1. Introduction
As an important cash crop in China, carrot has a vast planting area and remarkable export output. According to the World Food and Agriculture Organization (FAO), China’s carrot and turnip will have an area of 429,208 hectares and an output of 18,463,396.03 tonnes in 2023, and in spite of the vast planting area and remarkable export output, most areas are still dominated by manual and semi-mechanized production. As China’s urbanization process accelerates, the massive loss of young rural laborers has led to rising labor costs, which has seriously hampered the production development of the carrot industry. Currently, China is rapidly developing carrot gripper–puller combine harvesting equipment, which can complete the digging, gripper–puller and stem collection operations in one go, with a productivity of up to 6–8 mou/h, which significantly frees up the labor force and improves production efficiency [1,2,3].
Although gripper–puller carrot combine harvesters are playing an increasingly important role in carrot harvesting in China today, our research team found that existing machines generally have high damage and missed-pulling rates, resulting in huge annual carrot harvest losses, when investigating carrot harvesting operations in Jiangsu, Shandong, and Anhui in 2023–2024. The results of the study revealed that there are two main factors that cause high damage and missed-pulling rates during carrot harvesting: The first one is that the clamping and conveying effect of the clamping and conveying device is unstable, the reliability is low, and the effect fluctuates greatly under different working conditions. The second reason is that there are many carrot varieties in China, and the clamping and conveying device of a carrot combine harvester has different adaptability to different carrot varieties. This situation has caused worry and anxiety among carrot growers about the quality of carrot harvesting machines. Therefore, it is of great significance to explore the best clamping and conveying effect (low damage rate, low leakage rate, and high pulling rate) under different clamping and conveying devices and machines’ forward speeds for China carrots to be harvested with low loss, smooth operation, and high quality [4,5,6,7].
From the world carrot harvesting technology development and current situation, Japan, South Korea, and other developed countries conducted carrot joint harvesting research earlier; many years of improvement and innovation resulted in intelligent new technology, and the mechanization level continues to improve. The CH-201C carrot was developed by Kubota in Japan; the whole machine adopts a side suspension structure, HST machine-less variable speed operation, an output power of 14.6 kW, and an operating speed of 0.8 m/s. L-type loosening shovels are designed to loosen the soil for fruit–soil separation for subsequent plucking, but the automation of carrot collection is not realized, and the operation requires two operators, one responsible for driving and the other for loading and unloading carrots [8,9,10].
Judging from the development and present situation of carrot harvesting technology in China, Chinese scholars have made some progress in carrot harvesting in recent years.
Xu, 2021 established the finite element collision model of a carrot and a horizontal pulling rod based on Abaqus/Explicit, observed the visualization results, derived effective data by post-processing software, obtained the critical impact force of carrot collision damage in the simulation state according to the measured yield stress, analyzed the damage factors of the collision between carrot and horizontal pulling rod, and put forward loss reduction measures [11]. Zhao, 2024 established a discrete element simulation model of the digging shovel–carrot–soil interaction to solve the problem of the high leakage rate of carrots. Taking the length and width of the digging shovel surface and the inclination angle of the shovel blade as test factors and the digging resistance and soil fragmentation rate as test indicators, the carrot digging simulation experiment was carried out, and the related structural parameters and working parameters were deeply analyzed [12]. Liu, 2019 studied the mechanical properties of a radish harvester, taking green radish as the research object; the digging process of green radish was simulated and analyzed by using discrete element software EDEM, and then the power and mechanical strength of the digging part were determined. Finally, the parameters of key components of the radish combine harvester were optimized [13]. Shao, 2024 studied the movement and mechanical characteristics of carrot digging parts in order to solve the problems of carrot combine harvesters, such as difficulty in digging a shovel into the soil, inaccurate clamping caused by digging topsoil, and great digging resistance [14]. A mathematical model of the mechanical characteristics of digging parts and their interaction with soil was established, and the relationship among digging angle, digging stroke, digging resistance, and digging part structure was theoretically analyzed. With the help of EDEM discrete element simulation software, the digging stroke and the mechanical characteristics of shovel interaction were analyzed, and a field verification test was carried out. Yao et al., 2022 used the EEPA contact model in EDEM simulation software to build contact mechanics models between soil and a radish and simulated the pulling process under different soil compactness levels, scarifier installation positions, pulling angles, and pulling speeds [8]. A pull-out test was carried out to verify the accuracy of the simulation, and a field test was carried out for a radish combine harvester [15]. Li Xiang, 2020 established a component–soil–crop parameter model based on the discrete element method and carried out a virtual simulation test of a scarifier, explored the working mechanism of the scarifier, established a mechanical model of drag reduction and disturbance increase, and analyzed the influence of the structural parameters of the shovel wing on the forward resistance of the machine and the carrot pulling force during carrot harvesting [16]. Using Design-Expert8.0.6 software, the optimal parameter combination of the scarifier was determined, and the working performance of the high-efficiency drag-reducing scarifier was verified.
