Stiffness control of redundantly actuated parallel manipulators

In this paper redundant actuation is used to generate internal preload that would not interfere with the task. This preload is controlled in order to achieve a desired end-effector stiffness, i.e. a desired relationship of applied forces and resulting displacements. This active stiffness yields immediate counteractions to load variations and thus strengthens the integrity of the manipulators. Differential EE-stiffness is defined and a stiffness control scheme is proposed. Results are shown for a planar manipulator