Development of a Robotic End Effector for Apple Tree Pruning

Abstract. . Robotics and automation technologies are now extensively used in agriculture, while, production operations of tree fruit crops still largely depend on manual labor. The limited labor pool and associated costs have raised concern among fruit growers. Robotic pruning involves several challenges due to unstructured working environment. This study is focused on designing an end-effector prototype for branch pruning considering the maneuvering, spatial, mechanical, and horticultural requirements. Branch cutting force was measured with a thin force sensor to provide guideline information for the end-effector design. The test results indicated the relationship between the force required to cut different diameter branches with the R2 value of 0.87. The end-effector was developed using two rotary motors, a pneumatic cylinder, and a pair of by-pass shear blade pruning cutter. A three directional linear manipulator was built to house the end-effector for moving to the targeted locations. An embedded microcontroller system with user interface is developed in MATLAB environment to control the maneuvering of the end-effector and the manipulator. A series of field tests were conducted for the performance assessment of the end effector. The results indicated that the end effector with current parameter settings successfully cut the branches up to 12 mm in diameter. The results also showed that the proposed pruning end-effector could cut the branches of all orientation in a given 3D space. The robotic end-effector developed in this study is a core component in an automated pruning system for fruit tree.