  This paper investigates a problem of defending safety-critical infrastructure
from an adversarial aerial attacker in an urban environment. A circular arc
formation of defenders is formed around the attacker, and vector-field based
guidance laws herd the attacker to a predefined safe area in the presence of
rectangular obstacles. The defenders' formation is defined based on a novel
vector field that imposes super-elliptic contours around the obstacles, to
closely resemble their rectangular shape. A novel finite-time stabilizing
controller is proposed to guide the defenders to their desired formation while
avoiding obstacles and inter-agent collisions. The efficiency of the approach
is demonstrated via simulation results.
