MANIPULATOR TRAJECTORY SYNTHESIS FOR MINIMAL VIBRATIONAL EXCITATION DUE TO THE PAYLOAD

Abstract

As a manipulator is forced to track a desired trajectory, the required actuating torques (forces) may excite the natural modes of vibration of the robot manipulator. The harmonic content of the actuating torques and the relative magnitude of each harmonic indicate which of the system modes could be excited and the level of excitation that may be reached. In a recent study, the authors have studied the effects of the payload mass, size, and end-effector holding location on the vibrational excitation of robot manipulators during the motion. [1]. In the present paper, based on the aforementioned study, a method is developed to synthesize trajectories, that produce minimal vibrational excitation in the presence of a payload. By following such trajectories, load carrying robot manipulators can be operated at relatively higher speeds. As an example, trajectories for point to point motions with minimal potential vibrational excitation in the presence of payload are synthesized for a spatial 3R manipulator. For a given payload mass, the effects on the optimal trajectory of the object size and the location that it is held by the end-effector of the manipulator are determined. A number of related topics are discussed.