Analysis of the Pneumatic System Parameters of the Suction Cup Integrated with the Head for Harvesting Strawberry Fruit

Abstract

Fruit and vegetable harvest efficiency depends on the mechanization and automation of production. The available literature lacks the results of research on the applicability of pneumatic end effectors among grippers for the robotic harvesting of strawberries. To determine their practical applications, a series of tests was performed. They included the determination of the morphological indicators of the strawberry, fruit suction force, the real stress exerted by fruit suckers and the degree of fruit damage. The fruits’ morphological indicators included the relationships between the weight and geometrical dimensions of the tested fruit, the equivalent diameter, and the sphericity coefficient. The fruit suction force was determined on a stand equipped with a vacuum pump, and control and measurement instruments, as well as a MTS 2 testing machine. The necrosis caused by tissue damage to the fruits by suction cup adhesion was assessed by counting the necrosis surface areas using the LabView programme. The assessment of the necrosis was conducted immediately upon the test’s performance, after 24 and after 72h. The stress values were calculated by referring the values of the suction forces obtained to the surface of the suction cup face. The tests were carried out with three constructions of suction cups and three positions of suction cup faces on the fruits’ surface. The research shows that there is a possibility for using pneumatic suction cups in robotic picking heads. The experiments performed indicate that the types of suction cups constructions, and the zones and directions of the suction cups’ application to the fruit significantly affect the values of the suction forces and stresses affecting the fruit. The surface areas of the necrosis formed depend mainly on the time that elapses between the test and their assessment. The weight of strawberry fruit in the conducted experiment constituted from 13.6% to 23.1% of the average suction force.

Design and Development of Low-Level Automation for the Picking and Placing of the Object Using Pneumatic Suction

“…The air molecule present to the inner layer of pneumatic suction assembly, try to come out and it creates a partial vacuum. The magnitude of the force is determined by algebraically summing the pressure forces on the top and bottom surfaces of the flat surface [12]. When a perfect vacuum exists, the maximum lift force is produced.…”

End-Effectors Developed for Citrus and Other Spherical Crops

“…However, due to the inherent instability of the pneumatic system, the problem of fruit dropping due to unstable grasping may occur. Citrus grown in the natural environment can have large differences in size and ellipticity [17,18]. While the traditional finger-clamp end-effector mechanism is simple and can effectively grasp the fruit by clamping the fingers, the fruit stalk separation is prone to cause peel breakage of the fruit [19,20].…”

Analysis of suction-based gripping strategies in wildlife towards future evolutions of the obstetrical suction cup

“…While suction-based devices has been increasingly used in the field of obstetrics through the past 30 years, vacuum gripping was largely used for many industrial applications in which objects have to be handled [15][16][17]. It is particularly true within different types of industries (packaging, automotive, …), in which vacuum gripping may enable to handle and move objects of various surface roughness such as cardboard, glass or metals or even strawberries [18]. Likewise, more recent researches involved the development of wall-climbing robots [19] or window cleaning robots [20] using suction cups.…”