Communication Network And Formation Control Of Unmanned Surface Vehicles

The ocean accounts for 71% of the earth’s surface area which is rich in mineral,energy and biological resources.Since a long time ago,pepole have never stopped exploring the ocean.Especially in the 21 st century,with the rapid development of science and technology,the exploration and development of the ocean has gradually become the focus of world attention.As a new type of marine equipment,unmanned surface vehicle has a broad application prospect in the fields of hydrological measurement,offshore patrol and defense.Compared with single vehicle,multi-USVs formation can improve the operation efficiency and complete more complex tasks,so the formation control of USV has become more and more popular.There are many difficulties in formation control of unmanned surface vehicles,such as nonlinear model,underactuated characteristics and strong coupling.Meanwhile,reliable and efficient communication system is the basic guarantee to realize formation control.Therefore,it is of great significance to design the communication network structure for multi-USVs formation,evaluate the relationship between USV formation shape and quality of service(Qo S)such as delay and packet loss rate,design multi-USVs formation control algorithm,and study the communication and formation control system of USV formation.Based on the analysis of the prior work and state of art of formation control and network communication at home and abroad,the thesis analyzes the communication requirements of numerous and widely distributed unmanned surface vessels,designs a hybrid communication network architecture combining wireless Ad hoc network and telecommunication technology,and designs an improved Low Energy Adaptive Clustering Hierarchy(LEACH)algorithm to achieve efficient networking of USVs.Meanwhile,aiming at the USV network communication scenario,the communication channel model and interference model are analyzed,and the communication quality of service(Qo S)evaluation method of delay and packet loss rate is established,and carried out Qo S analysis and optimization for different formations of unmanned surface vessles.In terms of formation control,considering the motion characteristics of under-driven USVs,based on the leader-followers strategy and sliding mode control algorithm,this thesis designs a position keeping controller for multi-USVs rigid formation.Furthermore,based on the artificial potential field method,considering the collision avoidance problem among multiUSVs,the multi-USVs flexible formation motion controller is designed using the method of layered control,and based on the low-cost USV hardware platform,the actual multiUSVs formation experiment was carried out.The thesis systematically analyzes and studies the network communication technology and formation controller design of the unmanned surface vessels,which has certain innovation and research value.Specifically,the main contributions and research content of the thesis are summarized as follows.(1)The thesis firstly introduces the research background of this project and analyzes the existing problems in the research of USV formation control and network communication as follows: First,there is a lack of research on the communication system of unmanned surface vehicle.Most of the existing USV control systems are designed using digital radio,GSM or local area network to meet the basic communication requirement.There is no consideration of communication between the numerous and widely distributed USV nodes from the overall architecture,which has certain limitations.Secondly,the communication quality of service(Qo S)indicators is not fully considered in the existing research of USV formation control.The end-to-end delay,packet loss rate and connectivity rate between USV nodes have an impact on real-time control.A reasonable evaluation method should be proposed to evaluate the Qo S indicators of USV formation.Thirdly,the motion control algorithm of USV formation is more complex,and the research on the actual formation control test is not sufficient.(2)Based on the above situation,the thesis based on the ARM platform,PWM motor steering gear,GPS module,Zig Bee networking module,4G-DTU and other unit modules to form a low-cost,modular USV hardware platform.On this basis,the software functions,architecture and software flowcharts of USV control program(embedded C)and ground monitoring program(C# Winform)are introduced,which provides hardware and software platform for the subsequent algorithm development and practical test verification.The kinematics and dynamics model of USV are also introduced.(3)This thesis designs a hybrid communication network architecture combining wireless ad hoc network and remote communication technology.The hybrid network architecture designed in this thesis can realize the high-efficiency and reliable communication between numerous,widely distributed,and mobile USV nodes from the hardware level.This thesis proposes a LEACH networking algorithm with a correction factor at the algorithm level,and uses the idea of clustering to organize and manage the communication between numerous USV nodes.Meanwhile,considering the communication scenario of the USV formation,the communication channel and interference model is established,and the evaluation method of the quality of service indicators such as packet error rate and time-delay is proposed.The simulation evaluation and analysis of the Qo S indicators of several typical USV formations such as triangles,diamonds and column formations are carried out.Furthermore,considering the problem of the unmanned boat’s operating coverage area,considering the time delay constraints for the diamond and column formations,the USVs formation shape is optimized to improve operation efficiency.(4)Based on the leader-followers formation control strategy,the sliding mode control algorithm,this thesis designs the rigid formation controller of USVs.The rigid formation controller can realize the formation and maintenance of the diamond formation of four USVs by simulation.The control effect of sliding mode control algorithm and PID control algorithm is compared and analyzed.Meanwhile,considering the collision between USVs to form a flexible formation(flocking)control,this thesis uses artificial potential field method,vitual leader,and flocking control law is designed under the condition of connectivity maintenance.Using the idea of cascade control,the flocking control problem of USVs with nonlinear dynamic characteristics is transformed into the dynamic target tracking problem,and the flexible formation motion control of multi-USVs is realized.The simulation of flexible formation control algorithm is carried out for static and dynamic virtual pilot situations.(5)Based on the aforementioned low-cost USV platform,this thesis carried out software debugging and joint testing of multi-USVs formation control system.This thesis carried out a complete communication test and a multi-USVs formation control field lake experiment.The experiment verified the autonomous navigation functions such as straight line and circular trajectory,and the formation control function of the diamond formation form,maintenance and switching of multi-USVs.The test verifies the effectiveness of the control system.