**Academic Paper **
__Tetsushi Ueta__, Daisuke Ito, Kazuyuki Aihara, Can a Pseudo Periodic Orbit Avoid a Catastrophic Transition?, World Scientific, International Journal of Bifurcation and Chaos, Vol.25, No.13, pp.1550185-1-1550185-10, Nov. 2015.

**Abstract: ** We propose a resilient control scheme to avoid catastrophic transitions associated with saddlenode bifurcations of periodic solutions. The conventional feedback control schemes related to controlling chaos can stabilize unstable periodic orbits embedded in strange attractors or suppress bifurcations such as period-doubling and Neimark-Sacker bifurcations whose periodic orbits are kept existing through bifurcation processes. However, it is impossible to apply these methods directly to a saddle-node bifurcation since the corresponding periodic orbit disappears after such a bifurcation. In this paper, we define a pseudo periodic orbit which can be obtained using transient behavior right after the saddle-node bifurcation, and utilize it as reference data to compose a control input. We consider a pseudo periodic orbit at a saddle-node bifurcation in the Duffing equations as an example, and show its temporary attraction. Then we demonstrate suppression control of this bifurcation, and show robustness of the control. As a laboratory experiment, a saddle-node bifurcation of limit cycles in the BVP oscillator is explored. A control input generated by a pseudo periodic obit can restore a stable limit cycle which disappeared after the saddle-node bifurcation.

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