  The existence and properties of an exact universal excitation waveform for
optimal enhancement of directed ratchet transport are deduced from the
criticality scenario giving rise to ratchet universality, and confirmed by
numerical experiments in the context of a driven overdamped Brownian particle
subjected to a vibrating periodic potential. While the universality scenario
holds regardless of the waveform of the periodic vibratory excitations
involved, it is shown that the enhancement of directed ratchet transport is
optimal when the impulse transmitted by those excitations (time integral over a
half-period) is maximum. Additionally, the existence of a frequency-dependent
optimal value of the relative amplitude of the two excitations involved is
illustrated in the simple case of harmonic excitations.
