Parameter optimization of column-comb harvesting of litchi based on the EDEM

Abstract

Litchi is one of the most important commercial subtropical fruit with high nutritional and medicinal value widely planted in South China.With the problems of time-consuming, laborious and low mechanization in litchi harvesting continues to increase, growers need highly effective way to harvest litchi. To solve the problem mentioned above, this paper presented a flexible harvesting column-comb litchi harvester, a flexible column-comb device with an adjustable column-comb angle harvesting method and a collection device using a lifting and lowering adjustable folding collection method was proposed, which can complete the harvesting and collection of litchi fruits in the orchard at one time. A litchi harvester model was established, and a virtual simulation test was carried out in EDEM software by taking the distance of the column-comb rods d (A), the column-comb rod length l (B) and the column-comb axle angle amplitude a (C) as the test factors and the maximum compression force F of the litchi as the evaluation index. Through optimization analysis of the response surface, the optimal combination of parameters affecting the working performance of the litchi harvester was obtained. The simulation results showed that the factors d, l, and a affected the evaluation index F during the harvesting process; the optimal parameter combination after optimization was d = 66.69 mm, l = 673.80 mm, and a = 69.84, yielding F = 64.77 N, which was within the limit load of litchi damage. Under the optimal parameter combination conditions, the litchi harvesting test was conducted in a litchi orchard in Guangdong, China, the results of the orchard test showed that the breakage rate of the optimized column-comb harvester was 6.10%, the efficiency of mechanical harvesting was 2.2 times that of manual harvesting, which was basically meeting mechanized litchi harvesting requirements. To a certain extent, it was confirmed that the established EDEM model and the virtual test analysis were accurate and effective, providing a reference for the design and research of mechanized litchi harvesting equipment.