The Spherical Equivalent of Bresse's Circles: The Case of Crossed Double-Crank Linkages

Abstract

The subject of Bresse's circles is classical in the kinematics of planar mechanisms. These are the loci of the coupler points that exhibit either zero normal or zero tangential acceleration. Described in this paper is the construction of the spherical equivalent of Bresse's circles, which take the form of an inflexion spherical cubic and a Thales ellipse, respectively. An algorithm is developed to produce these loci for the case of the spherical antiparallelogram. As a byproduct, the corresponding polodes and their evolutes are obtained.