Position control of robot manipulators manipulating a flexible payload

Robotic manipulation of a flexible payload is a complex and challenging con trol problem. This paper demonstrates from both theoretical and experimenta l perspectives that through proper design of the control gains, the simple scheme of PD plus gravity compensation can control a flexible payload manip ulated by multiple robots to a desired position/orientation while damping t he vibrations of the payload at each contact. The suppression of the vibrat ion at each contact is helpful to suppress all vibrations of the flexible b ody. If the payload has a large stiffness or small mass, the proposed schem e can regulate the deformations at the contacts to zero, and also, the offs ets of all static deformations of the payload with reference to the origina l positions decay to zero. A "clamped-free" model is used to decompose the dynamics of the payload into two distinct dynamic subsystems. This allows u s to treat these dynamic subsystems separately and prove that desired motio n trajectories can be achieved with the proposed scheme. As an example, the experiment of manipulating a flexible sheet using two CRS A460 robots is f urther described.