Research and development of a 3-axis robotic strawberry harvester in a greenhouse using image processing

Abstract

This research focuses on the development of a robotic strawberry harvester for greenhouse cultivation, aimed at reducing dependence on manual labor and improving harvesting precision. The robotic system features a three-dimensional Cartesian structure with dimensions of 150 × 200 × 140 cm (Width × Length × Height), driven by three stepper motors with a step angle of 1.8^o. The system is controlled using a single web camera with a resolution of 1280 × 720 pixels (720p/30fps), which captures images to detect the position and ripeness of strawberries. Image processing is performed using LabVIEW software, which guides the movement along the X, Y, and Z axes to position the gripper precisely at the harvesting location. The gripper is designed to grip and cut the stem of the strawberry, minimizing post-harvest damage to the fruit. Field tests conducted in a greenhouse demonstrated that the robot could accurately classify strawberry ripeness with 100% accuracy. At motor speeds of 1100, 1200, and 1300 rpm corresponding to linear speeds of 0.11, 0.12, and 0.13 m/s the robot achieved target positioning accuracy of 100, 96.66, and 100%, respectively. The average harvesting times per fruit were 53.9, 52.7, and 50.8 s. In addition to its technical performance, an engineering economic analysis showed that the robotic system offers a payback period of 9.6 months and a break-even point at 180.59 h/time/y. These results indicate that the robotic harvesting system is a cost-effective investment for medium- to large-scale greenhouse farming operations.