Through the above international literature retrieval and analysis, it is found that the current research mainly includes three aspects: One is the simulation and analysis of the harvesting process through the discrete element simulation model, and another is the improvement and optimization of the structural parameters, motion parameters, and structural configuration of the clamping and conveying device. Thirdly, there is little research on carrot harvesting machines in the world at present, and even less research on the relationship between the clamping conveyor and carrot harvesting quality. Therefore, this paper innovatively analyzes and evaluates the harvesting quality effect of a carrot clamping conveyor, hoping to provide more scientific research data for the problems of a high damage rate and high leakage rate of carrot harvesting machines in China [17,18,19].
2. Materials and Methods
2.1. Material Preparation
The experimental area is located in Xuzhou City (117 8′ E, 34 21′ N), Jiangsu Province, and the research team tracked the planting and harvesting of carrots in the experimental area in 2023–2024. The experimental carrot varieties were ‘Xiahong2’ and ‘Sanhong’, the two varieties were used for standardized sowing in February of the year. The two varieties were sown in February of the same year, and then effective fertilizer and water supply and growth observation were carried out during the growing period, and integrated pest and weed control was carried out. In June of each year, test plots with uniform growth were selected for the hanging test to collect relevant data.
The soil physical characteristics of the five test sites were statistically assessed, as shown in Table 1. It can be seen that, in addition to the large standard deviation of soil hardness index in the five test sites, the difference between soil water content and soil weight index is not large; it can be seen that, in addition to the large difference in soil hardness in the five test sites, the difference between soil particle size and moisture content is not obvious, and to a certain extent, it also reflects the error of the hand-held soil hardness tester in the process of the test. As shown in Table 1, the average soil moisture content of the five test sites was 25.12%, the average soil hardness was 1118.02 kPa, and the average soil bulk density was 1.28 g/cm3 [20,21,22].
The developed extracting carrot combine harvester was subjected to a field performance test at the carrot planting site in Xuzhou City, and the test equipment included a clamping and extracting carrot combine harvester, a soil firmness meter, a tape measure, a tape measure, electronic scales, and a stopwatch. The field test site is shown in Figure 1. The temperature was 26 °C, and there was no rainfall at the trial site before harvest. The test site was a sandy loam soil with a total length of 240 m and a width of 60 m.
2.2. Carrot Holding and Extraction Test Platform
The carrot clamping and extracting test platform is mainly composed of a clamping and extracting device, a conveying device, etc., which can complete the carrot plant clamping, extracting, and conveying and the carrot stem and piece collection test at one time. When working, the carrot clamping and extracting test platform advances with the traveling system at a certain speed, the loosening mechanism underneath loosens the soil, the clamping and extracting conveying mechanism clamps the carrot tassels and leaves and conveys them backward, and finally, the carrot tassels and leaves fall into the bag collection mechanism at the end of the tail.
2.3. Measurement Methods
The preliminary test showed that the structure and form of the clamping and conveying device affect the high damage rate and the high leakage rate in the process of carrot clamping and pulling. During the test, the clamping speed was divided into four test levels: 0.40 m/s (T1), 0.85 m/s (T2), 1.30 m/s (T3), and control test (CK), and each test level was carried out three times at different forward speeds.
During the test, four groups of carrot test fields with the most similar growth were selected, and the four types of clamping and plucking clamping test platforms were advanced at a speed of 0.95 m/s in sequence. In T1, T2, and T3, three experimental plots of each variety at each clamping and conveying speed level were randomly selected by a random sampling method, and the average value was taken. The ground in the experimental area was flat, and the wind speed was suitable. The test instruments also included a stopwatch, a balance, a tape measure, a ruler, a BS200S electronic balance (Sai Dolis Company, Gottingen, Germany), an FT-DLY-1063A anemometer (Delixi Group Instrument Co., Ltd., Wenzhou, China), a calculator, and a sample collection bag. In order to ensure the similarity of external test conditions such as wind speed and temperature, this study determined the relevant external physical conditions during the test, in which the humidity and temperature were measured by hand-held detectors, and the relevant data are shown in Table 2 [23,24].
