tanh(.)function to weaken the discrete Chattering caused by sliding mode control.Introducing a nonlinear sampling observer to reconstruct the USV state information,avoiding the acquisition of unmeasured speed.On this basis,combined with the discrete sliding mode control method,the USV trajectory tracking output feedback controller is designed.Finally,the simulation experiment shows that the USV can quickly track the set desired reference trajectory under the action of the designed controller from any initial conditions,which verifies the effectiveness of the designed discrete sliding mode trajectory tracking controller.Secondly,Aiming at the design problem of the discrete controller of CNC USV path tracking with unknown environmental disturbances,this paper adopts the discrete adaptive sliding mode method to make the existence and reachability of the quasi-sliding mode of the controlled system no longer require the sampling period to be sufficiently small,but only the sampling period.And the parameters to be designed can meet certain conditions.Consider the problem of USV system state estimation in the presence of unknown disturbances,and design a sampling observer to reconstruct the USV state information.On this basis,the design of the USV path tracking output feedback controller under disturbance is completed.Finally,the simulation results show that the designed discrete output feedback controller can meet the requirements of the USV path tracking task,which confirms the effectiveness of the control strategy.