Controlled chaos in ferroelectric systems

The value of nonlinear coefficients in ferroelectric crystals grows near the phase transition. Therefore a series resonance circuit consisting of a linear coil and a nonlinear capacitor that is made of ferroelectric material can show all features of nonlinear dynamical systems: period-doubling, hysteresis and chaotic behavior. In periodic windows we can fit experimental data-sets to a model equation. In the chaotic region it is necessary to use a method of controlling chaotic systems to switch into periodic behavior. This method perturbates the system only in a very small range. The advantage of the control method introduced by Ott, Grebogy and Yorke (1990) is that one can get all the needed parameters of control only by system measurements without using any kind of model. In a real physical system it is very difficult to determine these perturbations as fast as is needed. That's why we achieve control of chaos using a universal electronic unit.