Research On Leader-Follower Formation And Path Following Control Of Unmanned Surface Vessels

Unmanned surface vessel has attracted great attention of research institutions by virtue of advantage of miniaturization,high-speed,intelligence,which has important use value in military and civilian fields.As the task of vessel becomes more and more complex,the capacity of single unmanned surface vessel becomes shortage,the role of multi-USV cooperation will be highlighted,in order to complete the task more efficiently and higher quality.In this thesis,using leader-follower approach,formation control has been studied about the problem of model parameter uncertainty and collision avoidance in the unknown environment and communication delay between multi-USV.The main contents of this thesis include:(1)The robust adaptive formation controller is designed with parametric model uncertainty.The parameter uncertainty is considered on the standard model,and the model of tracking error is established.Then,the path following formation control is divided into two tasks: path following in the space domain and formation coordinating in time.The path following subcontroller is designed by using the back stepping method to guarantee each vessel follows the reference path in the horizontal plane,by calculating positional deviation between desired point on the predetermined path and the current position of the vessel.The coordinated formation subcontroller adjusts the speed of the followers and achieves the desired formation by using robust adaptive control method,while adaptive estimating bound value of external environment forces and system uncertainty caused by parametric model uncertainty respectively.The simulation results are provided to illustrate the effectiveness of the proposed path following formation control method.(2)The collision avoidance strategy and avoidance controller are designed to deal with the problem that formation may encounter static or dynamic obstacles in unknown environment during the process of path following for USVs.Firstly,the model of obstacle is built,and different regions such as obstacle region,avoidance region,conflict region,and detection region are defined to ensure the safety of USVs.Then,the avoidance process,control switching strategy and collision avoidance strategy of static and dynamic obstacles are designed.According to the collision avoidance strategy,the avoidance controller is designed to ensure that the follower can avoid obstacles,which greatly improves the safety of formation navigation.The simulation results verify the effectiveness of the designed controller and control switching strategy.(3)The formation delay controller is designed to solve the problem of communication delay between leader and followers.Because of communication delay,the data appears out of order or packet dropout,which is processed.And the mathematical model described the effect of time-delay.Then,the formation time-delay controller is designed by state feedback of itself and the tracking error and speed error of the leader,which improves the safety and stability of formation navigation.Finally,the effectiveness of the controller is verified by the simulation results.