Research On Analytical Model Based Fault Diagnosis And Fault Tolerant Control For AUV Actuators

In recent years,the exploration and development of marine resources has gradually become a research hotspot in various fields.Autonomous underwater vehicle(AUV),as a tool for human exploration and development of marine resources,plays an important role in marine related research fields.However,objective factors such as the uncertainty of the underwater environment and the complexity of underwater motion pose great challenges to the fault diagnosis and fault tolerant control for AUV actuators.This thesis will study the fault diagnosis and corresponding fault-tolerant control of the AUV actuator based on the analytical model method when the model parameters are known.The main work is as follows:(1)The AUV model and its system structure are briefly introduced.Through the analysis of coordinate system transformation,hydrodynamic force and interference force,the six-degree-of-freedom dynamic motion model of the AUV is finally introduced,which provides a prerequisite for subsequent fault diagnosis and fault-tolerant control research.(2)A fault detection and estimation method via adaptive threshold and extended state sliding mode observer(SMO)is proposed in this thesis.Firstly,new expanded state variables are achieved to obtain the diagnosis residuals between actual and estimated outputs.Then,an improved adaptive threshold is designed to monitor the change of residuals,aiming at further reducing the fault mis-diagnosis.Further,the gain solution is transformed into the linear matrix inequality(LMI)constrained optimization problem based on the extended-state structure.Finally,by designing dynamic sliding surface,the chattering phenomenon is suppressed and the convergence can be guaranteed.(3)A fault isolation and identification method is proposed for AUV based on fault factor and multiple observers scheme.Firstly,the fault isolation and identification of AUV actuators is divided into two levels based on the concept of fault factor.Secondly,the fault isolations focusing on rudder,propeller and actuator based on extended state observer(ESO)and isolation logic rules are proposed.According to the relationship between the output force and torque,further identification can be realized via internal information analysis of fault factors.(4)According to the fault condition of the actuator,the fault tolerant control of the AUV carrier is designed to achieve the established control objectives.Considering the steady-state and dynamic performance of the control system,a T-S fuzzy controller is designed,taking into account the redundant arrangement of the AUV actuator,normalizing the output force and torque,and implementing fault tolerant control of the AUV actuator using a pseudo inverse method under thrust distribution.Due to the control limitation of the AUV actuator under actual operating conditions,a quadratic programming method is proposed to achieve compensation for input control quantities.