Nonlinear dynamic model identification methodology for real robotic surface vessels

Abstract

This paper presents a methodology for identifying the nonlinear dynamic model of underactuated surface vessels for the purpose of model-based controller design. The methodology outlines the required tests that need to be performed and the formulations that need to be used for sequentially identifying the model parameters one by one. The identification methodology is performed on a robotic vessel by testing in outdoor environments and the accuracy of the dynamic model is verified. The physical control inputs to the vessel are a propeller rotational speed and a rudder angle. 3 degrees of freedom are assumed for the nonlinear dynamic model of the surface vessel. Finally, an approach is proposed that discusses how the identified full nonlinear dynamic model can be used for control design. Results of typical closed-loop control tests are presented.

Keywords:

• nonlinear dynamics
• surface vessel
• system identification
• trajectory tracking
• control
• experimental

Acknowledgements

This research was funded by the Office of the Vice President for Research, UAHuntsville, Huntsville, Alabama, USA.

Notes

Speeds resulting from tests with n₁ = 69.2 and n₂ = 98 rps.

Speeds resulting from tests with n₂ = 98 and n₃ = 120 rps.

Speeds resulting from tests with n₁ = 69.2 and n₃ = 120 rps.