An enhanced and more precise criterion for Kapitza's pendulum stability

Abstract

In preceding papers of the author about the pendulum with an oscillating pivot a clear physical explanation of the dynamic stabilization of an inverted pendulum was presented [1], and a close relationship between subharmonic parametric resonances and conditions of dynamic stabilization was established [2]. In the present paper, on the basis of this relationship, more exact values of the lower and upper boundaries of dynamic stabilization are obtained. These values are valid in a wider region of the system parameters than previous results. In particular, the established boundaries are applicable for relatively low frequencies, for which separation of rapid and slow motions is inadmissible, and the commonly known criterion of the inverted pendulum stability does not work. Computer simulation of the physical system aids the analytical investigation and proves the enhanced criterion of dynamic stability.