Research On Motion Control Of An Underwater Vehicle Based On Fuzzy PID

A remoted operated underwater vehicle ROV plays an important role in submarine object detection,halobios observation,petroleum exploration,rescue,etc.There’re many factors that affect the motion of ROV during the subsea operation,such as wind waves,ocean currents,hydraulic pressure,and so on.Therefore the control of its balance and depth are the main task of ROV motion control research when a ROV executes various tasks.Optimization design and research of the control,modelling and simulation are carried out to an underwater vehicle in the thesis.Its main research contains as follows:(1)Six-degree-of-freedom system modeling of an underwater vehicle.The kinematics model and the dynamics model of an underwater vehicle are established on the basis of selecting of the earth fixed coordinate system and the underwater vehicle fixed coordinate system as a system modeling reference system.Furthermore,the depth control model of the fixed depth motion is deduced and the simplified depth control transfer function of the underwater vehicle is substituted by the parameter values which lays a foundation for the follow-up control and simulation.(2)The control system design of an underwater vehicle.A FPID control method is proposed aimed at the six-degree-of-freedom motion system of an underwater vehicle with time-varying and nonlinear and strong coupling characteristics with fault-tolerant fuzzy logic idea and PID control method in order to overcome the disadvantages of weak robustness and large overshoot of a traditional PID controller.The FPID controller has achieved the transient performance and the steady-state performance requirements of an underwater vehicle motion control.(3)Depth control simulation and performance test of an underwater vehicle.A depth control model of an underwater vehicle is established by MATLAB Simulink and simulation is carried out to the depth control with different fixed depth by the traditional PID controller and the FPID controller and both controllers are analyzed and compared from the aspects of transient performance and steady-state performance.The simulation results show that the average overshoot of the traditional PID control is 13.36% in the transient performance while that of the FPID controller is 6.02% although both controllers can stabilize the system and the rising time of FPID control is effectively shortened more than 30% and the adjustment time is effectively shortened more than 36%in aspects of transient performance compared with a traditional PID control.It shows that the stability of the FPID control is better than a traditional PID control.Moreover,the robustness and the disturbance rejection are checked to further proved that the FPID controller is better in the transient and steady-state performance of the system.The thesis has some engineering significance and reference value to the design and research of an underwater vehicle motion control system.