Researches On Path Planning And Trajectory-Tracking Control For Autonomous Underwater Vehicle

The motion control of AUV has received more and more attention in recent years because AUV has been widely used in military,commercial and scientific research fields.Two issues are investigated in this dissertation.One is the path planning for AUV.Path planning enables the AUV to perform tasks safely and reach the destination quickly with the limited energy.The other is the trajectory-tracking control for AUV.Trajectory-tracking control is much more complicated than path planning,which not only considers the kinematic characteristics and the dynamic characteristics of the underactuated AUV,but also considers the external disturbances and the faults.External disturbances and the faults will reduce the tracking accuracy and the stability of the underactuatea The main research contributions are as follows:(1)Obstacle avoidance path planning for AUV.Two(?)ms are solved.One is the underwater obstacles avoidance.And the other is the pa(?)timization.Underwater obstacles are mainly divided into two categories:static obstac(?)d dynamic obstacles.Static obstacles mainly consist of the underwater terrain.The dynamic obstacles mainly consist of aquatic life.The static obstacles are considered in this dissertation.In order to enable AUV to avoid obstacles quickly and reach the destination safely,this dissertation proposes an improved ACO algorithm based on the PSO algorithm for the obstacle avoidance plan planning of the AUV.Firstly,the mathematical model of the AUV and the three-dimensional space for path planning are constructed.Secondly,the three-dimensional grid method is used to divide the three-dimensional path-planning space.Thirdly,an improved ACO algorithm based on PSO algorithm is designed for the obstacle avoidance plan planning of the AUV with the attitude angle constraints of the AUV.Finally,the effectiveness of the algorithm is verified by simulation results.(2)Trajectory-tracking control problem for underactuated AUV with or withouttime-varying disturbances.Firstly,the trajectory-tracking control problem for the underactuated AUV without time-varying disturbances is investigated.The error tracking system is established based on the kinematic model,the dynamic model and the desired trajectory of the underactuated AUV.The trajectory-tracking control problem is transformed into the optimal control problem.An online dual-iteration ADP controller is designed and the stability of the error tracking system is analyzed based on the Lyapunov theory.The simulation results are given to verify the effectiveness of the controller.Secondly,the trajectory-tracking control problem for the underactuated AUV with time-varying disturbances is investigated.Based on the kinematic model of the underactuated AUV,a virtual velocity control vector is proposed using backstepping method.The error tracking systems with time-varying disturbances is established based on the kinematic model,the dynamic model with time-varying disturbances,the desired position and attitude vector and the virtual velocity control vector of the underactuated AUV.The neural network is used to design a predictor to estimate the time-varying disturbances and the online strategy iteration based ADP controller is designed.The stability of the error tracking system with time-varying disturbances is analyzed based on the Lyapunov theory.The simulation results are given to verify the effectiveness of the controller.(3)Fault-tolerant tracking control problem of AUV with thruster faults or rudder fauts.Firstly,the fault-tolerant tracking control for fully-actuated AUV with rudder faults and ocean current disturbances is investigated.The error tracking systems with rudder faults and ocean current disturbances is established based on the kinematic model,the dynamic model with rudder faults and ocean current disturbances,and the desired trajectory of the fully-actutated AUV.The neural networks are used to design two predictors to estimate rudder faults and ocean current disturbances respectively,and an online strategy iteration based ADP controller is proposed,and the stability of error tracking system with rudder faults and ocean current disturbances is analyzed based on the Lyapunov theory.The simualtion results are given to verify the effectiveness of the controller.Secondly,the fault-tolerant tracking control for underactuated AUV with thruster faults is investigated.The output-feedback error tracking systems with thruster faults is established based on the kinematic model,the dynamic model with thruster faults and the desired trajectory of the underactutated AUV.The neural network is used to design the observer to approximate the thruster faults,and an online strategy iteration based ADP controller is proposed,and the stability of error tracking system with thruster faults is analyzed based on the Lyapunov theory.The simualtion results are given to verify the effectiveness of the controller.(4)Trajectory-tracking control of zero-sum game of underactuated AUV.Under the influence of the continuous and unknown disturbances,the underactuated AUV becomes unstable and the tracking accuracy decreases.Therefore,the disturbance and underactuated AUV controller are regarded as a two-person game,and a zero-sum game mechanism is introduced.Firstly,based on the kinematic model of the underactuated AUV,a virtual velocity control vector is proposed using backstepping method.Secondly,the error tracking systems with external disturbances is established based on the kinematic model,the dynamic model with external disturbances,the desired position and attitude vector and the virtual velocity control vector of the underactuated AUV.The trajectory-tracking control problem is transformed into a zero-sum game problem.Thirdly,an online strategy iteration based single-critic-network ADP controller is designed and the stability of the error tracking system is analyzed based on the Lyapunov theory.Finally,the effectiveness of the controller is verified by simulation results.