2.4. Test Indicators and Methods
The test inspection was conducted in accordance with the related standard [25]. In the carrot operation area, 30 m was selected as the test area in the test plot, 10 m in front of the test area was set as the adjustment area of the machine, and the speed was accelerated to a uniform state in the adjustment area at the beginning of each test. Under the same level of clamping speed, different forward speeds were used to count the total mass of carrots, damage mass, and missed digging mass, and the test was repeated three times. The test indices mainly included the damage rate and missed digging rate. Figure 2 shows the test site and test process.
2.4.1. Damage Rate Measurement Method
The damage rate is the percentage of the mass of damaged carrots to the total mass of carrots after the operation. The measurement procedure is as follows: from the carrots held in each test plot, 3 plots are randomly selected, the total mass of damaged carrots in the 3 plots is weighed, and the mass of all harvested carrots is calculated to calculate the damage rate, and the damage rate measurement method is shown in Formula (1).
(1)
Here, S1 is the damage rate, %; W1 is the total mass of damaged carrots in the three plots, g; and W2 is the mass of all harvested carrots, g.
2.4.2. Measurement of Leakage Rate
The leakage rate is the percentage of the mass of missed carrots to the total mass of carrots after the operation. The measurement procedure is as follows: from the carrots held in each test plot, 3 plots are randomly selected, the total mass of missed carrots in the 3 plots is weighed, and the mass of all harvested carrots is calculated to calculate the leakage rate; the leakage rate calculation is shown in Formula (2).
(2)
Here, S2 is the high rate of missed uprooting, %; W2 is the mass of all harvested carrots, g; and W3 is the total mass of missed uprooted carrots, g, in the three plots.
3. Results
3.1. Influence of Clamping Conveyor on Damage Rate at Different Forward Speeds
Table 3 is the variance test table for the four test levels (T1, T2, T3, and CK). From the table, it can be seen that the four test levels and the forward speed are extremely significant, and at the same time, there is an interaction between the four test levels and the forward speed; the interaction of the four test levels and the forward speed is p = 0.003, which shows that the interaction between the test level and the forward speed has a significant impact on the test results, which proves the rationality and scientificity of this test.
Table 4 is the regression analysis table of T1, T2, T3, and CK experimental levels and different forward speeds. From the table, it can be seen that the non-standardized coefficient of experimental level is 1.199, which indicates that every unit change in experimental level may have an impact on carrot injury rate by 1.199 units, and the non-standardized coefficient of forward speed is 0.535, which indicates that every unit change in experimental level may have an impact on carrot injury rate by 0.535.
Figure 3 is the test result curve of the leakage rate of two kinds of carrots. From the figure, it can be seen that the damage rate of CK in the control group is stable at 81.2% to 91.9%. The reason for this damage rate is that the carrot stem block in the growth pit is damaged due to the collision between the carrot stem block and the mechanical parts (loosening mechanism, auxiliary loosening mechanism, etc.) below the test bed during the movement of the test bed. Figure 3 shows that under three kinds of clamping and conveying speeds (T1, T2, and T3), the change trend of the damage rate of two carrot varieties under the action of clamping and conveying devices is extremely consistent, with the average damage rates of Xiaohong2 being 6.13%, 3.53%, and 9.36% in two years, Sanhong being 6.22%, 3.76%, and 9.88% in two years, and Xiaohong being the same.
