US Patent 7495999 Underwater guidance systems, unmanned underwater vehicles and methods

An unmanned underwater vehicle for use in water and with at least one acoustic signal source includes a vehicle body, a steering mechanism to direct the vehicle body through the water, a propulsion device to force the vehicle body through the water, and an adaptive Doppler guidance and control (ADGC) system. The ADGC system is configured to receive acoustic signals from the at least one acoustic signal source and to control the steering mechanism using changes in at least one frequency component of the received acoustic signals caused by Doppler shifts.