| Legged mobile robots move by executing patterns of leg joint angles called gaits. Synthesizing gaits by hand is a complex and time-consuming task that is even more challenging when the vehicle operates in the underwater domain. When the vehicle is suspended in a fluid any motion of the limbs, no matter how small, causes drag which applies forces to the vehicle. Underwater gaits must therefore be constructed to mitigate these unwanted forces so that joint-angle changes apply a net force in the desired direction. This thesis presents an automatic gait synthesis system for underwater legged vehicles. The process has two stages: First, a simulated annealing engine is used to build an alphabet of short duration gaits that can be used to reposition and reorient the robot in the six-degrees-of-freedom space. Second, an obstacle-aware path planner combines members of the gait alphabet to form more complex motions. The technique is applied to synthesize gaits for a simulated version of the AQUA amphibious hexapod although it is general enough to be applied to other legged vehicles. |