The significant difference in damage rate was caused by the different clamping and conveying speeds of T1, T2, and T3. Although the value of T2 was greater than T1, its clamping and conveying speed made the carrot have a stable strength of clamping and pulling out of the pit. The matching degree between the clamping and pulling strength of carrot tassels per unit time and the advancing speed of the machine is the highest, and the whole process of pulling and conveying is relatively coherent, so the average damage rate is the lowest. Under the condition of the T1 test, due to the low clamping and pulling speed, some carrot tassels are not clamped during the advancing process of the test bench, resulting in missed carrot stalks, and the mechanical parts below the test bench (scarifying mechanism, auxiliary scarifying mechanism, etc.) lead to the damage of carrot stalks in the growth pit, and at the same time, the carrot stalks in the pit mechanically collide with the scarifying mechanism and the auxiliary scarifying mechanism before leaving the pit, which leads to the damage of some carrot stalks, and then the damage rate of carrot stalks is increased. Under the condition of the T3 test, due to the high speed of clamping and pulling, more carrot tassels are clamped at the same time than in T2. During the progress of the test bench, some carrot tassels are not clamped in time, and the carrot stalks in the pit mechanically collide with the scarifying mechanism and the auxiliary scarifying mechanism before leaving the pit, which leads to damage to some carrot stalks, which will also increase the damage rate of carrot stalks. T3, on the other hand, has the fastest clamping and conveying speed, and the lowest matching degree between the clamping and pulling strength of carrot tassels per unit time and the forward speed of the machine, so its average damage rate is the highest. At the same time, this kind of control test law between the same variety and different varieties proves the scientific nature of the test arrangement.
3.2. Influence of Different Test Levels on Leakage Rate
Figure 4 shows the variation in the carrot pulling leakage rate of the two carrot varieties by different test treatments with the clamping and conveying speed during the test cycle. During the two years of the experiment, the average carrot leakage rate of Xiahong2 and Sanhong was 3.68% and 4.14%, respectively, and it can be seen in Figure 4 that the carrot leakage rate in the CK group of Xiahong2 and Sanhong was high and stable at 96.2% to 97.5% because there was no gripping and conveying device for carrying out the gripping and pulling process, and 3.8% to 2.5% of the carrots were pulled out due to the collision of the carrot plants with the mechanical parts (gripping and pulling mechanism, conveying mechanism, etc.) during the movement stroke before entering the gripping and conveying device, which resulted in carrots being out of the normal pit position. At the same time, the overall trend of the carrot leakage rate under different clamping and conveying speeds was similar for T1, T2, and T3 for the two carrot varieties, and this control test also proved the scientific and accurate experimental arrangement, with the average carrot leakage rate of T1, T2, and T3 for Xiahong2 being 3.91%, 3.42%, and 6.22%, and that of T1, T2, and T3 for Sanhong2 being 3.91, 3.42, and 6.22 percent. Sanhong had a high average carrot leakage rate of 4.06%, 3.58%, and 6.08%; therefore, the quality of carrot clamping and pulling was good to poor in the order of T2, T1, and T3. The reason may be that the matching degree between the conveying speed of T2 and the traveling speed of 1.0 m/s is higher, and the clamping and pulling are smoother, while the missed-pulling rate of T3 for two carrot varieties is significantly higher than that of T1 and T2. The possible reason may be that the clamping and pulling are too fast under T3 conditions, and some carrot tassels are not pulled in time, resulting in a higher missed-pulling rate.
3.3. Effects of Different Levels of Carrot Tassel Height on Injury Rate
Table 5 is the regression analysis table of the damage rate at different heights and different forward speeds. From the table, it can be seen that the VIF values at different heights and different forward speeds are all 1. Therefore, there is no serious multicollinearity problem between variables. The regression coefficients of the damage rate at different heights and different forward speeds are significant, among which the regression coefficient of the experimental level is −0.624, which shows that the height is negatively correlated with the damage rate, that is, the higher the height, the smaller the damage rate may be, and the regression coefficient of the forward speed is 2.336, which shows that the forward speed is positively correlated with the damage rate, that is, the higher the forward speed, the greater the damage rate.
