<p>An Underwater Vehicle-Manipulator System (UVMS) is a complex and highly non-linear multi-body dynamic system used in Inspection, Maintenance, and Repair (IMR) operations. Beyond the disturbances caused by the hydrodynamic forces, the UVMS is also subjected to the dynamic coupling between the Underwater Robotic Vehicle (URV) and the manipulator. This coupling affects the position and attitude of the URV, which should remain rather stationary while the manipulator moves. The correct compensation of such coupling could be achieved through precise model-based control or with the signals produced by a force/torque sensor placed on the connection between the URV and the manipulator. However, the former approach is almost impossible to achieve in practice and the latter is very difficult to be implemented. In view of these problems, this paper proposes a station-keeping control scheme based on the utilization of Reactions Wheels (RWs) as inertial actuators for the attitude stabilization of a URV under the action of the disturbances induced by the manipulator. First, a detailed mathematical model of a UVMS is developed according to the Euler-Lagrange approach, considering modified kinetic and Potential energy functions to include the hydrodynamic and hydrostatic forces. Semi-empirical models already validated in the literature are used for the hydrodynamic forces, while ad-hoc models are used for the thrusters and electric motors. Then the controller is formulated exploring the inertial coupling between the URV and RWs. Also, the Sliding Mode Control (SMC) algorithm is incorporated into the design in order to provide robustness to this approach. The effectiveness of the proposed control system is validated here through numerical simulations, taking as a case study a planar UVMS consisting of a URV and a two-link serial manipulator. Seeking to perform realistic simulations, the sensors' measurements are added to the simulations and an Extended Kalman Filter (EKF) is used to perform the state estimation. The numerical simulations are performed in the MATLAB/Simulink® environment through the numerical integration of the UVMS's model with the proposed control approach. Two scenarios as considered in the simulations: 1) the manipulator performs a swing motion with its joints in-phase, and 2) out-of-phase. Regarding the results, the proposed&nbsp;control scheme not only provides superior performance on the station-keeping in both scenarios when compared with a standard model-based decoupling controller, but it also leads to lower energy consumption in terms of thrusters' usage and overall energy efficiency, which can increase the autonomous capability of the UVMSs in the future.</p>

Modeling and Station-Keeping Control of an Underwater Vehicle Manipulator System Through Reactions Wheels

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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