DYNAMIC ANALYSIS AND DETERMINATION OF THE JOINT CHARACTERISTICS OF PARALLEL-DRIVE ROBOT MANIPULATORS

This article presents a theoretical and experimental study on structur al dynamic response and determination of the joint characteristics of a five degree-of-freedom industrial robot manipulator with a parallel- drive mechanism. The joints were modeled as a linear spring in paralle l with a viscous damper while the link members were assumed to be rigi d in this study. The dynamic equations of motion of the robot manipula tor were derived using the principle of virtual work. Based on these e quations, the complex structural characteristics of the manipulator we re simplified by carefully arranging the manipulator in proper arm con figurations to avoid coupling effects among joints. Hence, the joint s tiffness and damping ratio of each joint were determined experimentall y. Meanwhile, the dynamic responses of the robot manipulator were also investigated. Good correlation between computer simulations and exper imental results was achieved. From the experimental study, an addition al troublesome flexural mode of about 10 Hz that tends to dominate the whole dynamic response and influence the positioning accuracy of the manipulator was found due to the weakness of the structural member at the base rotation joint, which was not modeled in the dynamic equation s. The results of this study will be useful in providing a basis for i mproving the design of mechanical components and the articulating memb ers of industrial robot manipulators. (C) 1993 John Wiley & Sons. Inc.