Optimum design of 3-DOF spherical parallel manipulators with respect to the conditioning and stiffness indices

This paper concerns the use of evaluation criteria, such as, the conditioning index, the stiffness to select the link lengths of 3-DOF spherical parallel manipulators (3-DOF SPMs) and analyze their operational performance. The atlases of the global conditioning index and the global stiffness index are obtained in the solution space to optimize the link lengths of 3-DOF SPMs; the dexterity and stiffness maps of the manipulators are presented to analyze the operational performance, from which we can see that the global or local conditioning index is identical with global or local stiffness index. A method for obtaining these maps for 3-DOF SPMs is presented. The maps will reveal the existence of zones where the stiffness is not acceptable and will also help the designer by proving a more accurate representation of the properties of the manipulator. The technique has wide application in the design of the serial and parallel robots. (C) 2000 Elsevier Science Ltd. All rights reserved.