Physics 427

Dr. Ayars

Chaos in a physical pendulum

The driven damped physical pendulum is a classic problem in computational physics. This physical model of that system uses an optical encoder for position measurement and a Helmholtz coil driving a dipole magnet on the pendulum axis for the drive. Coil current, timing, and position sensing are all accomplished via a microcontroller which then sends all information to a computer via serial line at 256 time intervals on the drive waveform.

One can adjust the drive frequency and amplitude as well as the damping coefficient. At some drive parameters, the motion of the particle becomes chaotic. Interesting investigations could include creation of Poincare plots of the strange attractor, mapping bifurcations, and determination of Lyapunov exponent at different drive parameters.

This apparatus was designed and built by Eric Ayars and Brandon Thacker. Brandon (Class of '16) won the inaugural AAPT/ALPhA Award -$4000 plus travel to the national AAPT meeting- for best new lab equipment built by an undergraduate for his work on this apparatus. The prototype worked well, and a production version is now available. A LabVIEW application to run the entire apparatus is now available, see link below.

Picture of apparatus

Reading

Questions

Location

Room 108, Cabinet 108.052.

Equipment needed

Hazards

No serious hazards. The heat-sink fins on the controller board can become uncomfortably (but not dangerously) hot.

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