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Underwater Robotics: control of marine manipulator-vehicle systems
Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, Department of Engineering Cybernetics.
2014 (English)MasteroppgaveStudent thesis
Abstract [en]

For using underwater vehicle-manipulator systems (UVMS) in a challenging envi- ronment, it is important to have a good mathematical description of the system which accounts for disturbances such as ocean currents. The dynamics equation on matrix form is therefore derived and different properties such as positive definiteness and skew symmetry is obtained. Based on the derived equations, a sliding mode controller has been designed in order to track trajectories in the configuration space of the UVMS. The controller is robust when it comes to uncertainties in dynamics parameters and uncertainties in ocean current, yielding global asymptotic stability as long as the uncertainties are bounded. Furthermore, a kinematic control system has been designed for facilitating human operation of a UVMS, by allowing an operator to only control the end effector motion. The rest of the motion is then resolved through a weighted least-norm pseudo inverse solution of the Jacobian matrix, in order to avoid mechanical joint limits. Moreover, the vehicle’s motion is controlled by an event based algorithm to limit the motion of the vehicle. This is done by attaching a 3D meshed polygon to the vehicle frame and check if the end effector is inside or outside this mesh. The mesh then represents the space, relative to the manipulator, were the end effector is fully dexterous. The vehicle will then be commanded to move only when the end effector reaches the outside of the meshed polygon. A simulator has been implemented, based on the derived equations. The simula- tions of the UVMS, with the two controllers, yields good tracking results for tracking trajectories both in the workspace of the end effector and in the configuration space of the UVMS.

Place, publisher, year, edition, pages
Institutt for teknisk kybernetikk , 2014. , 106 p.
URN: urn:nbn:no:ntnu:diva-25875Local ID: ntnudaim:10675OAI: diva2:742046
Available from: 2014-08-29 Created: 2014-08-29 Last updated: 2014-08-29Bibliographically approved

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