  Feedback control schemes are a promising way to manipulate transport
properties of driven colloidal suspensions. In the present article we suggest a
feedback scheme to enhance the collective transport of colloidal particles with
repulsive interactions through a one-dimensional tilted washboard potential.
The control is modelled by a harmonic confining potential, mimicking an optical
"trap", with the center of this trap moving with the (instantaneous) mean
particle position. Our theoretical analysis is based on the Smoluchowski
equation combined with Dynamical Density Functional Theory (DDFT) for systems
with hard-core or ultra-soft (Gaussian) interactions. For either type of
interaction we find that the feedback control can lead to an enhancement of the
mobility by several orders of magnitude relative to the uncontrolled case. The
largest effects occur for intermediate stiffness of the trap and large particle
numbers. Moreover, in some regions of the parameter space the feedback control
induces oscillations of the mean velocity. Finally, we show that the
enhancement of mobility is robust against a small time delay in implementing
the feedback control.
