  In this paper, we address optimal scheduling of control inputs given a hard
constraint on the number of input channels active at any time. For a sparsely
controllable system, we characterize the sparse actuator schedules that make
the system controllable, and then devise a greedy selection algorithm that
guarantees controllability while heuristically providing low control effort. We
further show how to enhance our greedy algorithm via Markov chain Monte
Carlo-based optimization.
