Design and Test of a Single-Row Harvesting and Cutting Integrated Handheld Garlic Harvester

Abstract

The current situation in which garlic cultivation is non-homogeneous and modular cannot be adapted to combine harvester operations. In this paper, a single-row harvesting and cutting integrated handheld garlic harvester is designed, and the structure and working principle of the machine are described. By analyzing the mechanics of the machine mechanism, mechanics of the machine harvesting process, and design principle of the machine chassis, the key factors affecting the garlic harvesting machine wounding rate, leakage rate, and net harvesting rate were determined. According to the force and parametric analyses of the test results, it was determined that the machine had the best harvesting effect with a conveying speed of 0.6 m/s, prop speed of 125.6 r/min, digging angle of 15°~25°, forward speed of 0.8 m/s, clamping point height of 62.15 mm, and rollover threshold value of 0.89. Compared with the traditional garlic harvester, the garlic injury rate was 57.1% lower, the garlic leakage rate was 25% lower, and the net harvest rate was 4.0% higher, which meets the requirements of the garlic harvesting operation.

1. Introduction

Garlic is nutritious and edible, is an indispensable condiment and adjunct in everyday cooking and many dishes [1,2,3], and is a common spice with many health benefits [4,5]. Garlic contains allicin, the active component of garlic, which has been shown to have antibacterial and anti-inflammatory properties [6,7,8], and has been used for thousands of years as a food and for medicinal purposes [9,10]. As of 2021, China’s garlic cultivation area is 10.13 million mu and garlic production is 21.625 million tons [11], which make it the largest garlic cultivation country in the world. China ranks first in terms of garlic production and export volume [12,13]. There is a low level of mechanization of the whole garlic process in China; the mechanization level of garlic sowing and harvesting in China is less than 5% and 20% [14,15], respectively. The harvesting of garlic in China still involves manual digging, picking, and processing, resulting in high labor intensity and low harvesting efficiency, which limits the development of garlic cultivation in China [16]. Manual harvesting cannot meet the requirements of harvesting effectiveness, and it is an inevitable choice to mechanize harvesting in the main garlic growing areas in China, given the large area and wide range of garlic cultivation [17,18].

Foreign garlic harvester models are primarily garlic combine harvesters [19]. For example, J.J. BROCH developed an ARCO-4 garlic combine harvester in Spain. In addition, garlic combine harvesters have been developed by ERME in France, Asa-lift in Denmark, Dewulf in Belgium, and Yanmar in Japan [20,21]. Combined harvesting is important for reducing production losses, saving labor resources, and improving product competitiveness [22,23]. The garlic excavation, soil cleaning, transportation, straw cutting, and collection steps have been highly mechanized in Western European countries and Japan [24]. However, they are not suitable for the closed cropping pattern used in China, and foreign machines are too large and expensive for harvesting operations in domestic garlic cropping patterns [25,26]. China introduced the Japanese Yanmar H1Z garlic harvester in 2019 to fill the gap of mechanized garlic harvesting in Tianjin. The machine’s working efficiency of 0.47 mu/hour improved the operating efficiency by 12 times compared with manual, reduced production costs and labor intensity, and achieved good economic and social benefits [27].

Garlic grown in China is characterized by high straw, high planting density, and narrow row spacing (<20 cm) [28,29]. In China, Li Jinlei [30] and Cao Tokyo et al. studied the 4s-85 garlic harvester and found a 97.8% clear garlic rate, 0.5% damage rate, and 1668 m²/h productivity, and the technical performance met and exceeded the design index. Li X. [31] and Cui J. et al. studied the 4DS-40 garlic harvester. The loss rate and injury rate of garlic in operation were less than 1.5%, and the total operation time was 131 h, with two failures, a total time of 2.5 h for fault diagnosis and repair, and an average time between failures of 55.5 h. The reliability of use was 98%. Ding Anlan [32] and Peng Baoliang et al. studied the design of a machine vision-based automatic digging depth control system for garlic combine harvesters based on the principle of visual recognition and regulation, and Chaoyang Yu [25] and Ke Yang et al. studied the parameter optimization and simulation analysis of the floating root cutting mechanism of garlic harvesters based on the root cutting principle. In recent years, China has also developed the 4DBL-2 successively in combination with mature foreign technologies. Similarly, the 4DBL-2 semi-feeding self-propelled garlic combine harvester and 4S-85 full-feeding self-propelled garlic combine harvester have been developed in China, but they are generally in the prototype or pilot stage, and the quality, reliability, and economy of operation still need to be improved [33,34]. In complex harvesting environments such as mountains and hills, garlic harvesting at a low cost is defective.

