Vsa-Ii: A Novel Prototype Of Variable Stiffness Actuator For Safe And Performing Robots Interacting With Humans

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 codesign 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.