Since the height of the carrot tassel has a significant impact on the clamping position of the clamping mechanism, as well as on the collision position of the carrot stem pieces with mechanical components such as the loosening mechanism, which in turn affects the damage of carrots, the height of the carrot tassel was tested according to the three kinds of short (carrot tassel height ≤ 22 cm) (H1 treatment), medium (22 < length < 42 cm) (H2 treatment), and tall (42 ≤ length ≤ 62 cm) (H3 treatment) carrots; from the test results, it can be seen that the test damage data have a clear distribution pattern. Figure 5 shows the distribution of damage rate under the conditions of H1, H2, and H3, showing that the distribution of the role of the damage rate of the H1, H2, and H3 conditions showed a clear consistency. For Xiahong2, considering the damage of the three types of carrots, short, medium, and high, the damage rate under the H1 test conditions was 5.12%, the damage rate under H2 test conditions was 4.73%, the damage rate under H3 test conditions was 6.19%, and the average weight ratio of damage for short, medium, and tall carrots was 2.9:3.2:5.4; for Sanhong, the damage of tassels of short, medium, and tall carrots after the H1 test was 5.69% under H2 test conditions, 5.24% under H2 test conditions, and 6.78% under the H3 test conditions, and the average weight ratio of the damaged carrot tassels of the three types of carrots, short, medium, and tall, was 2.8:3.1:5.9; for Sanhong, the distributional effects of H1, H2, and H3 on the damage rate at different clamping and conveying speeds showed obvious consistency, and the test showed that carrots with tassel heights ≤ 22 cm were more damaged. The reasons for this situation are as follows: Shorter carrots are not easy to clamp, so they easily fall off during the clamping process, and the carrots that fall off are damaged by the collision of the mechanical parts, while the carrots with a height of carrot tassel ranging from 22 to 42 cm are firmly clamped and not easily detached from the clamping device because the clamped position is just in the middle of the carrot tassel, and the carrot stem is not easily detached from the clamping device in the clamping parts and bottom loosening parts and the auxiliary parts. Between the clamping part and the bottom loosening part and auxiliary part, the carrot stem is not easily hit and not easily damaged, while the carrot tassel in the height range of 42~62 cm is also clamped firmly and not easily detached from the clamping device, but the size of the carrot stem block of this height tends to be larger, and the size of the carrot stem block is easily larger than the size of the space between the clamping part and the bottom loosening part and auxiliary part in the clamping process, so it is easily hit and easily damaged. The carrot stems are easily hit and easily damaged.
4. Discussion
At present, the carrot clamping and pulling operation is becoming one of the most important carrot clamping modes in China, the carrot damage and leakage rates during the operation of this mode directly affect and even determine the influence of this mode, so it is necessary to study different clamping and conveying devices for different carrot varieties at different clamping and conveying speed levels and under different speeds of damage, leakage rates, and degrees of broken carrots. It is of great theoretical and practical significance to improve the operational performance of carrot harvesting implements and select the best clamping and conveying device and the most suitable clamping and conveying speed conditions for each carrot variety, so as to improve and reduce the leakage rate. In this study, the T1, T2, T3, and CK clamping and conveying devices were used to test representative carrot varieties grown in large areas of China’s carrot-producing areas, with the aim of evaluating and comparing the quality and adaptability of different structural clamping and conveying devices for typical carrot varieties by assessing the carrot damage and leakage rates, and the resultant data showed that the quality of clamping and pulling was in the order of good to poor for T2, T1, T3, and CK.
In order to obtain the optimal design parameters of a carrot tassel pulling separation device to obtain the best separation effect, Zeng et al., 2018 established a kinematic model of a tassel pulling separation device and qualitatively analyzed the effects of the relevant parameters on the kinematic characteristics of the pulling rod [1]. A carrot tassel separation test bench was designed, and an orthogonal test of tassel separation was carried out. After analysis, it was found that the rotational speed of the pulling rod had the greatest influence on the separation effect of carrot tassels, and the angle between the pulling rod and the conveyor belt had a significant influence on the separation effect of carrot tassels; at the same time, we obtained the optimal parameter combination of the carrot tassel separating device: the rotational speed of the pulling rod was 200 r/min, and the linear speed of the conveyor belt was 1.2 m/s. The damage rate of this combination was 7.7%, while the average damage rate of the test stand in this paper was 3.53% for Xiahong2 in two years and 3.76% for Sanhong in two years under the 0.85 m/s kind of clamping conveyor speed. In terms of the effect of the damage rate, the difference between these two studies is large; the possible reason is that Zeng et al., 2018 increased the research on the rotating speed of the drawbar, but this parameter was not studied because there was no drawbar device on the test-bed in this study, but other components and structures are very similar, so the research results are highly comparable with our research [1].
In terms of carrot damage rate, Yao et al., 2023 tested the damage rate of white radish, and the test result was that the damage rate was less than 2.7% [15]. Although white radish was different from the carrots studied in this paper, the appearance characteristics and planting characteristics of white radish were very similar to those of carrots studied in this paper, and the average damage rate of Xiaohong2 in this paper was 3.53% under the clamping and conveying speed of 0.85 m/s. The average damage rate of Sanhong in two years was 3.76%. In terms of the damage rate effect, the results of the two studies are similar. From the structural point of view, the structure of the test bed studied in this paper is very similar to that of Yao et al., 2023, so the results of this study further confirm the accuracy of the research results of Yao et al., 2023 [15].
