A System for Simple Robotic Walking Assistance with Linear Impulses at the Center of Mass

Arash Mohammadzadeh Gonabadi, Arash Mohammadzadeh Gonabadi, Prokopios Antonellis, Prokopios Antonellis, Philippe Malcolm, Philippe Malcolm

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Walking can be simplified as an inverted pendulum motion where both legs generate linear impulses to redirect the center of mass (COM) into every step. In this work, we describe a system to assist walking in a simpler way than exoskeletons by providing linear impulses directly at the COM instead of providing torques at the joints. We developed a novel waist end-effector and high-level controller for an existing cable-robot. The controller allows for the application of cyclic horizontal force profiles with desired magnitudes, timings, and durations based on detection of the step timing. By selecting a lightweight rubber series elastic element with optimal stiffness and carefully tuning the gains of the closed-loop proportional-integral-derivative (PID) controller in a number of single-subject experiments, we were able to reduce the within-step root mean square error between desired and actual forces up to 1.21% of body weight. This level of error is similar or lower compared to the performance of other robotic tethers designed to provide variable or constant forces at the COM. The system can produce force profiles with peaks of up to 15 ± 2% of body weight within a root mean square error (RMSE) of 2.5% body weight. This system could be used to assist patient populations that require levels of assistance that are greater than current exoskeletons and in a way that does not make the user rely on vertical support.

Original languageEnglish (US)
Article number9078836
Pages (from-to)1353-1362
Number of pages10
JournalIEEE Transactions on Neural Systems and Rehabilitation Engineering
Issue number6
StatePublished - Jun 2020


  • Aiding force
  • cable robotics
  • center of mass~(COM)
  • rehabilitation
  • walking

ASJC Scopus subject areas

  • Internal Medicine
  • Neuroscience(all)
  • Biomedical Engineering
  • Rehabilitation


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