Towards automatic identification of ship-ice contact using acceleration measurement

Abstract

When a ship navigates in ice-covered areas, its hull experiences motion and vibration responses due to ship-ice contact. The magnitude of such responses can be represented well by acceleration, which is easy to measure onboard ice-going ships. The level of acceleration is determined by the environmental and operational conditions through excitation via the ship-ice contact. Conversely, it is possible to infer excitation and environmental conditions using acceleration measurements via appropriate methods. Accelerations associated with such responses can also affect the functionality of the onboard equipment and therefore, should be quantified. Nevertheless, studies on shipborne acceleration measurements in ice fields and their links to prevailing excitations and environmental conditions are rare. This study explores the feasibility of using shipborne acceleration measurements to infer the corresponding excitations (i.e., ship-ice contacts) as a first step towards the inference of ice conditions via acceleration measurements. An automatic identification method for ship-ice contact is proposed that can effectively separate ship-ice contact events from acceleration measurement signals. The acceleration signals are decomposed in the time-frequency map obtained through a short-time Fourier transformation (STFT). An improved detection transformer (DETR) model was used to automatically identify ship-ice contact events and achieved good accuracy in the validation set. This model was then applied to automatically identify ship-ice contacts using acceleration signals under various environmental and operational conditions. The frequency of the identified ship-ice contact reasonably reflects its dependence on prevailing environmental and operational conditions, which confirms the validity of the proposed methodology.