In terms of the leakage rate of carrots, Yao et al., 2023 conducted a field test on the white carrot combine harvester, and the test results showed that the whole machine had stable performance and that the leakage rate was less than 1.8% [15]. Although white carrots are different from the carrots studied in this paper, the operating principle of this white carrot combine harvester is different, and the appearance and planting characteristics of white carrots and the carrots studied in this paper are very similar, and the leakage rate is less than 1.8%, while the leakage rates of Xiahong2 and Sanhong carrots in this paper are 3.68% and 4.14%, respectively; the average leakage rate of Xiahong2 is 3.53% in two years under the clamping and conveying speed of 0.85 m/s, and the average leakage rate of Sanhong is 3.76% in two years, so the two studies are similar only in terms of the effect of leakage rate. Only in terms of the leakage rate effect, these two studies had similar results, and from the structure point of view, the test stand studied in this paper was very similar to the structure of the white radish combine harvester of Yao et al., 2023, so the results of this study further confirmed the accuracy of the findings of Yao et al., 2023 [15].
Li, 2020 conducted field tests on a carrot combine harvester, and the results of the field tests showed that the machine had good operational performance when the forward speed was 0.7 m/s. The test speed of the carrot test stand studied in this paper was 0.85 m/s, and these two test speeds were close to each other, and the leakage rate of the carrot combine harvester designed by Li, 2020 was a maximum of 3.6% and a minimum of 2.7%, and the leakage rates of this paper for the two varieties of carrots of Xiahong2 and Sanhong were 1.89% and 2.12%, respectively. The reason for the large difference is that the structure of the digging mechanism of the carrot combine harvester studied by Li, 2020 [16] has a larger operating area and greater digging resistance than that of the digging mechanism of this paper’s test stand, and such a structure may result in generating a higher pulling leakage rate [22].
This study has achieved certain experimental innovations; however, there are certain limitations, detailed as follows:
(1). Due to subjective and objective factors such as time and conditions, this study analyzed the damage rate and leakage rate of two varieties of carrots by setting up tests at T1, T2, T3, and CK clamping and conveying speed levels and 10 forward speed levels, focusing on the macroscopic point of view, and did not conduct in-depth research on the characteristics and laws of the movement of the carrot plant and carrots in the different clamping and conveying devices, which will be analyzed in the next step with the help of high-resolution high-speed photography. The next step is to study the motion characteristics and laws with the help of high-resolution high-speed photography.
(2). Due to the limitations of the research program and experimental conditions, the test objects in this paper are only two carrot varieties, and the changes in the breaking force of the stem pieces, the breaking force of the stem pieces and their mechanical properties with the speed of clamping and conveying, and the changes in the various parts of the stem pieces and the various components of the clamping and conveying device and the way of the force are not the same in different carrot varieties, so in subsequent experiments, we will carry out research on more carrot varieties, and explore the different characteristics of the clamping and conveying device in different carrot varieties, and then we will investigate the characteristics and laws of different carrot varieties. In a subsequent test, we will study more carrot varieties, explore the operation index law of various clamping and conveying devices in different carrot varieties under different clamping and conveying speeds, and find out the most suitable clamping and pulling and conveying speeds and clamping and conveying devices under the advancing speeds suitable for various carrot varieties.
5. Application Value and Suggestions
Based on the relevant data obtained in this study, the existing carrot harvesters with similar structures in this paper should first compare the growth and varieties of carrots with the plant physical characteristics, row spacing, and plant spacing of the two varieties of carrots studied in this paper. If they are the same or similar, they can be carried out under the conditions of clamping and conveying speed = 0.85 m/s and machine forward speed v = 1.0 m/s, which may effectively reduce the damage rate and leakage compared with before. If the growth height of the carrots to be harvested is much shorter than that of the two varieties of carrots studied in this paper, according to the research results of this paper, the shorter carrots easily fall during the clamping process, and the fallen carrots are damaged by the collision of mechanical parts. Therefore, it is necessary to install relevant auxiliary devices or adjust the relevant parameters of the clamping devices to ensure good clamping and reduce the loss rate. If the growth height of the carrot to be harvested is much higher than that of the plants of the two varieties studied in this paper, according to the research results of this paper, although the carrot is firmly clamped, it is not easily separated from the clamping device, but the size of the carrot stem block at this height is often large. In the clamping process, the size of the carrot stem block easily exceeds the space size between the clamping part, the scarifying part at the bottom, and the auxiliary part, and it is easily hit and damaged. Therefore, it is necessary to install relevant auxiliary anti-collision devices or increase the free space of carrots to reduce the loss rate.
