Chaos control with adjustable control times

We investigate a quasi-continuous extension of the Ott, Grebogi and Yorke (OGY) control method [Phys. Rev. Lett., 1990, 64, 1196]. This extension allows one to raise the control frequency as high as is needed in order to stabilize unstable periodic orbits (UPOs) of high instability. To achieve this, the control requirement has to be chosen such that one can also cope with complex eigenvalues of the linearized flow. For this purpose, we use a variant of the pole placement technique. In a bronze ribbon experiment, we show the feasibility of this quasi-continuous control method. All control vectors are determined solely from the analysis of a scalar measurement signal. Finally, we show how the number of control steps needed can be minimized.