  In this paper, we propose an algorithm for the formation of multiple UAVs
used in vision-based inspection of infrastructure. A path planning algorithm is
first developed by using a variant of the particle swarm optimisation, named
theta-PSO, to generate a feasible path for the overall formation configuration
taken into account the constraints for visual inspection. Here, we introduced a
cost function that includes various constraints on flight safety and visual
inspection. A reconfigurable topology is then added based on the use of
intermediate waypoints to allow the formation to avoid collision with obstacles
during operation. The planned path and formation are then combined to derive
the trajectory and velocity profiles for each UAV. Experiments have been
conducted for the task of inspecting a light rail bridge. The results confirmed
the validity and effectiveness of the proposed algorithm.