6. Conclusions
Through the continuous tracking of three different forms of clamping conveyor devices on two carrot varieties at different clamping conveyor speed levels, this comparative experimental research was conducted to obtain different damage laws and carrot leakage laws, to solve the high damage rate and high leakage rate problems, and to provide a theoretical basis for carrot clamping conveyor performance optimization.
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(1). At the level of T1, T2 and T3, the effect of the change trend of the damage rate of the two carrot varieties at the clamping and conveying speed showed high consistency, the average damage rate of Xiahong2 in the two years was 6.13%, 3.53%, and 9.36%, and the average damage rate of Sanhong in the two years was 6.22%, 6.53% and 9.36%. The average damage rates were 6.13%, 3.53%, and 9.36% for Xiahong2 and 6.22%, 3.76%, and 9.88% for Sanhong.
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(2). The average carrot missed-pulling rate of two consecutive years corresponding to two carrot varieties, Xiaohong2 and Sanhong, was 3.68% and 4.14%, respectively. As can be seen from the figure, the carrot missed-pulling rate of the control group CK of two carrot varieties, Xiaohong2 and Sanhong, was high and stable at 96.2% to 97.5%. At the same time, T1, T2, and T3 have a similar overall carrot leakage rate trend for two carrot varieties at different clamping and conveying speeds. The average carrot leakage rate of T1, T2, and T3 for Xiahong2 is 3.91%, 3.42%, and 6.22%, and that of T1, T2, and T3 for Sanhong is 4.06%, 3.58%, and 6.08%.
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(3). The distributional effects of damage rates under the H1, H2, and H3 conditions showed obvious consistency. For Xiahong2, the damage of the three types of carrots, short, medium, and tall, after the T1 test was 5.12% under the H1 test condition, 4.73% under the H2 test condition, and 6.19% under the H3 test condition, and the average damaged weight ratio was 2.9:3.2:5.4; for Sanhong, the damage of three carrot types, short, medium, and tall, after the T1 test was 5.69% under the H1 test condition, 5.24% under the H2 test condition, and 6.78% under the H3 test condition, and the average damaged weight ratio of the three carrot types, short, medium, and tall, was 2.8:3.1:5.9; for Sanhong, the distributional effects of T1, T2, and T3 on its damage rate under different clamping and conveying speeds showed a clear consistency, and the test showed that carrot tassel heights ≤ 22 cm were more susceptible to being damaged.
Conceptualization, B.W. and F.G.; methodology, Z.H. and B.W.; software, B.W.; validation, B.W.; formal analysis, F.G.; investigation, F.W.; resources, F.G.; data curation, B.W.; writing—original draft preparation, B.W.; writing—review and editing, B.W.; visualization, F.G. and B.W.; supervision, F.G.; project administration, B.W.; funding acquisition, B.W. All authors have read and agreed to the published version of the manuscript.
Not applicable.
The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.
The authors would like to thank their teacher and supervisor for their advice and help during the experiments. We also appreciate the editor and anonymous reviewers for their valuable suggestions for improving this paper.
The authors declare no conflicts of interest.
Footnotes
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Enlarge this image.Figure 2. Test scene. (a) Measurement of carrot growth height; (b) clamping harvesting visual angle 1; (c) overlooking angle; (d) clamping harvesting perspective 2; (e) damaged carrots weighed; (f) missed carrots weighed.
Enlarge this image.Figure 2. Test scene. (a) Measurement of carrot growth height; (b) clamping harvesting visual angle 1; (c) overlooking angle; (d) clamping harvesting perspective 2; (e) damaged carrots weighed; (f) missed carrots weighed.
Enlarge this image.Figure 3. (a) Breakage rate of Xiahong2 in 2023; (b) breakage rate of Sanhong in 2023; (c) breakage rate of Xiahong2 in 2024; (d) breakage rate of Sanhong in 2024.