In response to the above situation, a low-cost single-row harvesting and cutting integrated handheld garlic harvester was developed in the hills of central Shandong in this study to improve the low-cost harvesting of garlic in complex environments in China. This machine can accomplish modular and homogeneous harvesting in complex areas, such as hills, and improve the harvesting efficiency of garlic in hilly and complex areas. Compared with the existing machines, all the power of this machine is provided by a gasoline engine, and the output power of the gasoline engine is used for walking, cutting, clamping and conveying, which consumes less energy and helps to protect the environment.

2. Materials and Methods

2.1. Overall Structure and Working Principle of the Machine

2.1.1. Overall Structure of the Machine

The single-row harvesting and cutting integrated handheld garlic harvester as a whole is powered by a gasoline engine for each part of the structure, which can adapt to different soil environments for breaking, and integrates functions such as clamping, cutting, collecting, walking, and speed regulation. The single-row harvesting and cutting integrated handheld garlic harvester adopts the form of single-row harvesting, and the main structures are an (1) engine, (2) reduction box device, (3) clamping and transporting device, (4) restricting and cutting device, and (5) lifting and digging device. The overall mechanical model is shown in Figure 1.

2.1.2. Working Principle and Main Technical Parameters

The single-row harvesting and cutting integrated handheld garlic harvester adopts the process scheme of single-row harvesting, gathering and clamping, and cutting and harvesting. During field operation, the degree of soil loosening varies in different garlic planting environments, and the operator adjusts the height-adjustable soil-breaking mechanism according to the degree of soil loosening so that the digging shovel can be adjusted to a suitable height for digging garlic. The supporting gathering device can hold up the fallen garlic seedlings in the field so that the digging work can proceed normally. The cutting knife in the cutting and collecting system can cut the garlic on the chain to achieve the effect of separating the garlic seedlings and the garlic head. The garlic seedlings are transported to the rear end of the machine with the clamping chain, and the garlic head falls into the bottom collection box to complete the garlic harvesting process. The power of the gasoline engine is transmitted through the belt drive, and the clamping chain, cutting knife, and front-end power wheel are powered by one axis and multiple motions simultaneously. The speed of the cutting knife and front power wheel can be controlled by a speed reducer, which is equipped with four gears to meet the requirements of machine speed control during garlic harvesting.

The main technical parameters of the whole machine are shown in

Table 1. Main technical parameters of garlic harvester.

Parameter	Number
Dimensions (L × W × H)/(mm × mm × mm)	1100 × 550 × 970
Overall machine mass/kg	90
Mating engine power/kw	90
Calibrated engine speed/(r/min)	1440
Number of rows/row harvested	1
Working width/mm	500
Digging depth/mm	110
Breaking angle/°	0~60

.

A workflow diagram is shown in Figure 2.

2.2. Key Component Design

2.2.1. Height-Adjustable Groundbreaking Device

This makes it necessary to dismantle the shovel when it is not working to walk on the ground, which is time-consuming and uncertain. Height-adjustable breakers can adjust the height of the shovel and lock it to avoid the disassembly process, which is convenient for garlic farmers.

The soil-breaking device mainly includes the soil-breaking shovel and the related connection structure, which is connected to the shovel handle by the ratchet wheel on the same axis so that the shovel can be rotated around the handle up to 60°, and the height of the shovel can be adjusted by the rotation to adapt to different soil conditions. The shovel of the garlic harvester breaks the soil and digs the garlic from the garlic field, which is then picked up by the clamping and transporting device to complete the subsequent operation. The lifting principle of the soil-breaking device is to lock the shank to the desired position using a ratchet and snap. The ratchet wheel can be rotated by releasing the snap, and the ratchet wheel can rotate the shank to lift the shovel. In this structure, the ratchet and snap are the standard parts, and the most stressed part is the shank holder. The static stress, static displacement, and static strain analyses of the shank holder are shown in Figure 3.

