Abstract
A spatial link mechanism is investigated theoretically using moving frame attached to each link. Relative infinitesimal movement of a link with respect to other link is represented by the differential form. Velocity and acceleration relations between arbitrary two points on a link are derived using the form. By the velocity relation, a link is proved to move around a screw axis relative to another link along which axis the link rotates and translates simultaneously. A planar link mechanism is regarded as a special case where the translational velocity along the screw axis vanishes. The Hook’s joint is analysed as an example using the screw axes to derive the relative angular velocities of the two axes on the crosspiece.
