Introducing Series Elastic Links for Affordable Torque-Controlled Robots

Robotics have the potential to become a revolutionary technology in the next future and if we want to spread it among the population we must start accounting for affordability in robot research and design. Plastic robots are an emerging example of affordable design where expensive metal structures are replaced by low-cost plastic materials. Plastic materials are not only cost effective but, thanks to their inherent compliance and lightweight, lead to significant advantages in terms of safety and force controllability. Inspired by the idea of Series Elastic Actuator (SEA) this paper introduces the new concept of Series Elastic Link (SEL) which exploits the inherent flexibility of plastic links to implement series compliance. This paper elaborates on the concept of SEL and highlights a parallelism with SEAs. Then, focusing on a single-DOF setup it shows that, beyond their economic advantage, SELs leads to enhanced safety and more accurate force control with respect to traditional SEA implementations. The proposed argumentations are theoretically supported and experimentally validated.