Fault Diagnosis And Fault-Tolerant Control For Actuators Of Unmanned Underwater Vehicles

A great amount of natural resources that would support the development of hu-man society have being contained in the oceans. The advancements of science and technology promote the ocean exploration and exploitation rapidly. As one of the main instruments for the march to the sea,the underwater vehicles usually work un-der complicated environments which could bring a variety of faults to the actuators in the motion control system.The faults can easily threaten the security of personnel and apparatus. Thus,to take the actions such as fault diagnosis and fault-tolerant control give great significance to the security.The researches conducted on the fault diagnosis and fault-tolerant control for the underwater vehicles have exceeded two decades,whereas there aren’t enough system-atical solutions for the actuator faults. In the light of this,this dissertation carries out the study of actuator fault diagnosis and fault-tolerant control for the common gyro-rotor and the frame unmanned underwater vehicles(UUV).The study includes the fault estimation and detection for the linear and nonlinear systems,the fault lo-cation and identification for the UUV actuators,and the fault accommodation and control reconfiguration fault-tolerant control for the motion control system.The main contents of this dissertation are interpreted as below.(1)To study the fault estimation and detection for the model control input. In the fault estimation and detection stage,the additive and multiplicatiplicative fault factors are defined for describing the faults in the model control inputs of linear and nonlinear dynamic models.Based on the proposed H∞ filter,linear observer,and continuous-discrete unscented Kalman filter,the estimations for the fault factors are obtained, with which the fault detection functions are given to generate values for comparing with the fault threshold to detect the faults.The simulations prove the effectiveness of the proposed methods.(2)To study the fault location and identification for the actuators of the gyro-rotor UUV.Based on the results of fault estimation and detection of model control input,the faults occurred on the actuators of the attitude control and the dynamic propulsion subsystems,such as the rudder surface,the steering gear,the propeller, and the propulsion motor are located and identified by analyzing the control input equation.The simulation verfies the effectiveness of the algorithm.(3)To study the fault location and identification for the actuators of the frame UUV.Based on analyzing the control matrix,the redundancy analysis algorithm is produced for the commonly used actuator of the frame UUV,i.e.thruster;meanwhile. the hypothesis for fault location and identification of the frame UUV is given.Then, the faulty thrusters that are mounted on the scalar or vector propulsion UUVs are located and identified,based on which the algorithm of fault location and identifica-tion for the scalar or vector propulsion UUV is generalized.The effectiveness of the proposed algorithm is verified through simulation experiments by utilizing the scalar and vector propulsion UUVs,respectively.(4)To solve the fault-tolerant control problem for tolerating the actuator fault based on the research of fault diagnosis while the UUV is still controllable.The fault accommodation and the control reconfiguration fault-tolerant control algorithms are proposed,which are suitable for faulty but still controllable and placed with redun-dancy actuators,respectively.The fault accommodation mainly modifies the feedback control inputs to realize the fault-tolerant control.Whereas the control reconfigura-tion adjusts usts the control structure to achieve the fault-tolerant control,which contains redundancy compensation and redundancy planning.The simulations built with gyro-rotor and frame underwater vehicles verify the effectiveness of fault accommodation and control reconfiguration,respectively.