  A class of nonlinear control-affine systems with bounded time-varying drift
is considered. It is assumed that the control vector fields together with their
iterated Lie brackets satisfy Hormander's condition in a neighborhood of the
origin. Then the problem of exponential stabilization is treated by exploiting
periodic time-varying feedback controls. An explicit parametrization of such
controllers is proposed under a suitable non-resonance assumption. It is shown
that these controllers ensure the exponential stability of the closed-loop
system provided that the period is small enough. The proposed control design
methodology is applied for the stabilization of an underwater vehicle model and
a front-wheel drive car.
