Abstract
Free vibration of a pendulum supported asymmetrically is considered. We found that a pendulum supported asymmetrically changes its swinging direction during free vibration, and spatial motion occurs. Deriving the equation of motion and analyzing it, it is found that this phenomenon is a kind of parametric excitation. It is shown form numerical simulation that various spatial motions occur depending on initial condition and magnitude of asymmetry of the system. Experimental analysis is also conducted, which confirms the validity of the theoretical analysis.