A Comparison between Five Principle Strategies for Adapting Shaking Force Balance During Varying Payload

Abstract

Dynamic balance has been studied to eliminate the shaking forces and vibration at the base induced by rapid motion of robotic devices. This is done by designing the mass distribution such that the total center of mass of the mechanism is stationary for all motions. However, when the payload changes, for example during pick-and-place action, the dynamic balance cannot be maintained, and vibrations will appear, reducing the accuracy. In this paper, five strategies are described to adapt the dynamic balance under varying payload conditions. Three of these strategies rely on reconfiguration of the mechanism; by changing position the counter weights (I), by changing the joint locations (II) or by altering the amount of counter weight (III). The last two strategies use active control of additional linkages to steer the mechanism in over a reactionless trajectory. These additional linkages can be placed at the base as a reaction mechanism (IV), or within the kinematic chain with redundant joints (V). The implications and differences of these strategies are shown by applying them to a 3 degree of freedom (DOF) planar mechanism. All strategies can provide adaptive dynamic force balance, but have different features, especially added complexity (II & III), reconfiguration force (I & III), or energy consumption (IV & V)