Research On The Stability And Floating Attitude Recovery Of Unmanned Surface Vehicle

Unmanned Surface Vehicles (USV) with a high sailing speed, are capable of Intelligence Surveillance & Reconnaissance (ISR), arm protection, mines sweeping, anti-submarine, precision strikes and other functions, widely display the great value of military application. However, complicated motion control requisition, poor sea and the unexpected risks in the process of executing tasks are huge challenges for USV which adopts autonomous control system. With excellent stability in the ocean, avoiding overturning will guarantee the accomplishment of USV's design functions. And when USV capsized in accident, making it easily recover to upright floating attitude with limited outside disturbances or active measures, directly relates to the vitality and battle effectiveness of USV. So, this paper mainly analyzed a USV's stability and the ability of floating attitude recovery.1) Based on the displacement equality method and instantaneous wet surface method, by making use of VB program language, the hydrostatics and waves stability of USV were calculated and analyzed, then the influence of wave-ship relative positions, heading Angle, wavelength, wave-height for USV's stability were discussed, finally the most dangerous conditions for sailing was forecasted.2) In virtue of CFD technology, respectively adopt 2D and 3D calculating method, the influence of the hydrodynamic pressure generated by high sailing speed for righting arm were analyzed. When using the 2D method for calculation,2D+ t theory was used to simplify the 3D hydrodynamic analysis into the slamming research of water entering of wedge. In the process of calculation, Fluent software was used to simulate the slamming force, and according to the results, by numerical fitting and integrating, finally the righting arm was obtained when USV heels a certain degree in a high sailing speed; then, CFX software was utilized to directly simulate the 3D flow around USV which heels a certain degree in a high sailing speed. Vertical force and the transverse righting moment were predicted, and the hydrodynamic distribution of USV, free-surface shape was discussed. In the end, the calculated results generated by the two different methods were analyzed and compared.3) For the simulation of floating attitude recovery, the mathematical model was established, and then the influence of broadside airbag and superstructure for the effectiveness of floating attitude recovery were analyzed particularly. According to the analysis, designed two different effective auxiliary devices to assist USV recover to upright floating attitude. Finally, the recovery process and effect of floating attitude recovery were simulated after USV capsized.