The inverted pendulum with a periodic parametric forcing is considered
as a bifurcation problem in the reversible setting. Parameters are gi
ven by the size of the forcing and the frequency ratio. Normal form th
eory provides an integrable approximation of the Poincare map generate
d by a planar vector field. Genericity of the model is studied by a pe
rturbation analysis, where the spatial symmetry is optional. Here equi
variant singularity theory is used.