Obstacle avoidance

Obstacle avoidance
Once the navigation and mapping error has been bounded,
an adaptation of the trajectory and waypoints is required
during mission when unexpected events on the planned trajectory
are sensed. Collision avoidance and escape is a key
capability for underwater vehicle navigation.
Traditional approaches to collision avoidance and escape
are purely reactive and usually involve an algorithmic formulation
of response dictated by the objects geometries and
locations and the relative location of the vehicle. Recent approaches
in rules of collision (Benjamin et al. 2006) and
obstacle avoidance and escape scenarios (Evans et al. 2007)
have focused on reducing susceptibility by looking at the
adaptation of the vehicle’s trajectory plan. These deliberative
behaviours provide the defined and bounded event responses
that link to geometric methods of trajectory planning.
At the trajectory planning level, lifelong planning incremental
search methods have been found to decrease computation
time while still locating the shortest trajectory between
vehicle and goal (Koenig, Likhachev, and Furcy

2004). Instead of starting from scratch every time a trajectory
must be adapted, they reuse data found in previous
searches to save on computation time. Wave propagation
techniques can also provide with smoother and shorter trajectories
than classic discrete search approaches. This fast
marching methods are capable of dealing with uncertainty,
dynamic objects and kinematics of the vehicle during the
adaptation process (Pˆetr`es et al. 2007). A real application of
these techniques in the underwater environment is shown in
Fig. 8.