Two graphical methods for planar contact problems

Graphical methods are often applied to planar mechanics problems, especially in the context of robotic manipulation, but there are limitations. In particular, the friction cone is an elegant representation of the set of forces generated by a single frictional contact, but there was previously no simple extension to problems of multiple frictional contacts. The paper shows a simple generalization of the friction cone to include multiple contacts. It demonstrates applications to dynamics problems and manipulation planning problems