  Currently, the general aim of flocking and formation control laws for
multi-agent systems is to form and maintain a rigid configuration, such as, the
alpha-lattices in flocking control methods, where the desired distance between
each pair of connected agents is fixed. This introduces a scalability issue for
large-scale deployment of agents due to unrealizable geometrical constraints
and the constant need of centralized orchestrator to ensure the formation graph
rigidity. This paper presents a flexible distributed flocking cohesion
algorithm for nonholonomic multi-agent systems. The desired geometry
configuration between each pair of agents is adaptive and flexible. The
distributed flocking goal is achieved using limited information exchange (i.e.,
the local field gradient) between connected neighbor agents and it does not
rely on any other motion variables measurements, such as (relative) position,
velocity, or acceleration. Additionally, the flexible flocking scheme with
safety is considered so that the agents with limited sensing capability are
able to maintain the connectedness of communication topology at all time and
avoid inter-agent collisions. The stability analysis of the proposed methods is
presented along with numerical simulation results to show their effectiveness.
