Contact web

The contact web is a 3D graphical representation of the effective contact between the hand and the held object. It is the basis of the grasp taxonomy used to recognize the human hand grasp employed in the grasping task.

Human fingers are pliant and soft; the finger surfaces conform to some extent to the local object surface as it is being grasped. In order to be able to recognize the human grasp, we should be able to extract some contact information between the hand and the object. Contact between the hand and the object is represented by single effective points of contact; each effective point of contact represent the contact between a particular finger segment (the palm counts as a "finger segment") and the object. These points of contact are shown below:

The filled triangle represents the palm while the thick circle and square represent the fingertips. The thinner circles and squares represent the more proximal finger segments. The contact web is the 3D graphical structure connecting the palm contact with the rest of the contacts illustrated below:

Associated with each contact point are the 3D location and the object normal at the effective point of contact (the latter to approximate the force exerted). This structure is used as the basis for the construction of the grasp taxonomy, from which the human grasp used in the task is recognized.


  1. S.B. Kang and K. Ikeuchi, "A grasp abstraction hierarchy for recognition of grasping tasks from observation," Proc. IEEE/RSJ Int'l Conf. on Intelligent Robots and Systems, Yokohama, Japan, July 1993.
  2. S.B. Kang and K. Ikeuchi, "Grasp recognition using the contact web," Proc. IEEE/RSJ Int'l Conf. on Intelligent Robots and Systems, Raleigh, NC, July 1992.
  3. S.B. Kang and K. Ikeuchi, "Toward automatic robot instruction from perception: Recognizing a grasp from observation," IEEE Int'l Journal of Robotics and Automation, vol. 9, no. 4, Aug. 1993.

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