This is the presentation video for the paper /"A Compliant Mechanism with Progressive Stiffness for Robotic Actuation/" by Eamon Barrett, Jörn Malzahn and Nikos G. Tsagarakis, presented at the 2021 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM 2021) .

Abstract:
Softer series elastic actuators exhibit higher torque resolution and better torque transparency, enabling gentle physical interaction of robots with their environment. Stiffer elastic actuators from the series promote fast, strong and powerful physical interaction between the robot and the environment. Passive compliant elements with a progressive stiffness characteristic could make the actuator inherently soft at low interaction torque levels and much stiffer at higher interaction torque levels, overcoming common design trade-offs of linear series elastic actuators. This paper proposes a compact solution that realizes such a passive elastic element without complex nonlinear transmissions. The solution is based solely on a number of radially oriented linear springs. The paper presents two different implementations using i) an assembly of concentrated tension springs and ii) a monolithic arrangement of distributed bending beams. Detailed theoretical analyzes and experimental prototype validations lead to design guidelines and confirm a cubic polynomial torque-deflection characteristic combined with a low hysteresis.

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