Research On Anti-interference And Fault-tolerant Control Method Of AUV Based On Interference And Fault Estimatio

With the rapid development of today’s society,people are eager to discover new resources and development directions.The mysteries and abundant resources in the ocean attract people’s attention,so people accelerate the pace of exploration of the ocean.Autonomous Underwater Vehiele(AUV)has become one of the important tools to explore the ocean because of its small shape,strong flexibility and large range of activities.AUV is susceptible to disturbance such as ocean currents in the ocean;the thrusters,rudder systems,sensors and other components are also prone to failure during operation.AUV needs to have good performance and complete the task stably in the unpredictable complex working environment.Therefore,aiming at the attitude and motion control system of AUV,this thesis designs an anti-disturbance fault-tolerant controller to suppress external disturbance and ensure that AUV has good fault-tolerant ability.The main contents include the following aspects:(1)For the horizontal plane system of AUV,an observer-based backstepping faulttolerant controller is designed to ensure that AUV can still complete the task according to the expected yaw angle under the condition of vertical rudder failure and external disturbance.Firstly,the system model of AUV is simplified under certain conditions,and the horizontal state equation is obtained by decoupling.Aiming at the fault of vertical rudder in underactuated AUV actuator and the influence of external ocean current disturbance,an observer is designed to estimate the fault and disturbance in real time.Then,an anti-disturbance fault-tolerant controller is designed by combining the observer with the backstepping controller,and the asymptotic stability of the closed-loop system is proved by Lyapunov stability theory.Finally,the simulation results show that the controller has good anti-disturbance ability and fault tolerance.(2)For the vertical plane system of AUV,in order to ensure that the underactuated AUV still has good depth control performance under external disturbance and horizontal rudder failure,a sliding mode fault-tolerant controller based on disturbance fault observer is proposed.Firstly,the vertical plane model of AUV is obtained by decoupling the AUV six-degree-of-freedom system model with disturbance and fault terms,and it is transformed into vector form.Then,a disturbance fault observer is designed to observe the disturbance and fault,and an anti-disturbance sliding mode fault-tolerant controller is designed from the observed disturbance and fault values.Finally,the stability is proved by Lyapunov theorem and verified by simulation.The results show that the proposed controller has good depth control effect.(3)Aiming at the overall system model of AUV,in order to ensure that the underactuated AUV can complete the trajectory tracking task according to the expected three-dimensional trajectory under the condition of environmental disturbance and failure,an observer-based backstepping sliding mode controller is proposed.Firstly,the trajectory tracking task is transformed into a stabilization problem of a nonlinear system based on AUV kinematics and dynamics equations.Then,based on the disturbance and fault observer,a backstepping sliding mode anti-disturbance fault-tolerant controller is designed to gradually make each state quantity of the system approach the expected value.Finally,the simulation results show that the designed controller can ensure the AUV to complete the three-dimensional path tracking smoothly and stably.This paper solves the problem of anti-disturbance fault-tolerant control of AUV under the condition of disturbance and fault.The proposed observer-based controller has higher stability and anti-disturbance fault-tolerant ability than the traditional controller without observer,which can ensure that AUV has better attitude and motion control performance.