Comfort of two shoulder actuation mechanisms for arm therapy exoskeletons: a comparative study in healthy subjects

  • Tobias NefEmail author
  • Robert Riener
  • René Müri
  • Urs P. Mosimann
Original Article


Robotic exoskeletons can be used to study and treat patients with neurological impairments. They can guide and support the human limb over a large range of motion, which requires that the movement trajectory of the exoskeleton coincide with the one of the human arm. This is straightforward to achieve for rather simple joints like the elbow, but very challenging for complex joints like the human shoulder, which is comprised by several bones and can exhibit a movement with multiple rotational and translational degrees of freedom. Thus, several research groups have developed different shoulder actuation mechanism. However, there are no experimental studies that directly compare the comfort of two different shoulder actuation mechanisms. In this study, the comfort and the naturalness of the new shoulder actuation mechanism of the ARMin III exoskeleton are compared to a ball-and-socket-type shoulder actuation. The study was conducted in 20 healthy subjects using questionnaires and 3D-motion records to assess comfort and naturalness. The results indicate that the new shoulder actuation is slightly better than a ball-and-socket-type actuation. However, the differences are small, and under the tested conditions, the comfort and the naturalness of the two tested shoulder actuations do not differ a lot.


Arm therapy robot Exoskeleton Shoulder actuation Comfort 



We would like to thank Angela DeMarco and Thomas A. Giuliani from the Catholic University of America in Washington, D.C. for supporting the data collection. Also, we thank the participants of this study. Disclaimer: Prof. Dr. –Ing. Robert Riener and Prof. Dr. sc. Tobias Nef are inventors of two patents describing the ARMin shoulder actuation. Owner of the patents is the ETH Zurich and the University of Zurich.


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Copyright information

© International Federation for Medical and Biological Engineering 2013

Authors and Affiliations

  • Tobias Nef
    • 1
    • 2
    Email author
  • Robert Riener
    • 3
    • 4
  • René Müri
    • 1
    • 5
  • Urs P. Mosimann
    • 1
    • 6
  1. 1.Gerontechnology and Rehabilitation Group, University of BernBernSwitzerland
  2. 2.ARTORG Center for Biomedical Engineering Research, University of BernBernSwitzerland
  3. 3.Sensory-Motor Systems Lab, Institute of Robotics and Intelligent Systems, Department of Health Sciences and Technology, ETH ZurichZurichSwitzerland
  4. 4.Spinal Cord Injury Center, University Hospital Balgrist, University of ZurichZurichSwitzerland
  5. 5.Division of Cognitive and Restorative Neurology, Department of NeurologyInselspital, University of BernBernSwitzerland
  6. 6.Department of Old Age PsychiatryUniversity Hospital of Psychiatry, University of BernBernSwitzerland

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