  The paper proposes a new method to determine a binary control signal for an
analog linear system such that the state, or some output, of the system follows
a given target trajectory. The method can also be used for digital-to-analog
conversion. The heart of the proposed method is a new binary-enforcing NUV
prior (normal with unknown variance). The resulting computations, for each
planning period, amount to iterating forward-backward Gaussian message passing
recursions (similar to Kalman smoothing), with a complexity (per iteration)
that is linear in the planning horizon. In consequence, the proposed method is
not limited to a short planning horizon.
