Non-destructive Buffering Study Of Fresh Apples Based On Vacuum Suction End Effector

As the largest producer of apples in the world,China ranks first in size and output.The current main harvesting method is manual picking with auxiliary equipment,which has low efficiency,high labor intensity and high cost.In order to improve the picking efficiency and reduce the cost,automatic picking is an inevitable trend.Then an automated harvesting device based on vacuum suction has been developed.However,the contact between apple and end effector is likely to cause fruit damage and affect economic benefits.Therefore,the research on non-destructive buffer of end effector will be one of the key technologies to realize automation.In this paper,the red Fuji apple grown in the natural environment is taken as the research object.Based on the related research at home and abroad,the end effector that realizes vacuum suction is designed and developed.Through the combination of theory and experiment,the buffer measures of apple picking without damage are studied deeply.The main research is as follows:(1)The relationship between the characteristics of apples and buffer materials and damage was analyzed theoretically,and the physical characteristics of the picked objects were measured experimentally,which provided theoretical basis and data support for the establishment of buffer model.According to the design requirements,the two design schemes were compared and analyzed,the three-dimensional model of the preferred scheme was completed and the working principle was explained.(2)Analyzing the characteristics,shape and position of the buffer material,based on the Hertz theory and the dynamic friction theory of the elastic contact,the pressing frictional buffer model of the inner surface of the straight tube of the end effector was established to obtain the maximum pressing force,friction force,pressure and contact radius of the contact area.Based on Hertzian elasticity theory and Newton’s second law,the collision buffer model of concave buffer surface on the inner wall of buffer chamber of end effector was established to explore the relationship between the maximum collision speed of apple and the maximum contact stress on the surface.(3)The minimum value of suction satisfying the requirements of picking was measured in the experiment to analyze the movement trajectory of the apple inside the buffer chamber.Based on the three-dimensional model of the end effector,Fluent simulations obtained the air pressure cloud maps around the apple at different motion positions inside the buffer chamber.According to the principle of Bernoulli equation,the effect of the airflow buffer was quantitatively analyzed from the perspective of work done by the component force which was the same as the motion direction.(4)The prototype of the end effector was fabricated,and the pressing frictional buffer experiment was carried out.The contact radius and the pressing force value of the theoretical calculation and the actual measurement were linearly fitted to verify the feasibility of the pressing buffer model.At the same time,the simulation picking experiment was carried out to explore the realization degree of the prototype according to design requirements and obtain the lossless rate of harvesting.By comparing and analyzing the damage caused by different collision speeds of apples in the buffer chamber,the feasibility of the collision buffer model was verified.