Research On Connectivity-preserving Flocking Of A Swarm Of Autonomous Surface Vehicles

Nowadays,all countries are paying more and more attention to the ocean space,and the exploration,development and utilization of the ocean has become a research hotspot in the field of ocean.Autonomous surface vehicle(ASV),also known as unmanned surface vehicle,is a kind of miniaturized,intelligent,autonomous marine vehicle.Having the ability to carry different modules for various missions,ASV can be used as a small surface carrier platform,and has become an important tool for human to study the ocean.The cooperation of multiple autonomous surface vehicles can accomplish many tasks which are difficult for a single ASV.As a result,the cooperation of AS Vs has become a research hotspot recently.Flocking control is a multi-agent control mode inspired by a variety of animal group behaviors in nature,and takes the features of good flexibility and robustness.Flocking control has broad application prospects in search and rescue,detection,military cluster and other fields.In this paper,flocking control problem with connectivity preservation based on the leader-follower structure for multiple ASVs is studied.The speyific work is as follows:Firstly,to solve the connectivity-preserving flocking control problem of multiple fully actuated ASVs with model uncertainty and external unknown disturbance,an extended state observer is designed to estimate the model uncertainty and external unknown disturbance.A path following controller of the leader is designed by the backstepping method.A connectivity-preserving flocking controller is designed combined with the backstepping method and the artificial potential field method.A distributed speed observer is designed to solve the problem that only some ASV have the access to the leader.A new method based on the leader-follower structure is proposed to achieve the connectivity-preserving flocking control of multiple fully actuated ASVs.The input to state stability(ISS)of the closed-loop system is proved by ISS theorem and cascade system stability theorem.The simulation results show that the proposed method can achieve the path-guided connectivity-preserving flocking control of multiple ASVs.Secondly,considering the output feedback,that is,only the position and yaw angle of the ASV can be measured,an extended state observer based on position and yaw angle is designed to estimate the speed information,the model uncertainty and the unknown disturbance of ASV.A path following controller of the leader is designed by the backstepping method.A connectivity-preserving flocking controller is designed combined with the backstepping method and the artificial potential field method.In order to solve the problem that the speed of the leader ASV needs to be known globally,a distributed speed observer based on position and yaw angle is designed.A new method is proposed to achieve the output feedback connectivity-preserving flocking control of multiple fully actuated ASVs.The input to state stability of the closed-loop system is proved by IS S theorem and cascade system stability theorem.The simulation results show that the proposed method can achieve the output feedback path-guided connectivity-preserving flocking control of multiple ASVs.Thirdly,considering the problem of multiple underactuated ASVs with model uncertainty and external unknown disturbance,an extended state observer is designed to estimate the model uncertainty and external unknown disturbance.A path following controller for the leader and a connectivity-preserving flocking controller for the followers based on the artificial potential field method are designed for the underactuated ASVs.A distributed speed observer is also designed for the problem that the speed of the leader ASV needs to be known globally.The input to state stability of the closed-loop system is proved by ISS theorem and cascade system stability theorem.The simulation results show that the proposed method can achieve the path-guided connectivity-preserving flocking control of multiple underactuated ASVs.