# Robotic Button Mushroom Harvesting Systems: A Review of Design, Mechanism, and Future Directions
## 5 Discussion  
Research on automated mushroom harvesters has primarily focused on designing, developing, and testing robot manipulators, end-effectors, and computer vision systems. Although collector and mobile platform components are used, they have not been extensively studied. Camera-based vision systems are common, but other detection technologies like LIDAR have yet to be fully explored. Mushroom harvesting robots typically use Cartesian or SCARA manipulators, chosen for their suitability with the standard mushroom shelf design, which features a horizontal workspace. These manipulators excel in broad planar coverage, crucial due to the limited space between shelves (11-14 inches for standard aluminum Dutch shelves) [3,46], which restricts the use of cylindrical or spherical manipulators. As a result, other manipulators must operate outside the shelves, increasing the travel time. For mushrooms grown in open spaces or 3D structures like wooden logs, universal or spherical manipulators would be more appropriate. Commercial systems occasionally employ multiple manipulators to enhance the picking speed, though this approach is used by only a few companies. Figure 9 illustrates the workspace comparisons for different manipulators. Graspers and vacuum suction cups are the main end-effectors used for mushroom harvesting. Vacuum suction cups, which use pneumatic actuation to create negative pressure, perform well with clustered mushrooms by grabbing the exposed cap without penetrating the cluster. However, they require a higher gripping pressure, which can cause mushroom damage, as listed in Table 1. In contrast, graspers surround the mushroom cap from multiple sides, allowing for a lower gripping force and reducing the risk of  
Figure 9: Workspace (covered by white grids) for different manipulators: (**a**) Cartesian, (**b**) SCARA, (**c**) six-DOF UR, and (**d**) six-DOF industrial manipulator. damage. However, they face challenges when picking clustered mushrooms because they must navigate within the cluster to grasp individual mushrooms. Improving grasper designs could address these issues. Commercially, two-finger graspers are preferred due to their compact size compared to the three-finger or closed graspers. Graspers designed for delicate fruits like tomatoes and strawberries could offer insights for mushroom harvesting. Comparing the end-effector performance, hand picking remains superior in speed and for minimizing mushroom injuries. Yet, with advancements in design, optimal force application, and integration of sensors and actuators, end-effector performance could improve. Additionally, using multiple end-effectors on manipulators could enhance overall harvesting efficiency. Collection units for mushroom harvesting can be either on-shelf or off-the-shelf. On-shelf collectors, positioned close to the manipulators, reduce the pick-and-drop time but are generally installed on horizontal planes, which makes reaching other processing units slower. In contrast, off-the-shelf collectors, typically vertical, shorten the mushroom travel time and can be relocated to different shelves. However, moving these collectors requires more time and energy. The choice between on-shelf and off-the-shelf collectors depends on the shelf design. On-shelf collectors are ideal for scenarios with sufficient space between shelf layers, allowing direct connection to post-harvesting mechanisms. When shelf gaps are narrow, off-the-shelf collectors are more practical. These vertical collectors can also incorporate post-harvesting mechanisms to handle tasks while transporting mushrooms. The collector's design and installation are influenced by the type of manipulators and mobile systems used. Off-the-shelf collectors require a mobile mechanism for relocation. Detailed study of collector designs and their integration with other systems is essential for optimizing their performance. Mobile platforms for mushroom harvesting can be on-shelf or off-the-shelf.