Experimental evaluation of a MEMS inertial measurements unit for Doppler navigation of underwater vehicles

This paper reports the results of an in-water laboratory experimental evaluation of the attitude estimation accuracy of a low-cost micro-electro-mechanical systems (MEMS) attitude and heading reference system (AHRS), and the effect of the accuracy of this sensor on Doppler-based underwater navigation. We report a comparative analysis of Doppler navigation obtained employing MEMS AHRS in comparison to Doppler navigation obtained with a high-accuracy inertial navigation system (INS) including a true-North-seeking gyrocompass and high precision accelerometers. The data indicate that Doppler navigation performance with MEMS AHRS is sensitive to instrument calibration including Doppler/AHRS alignment calibration, calibration of AHRS magnetometers for hard-iron & soft-iron errors, and calibration of AHRS angular rate sensors. When carefully calibrated, MEMS AHRS Doppler navigation error is shown to be within an order-of-magnitude of that obtained with high-end INS for the conditions and vehicle trajectories studied. The goal of this evaluation is to quantify Doppler navigation performance using MEMS AHRS. These results may be useful in the development of lower-cost Doppler navigation systems for small and low-cost underwater vehicles.