Gravity-balancing of classes of industrial robots

Gravity balancing of industrial robots is an important issue because these robots may have massive links in order to manipulate large payloads. In this paper, we present techniques to gravity balance the weight of moving links in industrial robots with various arrangements of joints. In a typical industrial robot, the first joint axis is parallel to the gravity vector, hence, the weight of the first moving link does not have any effect on gravity balancing of the robot. Our approach for gravity balancing of industrial robots uses two steps: (i) we locate the center of mass of distal segments of the robot using auxiliary parallelograms; (ii) we connect springs between the center of mass and other members in the robot such that the total potential energy of the system is invariant with configuration. In this paper, we present designs for gravity balancing of classes of industrial robots with revolute and prismatic joints