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An underwater acoustic beacons positioning method using single hydrophone

When an aircraft crashed the sound emitted by the beacon would help to detection and location the black box. While in the deep sea research, it is hardly to use the USBL, SBL and LBL as usual. In this paper a new method was introduced. In this method, the beacon could be located with only one hydrophone. The time difference of the hydrophone at different place was used to located the beacon. To verify the performance of this method, the simulation was processed. The results show that this method is effectively.


Introduction
When an aircraft crashed the sound emitted by the beacon (pinger) would help to detection and location the black box for prompt recovery and analysis. Because the Operating Life of the Beacons is limited, it is very important to search and location the beacon as quickly as we can [1,2].
It is well known that the traditional technique for localization acoustic beacons is Long Baseline, Short Baseline and Ultra Short Baseline. USBL uses phase differencing measurements between closely spaced (< 1 m) hydrophones to estimate the direction and elevation angle of an incoming signal. These are combined with travel time measurements to estimate range for pinger positioning. SBL is based on a similar concept, except that the hydrophones are more widely spaced (5 -20 m) and instead of phase differencing, time difference of arrival is used. Both USBL and SBL systems are commonly mounted on vessel hulls, but can also be moored on the bottom or mounted in buoys at the surface. LBL systems measure travel-times between an array of transponders and a moving pinger. With multiple travel time, or range measurements, a least squares algorithm can be used to estimate the position of the pinger using either a hyperbolic or spherical solution. However sometimes only have one hydrophone especially in a deep ocean search. The attitude of the hydrophone array can't be obtained easily in a deep ocean search. Therefore, the common methods were hard to be used at this time [3][4][5][6].
In this paper, we will propose a method to locate the acoustic beacon with only single hydrophone. This paper is organized as follows: In the section 2, we introduce the location method. In section 3, we present solution of the method.

Basic Principle
The acoustic beacon is at M ) , ( y x . The receive is a single hydrophone, which goes along 1 Each position and time of 1 Solved the equation, then the positon of M can be obtained.

The Solution
As the same one, we can get Then the equation can be re-write as

 
The equation of (1) and (2) can be solved, as

Simulation Results
To verify the performance of this method, the simulation has been processed. In the simulation, the time error is less than 0.1s, and the location error of the hydrophone is less than 0.1m. The simulation results (the location errors of the beacon) are shown in Fig.3. The error of locating is less than 500m in 6km.

Summary
In this paper, we tackles the problem of localization the underwater acoustic locating beacons of the "black box". In the deep-sea research, it is hardly to use the USBL, SBL and LBL. So a new method is introduced. In this method, the beacon was located with only one hydrophone, by the time difference of the hydrophone at different place. To verify the performance of this method, the simulation has been processed. The error of locating is less than 500m in 6km in the simulation. The results show this method is effectively.