This Project is Supported by the Italian National Council of Research under the special project on robotics
The goal of the AGROBOT project is the implementation of a robotic system for agricultural operations in greenhouses. The robot is composed by a vehicle carrying a 6 d.o.f. arm, a gripper/hand, a 2 d.o.f. head and a system controller. A color stereoscopic vision system is used to drive an anthropomorphic arm with a gripper/hand, for the greenhouse cultivation of tomatoes, and a mobile robot, able to navigate between rows of tomato plants. The robot will perform some important operations as spraying of flowers and fruits and picking of ripe tomatoes. During the navigation phase the vision system controls the moving direction and keeps the vehicle at the center of the free path, the robot will stop in correspondence of each plant to analize it. During the stop phase a robotic head is used to explore the plant; after significant objects are identified and localized by the vision system, spraying or manipulation are made.
The vision system is based on a VME bus architecture and on a pair of PAL video microcameras. The vision system has been developed specifically for the project by Video Display Systems (VDS) (hardware) and AITEK (software) in collaboration with LIRA-Lab and is now a commercial product. In the final version of the system, images are processed, after a HSI color conversion, by a 88110 CPU with a fast connection with the acquisition board, a stereo algorithm is used to localize objects. Color based segmentation is basilar to simplify and therefore to speed up the following distance evaluation phase based on the matching of corresponding regions in stereo images. During navigation control, one of the two color video cameras is used to get images of the corridor between the rows of plants. The localization of a color target positioned at the end of the corridor is used to keep the vehicle at the centre of the corridor.
Two degrees of
freedom pan/tilt binocular head
The head was studied ad hoc for the project and realized by TELEROBOT to permit complete visibility of the overall area and has two degrees of freedom: pan and tilt. Pan range is from +90 to -45 degrees, tilt range is from +70 to -60 degrees; the vision system drives the head to point the path during navigation or to explore the plants looking for the objects to treat. During exploration phase, pan movement will permit to analyze in real time horizontal bands of plants while tilt movement will permit to change height of the explored horizontal band up to the top of plants. We use two Harmonic Drive RH8 - 1502 Mini DC Servo actuators for head motion; they are current driven, are very small and have a reduction ratio of 1:100, for these characteristics they are particularly apted to our needs.
The sequence (mpeg about 700K) shows the stereo camera head scanning the scene and driving the robot arm to catch a tomato. The experiment is performed in our experimental green-house.
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