Design, Assembly and Test of a Low-Cost Vacuum Based Apple Harvesting Robot

The timely harvesting of fresh apples faces challenges due to labor shortages. Robotic harvesting has the potential to alleviate the labor intensity on operators and liberate additional agricultural labor. However, the current success rate of apple-picking robots is low, resulting in fruit damage, high operational costs, and an inability to meet market demand. In this research, a prototype apple harvesting manipulator was designed and constructed, providing a solid foundation for future advancements. The manipulator prototype includes a vacuum three-rotational (3R) degrees-of-freedom (DoF) end-effector, a 3-DoF Cartesian system, an RGB-D camera, and a mobile vehicle. Vision-assisted positioning system and manipulator controller were designed to achieve precise positioning and separation motions of the manipulator. The harvesting experiment was conducted in a dwarf, densely planted spindle apple orchard. Results from the experiment indicate that the rotation followed by pull mode proved more effective than the pull mode for apple picking. In the critical negative pressure environment of − 65 kPa employed for apple picking, utilizing 33 mm suction cups has demonstrated an 81.7% separation success rate. The diameter center as the optimal theoretical point for adsorption with an allowable two-dimensional error mean value of 9.62%. The manipulator ensures essentially damage-free picking of target fruits, demonstrating a stem damage rate of 17.1%. The developed picking prototype successfully accomplishes the task of apple harvesting, boasting main advantages of compact size, low cost, non-destructiveness, and high flexibility.