Research On Multi-UUV Formation Control Method For Submarine Target Search

In recent years,aircraft,submarine,and ship accidents have occurred frequently.Unmanned Underwater Vehicle(UUV),as an important tool for effectively searching for underwater accident targets,has become more and more popular with researchers.Under the background of submarine targets,the research of multi-UUV formation control method was carried out.To sum up,this paper mainly achieves two major goals.The first goal is to sail the UUV at a fixed altitude relative to the sea floor,and the second goal is to maintain the formation of the formation in a stable horizontal plane.The main research contents of this paper are as follows: First,establish the inertial coordinate system and satellite coordinate system,and explain the mutual conversion relationship between the two coordinate systems.A five-degreeof-freedom kinematics and dynamics model of UUV was established in the model.According to the typical characteristics of the seafloor terrain,mathematical models of four typical terrains: uphill,downhill,convex and concave.Secondly,for the unknown sea floor terrain,a four-beam sonar sea floor terrain detection scheme is proposed.The data information collected by the sonar is filtered to remove interference to obtain the local terrain features of the sea floor.Then,UUV is proposed based on the local terrain features.The control strategy of sailing at a fixed height relative to the sea floor transforms the problem of controlling the relative height of the sea floor into a variable depth control problem at a relative sea level.Then,a variable depth controller is designed,and a robust analysis of the depth controller is performed.Finally,the proposed control strategy and controller are used to simulate four typical terrains: uphill,downhill,convex and concave,to verify the effectiveness of the proposed algorithm.Third,the UUV formation coordination control problem is decomposed into a spatial path tracking problem and a time speed coordination problem.Each UUV in the formation runs a path tracking controller to ensure that the motion trajectory converges to a given path.The status information exchanged,and a speed coordination controller designed for the formation to control the longitudinal speed of each UUV to maintain a stable formation.Aiming at the UUV path tracking problem,the kinematic path tracking controller and the dynamic path tracking controller are designed based on the backstepping method to realize position and velocity tracking.The stability of the path following controller is proved.In view of the narrow bandwidth of underwater acoustic communication channels,a method of exchanging only univariate state information is proposed,which can effectively reduce the communication volume in formations.Aiming at the problem of speed coordination,a coordination error model was established based on the relevant knowledge of graph theory,and a formation coordination controller was designed to realize the formation coordination control by controlling the speed of the virtual target point in path tracking.Finally,research was conducted on the coordinated control of UUV formations under environmental constraints.The interference of ocean currents was considered in the UUV path tracking problem,and the communication delay was considered when the formation members performed underwater acoustic communication.Aiming at the problem of path tracking under ocean current interference,an ocean current observer is designed to estimate the velocity of an unknown constant current.Aiming at the problem of communication delay in formation,a coordinated control strategy based on logical communication is proposed.The UUV estimates the state of itself and other UUVs through a state estimator.When the deviation between the estimated value and the actual value reaches a certain threshold.Each UUV updates the status information synchronously to achieve coordinated control of the formation.