A Time-Domain Approach to Control of Series Elastic Actuators: Adaptive Torque and Passivity-Based Impedance Control

Robots are increasingly designed to physically interact with humans in unstructured environments, and as such must operate both accurately and safely. Leveraging compliant actuation, typically in the form of series elastic actuators (SEAs), can guarantee this required level of safety. To date, a num...

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Bibliographic Details
Published in:IEEE/ASME transactions on mechatronics 2016-08, Vol.21 (4), p.2085-2096
Main Authors: Losey, Dylan P., Erwin, Andrew, McDonald, Craig G., Sergi, Fabrizio, OMalley, Marcia K.
Format: Article
Language:English
Subjects:
Actuators
Adaptation models
Adaptive control
Controllers
force control
human-robot interaction
Impedance
Passivity
rehabilitation robotics
Robots
Seas
Springs
Stability analysis
Time domain
time-domain analysis
Torque
Torque control
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Summary:Robots are increasingly designed to physically interact with humans in unstructured environments, and as such must operate both accurately and safely. Leveraging compliant actuation, typically in the form of series elastic actuators (SEAs), can guarantee this required level of safety. To date, a number of frequency-domain techniques have been proposed, which yield effective SEA torque and impedance control; however, these methods are accompanied by undesirable stability constraints. In this paper, we instead focus on a time-domain approach to the control of SEAs, and adapt two existing control techniques for SEA platforms. First, a model reference adaptive controller is developed, which requires no prior knowledge of system parameters and can specify desired closed-loop torque characteristics. Second, the time-domain passivity approach is modified to control desired impedances in a manner that temporarily allows the SEA to passively render impedances greater than the actuator's intrinsic stiffness. This approach also provides conditions for passivity when augmenting any stable SEA torque controller with an arbitrary impedance. The resultant techniques are experimentally validated on a custom prototype SEA.compliant actuation,frequency-domain techniquesundesirable stability constraints.
ISSN:1083-4435
1941-014X
DOI:10.1109/TMECH.2016.2557727