A Passive Inverted Ultrashort Baseline Scheme for Underwater Positioning Based on the Acoustic Frequency Combs

In this study, a self-localization method, an inverted ultrashort baseline based on a seafloor four-array base array is designed and implemented to achieve the practical application of autonomous spatial position sensing for small and low-cost autonomous underwater vehicles (AUVs) and reduce the cost of their autonomous localization simultaneously. First, an acoustic frequency comb (AFC) signal with stable time-frequency characteristics and high peak power is designed as the broadband signal. Second, each array element of the four-array base station deployed on the seabed responds with mutually orthogonal AFC signals, and the AUV receives the mixed AFC signals of each array element and then employs the matched filter method and phase analysis method to measure the one-way flight time of each signal coarsely and accurately. Finally, to realize the autonomous position solution of the A UV, the inverted ultrashort baseline positioning method is combined. The results show that the AUV only needs to carry a single receiving beacon to complete its own position sensing, which further reduces the cost and system complexity. Moreover, the results also prove the high reliability of the AFC signal, which can realize high autonomous localization accuracy at the AUV end.