Underwater Robot Navigation Through Compensation of Sensor Misalignment in Non-linear Space

This paper presents a novel approach to estimate and compensate for the misalignment between the Inertial Measurement Unit (IMU) and Doppler Velocity Log (DVL) sensors. Estimating the location and attitude of an ROV usually combines the attitude by IMU and the velocity by the DVL provided in the sensor coordinate system. The attitude is regarded as the attitude of the ROV and the velocity in the sensor coordinate frame is converted to the velocity in the inertial coordinate frame. Misalignment in the DVL and IMU causes errors in the converted velocity and results in the degradation of the navigation performance. The proposed method represents the misalignment using unit quaternion. Especially, the method utilizes the Lie theory to deal with the operations on unit quaternions which constitute a Lie group, called the 3-sphere group. Simulation and testing of the method in a marine environment validate its effectiveness and practical applicability.