Strawberry Harvesting Robot on Table-top Culture

Abstract

In this paper, it is reported that a robot was developed for harvesting strawberry grown on table top culture. The robot mainly consisted of a 4 DOF manipulator, a harvesting end-effector using sucking force and a visual sensor. As its manipulator, a Cartesian coordinate type was adopted and it was suspended under the planting bed of strawberry. The robot was capable of moving along the planting bed without a traveling device because one prismatic joint of the manipulator played the role of a traveling device. The end-effector could suck a fruit using a vacuum device and it could compensate detecting errors caused by the visual sensor. The visual sensor gave the robot two dimensional information based on an acquired image and fruit depth was calculated as an average value of previously harvested fruit depths obtained from end-effector positions when the robot actually harvested. The end-effector moved toward a target fruit based on the three dimensional position of the target fruit until the fruit was detected by three pairs of photo-interrupters on sucking head. After cutting the peduncle by using the robot's wrist joint, the fruits passed the tube and were transported to the tray. From the results of the harvesting experiments, it was observed that the robot could harvest all target fruits with no injury, and that depth measurement by a visual sensor was simplified because a distance between the robot and the fruits was kept an approximately constant by suspending the robot under the planting bed.