Human-Robot synchrony: Flexible assistance using adaptive oscillators

Renaud Ronsse, Nicola Vitiello, Tommaso Lenzi, Jesse Van Den Kieboom, Maria Chiara Carrozza, Auke Jan Ijspeert

Research output: Contribution to journalArticlepeer-review


We propose a novel method for movement assistance that is based on adaptive oscillators, i.e., mathematical tools that are capable of extracting the high-level features (amplitude, frequency, and offset) of a periodic signal. Such an oscillator acts like a filter on these features, but keeps its output in phase with respect to the input signal. Using a simple inverse model, we predicted the torque produced by human participants during rhythmic flexion-extension of the elbow. Feeding back a fraction of this estimated torque to the participant through an elbow exoskeleton, we were able to prove the assistance efficiency through a marked decrease of the biceps and triceps electromyography. Importantly, since the oscillator adapted to the movement imposed by the user, the method flexibly allowed us to change the movement pattern and was still efficient during the nonstationary epochs. This method holds promise for the development of new robot-assisted rehabilitation protocols because it does not require prespecifying a reference trajectory and does not require complex signal sensing or single-user calibration: the only signal that is measured is the position of the augmented joint. In this paper, we further demonstrate that this assistance was very intuitive for the participants who adapted almost instantaneously.

Original languageEnglish
Article number5609195
Pages (from-to)1001-1012
Number of pages12
JournalIEEE Transactions on Biomedical Engineering
Issue number4
Publication statusPublished - Apr 2011


  • Adaptation
  • adaptive frequency oscillator
  • assist-as-needed
  • flexibility
  • human-robot interaction
  • motor primitive

ASJC Scopus subject areas

  • Biomedical Engineering


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