CHAOS CONTROL WITH ADJUSTABLE CONTROL TIMES

We investigate a quasi-continuous extension of the Ott. Grebogi and Yo rke (OGY) control method [Phys. Rev. Lett., 1990, 64, 1196]. This exte nsion allows one to raise the control frequency as high as is needed i n order to stabilize unstable periodic orbits (UPOs) of high instabili ty. To achieve this, the control requirement has to be chosen such tha t one can also cope with complex eigenvalues of the linearized flow. F or this purpose, we use a variant of the pole placement technique. In a bronze ribbon experiment, we show the feasibility of this quasi-cont inuous 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. (C) 1997 Elsevier Sci ence Ltd.