Research On Motion Attitude Control Method Of Underwater Vehicles

Underwater vehicles have the advantages of high flexibility,high operability,safety and reliability,and are widely used in marine resource exploration,ecosystem monitoring,rescue and search,etc.A motion control system with high precision and maneuverability is an important guarantee for stable and effective operation of underwater vehicles.However,there are problems of model nonlinearity,complex hydrodynamic coefficients and environmental disturbances in the control system of underwater vehicle,which make it face great challenges in real-time and robustness.In this paper,the dynamic positioning control strategy and the trajectory tracking control strategy of CHASING M2 ROV(Remotely Operated Vehicle)are thoroughly studied.The main research contents are as follows:Firstly,the inertial coordinate frame and body-fixed frame of ROV are established,and the kinematic parameters of ROV are defined,and the kinematic model of ROV is established by the Euler angle method.The ROV six DOF dynamic error model with model parameter uncertainty is established by analyzing the underwater stresses of ROV and considering the effects of modeling errors and unknown external disturbances.In order to deal with the problems of low positioning accuracy and poor stability caused by model parameter uncertainty in the ROV dynamic positioning control system,the ROV dynamic positioning controller is designed based on the backstepping method.The virtual control law is approximated by command filter,which solves the problem of "computational complexity" in traditional backstepping method.To improve the positioning accuracy of the ROV,the fuzzy logic system is used to deal with the model uncertainties in the system,and the error compensation mechanism is designed to eliminate the effect of filtering errors.Then,Considering the existence of external disturbances that are difficult to measure during ROV underwater positioning,The fuzzy logic system is combined with a disturbance observer to estimate the lumped disturbances,and the error compensation mechanism is introduced to design the ROV dynamic positioning controller based on the finite-time command filter.Combining backstepping with the finite-time command filter control to improve the progressive convergence of the positioning signal.Finally,the stability of the closed-loop system is proved,and the effectiveness of the designed controller is verified by Simulink simulation.A trajectory tracking controller based on super-twisting nonlinear integral sliding mode is proposed for solve the modeling errors and external disturbances problems existing in ROV trajectory tracking control system,and the problem that the velocity of ROV is difficult to be measured directly in engineering practice.Meanwhile,the ESO is used to estimate the ROV’s motion velocity and lumped disturbance.A global nonlinear integral sliding mode surface with the saturation function and the attenuation function is constructed to eliminate the integral saturation phenomenon and improve the response speed of the system;and the adaptive super-twisting switching control law is designed to improve the accuracy of trajectory tracking and reduce the chattering of control variables.Finally,the stability of the closed-loop system is demonstrated,and the comparison by Simulink simulation verifies that the designed controller can effectively suppress the system lumped disturbances with high control accuracy and robustness.An experimental test platform consisting of the ground station and underwater control system is built,and the depth control,directional navigation control and plane trajectory tracking control experiments are carried out using the control methods designed in this paper.The experimental results show that the designed dynamic positioning controller and trajectory tracking controller have better control effect compared with the traditional PID controller.