Research On Depth And Trajectory Tracking Control Of Underwater Vehicle With Uncertain Parameters

The autonomous underwater vehicle plays an major role in the exploration of ocean,in scientific and military missions.The Autonomous underwater vehicle systems have the features that nonlinear dynamics,the system's uncertainties and the strong coupling,making the modeling and control of underwater vehicle a challenging task.These challenges make the problem of controlling the underwater vehicles very attractive to researchers.In this paper,the advanced control algorithm is studied to realize the depth control of the vertical plane and the trajectory tracking control of the horizontal plane for the underwater vehicle with unknown parameters,external disturbances and dead zone inputs.The contents are as follows:The inertial reference frames and the body-fixed reference frames are established to give the six degree of freedom(6DOF)kinematic and dynamic models of underwater vehicle.The 6DOF model of the underwater vehicles is decoupled,and the 3DOF model of vertical plane and the 3DOF of horizontal plane is obtained.An adaptive fuzzy sliding mode controller is proposed for the depth control of an underwater vehicle with parameter uncertainties an external disturbances.The issues on undesirable high frequent chattering in sliding mode controller are resolved using an adaptive fuzzy scheme.The robust term reduces the impact of uncertainties on the system and improves the control quality of the system.The proposed adaptive fuzzy control scheme consists of two components:the main fuzzy controller component and the auxiliary fuzzy controller component,which can be adjusted according to various uncertainties in system parameters and external disturbances.It is demonstrated from simulation results that the effective depth control can be accomplished in the presence of various uncertainties.For the depth control of underwater robots with uncertain dead zone inputs,a compound adaptive fuzzy controller based on the calculated torque control method is designed.The uncertainty compensation part consists of two adaptive fuzzy controllers:an adaptive fuzzy controller is designed for parameter uncertainties and external disturbances to compensate the reference input of the system.In order to eliminate the adverse effect of the dead zone inputs on the system performance,another adaptive fuzzy control compensation is designed for the uncertain dead zone inputs.Finally,underwater vehicle's depth control simulation experiments indicate that the proposed calculation torque control method based adaptive fuzzy control algorithm has better steady state performance and stronger robustness than the calculated torque algorithm.Aiming at the horizontal trajectory tracking problem of the underwater vehicle,a trajectory tracking control scheme combined with calculated torque method and sliding mode control is proposed.The calculated torque algorithm can realize the decoupling of the nonlinear horizontal plane model.The sliding mode control provides robust performance when external disturbances are acting on the underwater vehicles or with parameter uncertainties.The trajectory tracking control simulation experiments of the underwater vehicle indicate that the proposed linear feedback sliding mode control scheme has good steady-state performance and robustness.