| Autonomous Underwater Vehicle(AUV)formation has the advantage of improving the efficiency of underwater operation.The formation based on pilot following method is widely used in mapping,investigation,search and transportation.The coordinated control of AUV formation requires each individual to have the ability to accurately obtain the state of other members,but the characteristics of underwater acoustic communication increase the difficulty of AUV formation control and research.Based on the single model of underwater vehicle,combined with the pilot following method and the requirements of formation coordination,this paper constructs a formation control system based on feedback linearization,and studies and analyzes the coordinated control of AUV formation when communication is limited.The main research contents of this paper include the following points:1.Based on the five-degree-of-freedom nonlinear model of fully driven AUV,the second-order integral model of AUV was obtained by using feedback linearization method.Based on the consistency theory and the pilot following method,the coordination controller of the follower in the formation is designed under the directed topology.Lyapunov-Razumikhin theory is used to obtain the desired path on the formation tracking and keep the boundary condition stable.Simulation experiments based on 3d spiral trajectory are constructed to verify that the designed controller can meet the requirements.2.In order to solve the collision problem between members in formation,the artificial potential field method is used to design the potential field function,and the collision avoidance term is added to the formation coordination controller to obtain the controller with collision avoidance ability.Different collision avoidance radii are designed for each member to improve the convergence speed of the formation,and it is proved that there is no collision between the formation members in the simulation.Then,considering the existence of communication delay in formation control,the Lyapunov Krasovskii functional is established by using the method of designing control gain to verify the stability of the designed controller.3.In order to make the controller keep the formation stable even with large time delay,and to solve the problem that the existing literature on cascade predictors fails to combine with the actual nonlinear model,the output of cascade predictors is used as the input of second-order integral model controller,and then converted to the nonlinear model through feedback linearization.Firstly,a delay state predictor is designed to predict the real state of the hour-long delay.Then,multiple delay state predictors are combined,and each sub-predictor is responsible for predicting one hour delay.Finally,the actual value of the formation with large delay can be obtained.Lyapunov function was established and matrix inequality was used to prove the stability of the system.Three groups of comparative experiments were designed to analyze the effects of different numbers of subpredictors on the cascade predictors and formation.4.Aiming at the problem that AUV communication is unstable,that is,there is communication interruption,Markov random transformation topology is used to simulate the possible interruption and analyze the stability.Firstly,the formation coordination controller with switching topology and the same delay is designed,and the stable boundary conditions are obtained by calculating the expectation of Lyapunov function in the stability proof.Then,aiming at the slow convergence speed of the controller using pilot following method and P control,the controller is designed using a method similar to PD control,and different values are designed for the adjacency matrix of directed topology.In the simulation verification,the comparison of the two controllers under the same conditions is given.The results show that the PD controller can meet the application requirements and converge faster under unstable communication. |
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