  Having accurate localization capabilities is one of the fundamental
requirements of autonomous robots. For underwater vehicles, the choices for
effective localization are limited due to limitations of GPS use in water and
poor environmental visibility that makes camera-based methods ineffective.
Popular inertial navigation methods for underwater localization using
Doppler-velocity log sensors, sonar, high-end inertial navigation systems, or
acoustic positioning systems require bulky expensive hardware which are
incompatible with low cost, bio-inspired underwater robots. In this paper, we
introduce an approach for underwater robot localization inspired by GPS methods
known as acoustic pseudoranging. Our method allows us to potentially localize
multiple bio-inspired robots equipped with commonly available micro
electro-mechanical systems microphones. This is achieved through estimating the
time difference of arrival of acoustic signals sent simultaneously through four
speakers with a known constellation geometry. We also leverage the same
acoustic framework to perform oneway communication with the robot to execute
some primitive motions. To our knowledge, this is the first application of the
approach for the on-board localization of small bio-inspired robots in water.
Hardware schematics and the accompanying code are released to aid further
development in the field3.
