Research On Control Method Of Underwater Vehicle Based On Rotatable Thruster

Oceans are rich in resources,the human demand for resources makes attention of great powers to the ocean,the development and utilization of the ocean has become a new hot topic.People can't explore the ocean without underwater robots which has an irreplaceable position in the ocean inspection and seabed operations.In order to adapt to the deep sea investigation and effectually prolong the underwater operating time of underwater vehicle,an underwater vehicle based on rotating propeller is designed by Shenyang Institute of Automation.Based on the characteristics of the rotatable thruster,the mathematical modeling of the underwater vehicle is carried out,and the kinematics equation and kinetic equation of the underwater vehicle are analyzed,and the viscous hydrodynamic force and inertial water of the underwater robot are analyzed.The six-degree-of-freedom state space equation of the underwater robot is obtained.Based on the characteristics of underwater motion of the underwater vehicle based on the rotatable thruster,designed the basic navigation task for the underwater vehicle,including the water surface orientation,the underwater depth,the underwater height and the underwater navigation.The control algorithm is designed based on the above mission.The model predictive control method is used to control the underwater robot.The constraint function of the control rate and the change rate of the control variable makes the algorithm more practical.The objective function of the model predictive control is combined with the Lagrange multiplier.The new objective function is constructed,the useful constraint is selected by the idea of effective set,the optimal control law of variation is obtained by Hildreth programming,and the control of the model predictive control algorithm to the underwater robot is realized.Following the model predictive control algorithm,another robot control algorithm is used,which combines the idea of fuzzy control with the traditional PID control to realize the self-tuning of PID parameters.This algorithm is called fuzzy PID control.The simulation results of model predictive control are compared with those of fuzzy PID control,which proves that the model predictive control can play an important role in the control of underwater robots.By comparing the model predictive control with the fuzzy PID control,we find that the controller parameters of the model predictive control algorithm are more convenient than the fuzzy PID controller,and the control effect is also more ideal.Based on this viewpoint,the model predictive control algorithm is used to design a more detailed simulation experiment.On the basis of the deep-set and directional tasks of the foundation,the auther also continues to research the underwater robot's search mission and the walking path of vehicle reflects the control effect.