Enlarge this image.Figure 4. (a) Carrot leakage rate of Xiahong2 in 2023; (b) carrot leakage rate of Sanhong in 2023; (c) carrot leakage rate of Xiahong2 in 2024; (d) carrot leakage rate of Sanhong in 2024.
Enlarge this image.Figure 5. Distribution diagram of damage rate under H1, H2, and H3 conditions: (a) 2024 Xiahong2 damage rate under H1 conditions; (b) 2024 Xiahong2 damage rate under H2 conditions; (c) 2024 Xiahong2 damage rate under H3 conditions; (d) 2024 Sanhong damage rate under H1 conditions; (e) 2024 Sanhong damage rate under H2 conditions; (f) 2024 Sanhong damage rate under H3 conditions.
Soil physical property parameters.
| Statistical Indicators | Max | Min | Mean | Standard Deviation | Coefficient of Variation |
|---|---|---|---|---|---|
| Soil moisture content (%) | 29.32 | 23.85 | 25.12 | 0.29 | 0.01 |
| Soil hardness (kPa) | 1450.45 | 769.95 | 1118.02 | 180.85 | 0.16 |
| Soil Bulk Weight (g/cm3) | 1.35 | 1.10 | 1.21 | 0.08 | 0.06 |
Different level settings and corresponding environmental conditions.
| Level | Subdivision No. | Wind Speed/(m/s) | Relative Air Humidity/(%) | Air Temperature/(°C) |
|---|---|---|---|---|
| CK | 3 | 1.92 | 50% | 19.2 |
| 7 | 1.85 | 54% | 21.3 | |
| 9 | 2.36 | 52% | 22.0 | |
| T1 | 22 | 1.91 | 52% | 19.5 |
| 25 | 1.92 | 55% | 20.3 | |
| 4 | 2.01 | 51% | 20.5 | |
| T2 | 8 | 1.91 | 50% | 18.3 |
| 13 | 1.92 | 54% | 19.1 | |
| 11 | 2.01 | 53% | 20.5 | |
| T3 | 6 | 1.91 | 53% | 21.3 |
| 11 | 1.92 | 58% | 21.4 | |
| 2 | 2.01 | 52% | 21.5 |
Variance test table.
| Source | Sum of Squares | Freedom | Mean Square | F | p |
|---|---|---|---|---|---|
| Modified model | 510.394 | 29 | 17.600 | 26.445 | 0.000 |
| Intercept | 2996.832 | 1 | 2996.832 | 4503.038 | 0.000 |
| Experimental level | 204.554 | 2 | 102.277 | 153.682 | 0.000 |
| Speed of advance | 268.501 | 9 | 29.833 | 44.828 | 0.000 |
| Interaction between experimental level and forward speed | 37.339 | 18 | 2.074 | 3.117 | 0.003 |
| Error | 19.965 | 30 | 0.666 | ||
| Amount to | 3527.191 | 60 | |||
| Revised total | 530.359 | 59 |
Regression analysis table.
| Model | Non-Standardized Coefficient | Standardized Coefficient | t | p | 95.0% Confidence Interval | ||
|---|---|---|---|---|---|---|---|
| B | Standard Error | Beta | Lower Limit | Upper Limit | |||
| Experimental level grouping | 1.199 | 0.377 | 0.329 | 3.175 | 0.002 | 0.442 | 1.955 |
| Speed of advance | 0.535 | 0.107 | 0.517 | 4.987 | 0.000 | 0.320 | 0.750 |
Regression analysis table of damage rate of different height groups.
| Category | Coefficient of Regression | 95% CI | Collinear Diagnosis | |
|---|---|---|---|---|
| VIF | Tolerance | |||
| Constant | 4.159 *** | 3.186~5.132 | - | - |
| Height grouping | −0.624 * | −1.150~−0.097 | 1.000 | 1.000 |
| Speed of advance | 2.336 *** | 1.878~2.794 | 1.000 | 1.000 |
| R 2 | 0.649 | |||
| Adjust R2 | 0.636 | |||
| F | F (2,57) = 52.646, p = 0.000 | |||
| D-W | 1.701 | |||
Note: * p < 0.05, *** p < 0.001, F is F statistic, which is used to test the significance of the whole regression model.
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