SUMMARY

The development of underwater landmarks has been a subject of keen interest in the last decade as a technique to facilitate underwater navigation for autonomous underwater vehicles (AUV) due to the increase of AUVs deployment for underwater operations. The predominant method for AUV localization and navigation is the use of active transponders that constantly emit a known acoustic pulse from a known spatial location. Also, there has been an increase in the use of a newer optical-based method using underwater cameras that can be detected over a limited range of operations.
My PhD proposal illustrates the practicality of employing a newer method for AUV localization and navigation using a passive underwater acoustic marker called Acoustic Identification (AID) tags. These AID tags contain multi-layer stratified hemispherical reflective layers that backscatter a uniquely engineered acoustic signature, composed of the multiple reflections created by the layer interfaces. These acoustic signatures can later be detected by an AUV when interrogated by an acoustic source. All the experiments have been done in Georgia Tech for a distance of around 5m. A 1 MHz transducer is used as the source mounted on the XYZ moving stage to simulate an AUV approach.
The unique backscatter from the AID tags serves as a basis for developing a classifier that can be trained to accurately predict the tag's signatures as well as their location based on the time of arrival and can be used to convey specific instructions or directions to the AUV which depends on the type of underwater operation that the AID tags are used for. These passive AID tags can be detected by an AUV instrumented with a high-frequency sonar transducer at significantly greater distances than conventional optical methods, especially in turbid waters. A specific signal processing detection methodology is being used to improve the detectability of AID tags.