The shank holder is made of 45-gauge steel, and its yield stress is 5.3 × 108 N/m². After the static stress analysis in SolidWorks, the maximum stress of the part appeared in the middle position of the mounting ratchet and snap, and its stress was 4.138 × 107 N/m². After the static displacement analysis in SolidWorks, the maximum static displacement of the part was 7.153 × 10⁻² mm in the position where the front end of the shank holder is connected to the ratchet and the snap. After the static strain analysis in SolidWorks, it was found that the maximum static strain of the part was 2.564 × 10⁻⁴ in the middle of the mounting ratchet and the snap. The static stress analysis, static displacement analysis, and static strain analysis all reasonably prove that the part meets the requirements for use in working conditions. The height-adjustable breaking device has the following three benefits: raising the shovel in the non-working condition, avoiding the disassembly process and improving the flexibility of the garlic harvester; the angle of the shovel blade can be adjusted, which can reduce the uneven force on the shovel and improve the self-cleaning ability of the shovel to ensure the shovel’s continuous and stable work; and adjusting the breaking angle of the shovel before the machine is used according to the local soil environment. The adjustment of the breaking angle can make the machine suitable for different soil environments, which can guarantee the removal of all garlic and improve the harvesting efficiency effectively, and solve the problem of existing garlic harvesters on the market being limited by soil problems.

2.2.2. Clamping Transport Device

The clamping and transportation device is located behind the height-adjustable soil-breaking device and carries out the chain drive by clamping the garlic seedlings, which eventually fulfills the function of transporting garlic to the limit cutting device. The power of the clamping chain is provided by the gasoline engine, and the power is delivered to the clamping chain for rotation by the belt, chain, and straight conical tooth drives. The clamping chain uses a four-part sharp-tooth chain to effectively hold the garlic seedlings, and each side of the chain is held in place by five four-part sprockets. Four of the quarter sprockets are fully fixed, and the other quarter sprocket can be adjusted to keep the quarter chain taut to ensure the efficiency of the clamping and transportation device [35]. The clamping and transporting device was designed with a 40° inclination angle, low in the front and high in the back, and the soil on the garlic was shaken off by the machine’s forward movement while clamping and transporting so that the garlic could be harvested more easily and cleanly. A specific three-dimensional structure is shown in Figure 4.

2.2.3. Gearing

Garlic harvesters on the market have multistage gearing, and because multistage gearing is very prone to failure, we decided to remove the complex multistage gearing. Instead, we replaced it with a gearbox that controls the speed of the garlic harvester, which can control the garlic harvester moving forward and backward with two gears: high and low. The control lever of the gearbox reached the armrest position, making it easier to operate.

The gearbox can roughly control the speed of the garlic harvester. The control makes the single-row harvesting and cutting integrated handheld garlic harvester run at three speeds: v₁ = 0.4 m/s, v₂ = 0.8 m/s, and v₃ = 1.2 m/s. There is also a control oil circuit device at the control handrail of the single-row harvesting and cutting integrated handheld garlic harvester that controls the amount of oil going in and out of the gasoline engine. The running speed of the garlic harvester can be finely controlled using this device. The above two devices can better control the operation of the garlic harvester and enable farmers to perform garlic harvesting better and increase its adaptability.

