  This paper proposes two algorithms, namely "back-tracking" and "history
following", to reach consensus in case of communication loss for a network of
distributed agents with switching topologies. To reach consensus in distributed
control, considered communication topology forms a strongly connected graph.
The graph is no more strongly connected whenever an agent loses
communication.Whenever an agent loses communication, the topology is no more
strongly connected. The proposed back-tracking algorithm makes sure that the
agent backtracks its position unless the communication is reestablished, and
path is changed to reach consensus. In history following, the agents use their
memory and move towards previous consensus point until the communication is
regained. Upon regaining communication, a new consensus point is calculated
depending on the current positions of the agents and they change their
trajectories accordingly. Simulation results, for a network of six agents, show
that when the agents follow the previous history, the average consensus time is
less than that of back-tracking. However, situation may arise in history
following where a false notion of reaching consensus makes one of the agents
stop at a point near to the actual consensus point. An obstacle avoidance
algorithm is integrated with the proposed algorithms to avoid collisions.
Hardware implementation for a three robots system shows the effectiveness of
the algorithms.
