A Study On Position And Attitude Control And Stability Of Underwater Robot

Underwater robots,as crucial tools for human marine development and exploration,have been widely applied in practical engineering and play an irreplaceable role.During marine operations,underwater robots face external disturbances such as ocean currents,making pose control accuracy and self-stability crucial for efficient and safe operations.Therefore,this paper focuses on the research of underwater robot motion control technology and thrust allocation methods to improve the pose control accuracy and self-stability of underwater robots.Firstly,this paper selects the inertial coordinate system and the motion coordinate system to describe the motion of underwater robots and establishes the kinematic mathematical model of underwater robots.Then,the motion of underwater robots is analyzed in terms of forces,and the dynamic mathematical model of underwater robots is established after simplifying the force model.Secondly,the dynamic mathematical model of the underwater robot is transformed from the motion coordinate system to the inertial coordinate system.Taking into account the strong nonlinearity and uncertainty of the underwater robot system,an adaptive backstepping sliding mode controller based on improved fast terminal sliding mode is designed as the six-degree-offreedom motion controller for the underwater robot.This controller improves the pose control and stability performance of the underwater robot,and the stability of the controller is proven by constructing a Lyapunov function.Stability simulation experiments for the underwater robot are conducted in MATLAB/Simulink software,and the simulation results demonstrate good motion stability performance of the underwater robot.Furthermore,a comparative analysis is carried out between this algorithm and the classical PID controller,as well as the adaptive backstepping sliding mode controller based on constant convergence rate.Simulation experiments are performed to compare and validate the algorithm’s performance.The simulation results show that the designed controller has excellent trajectory tracking ability and disturbance rejection capability,and the pose control is superior to traditional controllers.Finally,this paper designs an improved segmented thrust allocation method based on pseudoinverse method to address the influence of dead-zone characteristics of underwater robot thrusters on precise pose control.Simulation comparison experiments are conducted in MATLAB/Simulink software with the traditional pseudoinverse method.The simulation results demonstrate that this thrust allocation method can effectively eliminate the impact of thruster dead-zone characteristics on the control performance of underwater robots and significantly improve stability.