1. Introduction
The pepper planting area in Jiangsu Province is mainly concentrated in Feng County and Pei County in Xuzhou City. While there is also a small amount of pepper planting in other areas, the scale is small and the varieties are mixed. According to information, in 2020, Pei County’s pepper planting area covered 17,000 acres, where a total of 158 registered varieties of pepper were grown, of which the “Su Heng Run”, “Su Run”, and “Run La” brands also won the “China Well-known” award. Three brands have won the title of “China Famous Brand”, and cultivated more than 3000 new vocational and technical farmers, the annual output value exceeded 500 million yuan, and effectively driving the local farmers to increase their income by 250 million yuan; in 2021, Feng County pepper planting area reached more than 30,000 acres; the economic output value reached about 150 million yuan, effectively driving farmers to increase income and get rich, and now it has become an important poverty alleviation industry. Pod pepper picking is labor intensive; relative to the value of the product, the cost of labor continues to increase, making the economic benefits of pod pepper planting decline. The farmers planting pod peppers decreased, resulting in pod pepper planting areas continuing to shrink. The development of a small hand-held pod pepper harvester with a high picking rate, low loss rate, and compact structure adapted to small field operations is a key technical problem that needs to be solved in China at present. Therefore, expediting research on key technologies, such as the spiral comb finger picking device, holds substantial significance for advancing China’s pepper industry, fostering increased income and wealth among farmers.
There exists a significant disparity between the research levels of domestic and foreign pepper harvesters. Foreign pepper harvester technology is very mature; pepper harvesting research has a longer history in other countries including the United States [
1], Mexico [
2,
3], South Korea [
4], Europe, and other countries. Although the foreign pepper harvester has advanced technology, the price is relatively high, and the domestic pepper planting mode is not applicable, making it difficult to meet the domestic pepper harvesting market. Domestic development of pepper harvesters started late. At present, individual enterprises and research institutions in Xinjiang Province [
5,
6], Shanxi Province, Jiangsu Province [
7], and Guizhou Province [
8,
9] carry out the development of pepper harvesters. The development of pepper harvesters is mainly used for large field operations. In Guizhou Province, Shandong Province, Henan Province, Jiangsu Province, and other places where pod pepper is grown, pepper planting in small fields and individual households planting mainly rely on manual picking, but the manual picking cost is high and the harvesting cycle is long, affecting the planting of the next season’s crop. In Guizhou Province, Shandong Province, Henan Province, Jiangsu Province, and other places where pod pepper is grown, the pepper harvest is faced with artificial picking costs that increase year by year. The pepper harvest “no machine available” problem is becoming more and more prominent.
The inclined double-helix picking device has the advantages of compact structure, high flexibility, wide picking range, etc., which can achieve the continuous combing action of pepper, and has been studied by a large number of scholars. Among them, in 1997, E. Palau et al. [
10] developed a hydraulically-driven single-row pepper harvester, which brushes the peppers from the plants through the reverse rotation of the combing drums and throws the pepper fruits to the conveyor belts on both sides, and the conveyor belts convey the peppers while the fan clears and separates the impurities left in them, and finally conveys the peppers to the bins; in 2018, Byum et al. [
11] used discrete element simulation software EDEM to analyze the effect of pepper harvesting and picking components on the effect of pepper picking; In 2021, Yuan et al. determined the main factors affecting pepper harvesting by analyzing the force on the spiral steel bar in contact with the pepper and conducting a field test [
12], and determined the range of factors selected in the optimization test by using a one-way trial. In 2024, Du et al. [
13] used EDEM to carry out simulation tests on the roller comb-finger-type pepper picking device and carried out simulation analysis through the response surface orthogonal test method to determine the main factors affecting the loss rate of pod peppercorns falling on the ground and their optimal parameter combination values. At present, there is less research on the spiral comb finger picking device, the test results fail to meet the expected performance requirements, the breakage rate and ground loss rate are high, the comb finger structure, material and arrangement still need to be studied, and the structural parameters and movement parameters of the pepper picking device still need to be optimized.
This article develops a high-clean and low-loss small hand-held pod pepper harvester through the discrete element simulation software EDEM, establishes a discrete element model of pod pepper, builds a simulation platform of ground drop loss of pod pepper picking device, and explores the movement trajectory and speed change of the discrete element model of pod peppers. Taking the rate of ground drop loss of pod peppers as the evaluation metric, the influence of picking roller speed, feeding speed of pod peppers, and spacing between two picking rollers on the ground drop loss of pod peppers is analyzed through a one-factor simulation test, and the better value range of each factor is determined. Based on the results of the single-factor test, the Box–Behnken response surface test was used to optimize the working parameters of the picking device, to analyze the significant relationship between the picking roller speed, feeding speed of pod peppers, and the spacing between the two picking rollers on the ground loss rate of pod peppers, and to explore the optimal working parameters of the picking device.
5. Conclusions
In this study, through the analysis of hand-picking pod peppers, we extracted the structural morphology of fingers, designed a bionic comb finger pod peppers picking device, and developed a high-efficiency and low-loss hand-held pod peppers harvester. Firstly, a discrete meta-model of pod peppers was established, and a simulation platform for the ground drop loss of the pod peppers picking device was built to explore the motion trajectory and speed change of the discrete meta-model of pod peppers. At the same time, the effects of the picking roller speed, the feeding speed of pod peppers and the distance between two picking rollers on the ground drop loss of pod peppers were analyzed. In order to evaluate the loss rate of pod peppers ground drop, a one-factor simulation test was conducted to derive the effects of each factor on the loss rate and to preliminary determine the optimal operating parameters of the picking device. Based on the results of the single-factor analysis, the operating parameters of the picking device were optimized using the Box–Behnken response surface test, and the optimal combination of operating parameters was obtained: a picking roller speed of 680.41 rpm, a pod pepper feeding speed of 0.5 m/s, and a spacing of 12 mm between the two picking rollers. Under these conditions, the pod peppers ground drop loss rate was 3.526%. Through the harvesting test, it was learnt that the net harvesting rate of the pod pepper harvester was 96.25%, and the ground drop loss rate was 8.39%. Although there is a certain relative error between the harvesting test and the simulation test, the error is small. Therefore, the discrete element simulation test results of the harvesting device were verified to be reliable.