Series elastic actuators (SEA) are widely used for impact protection and compliant behavior, but they typically fall short in tasks calling for accurate position control. In this paper, we propose a simple and effective heuristic for tuning series elastic actuator controllers to a high impedance position control behavior, which compares favorably with previous publications. Our approach considers two models, an ideal model and a nonideal model with time delays and filtering lag. The ideal model is used to design cascaded proportional-derivative (PD)-type outer impedance and inner force loops as a function of critically damped closed-loop poles for the force and impedance loops. The nonideal model provides an estimate of the phase margin of the position controller for each candidate controller design. A simple optimization algorithm finds the best high-impedance behavior for which the nonideal model meets a desired phase margin requirement. In this way, the approach automates the trade-off between force and impedance bandwidth. The effect of important system parameters on the impedance bandwidth is also analyzed and the proposed method verified with a physical actuator.
A Fixed Structure Gain Selection Strategy for High Impedance Series Elastic Actuator Behavior
Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT,AND CONTROL. Manuscript received February 6, 2018; final manuscript received August 24, 2018; published online October 10, 2018. Assoc. Editor: Dumitru I. Caruntu.
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Isik, K., Thomas, G. C., and Sentis, L. (October 10, 2018). "A Fixed Structure Gain Selection Strategy for High Impedance Series Elastic Actuator Behavior." ASME. J. Dyn. Sys., Meas., Control. February 2019; 141(2): 021009. https://doi.org/10.1115/1.4041449
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