  After a grasp has been planned, if the object orientation changes, the
initial grasp may not have to be modified to accommodate the orientation
change. For example, rotation of a cylinder by any amount around its centerline
does not change its geometric shape relative to the grasper. Objects that can
be approximated to solids of revolution or contain other geometric symmetries
are prevalent in everyday life, and this information can be employed to improve
the efficiency of existing grasp planning models. This paper experimentally
investigates change in human-planned grasps under varied object orientations.
With 13,440 recorded human grasps, our results indicate that during
pick-and-place task of ordinary objects, stable grasps can be achieved with a
small subset of grasp types, and the wrist-related parameters follow normal
distribution.
