Since the known paper о L.Pontryagin, А. Andronov and А. Vitt (1933) а lot of problems were considered in nonlinear dynamics, associated with the study of the transition of a multistable system from one stable state to another under the influence of noise. In the recent years new problems emerged in the studies of complex vibrational systems. These problems deal with the transitions of test particles in the 2D potential relieves with the fluctuating or periodically changing parameters. As a complex relief is a variant of Sinai billiards, the motions of test pasticles therein become stochastic even without any
external action. The examples of the cluster dynamics of macromolecules are considered. The dependencies are established of the time of transition of a test particles from the area of one minimum to the zone of attraction of another one on the frequency of the periodic changes of the parameters of the potential relief. The study of these processes will allow us to get closer to the comprehension of principles of molecular machines.