Chapter 2 : Historical Review of Robotic Orienting Devices

The wrist plays a critical role in the performance of the overall manipulator system, Payload capacity, workspace, range of motion, and other performance parameters are often limited by the capabilities of the wrist. Therefore, robotic wrist design has been an area of prime interest among researchers and industry alike. Research in the mechanics of robotic wrists has focused on serial architecture manipulators. Because of the desired spherical nature of the wrist, the serial-type construction dictates that the revolute axes must intersect. Such wrists can be modeled as a gimbal, with the third axis attached (when needed) such that it intersects the first two. One example of the structure of such a wrist is shown in Fig. 2.1. The classical roll-pitch-yaw and roll-pitch roll wrists are directly derived from this model, based on the initial orientation of axes one and two, and the orientation of the third axis (Rosheim, 1989). From this basic model, many serial robotic wrists have been derived. Mark Rosheim has been at the forefront of robotic wrist research and has written a text cataloging the advances in serial robotic wrists (Rosheim, 1989). From this text, some of the more prominent serial wrists are mentioned. Several variations in the rolepitch-roll wrist have been proposed. The three-roll wrist, the wrist used on Cincinnati Milacron T3 robots was invented by Theodore Hahn Stackhouse in 1976 (Fig. 2.2) and has been a popular industrial application because of its range of motion. The three-axis wrist invented by Antonio J. Malarz and Gerald C. pitch yaw