Design and Evaluation of a Cable-Actuated Palletizing Robot With Geared Rolling Joints

In the structure of a palletizing robot, auxiliary links are generally used to drive rotational links and maintain the horizontal orientation of the robot end-effector. However, with recent developments in manufacturing technologies and the increasing diversity of tasks, there is a demand for reducing the space occupied by auxiliary links with lightweight robot designs. In this article, a new method to reduce the size and weight of palletizing robots by replacing the existing auxiliary links with cable-actuation is proposed. First, the kinematics of a palletizing robot with parallelogram linkages based on geared rolling joints is explained. Additionally, the effects of multiple cable windings on the joint speed reduction are examined. A theoretical analysis of the relationship between the joint angle and cable length confirms that serially connected geared parallelograms can decouple joint motion. Furthermore, the effect of the cable length from the motor to the actuation joint on the stiffness is analyzed. Finally, experiments are conducted using a manufactured robot prototype to verify the effectiveness of cable windings, decoupled joint motion, and robot stiffness, and to confirm the accuracy of distal position and orientation. Consequently, the proposed cable-actuated palletizing robot is expected to be applied in various industrial robot designs.