文摘
This paper presents the existence of ?i¡¯lnikov orbits in two different chaotic systems belong to the class of Lorenz systems, more exactly in the L¨¹ system and in the Zhou¡¯s system. Both systems have exactly two heteroclinic orbits which are symmetrical with respect to the z-axis by using the undetermined coefficient method. The existence of the homoclinic orbit for the Zhou¡¯s system has been proven also by using the undetermined coefficient method. As a result, the ?i¡¯lnikov criterion along with some technical conditions guarantees that L¨¹ and Zhou¡¯s systems have both Smale horseshoes and horseshoe type of chaos. Moreover, the geometric structures of attractors are determined by these heteroclinic orbits.