Biologically motivated adaptive sonar system

Abstract

An active sonar system is described that adaptively changes its configuration in response to the echoes it observes. The system mimics biological sonar systems in that there is a movable center transmitter flanked by two adjustable receivers and the interrogation pulse rate is adaptive. When echoes are received, the sonar rotates to point the transmitter at the echo-producing object to maximize the incident acoustic intensity. The receivers rotate and point toward the object to maximize the echo amplitude and bandwidth and to minimize the echo-producing region. This adaptation in configuration standardizes the location of the object within the beam patterns making object recognition from echo waveforms feasible. A change in elevation of the object produces a systematic attenuation in the high-frequency components in the echoes that may prove useful for elevation determination. The sonar is controlled with three stepper motors that define a discrete-state system that points to a finite number of locations in its field. Microscopic perturbations of the object position at the boundaries between these locations cause macroscopic transitions to occur. Making an analogy with the discrete nature of neurons in biological systems provides a possible explanation of the hyperacuity reported in bat ranging experiments.