Design and Experimental Evaluation of Multiple 3D-Printed Reduction Gearboxes for Wearable Exoskeletons

The recent development of Wearable Exoskeletons has stressed their effectiveness in assisting humans for rehabilitation and augmentation purposes. These devices interact with the user, therefore their actuators and power transmission mechanisms are fundamental for improving physical Human-Robot Interaction (pHRI). The enhanced advancement of 3D-printing technology as a valuable approach for creating light and efficient gearboxes allows for exploring multiple reducers’ designs. However, to the authors’ knowledge, only sporadic implementations with relatively low reduction ratios are reported, and the respective experimental validations usually differ from each other, preventing a comprehensive evaluation of different design and implementation choices. In this paper, we design, develop, and examine experimentally multiple 3D-printed gearboxes conceived for wearable assistive devices. Two relevant transmission ratios (1:30 and 1:80) and multiple designs, that include single and double-stage compact cam cycloidal drives, compound planetary gearboxes, and the series of cycloidal and planetary architectures have been compared to assess the worth of 3D-printed reducers in Human-Robot Interaction applications. The resulting prototypes were examined by evaluating their weight, cost, back-driveability, friction, regularity of the reduction ratio, gear play, and stiffness. The results show that the developed gearboxes represent valuable alternatives for actuating wearable exoskeletons in multiple applications.