| Over the last decade, Autonomous Underwater Vehicles (AUV) are increasingly being used in ocean geology and have a wide range of applications in scientific and military fields.Due to the small surface and autonomous operation, it can face to the challenge of exploration of extreme environments. Meanwhile, the carried energy has greatly restricted. According to the limited energy, the endurance capacity of AUV cannot be pledged. It is worth mentioning that, when the AUV moves near the water surface, there would be violent oscillation generated due to the influence of surface waves. Simultaneously, the hydrostatic resistance is much more than that sailing in the deep water. What's more, the loss of thrust and torque of the structure is obvious due to the propeller rotating near the water surface. Under the effect of these two factors, the original propeller property is greatly damaged, and useful energy is wasted. This is not what we expected.In this work, it is proposed the modeling of the relationship of the pitching motion and sailing resistance according to a numerical (CFD) simulation and potential flow theory. The study has proved that the major factor increasing sailing resistance of AUV is violent pitching motion. In addition, this article does not only monitor the vertical posture and motions when designing AUV vertical attitude controller. It is proposed that controlling the motion of the AUV reduces the resistance. This is conducive to make sure the propeller working on match points. According to the veracity of the results, AUV propulsion system controller is designed.The loss of torque generated by the propeller regards as external disturbance. For further study of the robustness of propulsion system and anti-jamming capacity, a Fuzzy PID controller is generated and has an expected simulation results. Due to the integrated control of vertical motion and propulsion system, the match point would be assured and the energy would be save availably. |
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