control methods (Ott, Grebogi & York 1990; Lai 1996) we used, and then review what changes we applied to have a suitable control procedure.

The basic idea of OGY (from the name of Ott, Grebogi and York) method is to identify the unstable low-periodic orbits in the phase space embedded into a chaotic set (an attractor in dissipative case) and then applying a small control on a system parameter in such a way that the desired periodic orbit would be stabilized. The stabilization in this sense means practically to move the trajectory as close as possible to the stable manifold of the chosen unstable periodic orbit (UPO). The other method, [*proposed by Lai (1996)*]{}, deals with targeting and controlling fractal basin boundaries. This method uses small feedback control to drive trajectories to a pre-selected attractor. In performing the small perturbation to the system, one needs to have initial conditions close to the basin boundaries. This means that the magnitude of the control depends on how far the initial conditions lie from the desirable basin boundary. In other words, if there is a large contiguous domain associated to an undesirable attractor and the trajectory originates well inside this region, no small 