Research On Motion Control Method For Underwater Vehicles Based On Sliding Mode

In recent years,with the accelerating consumption of land resources,people have been forced to look to the ocean,and the exploration and development of Marine resources have attracted increasing attention from various countries.To complete the mission of the exploration and development of Marine resources,advanced technologies and equipment are required.Autonomous underwater vehicles have strong mobility in complex marine environments,and their working range is not limited by the length of cables,they are capable of autonomous operation in complex environments,so there is a broad prospect application of autonomous underwater vehicle.However,the motion control of autonomous underwater vehicle is interfered by many factors,such as the effect of ocean currents and control system modeling uncertainty.To improve the efficiency and reliability of completing tasks,studying the motion control method of underwater vehicle under the condition of external interference and parameter identification error is of important theoretical significance and practical value.In this paper,the autonomous underwater vehicle “UVIC-I” is taken as the research object,in order to provide a simulation platform for this autonomous underwater vehicle,the modeling method of its simulation model is firstly studied.This paper studies the representation method and coordinate conversion method of the underwater vehicle in the fixed and moving reference system,and establishes its kinematics and dynamics model and gives the parameter values in the model based on the autonomous underwater vehicle“UVIC-I”.In order to simulate the influence of ocean current disturbance and thruster fault on the motion control of autonomous underwater vehicle in ocean environment,the simulation mode of ocean current disturbance and thruster fault in simulation model is investigated.Aiming at the problem of poor control precision when conventional sliding mode controller is used for motion control of autonomous underwater vehicle,the whole system is divided into the position state quantity control of the outer loop and the speed state quantity control of the inner loop.The output of the outer loop controller is taken as the virtual control quantity of the inner loop controller.Aiming at the influence of system uncertainty including external interference and internal modeling deviation on control accuracy,RBF neural network il used to approach the system uncertainty online,and the control law of the controller was redesigned by using the estimated value.The result of the simulation shows that the improved controller can improve the steady state accuracy of underwater vehicle motion control.Aiming at the influence of system uncertainty including external disturbance and internal modeling deviation on nonsingular and fast sliding mode controller,an improved controller based on RBF neural network is designed;To improve the steady state accuracy of the controller,the sliding mode approach law of controller is redesigned with the boundary value estimation method of the neural network approximation error is improved;simulations are performed to verify that the improved method can improve the control effect of RBF singular fast terminal sliding mode controller,a lateral contrast simulation experiment is conducted with a double closed loop integral sliding mode controller that uses the RBF network to directly approach the total system uncertainty.Aiming at the problem of Doppler sensor faults caused by the marine environment noise,so the controller of underwater vehicle lacks the necessary speed state information to construct the control law,a velocity information observer based on super-twisting algorithm is designed in order to construct the motion control system of underwater vehicle.Simulations and pool experiment are carried out to verify that the designed underwater vehicle motion control system can effectively force the underwater vehicle to track the target trajectory.