  This paper examines the structural controllability for a group of agents,
called followers, connected to each other based on the consensus law under
commands of multiple leaders, which are agents with superior capabilities, over
a fixed communication topology. It is proved that the graph-theoretic
sufficient and necessary condition for the set of followers to be structurally
controllable under the leaders' commands is leader-follower connectivity of the
associated graph topology. This shrinks to graph connectivity for the case of
solo leader. In the approach, we explicitly put into account the dependence
among the entries of the system matrices for a consensus network using the
linear parameterization technique introduced in [1].
