Agriculture Reference
In-Depth Information
an estimated distance to target, the vision system grabs an image of the target. Then,
the manipulator jogs to a known offset position, and takes second image frame. It
then calculates the distance of the fruit by triangulation similar to stereo vision. The
hand then approaches the fruit using this calculated distance.
7.4.3.3 Harvesting End Effector
The end effector is pneumatically actuated with three custom-designed fingers for
gripping the fruit. When a fruit is harvested, the gripper's fingers close and grasp
the fruit. Then the detaching sequence is initiated to pull the fruit from the branch.
A number of different designs for end effectors have been developed. However, the
present design allows the end effector to approach the fruit at different angles. A
close-up view of the end effector is shown in Figure 7.35. In addition, the CCD cam-
era and ultrasonic sensor are also mounted on the end effector.
7.4.3.4 System Architecture
Figure 7.36 shows the system architecture of the vision-based robotic harvesting
system. This diagram can be used to visualize how the harvesting operation works.
The system's flow starts with the recognition and location of the fruits on the tree
using data from the machine vision system and the ultrasonic sensor. PC 1 performs
the image processing to detect fruits within the canopy and outputs the location of
the fruit to PC 2, whose responsibility it is to monitor systems status, execute visual
servo control, and provide the interface between the vision system and the manipu-
lator controller. PC 2 passes visual servo-based position control updates to PC 3.
PCÂ 3 is the real-time manipulator controller responsible for determining manipula-
tor forward and inverse kinematic, actuator joint torques, and position command,
and monitors the manipulator status. Once PC 3 receives the position update, it will
execute the inverse kinematics to establish the new joint angles required to reach the
desired tool frame destination. It also provides feedback to the visual servo control
systems of the current manipulator position. The manipulator control on PC 3 and
the visual servo control on PC 2 executes in real time under the INtime real-time
CCD camera
Ultrasonic sensor
End effector
End effector
Solenoid valve
Compressor
PC
To solenoid valve
End effector for citrus harvesting
Opening and closing control of end effector
FIGURE 7.35
Developed end effector with CCD camera and ultrasonic sensor for harvest-
ing oranges.
