To complete the acoustic task, the AUV uses an array of 4 Sparton PHOD-1 hydrophones positioned up front to pick up the pinger signals. The signals picked up by the hydrophones would then be pre-amplified before noise filtering with an analog high pass filter board which was developed by the Acoustics Research Laboratory, NUS. Thereafter the cleaned up signal would be sampled by the sbRIO9612 with the support of an Analog Input Module, NI9223, at a rate of more than 300kS/s simultaneously. From the input signal, the onboard microcontroller of the sbRIO9612 would employ a thresholding algorithm to acquire the portion of the ping and then translate it into time difference of arrival of each hydrophone.
The time difference of arrival will then be sent to the Core i7 Single Board Computer for triangulating computation which outputs the direction and position of the pizza box relative to the vehicle. To reduce the need for sway movement, the AUV will first turn towards the direction of the pinger signal, and then use its navigation system to move towards to the position of the pizza box.