High-precision acoustic localization of underwater target for mobile platform using ultra-short baseline array

Based on underwater mobile platform like AUV(Autonomous Underwater Vehicle),a fast convergence and high accuracy acoustic localization method using ultra-short baseline multi-element array was proposed.The CramerRao Lower Bounds(CRLBs) of different USBL multi-element arrays were compared to optimize the array structure the number of elements,which achieves that a 9-element cubic array should be optimal.Multiple localization results of the moving platform were combined to further decrease the localization deviation.And the gradient descent method was used to optimize the trajectory of the platform so that the system can converge to the required localization accuracy as soon as possible.The simulation results showed that the Root-Mean-Square(RMS) error of localization can be fast reduced to a required value of 0.2%within a distance of 1000 m by using optimal trajectory.Moreover,the effectiveness of the localization method using multi-element array in practical oceanic enviroment were verified by sea trials results which showed that for the targets about 700 m and 400 m away from the array,the standard deviations of localization with a 5-element array are 2 m and 1 m lower than that of a 4-element array respectively.