<p>Full-scale measurements were conducted on the portside propulsion shaft&nbsp;the S.A. Agulhas II, during the 2019/20 Annual SANAE Relief Voyage. The measurements included the&nbsp;shaft torque which was captured at two separate measurement locations, and the shaft rotational speed at one measurement location.&nbsp; Ice impacts were extracted from the full-scale data and&nbsp;analysed using two inverse models, which estimate&nbsp;the ice-induced propeller moments using the measured shaft responses as inputs.&nbsp; The first was&nbsp;a previously published discrete lumped mass model that relies on regularization due to the inverse problem being ill-posed.&nbsp; This model is only able to make use of the propulsion shaft torque as inputs.&nbsp; The second model is newly developed and employs modal superposition to represent the propulsion shaft as a combination of continuous modes, resulting in a well-posed problem.&nbsp; This new continuous model requires the additional measurement of the shaft rotational speed in order to perform the inverse solution.&nbsp; Based on the comparison of results between the models and the measurement locations themselves, it is shown that the continuous model is significantly more consistent and efficient.&nbsp; The efficiency of the continuous model would allow its use in real-time monitoring of propeller moments.&nbsp; It is also shown that since the continuous model takes the rotational speed of the shaft, and hence the effects of the motor control parameters, into account that more accurate results can be achieved.</p>

A Comparison of Inverse Models for the Estimation of Ice-Induced Propeller Moments on a Polar Vessel

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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