Agriculture Reference
In-Depth Information
Another manipulator mechanism adapted to the physical properties of the toma-
toes was presented by Kondo et al. (1996a) and is shown in Figure 7.27. The manipu-
lator prototype had 7 DOF with two prismatic joints and five rotational joints, making
it a redundant configuration. But the prismatic DOF were used only to position the
articulated five-jointed arm to cover all the fruit positions. The joints were powered
by electric motors. A two-finger end effector equipped with a suction pad to pull the
fruit into the end effector was used for normal sized tomatoes, and a modified end
effector with a nipper to cut the peduncle at the fruit-peduncle joint was used for
cherry tomato harvesting (Kondo et al., 1996b). A photoelectric sensor as well as a
color camera was used for visual sensing in the trials.
Ceres et al. (1998) presented a manipulator design for an aided fruit harvest-
ing robot (Agribot) that works under human guidance. The articulated manipulator
structure was designed based on a kinematic, dynamic, and geometric study that
took into account the fruit distribution on the tree. Figure 7.28 shows the parallelo-
gram structure of the Agribot's picking arm with 4 DOF (all rotational), including
the gripper. All of the joints were driven by electric motors. Fruit detection was done
by a human operator using a laser telemeter and a joystick and fruit detachment was
done through an end effector with a suction cup that pulled the fruit into a V-shaped
cutter.
Another development for a citrus harvesting manipulator in Italy was reported
by Cavalieri and Plebe (1996), Fortuna et al. (1996), and Muscato et al. (2005). The
first research prototype had two spherically configured picking arms mounted at
the tool point of a 4-DOF positioning platform. The picking arms were driven by
electric motors, whereas the platform was driven by hydraulic actuators. Figure 7.29
shows the arm structure. Muscato et al. (2005) also presented a second prototype
with two arms mounted on a 45° inclined platform carried on a caterpillar as shown
in Figure 7.30.
Both arms were of the Cartesian type and were driven by electric motors, but
the upper arm had a telescopic link in place of a prismatic link as in the lower arm
because of space constraints. The research also presented a variety of end effector
θ
5
ℓ
4
ℓ
5
θ
7
θ
6
θ
4
ℓ
3
ℓ
6
ℓ
7
θ
3
ℓ
2
s2
ℓ
1
s1
FIGURE 7.27
Tomato harvester manipulator mechanism:
s
1
and
s
2
are the prismatic joints,
and
θ
3
through
θ
7
represent the revolute joints. (From Kondo, N. et al.,
Adv. Robot.
, 104,
339-353, 1996a. With permission.)
