Evaluation of Dynamic Coupling Intensity and Passive Attitude Control of Underwater Vehicle-Manipulator Systems

Abstract

In the future, underwater manipulation tasks are intended to be performed by moving base robots, namely Underwater Vehicle-Manipulator Systems (UVMSs). However, the manipulation task induces reaction forces and torques on the underwater vehicle, affecting its positioning. Therefore, it is necessary to compensate for these disturbances to perform the coordinated control of the UVMS or the station keeping of the underwater vehicle. For this sake, this paper presents a new methodology to evaluate the intensity of the dynamic coupling as a function of the working frequency of the manipulator. With such information will be possible to predict the frequency range in which the dynamic coupling is significant. Also, this approach could be used on the task planning level to produce dynamically feasible reference trajectories, improving the control performance. Beyond the identification of a safe frequency range, the obtained results also provide interesting insights about the dynamic coupling influence for the attitude Degrees of Freedom (DoFs) of the underwater vehicle, which can be related to results reported in previous works. Moreover, motivated by the results obtained here and the originality of this application, a passive control is synthesized for the attitude of UVMSs. The simulation results show good attenuation for the pitch oscillations with the proposed control.