Research On Cooperative Formation Control For Multiple AUV Systems With Error Constraint

There has been increased awareness of marine resources with the progress of science and technology.In ocean exploration,Autonomous Underwater Vehicle(AUV)has a wide range of applications in resource exploration,geographic mapping,torpedo detection and underwater inspection due to its flexibility,good control performance and low cost.An AUV easily lose since the harsh marine environment and many unknown emergencies.An AUV is difficult to handle complex ocean exploration tasks.Therefore,multiple AUVs cooperative operation provides a new solution.In the multiple AUV systems,the defined tasks are performed cooperatively through information communication.Compared with an AUV,multiple AUV systems could accomplish more complex tasks and have the higher reliability.This thesis mainly investigates the cooperative formation control of multiple AUV systems.Based on the directed communication topology,this thesis designs AUV control algorithms to realize distributed constraint containment control for multiple AUV systems using neural network technology and Lyapunov stability theorem.The main research of this thesis are as follows.(1)The formation control for multiple AUV systems is investigated in presence of environmental disturbances.Under the directed topology,this thesis proposes a containment control algorithm with time-varying constraints for multiple AUV systems in presence of nonlinear model uncertainties.First,the auxiliary variable and first order filter are designed.Anti-windup saturation auxiliary system for control input saturation is constructed.Further,the adaptive law and neural network adaptive law are designed to compensate environmental disturbances and systems model uncertainties.Finally,in order to ensure the control performance of multiple AUV systems,the log-type Lyapunov function is introduced to realize time-varying constraint and ensure that the tracking error of multiple AUV systems are uniformly ultimately bounded.(2)Based on velocity observer,the distributed finite-time formation control for multiple AUV systems with error constraints is investigated.Considering the inaccuracy of the measured AUV velocity when the AUV velocity changes rapidly,the state observer is introduced to estimate the AUV velocity.As the neural network has the great ability to approximate unknown nonlinear functions,the neural network function is introduced to compensate environmental disturbances and systems model uncertainties and design neural network adaptive law.Since the thrust of AUV actuators is limited,saturation function is designed to control force and torque.In order to realize the formation control for multiple AUV systems rapidly,the finitetime technique and tan-type Lyapunov function are introduced.The time-varying error constraints and the finite-time formation control for multiple AUV systems are realized.(3)The fixed-time formation control for multiple AUV systems with error constraints is investigated.In the finite-time control algorithm for the multiple AUV systems,the convergence time of the system error is related to the initial position of the AUV.The settling time grows with the increment of initial positions of AUVs.It is difficult to obtain the initial positions of the AUVs in practical systems.It is hard to obtain the setting time of multiple AUV systems.It affects the application of finite-time technique.Therefore,the fixed-time control for multiple AUV systems are investigated.Considering the model uncertainties and environmental disturbances of the AUVs,the fixed-timetechnique and tan-type Lyapunov function are introduced to realize the time-varying error constraint formation control for multiple AUV systems.