This paper details a relatively inexpensive data acquisition/analysis system that was developed at the University of Maine to facilitate the measurement of nonlinear dynamic motion into the chaotic regime. The characteristics of the hardware and specially developed software will be discussed.
The testing system includes a software package, written in TURBO Pascal, that is used to reduce and graphically present the time-history of up to six channels of data simultaneously. The program contains algorithms for digital filtering, smoothing, and Fast Fourier Transforms. The data retrieval software was designed to maximize in-core storage of data and overcomes the current 64 kilobyte memory segment boundary of MS-DOS. Phase Plane projections and Poincaré sections can also retrieved. Analog differentiation and a pulse trigger used to control Poincaré section retrieval are described. A surface of section at any desired phase angle can be taken with this trigger device. A program called POINCARE acquires the signal and its derivative and automatically plots them on the CRT as the test is in progress. A case study of a cantilever beam attracted by two magnets is also presented.