Disquisition on nodes of Coupler curves of the Planar Four-link Mechanisms

This paper proves that the double points of the coupler curves of Planar four-link mechanisms are determined by solving the sixth order equation respect to the angular displacement of the driving link and they are classified into the nodes and the ordinary intersections by using the relative angular displacement between the coupler and the driven links.A method for determining the inflection points,the maximum and minimum curvature points and the number of rotation of the coupler curves is proposed.According to the numbers of these characteristic points and the number of rotation.the coupler.These curves are illustrated schematically together with their appearance frequencies.