  Studies of the dynamics of globular clusters assume different values of bar
parameters (mass, velocity, size) and analyse the results of orbit
classifications over the range of the chosen values. It is also a usual thing
that a spherical bulge component is converted into the bar to obtain a
non-axisymmetric potential from an axisymmetric one. The choice of bar
parameters and the way the bar is converted from the bulge introduce
systematics into the orbit classifications that we explore in the present
study. We integrate orbits of 30 bulge globular clusters residing in the inner
area of the Galaxy ($R \lesssim 5$ kpc) backwards in time for three different
potentials, two of which are obtained by fitting the rotation curve, and one is
taken from the surrogate $N$-body model representing our Galaxy. We analyse
each orbit in terms of dominant frequencies obtained from its coordinate
spectra. We find that the bar pattern speed is a key factor in orbital
classification. With an increase of it, frequencies deviate more and more from
the ``bar'' frequency ratio 2:1. The bar-to-bulge mass ratio (assuming the
total mass of the bar plus the bulge is fixed) and size of the bar play a
smaller role. We also find that, in the $N$-body potential, the fraction of
orbits that follow the bar is higher than in those obtained from fitting the
rotation curve.
