| With the development of science and technology and the expansion of oceanic applications,autonomous underwater vehicle(AUV)has been widely used in the field of ocean observation,maritime rescue,mine countermeasures,intelligence reconnaissance,etc.However,pursuant to the task requirements of high efficiency and large scale,an individual AUV has been unable to meet the requirements.By virtue of the high efficiency brought by the spatial and temporal distribution,and the reliability brought by the redundant configuration,multi-AUVs system provides a new way to solve complicated marine tasks.It's not only because of the increasing of AUV numbers,but also relys on the coordination and cooperation among individuals,thus the multi-AUVs system could fulfil the mission which an individual AUV is not competent.Formation control of a group of AUVs is a typical coordinate problem,and also the basis of studying other cooperative problems.In the operating process,it's a challenging work to overcome the instability of underwater communication.With the eyes of engineering utility,several issues raised by coordinate formation and cooperative search of multi-AUVs is studied.(1)The way-point following and path following problem of an AUV is addressed.AUV motion control is the cornerstone of multi-AUVs coordinated control.Aiming at the problem of way-point following,by using the pure orientation guidance method within the guidance-control framework,the sufficient conditions of global asymptotic convergence to the desired way-point is discussed based on the cascade system theory.Then,based on the S surface control algorithm,the path following controller is proposed,and the sea test is carried out.Aiming at the path following problem,the modified line of sight guidance law is designed under the guidance-control framework.Then,the stability analysis of the guidance-control system is put forward using Lyapunov stability theory.At last,the sea test is carried out.(2)The formation control problem of multi-AUVs based on path following is studied.An auxiliary point is introduced for each AUV.And the path following of individual AUV is indirectly achieved by driving corresponding auxiliary point along the path,then the formation control is realized by synchronizing the auxiliary points.The guidance law and synchronization law of the auxiliary points are designed based on the direct method of Lyapunov.The stability analysis of the system is given based on the cascade system theory.At last,the sea test is carried out.(3)The AUV target tracking problem is addressed.The motion state of the target obtained from the forward-looking sonar is estimated by using the unscented Kalman filter.According to the Lyapunov's direct method and the parallel guidance method,the target tracking guidance law is designed.In combination with the S plane control algorithm,the AUV target tracking is realized.Then,the tank test is carried out.(4)The formation control problem of multi-AUVs based on target tracking is studied.In order to get more stable and accurate position and velocity information of the leader under unstable communication environment,the maximum likelihood estimation method is used to fuse the information obtained from underwater acoustic modem and forward-looking sonar.With the target tracking control algorithm designed above,multi-AUVs formation control is realized and the sea test is carried out.(5)On the basis of formation control,the typical problem of AUV failure during cooperative search is studied,from the perspective of system structure,communication protocol and cooperative strategy.A message forwarding mechanism is proposed due to the unstable underwater communication environment.A method to conclude the failure of an AUV is presented through logical operation of the communication state.And A message based cooperative strategy is constructed.At last,the simulation experiment is carried out. |
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