2.2.4. Material Selection of Commutation Seat in Power Unit

The commutation seat of the single-row harvesting and cutting integrated handheld garlic harvester is located on the right side of the gearbox structure, which is the mechanism that limits the fixed large gear, and the power exported through this mechanism can act on the limit cutting device to provide rotational power to the cutting knife. The power export structure includes two gears: a 2-mode 60-tooth pinion gear and a 2-mode 144-tooth large gear, which are fixed directly at the end of the output shaft on the right side of the gearbox, and the large gear is fixed on the reversing seat through 6204 bearings. The position of the reversing seat is adjusted so that the pinion and large gear can cooperate with each other, and the reversing seat is then fixed to the main beam and the supporting beam by welding. The ratio of the number of large and small gears is approximately 3:8, and the outer side of the large gear is fixed with a sprocket of 5 min and 40 teeth so that it can rotate at the same angular speed, thus driving the rotation of the large gear to the rotation of the sprocket and then driving the rotation of the chain to finally reach the limit cutting mechanism. Power transmission through the large and small gears achieves the second deceleration of power, effectively reducing the rotation speed of the cutting knife. The main working part of the commutation seat is its transverse protrusion, and it was determined that the commutation seat is made of 1045 steel through several simulation tests. The analysis of the commutation seat includes (a) static stress analysis; (b) static displacement analysis; (c) static strain analysis. The static stress analysis diagram of the commutation seat is shown in Figure 5.

The inner side of the commutation seat must withstand the torque of the 6204 bearing and the rotation of the 2-mode 144-tooth gear, and the outer side must withstand the torque of the 6204 bearing and the rotation of the 5 min 40-tooth sprocket. The material analysis of the 1045 steel, which constitutes the commutation seat, is shown in

Table 2. 1045 steel quality analysis.

Parameter	Number
Elastic modulus/(N/m2)	2.1 × 1011
Poisson’s ratio	0.269
Mass density/(kg/m3)	7.85 × 103
Tensile strength/(N/m2)	6.25 × 108
Yield strength/(N/m2)	5.3 × 108
Thermal conductivity/(W/(m·k))	49.8
Specific heat/(J/(m·k))	486
Normalizing/(°C)	850
Quench/(°C)	840
Tempering/(°C)	600

.

Finally, after the field test, the whole machine of the single-row harvesting and cutting integrated handheld garlic harvester is in good running condition, and the simulation effect and data show that the garlic harvester meets the agronomic requirements of garlic harvesting.

The limit cutting device is powered by a gasoline engine. The limit cutting knife of the limit cutter also has a trapezoidal design, which has a sharper blade to cut garlic. The cut garlic heads fall into the collection box and the garlic rods are transported to the back end of the garlic harvester by the clamping device. This is more convenient.

2.3. Analysis of Garlic Harvester Dynamics

2.3.1. Analysis of Groundbreaking Device Dynamics

In the process of breaking the soil with the groundbreaking device, the shovel was subjected to more forces from the soil. To ensure that the shovel could withstand sufficient force to complete the breaking work, the researchers conducted a force analysis to determine the direction and magnitude of the force on the shovel during operation, drew a force diagram, and established a force balance equation, as shown in Figure 6.

Figure 6. Sketch of the force on the breaking shovel.

Figure 6. Sketch of the force on the breaking shovel.

$$F=F_1+F_N+G+F_2+F_3$$

(1)

where:

$F$—driving force provided by the soil-breaking shovel.

$F_1$—thrust of the lower soil layer on the breaking shovel (perpendicular to the lower shovel surface).

$F_2$—pressure of the upper soil layer on the breaking shovel (perpendicular to the lower shovel surface).

$F_3$—combined force of accelerating resistance and viscous force of the soil to which the soil-breaking shovel is subjected.

$G$—gravitational force on the soil-breaking shovel.

$F_N$—support force of soil on shovel.

F is the adhesion force between the soil and shovel, F_f is the acceleration resistance of the soil to the shovel, and T is the soil shear resistance.

To solve the resistance generated between the surface of the workpiece of the single-row harvesting and cutting integrated handheld garlic harvester excavating shovel and the land, it is calculated that approximately 60% of the traction power of the engine must be consumed. The acceleration resistance Ff of the soil to the breaking shovel is typically calculated using the following formula [35]:

$$F_f=f·F_N=0.6\times 1500=900 \mathrm{N}$$

(2)

The rest of the resistance combined is about 2000 N.

The output torque of the engine power to the tires is

$$T=\frac{9550P}{n}\times ni\times 60\%=\frac{9550\times 4}{3600}\times 135.5\times 60\%=862.68 \mathrm{N}\text{·}\mathrm{m}$$

(3)

Then, the driving force of the tire is

$$F=\frac{T}{r}=\frac{862.68}{0.27}=3.2>2.9 \mathrm{kN}$$

(4)

It can be seen that the power of the engine can meet the requirements of the garlic harvester for normal use.

