The use of kinematic redundancy in robot manipulators to achieve additional performance on top of tracing a given end-effector trajectory has been extensively examined. In the past few years, some methods were proposed, which resolves redundancy in order to avoid singularities, evade obstacles, and minimize joint torques, manipulator kinetic energy, end-effector contact forces, etc. However, these approaches have been associated mainly with rigid manipulators.
In this paper, we are dealing with flexible redundant manipulators and propose a new redundancy resolving algorithm to reduce the vibration when flexibility is present. The key question is how to choose the self-motion of structually flexible redundant manipulator to prevent undesired flexiblity effects. When self-motion capability is applied to this system, the motion-induced vibration can be reduced by altering the joint trajectory during and after motion, while maintains the end-effector tracing a given trajectory, because self-motion does not affect end-effector motion at all.
In this paper we aim to develop an efficient control algorithm to prevent motion-induced vibration by utilizing the self-motion inherent in flexible redundant manipulator. We investigate self-motion effects on flexure motion in modal space as an extension of the works done by Nguyen and Walker. Generally the available DOR is restricted to one or two but the number of degree of freedom(DOF) of flexure motion is much greater than the available DOR. Thus, modal space is introduced to reduce the flexure DOF without loss of accuracy. To prevent the flexibility effects, self-motion is evaluated to nullify the dominant modal force induced by the rigid body motion but not affecting the end-effector motion.
The effectiveness and applicability of the proposed algorithm have been demonstrated through numerical simulation with three-link planar robotic manipulators possessing the flexible links.
