Hindawi Publishing Corporation Discrete Dynamics in Nature and Society Volume 2012, Article ID 283179, 9 pages doi:10.1155/2012/283179 Research Article An Algorithm to Automatically Detect the Smale Horseshoes Qingdu Li,1, 2 Lina Zhang,2 and Fangyan Yang2 1 Key Laboratory of Network Control & Intelligent Instrument of Ministry of Education, Chongqing University of Posts and Telecommunications, Chongqing 400065, China 2 Institute for Nonlinear Circuits and Systems, Chongqing University of Posts and Telecommunications, Chongqing 400065, China Correspondence should be addressed to Qingdu Li,
[email protected] Received 9 August 2011; Revised 10 November 2011; Accepted 15 December 2011 Academic Editor: Nikos I. Karachalios Copyright q 2012 Qingdu Li et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Smale horseshoes, curvilinear rectangles and their U-shaped images patterned on Smale’s famous example, provide a rigorous way to study chaos in dynamical systems. The paper is devoted to constructing them in two-dimensional diffeomorphisms with the existence of transversal homoclinic saddles. We first propose an algorithm to automatically construct “horizontal” and “vertical” sides of the curvilinear rectangle near to segments of the stable and of the unstable manifolds, respectively, and then apply it to four classical chaotic maps the Duffing map, the Henon´ map, the Ikeda map, and the Lozi map to verify its effectiveness. 1. Introduction Among a variety of mathematical characteristics of chaos, the existence of a horseshoe by S. Smale has been recognized as the most important signature of chaos from geometrical point of view.