Modeling, Identification, and Analysis of Limit-Cycling Pitch and Heave Dynamics in a ROV

Savaresi S.M., F. Previdi, A. Dester, S. Bittanti, A. Ruggeri

The topic of this paper is the modeling, parameter identification, and analysis of the heave and pitch dynamics in a remote operated vehicle (ROV). The work presented here is
motivated by an unusual dynamic behavior experienced on the Gaymarine Pluto–Gigas ROV: if the depth is regulated using a proportional controller, the ROV exhibits permanent oscillations
at high forward speed. The purpose of this paper is to gain insight into ROV dynamics, so as to explain the reason for the oscillations. To this end, a dynamic gray-box model is developed
and its uncertain parameters are identified from real data. The analysis of such a model shows that the nonlinear dynamics of the ROV contains a limit cycle. This discovery explains the observed
oscillatory behavior. An interesting aspect of this limit-cycling behavior is that it is not due (as usual) to saturation effects of the actuators, but is intrinsic in the ROV dynamics.

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