Numerical study on multipath elimination algorithm for an iUSBL system using LFM signals

Abstract

In order to measure the underwater position of an underwater robot, a positioning system using acoustic waves is widely used. Recently, in order for underwater robots to directly measure their position, transceivers are mounted on the underwater robots as in inverted ultra-short baseline (iUSBL) equipment, which also uses USBL algorithms. Since the USBL or iUSBL algorithm uses time delay and phase information measured by each sensor unit, a bearing angle estimation error occurs due to signal distortion caused by reflected waves. In order to eliminate them, broadband signals (for example LFM) that can sufficiently distinguish delay time compared to direct waves should be used. However, narrow bandwidth of underwater acoustic transducers and computational power limitations of underwater signal processing systems confine the bandwidth and pulse length that can be implemented. In addition, the system must consume small power to be usable underwater for a long period of time, and a transmission signal considering the calculation time should be designed to maintain a high update rate around 1 s. In this study, an algorithm of multipath elimination is introduced when multipath interval is smaller than pulse length. Plus-shaped array configuration is assumed and numerical simulation is performed for various conditions and parameters. The results show that the proposed algorithm improves the performance of range and angle estimation. ？ 2023 IEEE.