Title :
Compact nonlinear springs with user defined torque-deflection profiles for series elastic actuators
Author :
Schepelmann, Alexander ; Geberth, Kathryn A. ; Geyer, Hartmut
Author_Institution :
Robot. Inst., Carnegie Mellon Univ., Pittsburgh, PA, USA
fDate :
May 31 2014-June 7 2014
Abstract :
Series elastic actuators often use linear metal springs in their drivetrains, which requires design compromises between torque resolution and actuation bandwidth. Nonlinear springs (NLSs), with variable stiffness, overcome this limitation, enabling both high torque resolution and high bandwidth. Current NLS designs combine variable cam structures with off-the-shelf linear springs, which increases the overall size of these torque transmitting elements. NLS size could be reduced by using other materials as an elastic element. We present an optimization-based synthesis method for NLSs that are compact and encode a user-defined torque-deflection profile using elastic elements with an arbitrary stiffness profile. We experimentally validate the proposed method by creating a NLS prototype and testing it on an actuator testbed. The prototype uses rubber as the elastic element, resulting in a compact design that generates the desired torque profile, although hysteresis of the rubber material partially compromises performance. The results suggest that the proposed method successfully generates compact NLS designs, but that rubber elements need to be carefully chosen to mitigate hysteresis.
Keywords :
actuators; elasticity; optimisation; springs (mechanical); torque; NLS; compact nonlinear springs; drivetrains; elastic element; linear metal springs; optimization-based synthesis; series elastic actuators; user defined torque-deflection profiles; variable stiffness; Actuators; Optimization; Prototypes; Rubber; Sea measurements; Springs; Torque;
Conference_Titel :
Robotics and Automation (ICRA), 2014 IEEE International Conference on
Conference_Location :
Hong Kong
DOI :
10.1109/ICRA.2014.6907350