2.3.2. Clamping Mechanism Dynamics Analysis

Through this research, we know that the height of mature garlic seedlings is 600 mm, the part clamped by the clamping point in the holding device is the white part of the garlic, and the height distance of garlic white from the head of the garlic is 100–150 mm, so the height of the clamping point of the clamping chain of the machine from the ground should be within this range. The height of the clamping point from the ground was 120 mm, the inclination angle α between the main frame and the ground was 40°, and the corresponding mechanical structure is shown in Figure 7.

The height h of the end of the holding chain from the ground can be obtained as follows:

$$h=H-(D+\frac{d}{2})·\sin \alpha$$

(5)

where:

h—height of the end of the holding chain from the ground (mm).

D—vertical distance between the sprocket and the sprocket axis (mm) can be easily derived as 60 mm from the installation position and the size of the frame.

d—diameter of the small sprocket (mm); diameter of 60 mm when the standard part is selected.

α—angle of inclination of the frame to the ground (°).

All parameters were substituted to derive the height of the clamping point from ground h = 62.5 mm.

The power of the clamping chain is provided by the gasoline engine, which can realize the integrated control of clamping, transportation, cutting, and walking through the adjustment of the gearbox. The running speed of the clamping chain is controlled by the gearbox, and the linear speed of the transport chain is constrained by the running speed of the garlic harvester, the speed of the limit cutting knife, the size of the diameter of the transport chain sprocket, and other important parameters. A reasonable linear speed is the basis for the coordinated and stable operation of all mechanisms of the garlic harvester and the key to the realization of each function. The relevant design and calculations are as follows.

Through the power provided by the gasoline engine and the adjustment of the gearbox and gear transmission, the running speed of the single-row harvesting and cutting integrated handheld garlic harvester was clarified to be v₁ = 0.4 m/s, v₂ = 0.8 m/s, and v₃ = 1.2 m/s speed gears, respectively. After analysis and testing, the optimal running speed of the garlic harvester was measured as v₂ = 0.8 m/s, and the planting spacing of garlic was derived from field investigation and research as D. By calculation, the time interval between two clamps of the transport chain of the garlic harvester to the garlic can be calculated.

$$t_1=\frac{d}{v_2}=\frac{0.15}{0.8}s=0.1875 \mathrm{s}$$

(6)

To ensure the good operation and cutting effect of the garlic seedling limit cutting mechanism, the spacing of garlic on the transport chain d₁ > 120 mm was used, and to ensure the quality of harvesting, the ideal linear speed of the transport chain with spacing d₁ = 140 mm was used:

$$v_1=\frac{d_1}{t_1}=\frac{0.14}{0.1875}=0.747 \mathrm{m}/\mathrm{s}$$

(7)

Before the garlic is transported to the clamping and transportation unit, it passes through the gathering device, which collects the fallen garlic and brings it together, ensuring that all garlic can enter the clamping mechanism. At the end of the clamping and transporting device, the sheared garlic heads were dropped into the collection box below, whereas the garlic seedlings were transported with the transport chain to the end of the garlic harvester and then dropped on both sides of the garlic row without affecting the movement of people.

2.4. Orthogonal Analysis Method

2.4.1. Test Conditions and Methods

At the beginning of the design of the mechanical structure of each part of the machine, modeling and simulation analyses were conducted using 3D software to select the best and most stable solution in terms of the operating conditions. Based on the preliminary investigation and design calculation data, the garlic field environment during garlic harvesting was designed and the garlic harvester was simulated, then the deficiencies and unreasonable parts of the design were corrected and optimized during the test. The final model of the whole garlic harvester was determined, the machine was processed and assembled according to the drawings, and the prototype was finally trial-produced.

The machine was initially designed using 3D software to complete the model construction, followed by simulation tests, machine processing after the completion of the simulation tests, and field tests after the completion of the processing. This section focuses on the overall design test process for the single-row harvesting and cutting integrated handheld garlic harvester. The machine was modeled and simulated in March 2022 and processed, fabricated, and tested in May and June. The experimental sites were located in a garlic plantation near Liaocheng City Changwu Machinery Factory and in the garlic plantation of Liaocheng University. The technical indicators derived from the measurements of the local garlic and field soil are shown in

Table 3. Physical characteristics and soil conditions of garlic in the experimental field.

