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.
Highlights
Due to the growing world population, the demand for fresh fruit and vegetables, and the limited amount of soil, higher agricultural productivity is increasingly required
The research shows that there is a possibility for using pneumatic suction cups in robotic picking heads
Strawberries of the San Andreas variety were used for all performance tests
Summary
Due to the growing world population, the demand for fresh fruit and vegetables, and the limited amount of soil, higher agricultural productivity is increasingly required. The performance of agriculture is dependent on the mechanization and automation of production. In the US, strawberry production covers almost 20% of the world’s cultivated area [1]. The search for alternative cultivation methods in which the production process is fully automated is one of the directions of modern research. Shamshiri [2] presented the results of using advanced technologies in a fully automated greenhouse (Green Factory). The direction of research is the possibility of reducing production costs by automating its individual stages. Bechar and Vigneault [3] presented the results of research related to the use of Sensors 2020, 20, 4389; doi:10.3390/s20164389 www.mdpi.com/journal/sensors
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