Summary: | Azimuth thrusters are widely used in maritime vessels, especially those operating in Arctic waters. These thrusters increase maneuverability, which is critical in harsh Arctic environments. However, component failures have been found in the thrusters. A common source of failure is torsional vibrations. Studying torsional vibrations through simulations is more cost-efficient and less laborious than measuring the vibrations in full-scale thrusters with sensors. In this thesis, transient torsional vibrations are simulated in a small-scale Azimuth thruster test bench. A simulation model is established using a finite number of lumped inertia elements. The model is represented mathematically in discrete-time state-space form. Simulations are conducted for a step, an impulse, and an ice-load excitations. The simulated torque response is compared with measurements from previous research. The simulated torque responses show similar trends to the measured responses. However, some differences are noteworthy. The simulated torque for all three excitations has a negative DC offset. In addition, the amplitude of the simulated responses is lower and decays faster. Possible reasons for this are incorrect damping parameters in the model and different controller parameters compared to the experiments. The highest amplitude peak in the frequency spectrum of the simulated torque response corresponds with measurements. However, two amplitude peaks are missing in the impulse response and one in the step response. This indicates that the simulation model might be more damped than the test bench. The simulated torque responses seem to correspond quite well with the measurements. Similar differences are seen for all three excitations, with an exception in the Fourier analysis. This indicates that the model is precise and has the potential to be tuned for better accuracy. Future research could be to optimize the damping parameters to see if they improve the prediction capability of the model. Azimutdrivsystem används i stor ...
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