A Novel Hollow Actuator for Heavy-Duty Robotics

This article introduces a novel high-torque actuator designed for heavy-duty robotics, featuring a planetary transmission system with the sun gear removed. To circumvent the limitations of traditional hollow gearboxes, which offer inadequate central space for power and control cables, the sun gear has been eliminated and motors have been repositioned off-axis, thereby maximizing the central passage. The three-stage transmission, boasting an ultrahigh ratio of 13 806:1, ensures compactness while meeting torque requirements. Integrated models have been developed to optimize the transmission ratio, efficiency (up to 58.0%), and stress distribution, creating a comprehensive design toolbox. A prototype has validated this approach, achieving an output torque of 139 kN·m and an impressively low elastic backlash of 4.86 arcmin. The results confirm the design’s viability, demonstrating high torque density, precision, and efficient cable routing capabilities, which are crucial for advanced heavy-payload robotics.