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Human Force Discrimination during Active Arm Motion for Force Feedback Design
July-Sept. 2013 (vol. 6 no. 3)
pp. 309-319
Seyedshams Feyzabadi, DFKI, Bremen
Sirko Straube, University of Bremen DFKI, Bremen Bremen
Michele Folgheraiter, DFKI, Bremen
Elsa Andrea Kirchner, University of Bremen DFKI, Bremen Bremen
Su Kyoung Kim, University of Bremen DFKI, Bremen Bremen
Jan Christian Albiez, DFKI, Bremen
The goal of this study was to analyze the human ability of external force discrimination while actively moving the arm. With the approach presented here, we give an overview for the whole arm of the just-noticeable differences (JNDs) for controlled movements separately executed for the wrist, elbow, and shoulder joints. The work was originally motivated in the design phase of the actuation system of a wearable exoskeleton, which is used in a teleoperation scenario where force feedback should be provided to the subject. The amount of this force feedback has to be calibrated according to the human force discrimination abilities. In the experiments presented here, 10 subjects performed a series of movements facing an opposing force from a commercial haptic interface. Force changes had to be detected in a two-alternative forced choice task. For each of the three joints tested, perceptual thresholds were measured as absolute thresholds (no reference force) and three JNDs corresponding to three reference forces chosen. For this, we used the outcome of the QUEST procedure after 70 trials. Using these four measurements we computed the Weber fraction. Our results demonstrate that different Weber fractions can be measured with respect to the joint. These were 0.11, 0.13, and 0.08 for wrist, elbow, and shoulder, respectively. It is discussed that force perception may be affected by the number of muscles involved and the reproducibility of the movement itself. The minimum perceivable force, on average, was 0.04 N for all three joints.
Index Terms:
Force,Humans,Joints,Force feedback,Wrist,Force measurement,Elbow,wearable computers,Perception,psychophysics,biorobotics,human factors
Citation:
Seyedshams Feyzabadi, Sirko Straube, Michele Folgheraiter, Elsa Andrea Kirchner, Su Kyoung Kim, Jan Christian Albiez, "Human Force Discrimination during Active Arm Motion for Force Feedback Design," IEEE Transactions on Haptics, vol. 6, no. 3, pp. 309-319, July-Sept. 2013, doi:10.1109/TOH.2013.4
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