A.2 Re-arrangement of the Mirtich and Canny quality index
Figure A.1: Finger trajectories evaluated by the local grasp planner (continuous
lines) and the corresponding sequence of grasp points on the reconstructed object's
surface (dotted lines).
a value of CEI higher than
; hence, all the remaining grasp configurations are
assumed to have forces lying in the same grip plane and can be further processed.
The next step consists in looking for an equilateral grasp configuration. To this
aim, for each grasp configuration, the unit vector normal to the object's surface
at each contact point is projected on the grip plane. Denoting with
between these projections for each of the 3 couple of points of the considered
configuration, an Equilateral Error Grasp Index (EEGI) can be defined as:
Clearly, the closer EEGI to zero, the nearer the configuration to an equilateral
grasp. The definition of a threshold
allows discarding all those configura-
tions with a value of EEGI higher than
; hence, all the remaining grasp
configurations are assumed to be equilateral.
Among all the equilateral configurations, the maximum circumscribing prism
has to be found; if the grasp configuration associated with the largest prism is
different from the current target configuration, this is taken as the new grasp
Notice that, in the case that the grasp configuration changes, the whole process
starts again with the new contact points, by considering the new contours and
applying the complete sequence of index-based tests. The algorithm stops if the