Design and Characterization of 3D Printed, Open-Source Actuators for Legged Locomotion

TL;DR

This paper introduces affordable, open-source 3D printed actuators for legged robots, with detailed characterization and thermal solutions, enabling accessible customization and optimization for researchers.

Contribution

It presents novel, low-cost 3D printed actuator designs with comprehensive performance characterization, facilitating democratized and customizable legged robot development.

Findings

Actuators built for under $200 each perform comparably to traditional metallic actuators.

Thermal management nearly doubles the torque limits of plastic actuators.

Actuators withstand extensive gait cycles with minimal efficiency loss.

Abstract

Impressive animal locomotion capabilities are mediated by the co-evolution of the skeletal morphology and muscular properties. Legged robot performance would also likely benefit from the co-optimization of actuators and leg morphology. However, development of custom actuators for legged robots is often expensive and time consuming, which discourages roboticists from pursuing performance gains afforded by application-specific actuator optimization. This paper presents open-source designs for two quasi-direct-drive actuators with performance regimes appropriate for an 8--15 kg robot, built completely with off the shelf and 3D-printed components for less than $200 USD each. The mechanical, electrical, and thermal properties of each actuator are characterized and compared to benchmark data. Actuators subjected to 420k strides of gait data experienced only a 2% reduction in efficiency and 26 mrad in backlash growth, demonstrating viability for rigorous and sustained research applications. We present a thermal solution that nearly doubles the thermally-driven torque limits of our plastic actuator design. The performance results are comparable to traditional metallic actuators for use in high-speed legged robots of the same scale. These 3D printed designs demonstrate an approach for designing and characterizing low-cost, highly customizable, and highly reproducible actuators, democratizing the field of actuator design and enabling co-design and optimization of actuators and robot legs.