  Using an ac driven asymmetric pulse we show how the Fermi acceleration
(deceleration) can be controlled. A {\it deformed} sawtooth (Ratchetlike) pulse
representing the moving wall in the static Fermi-Ulam model is considered. The
time integral from the pulse over one period of oscillation must be negative to
obtain deceleration and positive to obtain hyperacceleration. We show that
while the decelerated case is chaotic, for the hyperaccelerated case the
Lyapunov exponents converge to zero. Numerical simulations indicate that the
hyperaccelerated case is ergodic in velocity space. Switching between different
pulse deformations we are able to control the particle acceleration. Results
should be valid for any pulse for which the time integral can be manipulated
between positive and negative values.
