THE EXPERIMENTAL RESPONSE OF AN IMPACTING PENDULUM SYSTEM

This paper presents experimental results obtained from a harmonically excited pendulum system. The pendulum has rigid barriers which limit the amplitude variation from its central position. It is considered in both the normal (downward) position and in the upright (inverted) position. The overall dynamics of the pendulum include impacts with the rigid constraints, and the system response to sinusoidal excitation includes non-impacting motions, stable subharmonics, and chaotic motions. These were experimentally found to occur in the parameter regions predicted by previous analytical work. This system represents an example of a deceptively simple device which can undergo extremely complicated dynamics. For example, the inverted pendulum was found to have 10 distinct possible steady-state responses at a fixed driving amplitude and frequency, each of which was obtained simply by changing the initial conditions. In addition, the normal pendulum was found to be capable of having impacting steady-state dynamics which coexist with the non-impacting steady-state motion predicted from small oscillation theory. © 1990.