VSA-II: a Novel Prototype of Variable Stiffness Actuator for Safe and Performing Robots Interacting with Humans

• Published in: 2008 IEEE International Conference on Robotics and Automation pp. 2171 - 2176
• Main Authors: Schiavi, R., Grioli, G., Sen, S., Bicchi, A.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.05.2008
• Subjects: Actuators; Human robot interaction; Impedance; Injuries; Physical Human-Robot Interaction; Prototypes; Robotics and automation; Safety; Service robots; Testing; Torque; Variable Stiffness Mechanisms
• ISBN: 1424416469; 9781424416462
• ISSN: 1050-4729
• DOI: 10.1109/ROBOT.2008.4543528

This paper presents design and performance of a novel joint based actuator for a robot run by variable stiffness actuation, meant for systems physically interacting with humans. This new actuator prototype (VSA-II) is developed as an improvement over our previously developed one reported in [9], where an optimal mechanical-control co-design principle established in [7] is followed as well. While the first version was built in a way to demonstrate effectiveness of variable impedance actuation (VIA), it had limitations in torque capacities, life cycle and implementability in a real robot. VSA-II overcomes the problem of implementability with higher capacities and robustness in design for longer life. The paper discusses design and stiffness behaviour of VSA-II in theory and experiments. A comparison of stiffness characteristics between the two actuator is discussed, highlighting the advantages of the new design. A simple, but effective PD scheme is employed to independently control joint-stiffness and joint-position of a 1-link arm. Finally, results from performed impact tests of 1- link arm are reported, showing the effectiveness of stiffness variation in controlling value of a safety metric.