Active-impedance control of a lower-limb assistive exoskeleton

Gabriel Aguirre-Ollinger*, J. Edward Colgate, Michael A. Peshkin, Ambarish Goswami

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contribution

149 Scopus citations


We propose a novel control method for lower-limb assist that produces a virtual modification of the mechanical impedance of the human limbs. This effect is accomplished by making the exoskeleton display active impedance properties. Active impedance control emphasizes control of the exoskeleton's dynamics and regulation of the transfer of energy between the exoskeleton and the user. Its goal is improving the dynamic response of the human limbs without sacrificing the user's control authority. The proposed method is an alternative to myoelectrical exoskeleton control, which is based on estimating muscle torques from electromyographical (EMG) activity. Implementation of an EMG-based controller is a complex task that involves modeling the user's musculoskeletal system and requires recalibration. In contrast, active impedance control is less dependent on estimation of the user's attempted motion, thereby avoiding conflicts resulting from inaccurate estimation. In this paper we also introduce a new form of human assist based on improving the kinematic response of the limbs. Reduction of average muscle torques is a common goal of research in human assist However, less emphasis has been placed so far on improving the user's agility of motion. We aim to use active impedance control to attain such effects as increasing the user's average speed of motion, and improving their acceleration capabilities in order to compensate for perturbations from the environment.

Original languageEnglish (US)
Title of host publication2007 IEEE 10th International Conference on Rehabilitation Robotics, ICORR'07
Number of pages8
StatePublished - Dec 1 2007
Event2007 IEEE 10th International Conference on Rehabilitation Robotics, ICORR'07 - Noordwijk, Netherlands
Duration: Jun 12 2007Jun 15 2007

Publication series

Name2007 IEEE 10th International Conference on Rehabilitation Robotics, ICORR'07


Other2007 IEEE 10th International Conference on Rehabilitation Robotics, ICORR'07


  • Active impedance
  • Assist
  • Exoskeleton
  • Lower limb

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Electrical and Electronic Engineering


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