Preliminary feasibility study of cooperative navigation of underwater vehicles with range and range-rate observations

This paper reports a preliminary feasibility study of a method for combined underwater communication and navigation of underwater vehicles (cooperative navigation) in which synchronous-clock modems are employed to measure both range and range rate on every acoustic data transmission. Few previously reported studies have utilized acoustic range rate in addition to acoustic range for the general navigation of underwater vehicles. This paper reports an observation model for range-rate measurements and preliminary anecdotal simulation studies for cooperative navigation of one underwater vehicle client with one surface vehicle server employing both range and range-rate observations to estimate the vehicle states with a delayed-state extended Kalman filter. In the simulation studies presented, the underwater vehicle is equipped with Doppler sonar navigation, attitude, and depth sensors, and the surface vehicle is equipped with a GPS. The preliminary studies suggest that the addition of range-rate measurements may not significantly improve the filter´s estimate of the client´s state over the case of range-only observations. The present study is very preliminary, however, and directions for future study are suggested.