Improving backdrivability in geared rehabilitation robots

Nef, Tobias; Lum, Peter (2009). Improving backdrivability in geared rehabilitation robots. Medical & biological engineering & computing, 47(4), pp. 441-447. Springer 10.1007/s11517-009-0437-0

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Many rehabilitation robots use electric motors with gears. The backdrivability of geared drives is poor due to friction. While it is common practice to use velocity measurements to compensate for kinetic friction, breakaway friction usually cannot be compensated for without the use of an additional force sensor that directly measures the interaction force between the human and the robot. Therefore, in robots without force sensors, subjects must overcome a large breakaway torque to initiate user-driven movements, which are important for motor learning. In this technical note, a new methodology to compensate for both kinetic and breakaway friction is presented. The basic strategy is to take advantage of the fact that, for rehabilitation exercises, the direction of the desired motion is often known. By applying the new method to three implementation examples, including drives with gear reduction ratios 100-435, the peak breakaway torque could be reduced by 60-80%.

Item Type:

Journal Article (Original Article)


10 Strategic Research Centers > ARTORG Center for Biomedical Engineering Research > ARTORG Center - Gerontechnology and Rehabilitation

UniBE Contributor:

Nef, Tobias


600 Technology > 610 Medicine & health
600 Technology > 620 Engineering








Vanessa Vallejo

Date Deposited:

04 Jul 2014 09:23

Last Modified:

04 Jul 2014 09:23

Publisher DOI:


Uncontrolled Keywords:

Backdrivability, Friction, Breakaway friction, Human–robot interaction, Rehabilitation robotics


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