Common normal (robotics)
A model of a robotic arm with joints.
In robotics the common normal of two non-intersecting joint axes is a line perpendicular to both axes.[1]
The common normal can be used to characterize robot arm links, by using the "common normal distance" and the angle between the link axes in a plane perpendicular to the common normal.[2] When two consecutive joint axes are parallel, the common normal is not unique and an arbitrary common normal may be used, usually one that passes through the center of a coordinate system.[3]
The common normal is widely used in the representation of the frames of reference for robot joints and links, and the selection of minimal representations with the Denavit–Hartenberg parameters.