An integrated navigation system for autonomous underwater vehicles with two range sonars, inertial sensors and Doppler velocity log

This work presents an integrated navigation system for autonomous underwater vehicles with inertial and acoustic sensors. The integrated navigation system is based on a strap-down inertial measurement unit (IMU), where auxiliary navigation sensors are two range sonars, a Doppler velocity log (DVL), a magnetic compass and a depth sensor. The main idea of the paper is to improve the performance of the IMU-DVL navigation system by introducing additional range information. The range sonars can measure the distance and the incident angle from a reference transponder on an underwater station. The range sonars are modeled to improve the navigation algorithm, which could provide valuable information for the IMU-DVL navigation to reduce estimation error, especially when the DVL cannot detect the bottom reflection. Simulation was conducted with the 6-d.o.f. nonlinear numerical model of an AUV in lawn-mowing survey mode at tidal flow, where the bottom reflected DVL information is unavailable. Simulations illustrate the effectiveness of the integrated navigation system assisted by the additional range measurements.