Numerical Analysis on the Error Convergence of an Inertial-Acoustic Navigation System for Underwater Vehicles with a Range Sensor

Abstract

This paper presents an integrated navigation system for underwater vehicles to improve the performance of conventional inertial-acoustic navigation systems by introducing a complementary acoustic range sensor. The inertial-acoustic navigation system is based on an inertial measurement unit (IMU) and a Doppler velocity log (DVL) accompanying a range sensor, a magnetic compass and a depth sensor. A measurement model of the range sensor is modeled and augmented to the IMU-DVL navigation system. An extended Kalman filter is adopted to propagate the error covariance, update the measurement errors and correct the state equation when the external measurements are available. This paper demonstrates the improvement on the navigational performance of the integrated system with the range information, and strong points on the elimination of the estimation error of underwater vehicles having initial position error. Experimental data obtained from a rotating arm test with a fish model are used to estimate the navigational performance. The convergence speed and conditions of the initial error removal are examined with Monte Carlo simulation. In addition, numerical simulation was conducted with the 6-d.o.f. equations of motion of an AUV in lawn-mowing survey mode to illustrate the effectiveness of the IMU-DVL navigation system assisted by the complementary range measurement, especially for the removal of initial position error.