DVL is used in ultrasonic self-navigation to estimate the velocity
and direction vector according to the movement of vehicles
and the phase difference of ultrasonic waves reflected from
the seabed. This method examines the movement of robots relative
to the current position; moreover, it includes an informationupdate
cycle of several hertz. DVL estimates the new position
and direction relative to the current position, whereas the baseline
technique estimates the relative position of robots around
a node with a fixed position using the phase difference, TOA,
or AOA of ultrasonic waves. Ultrasonic position estimation is a
widely used verified system for estimating the relative position
of the robot from a ship in a wide range. However, because underwater
ultrasonic waves incur the multipath effect in shallow
water environments or in areas installed with complex structures,
estimation precision is reduced or incorrect information
may be obtained [10]. Furthermore, ultrasonic waves cannot be
used for close distance works involving manipulators and work
tools, such as for construction of structures that require a high
degree of precision. As an alternative, studies have been conducted
on a technique that estimates the underwater position
in a structured environment or at a near distance using signal