Simplified 4-DOF manipulator for rapid robotic apple harvesting

Fruit harvesting is time-consuming and laborious. Robots can harvest fruits with a high degree of automation, greatly reducing labor requirements, but are limited by their efficiency and high costs. In this research, a prototype apple harvesting robot was designed and constructed. The robotic prototype integrated a binocular camera, a 4-degree-of-freedom manipulator, a vacuum-based end-effector, and a mobile vehicle. The robot detected, positioned, gripped, detached, and placed apples. A manipulator controller was designed to realize rapid control execution. Picking experiments were conducted in a spindle apple orchard. Picking was tested using rotation-pull and pull patterns. The test results showed that the rotation-pull pattern was more effective picking apples than the pull pattern. The picking success rate of the rotation-pull pattern was 47.37% in the field orchard and 78% in the simulated orchard environment, with picking cycle time of ∼ 4 s. The stem damage rate in the field orchard was 11.11%. The developed picking prototype realized the task of picking apples. Its primary advantage was its competitive picking cycle time, which provides a solid foundation for the future improvement of harvesting efficiency.