Video-based spatial portraits of a nonlinear vibrating string

The article describes a systematic experimental study of a string vibrating nonlinearly. The string is tracked in real time using strategically located cameras; the video tracking enables a remote observation of the oscillator without perturbing its inherent nonlinearities. We show that our technique can help probe the parametrically excited oscillations and study phenomena such as elliptical and circular trajectories near resonance, resonance fold-over, jump, hysteresis, and subharmonic resonance. The experiment has been successfully employed in the advanced physics laboratory.