Ever wanted to command a submarine? This project explores the use of high frequency sound waves to communicate with underwater objects (both how it works and what the problems are).
Underwater ultrasonic data telemetry has many similarities to ultrasonics in air. However the water medium also creates some fundamental obstacles to be surmounted, such as cavitation (bubbles interfering with transducer operation), multipath/reflected signals, and interference.
Sound carries a long way underwater, but it is hard to produce a strong signal, and this has resulted in underwater data systems that cost many thousands of dollars, containing sophisticated error-correction software and hardware.
This project is aimed at producing a working communication system (on a limited budget). The system consists of separate transmit and receive circuits, driven by micro-controllers, and using underwater transducers. The transmitting circuit generates a high-voltage signal (of around 200kHz) that causes the transducer to resonate.
This ‘carrier’ signal is then used to transmit commands from a user – to a submarine or other underwater device. The receive circuit detects, amplifies and filters the signal before passing it on. Software in each micro-controller is used to help ensure reliable and robust communication – however it is highly dependent on the situation.
This project is a proof of concept – it replicates the functionality of a serial cable between (for example) two instances of hyper-terminal. It can be shown that half-duplex communication is possible by duplicating each circuit and adding some simple logic hardware. A very likely application could be to issue high-level commands to a test submarine – like the one below from California Polytechnic.
Source: UCLA
Author: Heungwoo Nam | Sunshin An
