Automatic on-line measurement of ship's attitude by use of a servo-type accelerometer and inclinometers

For an accurate automatic on-line measurement of the ship's attitude the paper develops an intelligent sensing system which uses one servo-type accelerometer and two servo-type inclinometers which are appropriately located on the ship. By considering the dynamics of the servo-controlled rigid pendulums of the inclinometers, linear observation equations are derived on the rolling and pitching signals of the ship. Moreover, one accelerometer is utilized to extract the heaving signal. Through the introduction of linear dynamic models and the linear observation equations for the three signals, their online measurement is reduced to the state estimation of the linear dynamic systems. A bank of Kalman filters is used to execute the on-line state estimation and to overcome changes in parameters in the dynamic models with time lapse.