3. Bond kinematics

This is one of the chapters of mechanics in which the most important developments have taken place. Today, it's still a rapidly developing field, and understandably so. A mechanism is an assembly of solids. What really distinguishes one mechanism from another is the way in which the solids that make it up are assembled together. Any invention of a new mechanism is simply the invention of the way in which a connection is made. In fact, as we shall see, there are only a limited number of connections in the mechanical sense. This point of view is very important, as a standard (NF E04-015), undoubtedly intended for construction and wrongly used in general mechanics, has created unfortunate confusion on a question where the great scientists (Hertz, Appel, Hadamard, Darboux, etc.) had provided all the necessary clarity. This is not an academic quarrel, but rather a practical problem.