A critical amplitude was found
for which the system can exhibit chaotic vibrations. The analytic results have been confirmed by numerical
simulations. In particular, the chaotic strange attractor was found for an excitation amplitude A at the critical
value, Ac, and a period doubling precursor for A ¼ 0:36 m. The transition to chaos appears to be present for
Ac ffi 0:36 m but could be lowered significantly for a smaller damping coefficient c2 (Fig. 7). Fortunately this
region is beyond the usual amplitude of road profile excitation. The chaotic solution appears just before the
escape from the potential well, which is similar to the system with a non-symmetric potential described by
Thompson [33].