Phases in a grasping task

There are three phases associated with a grasping task:
  1. Pregrasp phase

    This is the first phase of the grasping task which precedes the actual grasp. It is a combination of the trajectory of the hand ([1], [2]) (hand transportation), and the temporal changes in finger joint parameters in anticipation of the intended grasp ([1], [2]) (hand preshape). The trajectory of the hand is influenced by the distance of the object from the hand ([1], [3]) while the finger joint parameter changes are dependent on the shape of the object ([1], [3], [7]). The hand transportation and hand preshape components have been observed to occur in parallel.

  2. Grasp phase

    The pregrasp phase ends and the static grasp phase begins at the moment the hand touches and has a stable hold of the object. The type of grasp employed can be identified at this phase, and can be represented using a grasp hierarchy proposed by Kang and Ikeuchi [4].

  3. Manipulation phase

    The manipulation phase is characterized by hand motions resulting in the purposeful movement of the object relative to the environment. The grasp is chosen by the operator on the basis of the mobility and dexterity required to manipulate the object. A manipulative action can be as simple as just translating the object with respect to the environment. It can be as complex as simultaneously transporting (by hand transportation) and precision handling ([5], [6]) the object with the fingertips, changing its pose with respect to both the palm and the environment.


  1. M.A. Arbib, T. Iberall, and D.M. Lyons, "Coordinated control programs for movements of the hand," Hand Function and the Neocortex, eds. A.W. Goodwin, and I. Darian-Smith, Springer-Verlag, 1985, pp. 111-129.
  2. M. Jeannerod, "Intersegmental coordination during reaching at natural visual objects," Attention and Performance IX, Long, J., and Baddley, A. (eds.), Erlbaum, Hillsdale, NJ, 1981, pp. 153-168.
  3. M. Jeannerod, "The timing of natural prehension movements," Journal of Motor Behavior, vol. 16, no. 3, 1984, pp. 235-254.
  4. S.B. Kang, and K. Ikeuchi, "Grasp recognition using the contact web," Proc. IEEE/RSJ Int'l Conf. on Intelligent Robots and Systems, 1992, pp. 194-201.
  5. J.M.F. Landsmeer, "Power grip and precision handling," Ann. Rheum. Dis., Vol. 21, 1962, pp. 164-170.
  6. H. Liu, T. Iberall, and G.A. Bekey, "The multi-dimensional quality of task requirements for dextrous robot hand control," Proc. IEEE Int'l Conf. on Robotics and Automation, 1989, pp. 452-457.
  7. R. Tomovic, G.A. Bekey, and W.J. Karplus, "A strategy for grasp synthesis with multifingered robot hands," Proc. IEEE Int'l Conf. of Robotics and Automation, 1987, pp. 83-89.

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