Physical Parameters	Numerical Value
Garlic plant height/mm	200–300
Bulb depth/mm	50–80
Spacing/mm	150
Soil water content/%	450
Soil firmness/(kN/mm)	7.8 × 10−2
Row spacing/mm	220

.

This machine is capable of breaking, clamping, shearing, and collecting garlic and can meet all the needs of garlic harvesting. The process of the garlic harvester field test and the garlic status are shown in Figure 8.

2.4.2. Experimental Factors and Index Selection

Combined with the theoretical analysis, the conveying speed, tool rotation speed, breaking angle, and forward speed, which affect the quality of garlic harvesting, were selected as test factors, and the injury rate, leakage rate, and net harvesting rate, which affect the practical value of garlic, were selected as test evaluation indexes. The garlic flesh or bulb inner skin is damaged, the garlic left in the field is the missed digging, and the garlic harvested intact is the net harvest. The garlic injury rate is the ratio of the number of damaged garlic plants to the total number of garlic plants, the missed digging rate is the ratio of the number of missed garlic plants to the total number of garlic plants, and the net harvest rate is the ratio of the number of fully harvested garlic plants to the total number of garlic plants.

2.4.3. Orthogonal Experimental Design

Based on the actual operation of a single-row harvesting and cutting integrated handheld garlic harvester, the experimental design was carried out using the Box–Behnken central combination experimental method with the experimental factors coded as shown in

Table 4. Experimental factors.

Code Value	Influencing Factors
	Conveying Speed x1/(m/s)	Tool Speed x2/(r/min)	Groundbreaking Angle x3/(°)	Forward Speed x4/(m/s)
−1	0.50	120	15	0.4
0	0.75	130	20	0.8
1	1.00	140	25	1.2

. Thirty garlic plants were randomly selected for field harvesting trials in each group, in which the height of the garlic plants was 200–300 mm, the depth of the bulbs was 50–80 mm, the distance between plants was 120 mm, and the distance between rows was 220 mm.

2.4.4. Orthogonal Test Results

According to the actual field operation requirements, the wounding rate y1, leakage digging rate y2, and net harvesting rate y3 were determined as the performance indexes of the experiment. The conveying speed x1, tool speed x2, breaking angle x3, and forward speed x4 were used as the influencing factors for the experimental study. The experimental release cases and results are shown in

Table 5. Experimental protocol and results.

Serial Number	Influencing Factors				Performance Indicators
	x1/(m/s)	x2/(r/min)	x3/(°)	x4/(m/s)	y1/%	y2/%	y3/%
1	0.5	130	20	0.4	0.468	1.118	93.447
2	0.5	140	20	0.8	0.489	1.155	93.781
3	0.5	120	20	0.8	0.486	1.08	94.2
4	0.5	130	15	0.8	0.524	1.087	92.526
5	0.5	130	20	1.2	0.52	1.116	94.534
6	0.5	130	25	0.8	0.514	1.147	95.455
7	0.75	130	20	0.8	0.501	1.166	94.437
8	0.75	130	20	0.8	0.502	1.166	94.437
9	0.75	130	20	0.8	0.502	1.166	94.437
10	0.75	130	15	0.4	0.542	1.136	92.43
11	0.75	120	20	0.4	0.493	1.129	94.103
12	0.75	130	20	0.8	0.5	1.166	94.437
13	0.75	130	15	1.2	0.576	1.135	93.516
14	0.75	120	15	0.8	0.549	1.098	93.182
15	0.75	130	25	0.4	0.493	1.196	95.358
16	0.75	140	25	0.8	0.563	1.16	96.524
17	0.75	140	20	1.2	0.556	1.202	94.771
18	0.75	130	25	1.2	0.58	1.195	96.445
19	0.75	120	25	0.8	0.561	1.158	96.111
20	0.75	140	15	0.8	0.548	1.173	92.764
21	0.75	130	20	0.8	0.502	1.166	94.437
22	0.75	120	20	1.2	0.548	1.127	95.19
23	0.75	140	20	0.4	0.491	1.204	93.685
24	1	130	25	0.8	0.598	1.244	96.348
25	1	120	20	0.8	0.558	1.176	95.093

.

