Experiment with a Digital Twin of a Ship Scale Model

This page presents some experiments performed with a digital twin of ship scale model at TPN-USP as of January 2020.

Developed by Ícaro A. Fonseca, Henrique M. Gaspar, Pedro C. de Mello, Humberto A. U. Sasaki and Felipe F. de Oliveira.


The conception of the digital twin system followed a bottom-up approach: several subsystems already in use on the TPN workflow were aggreagated into an overarching digital twin with a web-based interface. The measuring and control system included:

  • Water elevation measuring system: a commercial system measuring the elevation of a sensing probe floating on the tank nearby the model.
  • Motion capture system: a commercial system measuring the motion of the ship model on the six degrees of freedom.
  • DP controlling system in MATLAB, connected to the model PSV via radio frequency and to the motion capture system via network.


A few simplifications were taken during the development of the digital twin. The wave condition was regular and taken always from the same known direction, which avoided the necessity to identify the direction with the digital twin during the experiment. The wave characteristics are obtained by reading through the water elevation log. When the algorithm identifies a zero-crossing on the signal, it fetches the last peak and valley to estimate the phase, period and height for the latest wave cycle. During experiments, the azimuth angles of both stern thrusters are locked by default for simplification of an over actuated control problem.

Experiment replay

The 2D plots are used for validation by comparing the motion measured during the experiment and the results calculated with a boundary element method software. In general, the plots show a good agreement and provide an interface for quick assessment of discrepancies between the measured and expected movement responses. When the experiment defines a new DP setpoint, the validation plots immediately to fetch the RAOs corresponding to the new heading values, leading to some momentary disgreements between computational and experimental values. The two plots tend to converge as the PSV maneuvers towards the new setpoint. While the propulsion rotation was measured and visualized during experiments, it is not displayed on the visualization below.

Position log converter

This utility converts the motion tracking logs generated during the experiment to the ISO 19848 standard. Upload the TSV file saved by the tracking software (see example here) to download the converted log in JSON.