The Research On The AUV Longitudinal Attitude Control Considering The Loss Of Propeller Thrust

Currently, for the automatic underwater vehicle (AUV) research, people are no longer confined to the study of deep-sea operation, but also investigate the task near surface, where the disturbance of waves is more severely. The research topic is concentrate on the attitude control, path tracking, the added resistance, and the electric propulsion control saving which attracts more focus. To solve the last problem, this paper selected the propeller model, which can improve thrust. Then investigating the longitudinal attitude of AUV based on the method of state-dependent Riccati Equation (SDRE) nonlinear control and adaptive terminal synovial nonlinear control (Terminal), respectively. The loss of the propeller thrust could be reduced by these two methods.For the studies, this paper established a movement mathematical model of six degrees freedom based on Newtonian mechanics Theorem, and then simplified the model of vertical movement and do the open-loop system simulation analysis. Since the AUV operations is disturbed by wave, random disruption of the waves against the AUV is featured with randomness, uncertainty and low signal to noise ratio and other characteristics, the wave in time domain and frequency domain was optimized, simulated and analyzed. And it was applied to nonlinear Anti-rolling systems model to obtain reasonable calculation results. It has an important meaning for further analyze the nonlinear anti-rolling model theory, and he MATLAB software is used to do the simulation analysis. The motion change of the AUV is caused by interference waves such as the Marine environment, not only generates additional sway resistance, but also affect the propeller load performance. Taking into account the propeller efficiency, although in theory, the greater the diameter of the propeller, the lower speed, to provide the higher propulsive efficiency, which is due to the interference, hull, and the influence of flow pattern. Different AUV is applied to different propellers, and different interference by the propeller load effect is different, so the study in this paper, the model of the propeller model selection and longitudinal attitude movement's influence on the performance of the propeller is simulated; So the SDRE controller design and Terminal synovial controller design is applied to the longitudinal attitude movement in this paper. The AUV vertical movement of the pitching and heaving displacement amplitude is reduced by the posture control. In order to reduce the loss of propeller thrust and torque loss as well as the additional energy consumption of the AUV, and improve the battery life prolonged underwater operation. This paper studied the longitudinal attitude control by adopting different control strategies, which combined the Terminal control theory, adaptive control theory, SDRE control method and ?-D approach.The simulation analysis shows that the impact of longitudinal motion interference to propeller load characteristic is mainly caused by the loss of the propeller thrust so SDRE controller and Terminal controller is designed for synovial longitudinal attitude motion control, which is designed for the attitude control reduces the amplitude of the AUV vertical motion of pitching and heaving displacement, so as to reduce the additional energy loss and loss of propeller thrust and torque AUV consumption, improve the endurance of prolonged underwater operation time. The result of comparing the simulation data of the two kinds of control also shows that the control model for the adaptive Terminal can better damping effect.