Research On UUV Vector Field Guidance Method For Recovery Task

Since the 21 st century,with the solution of some technical problems,Unmanned Underwater Vehicle(UUV)technology has become more mature,and quickly entered the application phase.When UUV performs long-term detection task,it is often necessary for UUV autonomously recovery to a platform for data exchange,charging,and maintenance.The process of autonomous underwater UUV recovery can usually be divided into three phases: collection,homing and docking.This paper is aimed at the guidance method of the homing stage in the recovery process,that is,the guidance path planning and the guidance path tracking.Firstly,aiming at the problem of path planning of sitting recovery,the position and heading of UUV enters the autonomous recovery stage are taken as the starting vector,and the position and heading of the recovery platform are taken as the end vector,the solution of a plane Dubins path planning is proposed under UUV kinematics and dynamics constraints.The growth generation method of four kinds Dubins paths is designed.In the presence of obstacle environment,this paper proposes a method of combining growth sampling RRT algorithm with Dubins curve and joins with the idea of directivity to get a recovery path based on G-D-RRT algorithm.The probability completeness and asymptotic optimality of G-D-RRT algorithm are analyzed and discussed.Simulation results show that the proposed method can generate smooth obstacle avoidance paths in the simulation environment and digital ocean environment.Secondly,a robust HGVF path-following algorithm is proposed to guide UUV to a planar target path in conjunction with the planned Dubins path.The construction method of linear vector field and arc vector field is given and the desired heading command of each point in the vector field is produced that is input to the low-level controller.The asymptotic decay of path following error in the case of constant current disturbance is proved by Lyapunov stability theory.The switching strategy of two different vector field is discussed and the guidance of the combined Dubins recovery path is achieved by combining the segmented guidance with the switching of different vector fields.The method of constructing the smooth curve vector field is given for the smoothing path guidance in the obstacle environment.At the same time,the change rate requirement of the heading angle and path tracking error are discussed in the paper.The simulation case proves the simplicity and efficiency of the proposed vector field path following algorithm.Then,a new method of generating the starting vector and the end vector space recovery guidance path in three-dimensional environment is proposed for the problem of intercept reccovery.By extending the mathematical representation of Dubins path to the three dimensional space,the three dimensional Dubins path planning of the starting vector and the end vector non-coplanar and coplanar are completed.The calculation method of the three dimensional shortest Dubins path is proposed when the recovery platform is in linear motion and circular motion,and the influence of the current flow on the recovery path is discussed.For obstacle-dense environment,based on the idea of rolling planning to moving target point,the method of constructing obstacle and target vector local map is constructed according to the distance and azimuth information of the obstacle.According to the local map,a three-dimensional LM-D-RRT method is proposed to generate planning path to the moving target region.The conditions of the collision-free path in the local path planning technology are discussed and the environmental characteristics of UUV can reach the specific target area.The problem of smooth connection of space obstacle avoidance path points is solved by using Bezier curve,which ensures the continuous change of heading angle and pitch angle of the planning path.Simulation results show that the proposed algorithm successfully solves UUV spatial path planning and multi-obstacle avoidance problem.Finally,the VGVF method for solving UUV 3D guidance path following with Lyapunov stability is solved.A simple global stable velocity vector field is generated in the three-dimensional space and the expected velocity at each point in the space is converted into heading angle and pitch angle angle command.For the space Dubins path,a method of constructing a space linear guidance vector field and a space arc guidance vector field are proposed to give the expected velocity vector at each point in the vector field.Based on the transformation strategy of different vector field forms,the combining Dubins path following method is gived from the starting vector to the end vector.A VGVF path following method for circular paths is proposed for the presence of obstacle environment.By considering the attracting operator and the cyclic operator in the vector field respectively,the Lyapunov method is used to generate the vector field with global attraction to the closed target path,and a nonzero expected velocity can be generated.At the same time,in order to make the generated velocity command satisfies the curvature and torsion of UUV,the velocity vector controller is designed in two vectors which perpendicular to and parallel to the current vector in the space.The simulation results show that the designed vector path tracking algorithm is simple and effective.