Research On Dynamic Positioning Control Technology For Autonomous Underwater Vehicle

Underwater vehicle(robot)is essential equipment for today countries to explore and develop marine resources,especially autonomous underwater vehicle(AUV)has become the most direct and effective means of deep-sea exploration.But its high degree of autonomy for the control technology adds lots of difficulty,how to achieve more maneuverability and handling while maintaining the stability of underwater motion,has been the focus of future research.The dynamic positioning system requires real-time control information based on the current position and attitude feedback information of the AUV.Then,the actuator performs control information to counteract environmental disturbances and ensure accurate AUV work tasks.Therefore,the dynamic positioning system is the necessary support system for underwater operations,especially for deep sea operations.This paper has conducted in-depth research on related technologies of dynamic positioning.This paper analyzed the vital and difficult points of AUV dynamic positioning control technology and it studied in depth on the dynamic building models,the design of dynamic positioning functional controller and the optimization strategy of thrust distribution in AUV complex environment.The main research contents and achievements are as follows:1.Taking into account the requirements of dynamic positioning for control accuracy,AUV precise model is established in a complex environment.In this paper,a complete kinematics and dynamics analysis of the AUV in the current environment is obtained,and the general vectorization of the six-degree-of-freedom space motion is obtained.Then taking into account the current factors,get a more realistic AUV mathematical model.2.In term of the existing characteristics of AUV operation process,which were nonlinear dynamic characteristics,model uncertainties and difficult to directly measure external interference,it designed a six-degree-of-freedom dynamic positioning controller,which was based on adaptive sliding mode control.At the meantime,an on-line current velocity observer was designed to estimate the current velocity to overcome the undiscovered steady current disturbance and an adaptive parameter estimation method was introduced into the control algorithm to overcome the possible model parameter perturbation in the control process.Two functions of fixed-point hovering and trajectory tracking were accomplished by adopted the designed controller.The simulation shows that the controller designed in this paper satisfies the accuracy of the operation and has strong robustness.3.In order to achieve more maneuverability,the arrangement method of multiple auxiliary propellers was designed.The dynamic positioning controller simply generates the thrust and torque commands required to meet the motion,and the thrust distribution logic performs a secondary distribution of these commands.In order to ensure the positioning accuracy and reduces the energy consumption and wear of the propulsion system,this paper proposes a multi-propeller thrust distribution strategy to establish a multi-objective quadratic programming model.Finally,the model was solved with SQP algorithm.The simulation shows that the thrust distribution strategy is implemented within a very small thrust distribution error.