A flexible thin steel beam was mounted vertically to a electromechanical shaker which provided a transverse sinusoidal excitation. The beam tip was placed near two rare earth magnets so as to provide nonlinear buckling forces. The beam was treated with a viscoelastic strip adhered to one side to provide a little damping. The addition of the damping treatment helps to form a more distinguishable fractal structure in phase space embeddings. A laser vibrometer was used to record the beam tip velocity and the analog signal streamed to a National Instruments data acquisition board. The data was sampled at 1000 Hz. The gain of excitation was adjusted until (seemingly) chaotic motion was observed.
William Constantine (1999), Ph.D. Dissertation: Wavelet Techniques for Chaotic and Fractal Dynamics, Mechanical Engineering Department, University of Washington.