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Development and analysis of series elastic actuators for impedance control of an active ankle–foot orthosis

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Journal of the Brazilian Society of Mechanical Sciences and Engineering Aims and scope Submit manuscript

Abstract

This paper deals with force and impedance control of a series elastic actuator specially designed for driving an ankle–foot orthosis. Series elastic actuators are devices where elastic components are introduced between the motor’s output and the load. From the deflection of these components, it is possible to measure the force applied to the load and to control it. Furthermore, the mechanical impedance of the actuator/load interface can be regulated to typical values of joint’s stiffness and damping presented by humans during walking. Experimental results of force and impedance control applied to an active ankle–foot orthosis driven by the series elastic actuator are presented. Also, a variable impedance control strategy is performed to reproduce the behavior of an actual ankle joint.

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Abbreviations

AAFO:

Active ankle–foot orthosis

BLEEX:

Berkeley lower extremity exoskeleton

CD:

Controlled dorsiflexion

CP:

Controlled plantarflexion

DARPA:

Defense Advanced Research Projects Agency

FSR:

Force sensitive resistors

LSU:

Louisiana State University

PP:

Powered plantarflexion

SEA:

Series elastic actuator

SP:

Swing phase

θ :

Angle of the ankle joint of the AAFO

l :

Length of the SEA

M :

Torque applied by the AAFO

F :

Force applied by the SEA

K :

Stiffness

B :

Damping

F m :

Force generated by the motor

F l :

Force applied to the load

F d :

Desired force

m m :

Equivalent mass of the SEA

x m :

Linear position of the SEA

x l :

Linear position of the load

b m :

Equivalent damping of the SEA

K p :

Proportional gain

K d :

Derivative gain

t :

Relative to the AAFO

v :

Relative to the SEA

References

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Acknowledgments

This work was supported by CNPq (Master scholarship) and FAPESP (Grant No. 2008/09530-4).

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Authors and Affiliations

  1. Department of Mechanical Engineering, School of Engineering of São Carlos, University of São Paulo, São Carlos, São Paulo, 13566-590, Brazil

    Bruno Jardim & Adriano A. G. Siqueira

  2. Center for Robotics of São Carlos and the Center for Advanced Studies in Rehabilitation, University of São Paulo, São Carlos, São Paulo, Brazil

    Adriano A. G. Siqueira

Authors
  1. Bruno Jardim
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  2. Adriano A. G. Siqueira
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Correspondence to Bruno Jardim.

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Technical Editor: Agenor Fleury.

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Jardim, B., Siqueira, A.A.G. Development and analysis of series elastic actuators for impedance control of an active ankle–foot orthosis. J Braz. Soc. Mech. Sci. Eng. 36, 501–510 (2014). https://doi.org/10.1007/s40430-013-0092-0

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  • DOI: https://doi.org/10.1007/s40430-013-0092-0

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