An alternative approach to eliminate the motion induced disturbances in dead-reckoning navigation

This paper presents the approach to eliminate the motion induced disturbances while the attitude determination for the purpose of dead-reckoning navigation that is alternative to the conventional one when an AHRS is used. The key point of the approach called “indirectly correctable pendulum” (ICP) is to use the raw accelerometer data and to account for the motion acceleration in the position components using the log data without differentiation. It is shown that in the case of “flat” motion the total compensation can be achieved applying the quadratic corrective term based on the log data, in the case of 3D motion additionally the inertial support should be provided. Two examples of 3D applications are examined: 1) when the positional gyros (ESG) are used the dead-reckoning can be provided with only one polar gyro and no loss in accuracy against two-gyro AHRS. 2) when 3-axes magnetometer is used for magnetic navigation the tilt errors caused by the motion acceleration can be cancelled without using AHRS. Based on the obtained results the general concept is stated: when the attitude is determined from two nonorthogonal vector observations (one vector is the gravity) the inertial vertical in the plane that contains both vectors can be constructed regardless of the other vector nature. The natural frequency of the inertial loop is defined by the nature of the second vector and can differ from the Schuler one.