Introducing Series Elastic Links for Affordable Torque-Controlled Robots

Robotics has 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 letter introduces the new concept of series elastic link (SEL), which exploits the inherent flexibility of plastic links to implement series compliance. This letter 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 lead to enhanced safety and more accurate force control with respect to traditional SEA implementations. The proposed argumentations are theoretically supported and experimentally validated.

[1]  Torsten Bertram,et al.  Collision Detection and Reaction for a Multi-Elastic-Link Robot Arm , 2014 .

[2]  Jörn Malzahn,et al.  Link elasticity exploited for payload estimation and force control , 2015, 2015 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS).

[3]  Joel Burdick,et al.  Design and analysis of planar rotary springs , 2017, 2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS).

[4]  Matthew M. Williamson,et al.  Series elastic actuators , 1995, Proceedings 1995 IEEE/RSJ International Conference on Intelligent Robots and Systems. Human Robot Interaction and Cooperative Robots.

[5]  Mouhacine Benosman,et al.  Control of flexible manipulators: A survey , 2004, Robotica.

[6]  Andrea Parri,et al.  A light-weight active orthosis for hip movement assistance , 2015, Robotics Auton. Syst..

[7]  E. Guglielmelli,et al.  Design and characterization of a compact rotary Series Elastic Actuator for knee assistance during overground walking , 2012, 2012 4th IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob).

[8]  R. H. Cannon,et al.  Experiments in control of flexible structures with noncolocated sensors and actuators , 1984 .

[9]  Jörn Malzahn,et al.  Vibration control of a multi-flexible-link robot arm under gravity , 2011, 2011 IEEE International Conference on Robotics and Biomimetics.

[10]  Paolo Fiorini,et al.  Impedance control of series elastic actuators based on well-defined force dynamics , 2017, Robotics Auton. Syst..

[11]  Antonella Ferrara,et al.  MIMO Closed Loop Identification of an Industrial Robot , 2011, IEEE Transactions on Control Systems Technology.

[12]  Wen-Hong Zhu,et al.  Force control: A bird's eye view , 1998 .

[13]  Daniel E. Whitney,et al.  Force Feedback Control of Manipulator Fine Motions , 1977 .

[14]  Vicente Feliu,et al.  Force control of a single-link flexible robot based on a collision detection mechanism , 2000 .

[15]  Fumitoshi Matsuno,et al.  Dynamics Based Force Control of a One-Link Flexible Arm Considering Bending and Torsional Deformation , 2002 .

[16]  Warren P. Seering,et al.  Understanding bandwidth limitations in robot force control , 1987, Proceedings. 1987 IEEE International Conference on Robotics and Automation.

[17]  Paolo Fiorini,et al.  On the Role of Compliance in Force Control , 2014, IAS.

[18]  Paolo Fiorini,et al.  Human-adaptive control of series elastic actuators , 2014, Robotica.

[19]  Paolo Fiorini,et al.  A Rationale for Acceleration Feedback in Force Control of Series Elastic Actuators , 2018, IEEE Transactions on Robotics.

[20]  Russell D Howard,et al.  Joint and actuator design for enhanced stability in robotic force control , 1990 .

[21]  David W. Robinson,et al.  Design and analysis of series elasticity in closed-loop actuator force control , 2000 .

[22]  Nevio Luigi Tagliamonte,et al.  Passivity constraints for the impedance control of series elastic actuators , 2014, J. Syst. Control. Eng..

[23]  R. Riener,et al.  ARMin - Exoskeleton for Arm Therapy in Stroke Patients , 2007, 2007 IEEE 10th International Conference on Rehabilitation Robotics.

[24]  Nevio Luigi Tagliamonte,et al.  A Novel Compact Torsional Spring for Series Elastic Actuators for Assistive Wearable Robots , 2012 .

[25]  Riccardo Muradore,et al.  Impedance control of series elastic actuators: Passivity and acceleration-based control , 2017 .

[26]  Paolo Fiorini,et al.  Understanding Environment-Adaptive Force Control of Series Elastic Actuators , 2018, IEEE/ASME Transactions on Mechatronics.

[27]  Riccardo Muradore,et al.  A Review of Algorithms for Compliant Control of Stiff and Fixed-Compliance Robots , 2016, IEEE/ASME Transactions on Mechatronics.

[28]  Jörn Malzahn,et al.  Dynamics identification of a damped multi elastic link robot arm under gravity , 2014, 2014 IEEE International Conference on Robotics and Automation (ICRA).

[29]  Manfred Morari,et al.  Automatic gait-pattern adaptation algorithms for rehabilitation with a 4-DOF robotic orthosis , 2004, IEEE Transactions on Robotics and Automation.

[30]  Jörn Malzahn,et al.  On the Stiffness Selection for Torque-Controlled Series-Elastic Actuators , 2017, IEEE Robotics and Automation Letters.