  Angle-constrained formation control has attracted much attention from control
community due to the advantage that inter-edge angles are invariant under
uniform translations, rotations, and scalings of the whole formation. However,
almost all the existing angle-constrained formation control methods are limited
to undirected triangulated sensing graphs. In this paper, we propose an
angle-constrained formation control approach under a Leader-First Follower
sensing architecture, where the sensing graph is directed and non-triangulated.
Both shape stabilization and maneuver control are achieved under arbitrary
initial configurations of the formation. During the formation process, the
control input of each agent is based on relative positions from its neighbors
measured in the local reference frame and wireless communications among agents
are not required. We show that the proposed distributed formation controller
ensures global exponential stability of the desired formation for an nagent
system. Furthermore, it is interesting to see that the convergence rate of the
whole formation is solely determined by partial specific angles within the
target formation. The effectiveness of the proposed control algorithms is
illustrated by carrying out experiments both in simulation environments and on
real robotic platforms.
