  We consider an oscillator model to describe qualitatively friction force for
an atomic force mi-croscope (AFM) tip driven on a surface described by periodic
potential. It is shown that average value of the friction force could be
controlled by application of external time-dependent periodic perturbation.
Numerical simulation demonstrates significant drop or increase of friction
depending on amplitude and frequency of perturbation. Two different oscillating
regimes are observed, they determined by frequency and amplitude of
perturbation. The first one is regime of mode locking at frequencies multiple
to driving frequency. It occurs close to resonance of harmonic perturbation and
driving frequencies. Another regime of motion for a driven oscillator is
characterized by aperiodic oscillations. It was observed in the numerical
experiment for perturbations with large amplitudes and frequencies far from
oscillator eigenfrequency. In this regime the oscillator does not follow
external driving force, but rather oscillates at several modes which result
from interaction of oscillator eigenmode and perturbation frequency.
