Path Following and Collision Avoidance for an Underwater Swimming Manipulator
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The Underwater Swimming Manipulator (USM) is a new type of autonomous unmanned underwater vehicle that combines the highly maneuverable design of the biologically inspired underwater snake robot (USR) with thruster actuators as typically used in more traditional underwater vehicle designs. The USM resembles a submerged multiarticulate manipulator arm with thrusters, and can use joint actuation, thruster actuation, or a combination of the two for motion. The thrusters increase the USM's controllable degrees of freedom (DOF), and by placing them strategically they can facilitate 6-DOF rigid-body movement almost independently of the robot's body shape. Together with the long and slender body, this maneuverability enables the USM to gain access to almost any area, that being the inside of shipwrecks or between the steel beams of subsea structure protection cages, and can be utilized to solve complex tasks. One of the most essential abilities of an autonomous mobile robot system is the ability to safely navigate the environment. This thesis proposes controllers for path following and collision avoidance that grants the USM this capability. Both controllers take advantage of the USM's unique design, with the path following controller using the flexible body to improve path following accuracy and reduce energy consumption, while the collision avoidance controller exploits the maneuverability of the robot to enable movement in highly cluttered areas.