Robotic Manipulation for Specialty Crop Harvesting: A Review of Manipulator and End-Effector Technologies

This paper reviews recent developments in manipulator and end-effector technologies for the robotic harvesting of specialty crops that include fruits, vegetables, nursery crops, and nuts among others. Quantitative performance measures and general review criteria, including methods of crop detachment and end-effector sensing, are used to evaluate technologies and determine state-of-the-art in the field. Challenges affecting commercial implementation, limitations of current mechanical designs, and best practices are then presented. Results of the review show that, in general, robotic manipulation during harvesting has been limited by lack of system optimization and insufficient robustness to position error accumulated during visual localization. Inconsistent reporting practices have also hampered research and development across the field. At the conclusion of the review, some avenues of future research that could potentially lead to improvements in system performance are proposed. Some of the proposed recommendations include specific horticultural practices, the development of modular, multi-functional designs, and the incorporation of robust grasping techniques used in many of today’s robotic hands.