Abstract Understanding the human motor control strategy during physical interaction tasks is crucial for developing future robots for physical human–robot interaction (pHRI). In physical human–human interaction (pHHI), small interaction forces are known to convey their intent between the partners for effective motor communication. The aim of this work is to investigate what affects the human’s sensitivity to the externally applied interaction forces. The hypothesis is that one way the small interaction forces are sensed is through the movement of the arm and the resulting proprioceptive signals. A pHRI setup was used to provide small interaction forces to the hand of seated participants in one of four directions, while the participants were asked to identify the direction of the push while blindfolded. The result shows that participants’ ability to correctly report the direction of the interaction force was lower with low interaction force as well as with high muscle contraction. The sensitivity to the interaction force direction increased with the radial displacement of the participant’s hand from the initial position: the further they moved the more correct their responses were. It was also observed that the estimated stiffness of the arm varies with the level of muscle contraction and robot interaction force.
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Factors affecting the sensitivity to small interaction forces in humans
Effective physical human-robot interaction
(pHRI) depends on how humans can communicate their
intentions for movement with others. While it is speculated that
small interaction forces contain significant information to
convey the specific movement intention of physical humanhuman
interaction (pHHI), the underlying mechanism for
humans to infer intention from such small forces is largely
unknown. The hypothesis in this work is that the sensitivity to a
small interaction force applied at the hand is affected by the
movement of the arm that is affected by the arm stiffness. For
this, a haptic robot was used to provide the endpoint interaction
forces to the arm of seated human participants. They were asked
to determine one of the four directions of the applied robot
interaction force without visual feedback. Variations of levels of
interaction force as well as arm muscle contraction were applied.
The results imply that human’s ability to identify and respond
to the correct direction of small interaction forces was lower
when the alignment of human arm movement with respect to the
force direction was higher. In addition, the sensitivity to the
direction of the small interaction force was high when the arm
stiffness was low. It is also speculated that humans lower their
arm stiffness to be more sensitive to smaller interaction forces.
These results will help develop human-like pHRI systems for
various applications.
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- Award ID(s):
- 1843892
- NSF-PAR ID:
- 10322031
- Date Published:
- Journal Name:
- 2021 43rd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC)
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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