Experimental and theoretical analysis of fruit plucking patterns for robotic tomato harvesting

Abstract Detachment of fruit from the plants is a basic and essential step either in manual or in robotic harvesting. Usually there are two methods involved in fruit detachment one is fruit cutting and the other is fruit plucking. Compared with fruit cutting, fruit plucking is more simple, low cost, and flexible in robotic harvesting. Different plucking patterns have been adopted in various prototypes for tomato, cherry tomato, apple and strawberry fruit harvesting. Although, it was found that there were differences in the success rate, efficiency and damage of different plucking patterns, moreover in-depth analysis still not carried out. In this paper, combining the classical load-deformation and fatigue break theory with the flexibility of the peduncle and pedicel are presented, theoretical modeling and discussion of different plucking based experimental results were performed. It was found from force transmission, that the load applied on the abscission layer was different from the motive power. Large deformation may happen in the whole peduncle and pedicel and lead to failure, inefficiency or even collision with obstacles in the canopy. Complex combined loading lead to the final break of the abscission layer. For reciprocating twisting pattern, long tomato peduncle and pedicel may take excessive swing times to realize the fatigue break of the abscission layer. In addition, the potential damage to fruit or the whole cluster can be well explained by this theory. The performance of different fruit plucking patterns may be related to the different species and cultivation modes, this research provides a good analytical basis for revealing the complex mechanisms of robotic fruit plucking and making a practical decision.