  Robotic harvesting of strawberries has gained much interest in the recent
past. Although there are many innovations, they haven't yet reached a level
that is comparable to an expert human picker. The end effector unit plays a
major role in defining the efficiency of such a robotic harvesting system. Even
though there are reports on various end effectors for strawberry harvesting,
but there they lack a picture of certain parameters that the researchers can
rely upon to develop new end effectors. These parameters include the limit of
gripping force that can be applied on the peduncle for effective gripping, the
force required to cut the strawberry peduncle, etc. These estimations would be
helpful in the design cycle of the end effectors that target to grip and cut
the strawberry peduncle during the harvesting action. This paper studies the
estimation and analysis of these parameters experimentally. It has been
estimated that the peduncle gripping force can be limited to 10 N. This enables
an end effector to grip a strawberry of mass up to 50 grams with a manipulation
acceleration of 50 m/s$^2$ without squeezing the peduncle. The study on
peduncle cutting force reveals that a force of 15 N is sufficient to cut a
strawberry peduncle using a blade with a wedge angle of 16.6 degrees at a
30-degree orientation.
