  In this paper, we study the problem of formation keeping of a network of
strictly passive systems when very coarse information is exchanged. We assume
that neighboring agents only know whether their relative position is larger or
smaller than the prescribed one. This assumption results in very simple control
laws that direct the agents closer or away from each other and take values in
finite sets. We show that the task of formation keeping while tracking a
desired trajectory and rejecting matched disturbances is still achievable under
the very coarse information scenario. In contrast with other results of
practical convergence with coarse or quantized information, here the control
task is achieved exactly.
