DESIGN OF END-EFFECTORS FOR THINNING APPLE IN THE GREEN FRUIT STAGE

Fruit thinning is an essential task for apple production, which plays a vital role in determining fruit quality. Robotic thinning can be applied as an alternative method that reduces labor costs while still being both accurate and precise. A robotic thinning system requires a well-designed end-effector to be effective, as it is the mechanism that removes excessive fruitlets. Two end-effector prototypes were designed using different thinning approaches based on the size and shape of fruitlets. The first end-effector model thins fruitlets one by one, while the second end-effector model preserves the king fruit (typically the largest) of the cluster while cutting off unwanted fruitlets. Both models were designed, and their motions were animated using SolidWorks (Dassault Systèmes, Waltham, MA, USA). The fabricated end-effectors were tested in the lab and in an apple orchard during the green fruit thinning season. A mechanism design was adopted to singulate fruitlets. The model 1 end-effector employed an iris dome mechanism to singulate each fruitlet. This mechanism can adjust the opening size to match the target fruitlet size. The model 2 end effector used the idea of a corkscrew to protect the king fruit and remove the unwanted lateral fruitlets. The singulation success rate in the orchard for model 1 was 100%, and 75% for model 2. Model 2 could be improved for better singulation performance in the future.