Research On Heading Control For The Unmanned Surface Vehicle In Network Environments

With the development of the international marine situation,the research on Unmanned Surface Vehicles(USVs)has being paid more and more attention all over the world.As a kind of intelligent marine motion platform,USVs are widely used in hydrographic survey,environmental monitoring,maritime searching,rescuing,scientific exploration,modern warface,etc.USVs have a wide range of application prospects.It has been an intense research area in intelligent marine equipment for many countries.In complex and variable marine environments,the autonomous navigation of unmanned surface vehicle heading keeping and heading tracking performance are the basic problem of its motion control.Therefore,designing a safe and reliable heading controller that can adapt to the complex marine environment is one of the most important contents of the USV's motion control.We all know that control for a USV usually based on a remote land-based or mother ship-based control station in network environments.The USV's states such as roll angle speed,and heading angle are sampled and transmitted to the control station through the sensor-to-control station communication network channel.When the sampled USV's states arrive at the control station,the control station constructs and transmites control inputs to the steering gear through the control station-to-actuator communication network channel.Correspondingly,it relizes the heading control and reduces the bow swing.The communication between the control station and the USV is realized through the wireless communication network.The use of communication networks instead of the traditional control system point-to-point control structure,which could interconnect gyroscope,control center and steering gear.Compared with the conventional systems,advantages of the USV control systems in network environments include: flexible structure,low cost,convenient maintenance and installation,etc.However,introducing communication networks into control systems inevitably induces network delays,packet dropouts,quantization and other networked phenomena,which may lower the performance of USV's heading system,and even loss its stability.So,studying the influence of network induced delays and packet dropouts on the heading control of an USV are very important.In this thesis,some basic problems in the control systems of the USV in network environments are considered.A new model of USV heading control system is established.Designing heading controller is considered to achieve the accurate heading for USVs in network environment.So,it could complete the sea operations successfully.The main research contents are as follows in this thesis:1.The mathematic model of the unmanned surface vehicle movement which is disturbed by wind,wave and current is established,and converted into the state space form for the convenience of controllerdesigning.Considering the actual environment of USV operation,the wave interference is modeled.2.The problem of USV's heading control in the control center-to-actuator network channel with network-induced delays and packet dropouts in network environments is studied.Network-based models for the USV subject to the wave-induced disturbance are established.Based on these models,the new heading control design criterias are derived to asymptotically stabilize the USV heading control systems,by defining an appropriate Lyapunov function and adopting the LMI method.The simulation results verify the effectiveness of the proposed control schemes and the designed controllers.3.Targeted at an USV heading control system,considering network-induced delays,packet dropouts exit in sensor-to-control station and control station-to-actuator,the design of observer-based heading controller has been studied.The linear estimation based artificial delay compensation method has been introduced,and the non-uniform distribution characteristic of network-induced delays and packet dropouts has been considered to establish network-based model for a USV.Based on the model,the sufficient conditions for the asymptotically stability mean-square of the USV are given.The simulation results verify the better performance of the proposed control schemes and the designed controllers and observers.