Factors influencing actuator’s backdrivability in human-centered robotics

Abstract

Human-Centered Robotics aims to use robotic devices to improve our life. In Europe alone, around 650.000 people live with limb amputations, 40 Mio. have jobs with high of lumbar injuries, and 40 Mio. are 80+ years. Worldwide, active prostheses, exoskeletons, and service robots could help improve these people’s lives. However, their adoption is unfortunately strongly hindered by technological limitations in the actuators powering these devices. Backdrivability characterizes an actuator’s ability to be driven from the load side, and it is a crucial property to enabling capable human-centered robotic devices. In this paper, we describe the underlying factors that determine actuator backdrivability in robotics and investigate suitable scaling laws to understand how these factors are conditioned by the motor and gearbox selection and the specific operational cycle of a robotic device. This analysis unveils the complexity and challenges faced to accurately model and predict this complex phenomenon, contradicting an extended hypothesis in the robotics community that sees low-ratio transmissions as the best strategy to build backdrivable, lightweight actuators.