Preliminary results with a low-cost fiber-optic gyrocompass system

This paper reports results of preliminary numerical simulation studies and preliminary static experimental evaluation of a true-North gyrocompass system employing a commercially available low-cost inertial measurement unit (IMU) comprising a 3-axis fiber optic gyroscope (FOG) with microelectro-mechanical systems (MEMS) accelerometers. Northseeking gyrocompass systems typically employ a microprocessor system to sample the IMUs low-level raw sensor values for angular-rate and linear-acceleration at a high sampling rate, compensate for sensor bias and alignment, and compute a highlevel estimate for true-North heading, pitch, and roll. We report the results of a numerical simulation study to evaluate the potential accuracy of the proposed system, and a numerical sensitivity study to evaluate how this accuracy will change with variation in the sensor measurement noise of the gyroscopes and accelerometers. We report preliminary experimental results for a static benchtop configuration of this system which utilizes 3-axis angular-rate data and 3-axis linear acceleration sensor data to estimate the instrument's 3-degrees of freedom (DOF) attitude (heading, pitch, and roll) without using magnetometry of the Earth's magnetic field. These preliminary results for a static benchtop IMU configuration are promising, and directly applicable to static instrument deployments, but further development, testing, and evaluation is needed for the case of dynamic IMU configuration typically found on moving marine vehicles.