2.4.5. Regression Modeling and Significance Testing

Multiple linear regressions and quadratic terms were fitted to the garlic harvester injury rate y1, missed digging rate y2, and net harvest rate y3 using Design-Expert software (

Table 6. Regression equation analysis of variance for garlic injury rate.

Source	Sum of Square	Df	Mean Square	F-Value	p-Value
Model	0.0382	14	0.0027	34.04	<0.0001	significant
A: Conveying speed	0.0173	1	0.0173	215.97	<0.0001
B: Tool speed	0.0000	1	0.0000	0.1755	0.6816
C: Groundbreaking angle	0.0001	1	0.0001	0.6491	0.4339
D: Forward	0.0092	1	0.0092	114.48	<0.0001
AB	0.0000	1	0.0000	0.0000	1.0000
AC	0.0000	1	0.0000	0.0000	0.4800
AD	0.0000	1	0.0000	0.0000	0.4800
BC	2.25 × 10−6	1	2.25 × 10−6	8.39	0.8694
BD	0.0000	1	0.0000	0.0000	0.5855
CD	0.0007	1	0.0007	0.0000	0.0104
A2	0.0018	1	0.0018	0.3185	0.0003
B2	0.0006	1	0.0006	1.64	0.0149
C2	0.0103	1	0.0103	1.64	<0.0001
D2	0.0008	1	0.0008	0.3185	0.0079

), and the quadratic regression equations for P1, P2, and P3, respectively, were obtained as

$$P1=0.5014+0.038\times A+0.0277\times D+0.0133\times CD+0.0166\times A^2+0.0398\times C^2+0.0109\times D^2$$

(8)

$$P2=1.17+0.0483\times A+0.0314\times B+0.0239\times C-0.0182\times BC-0.0063\times B^2-0.0063\times C^2$$

(9)

$$P3=94.44+0.4467\times A-0.1399\times B+1.53\times C+0.5433\times D+0.2078\times BC+0.0695\times B^2+0.0695\times C^2$$

(10)

Analysis of variance simulations of the regression equation using Design-Expert software yielded a table. From Table 6, it can be seen that the p < 0.0001 quadratic regression model for the injury rate of the single-row harvesting and cutting integrated handheld garlic harvester indicates that the regression model is highly significant. The analysis of variance showed that the conveying speed had a highly significant effect on the wounded garlic rate (p < 0.0001), and the forward speed had a significant effect on the wounded garlic rate (p < 0.0001). The CD interaction term p < 0.05, indicating a significant effect, proves that the breaking angle and forward speed have an interactive effect on the missed digging rate.

As shown in

Table 7. Analysis of variance for the regression equation of leakage digging rate.

Source	Sum of Square	Df	Mean Square	F-Value	p-Value
Model	0.0488	14	0.0488	21.96	<0.0001	significant
A: Conveying speed	0.0280	1	0.0280	176.65	<0.0001
B: Tool speed	0.0118	1	0.0118	74.63	<0.0001
C: Groundbreaking angle	0.0069	1	0.0069	43.25	<0.0001
D: Forward	8.333 × 10−6	1	8.3 × 10−6	0.0525	0.8221
AB	0.0000	1	0.0000	0.0000	1.0000
AC	0.0000	1	0.0000	0.0000	1.0000
AD	0.0000	1	0.0000	0.0000	1.0000
BC	0.0013	1	0.0000	8.39	0.0117
BD	0.0000	1	0.0000	0.0000	1.0000
CD	0.0000	1	0.0000	0.0000	1.0000
A2	0.0001	1	0.0001	0.3185	0.5814
B2	0.0003	1	0.0003	1.64	0.2212
C2	0.0003	1	0.0003	1.64	0.2212
D2	0.0001	1	0.0001	0.3185	0.5814

, the p < 0.0001 quadratic regression model for leakage digging of the single-row harvesting and cutting integrated handheld garlic harvester indicates that the regression model is highly significant. The analysis of variance shows that the conveying speed p < 0.0001, which indicates that the conveying speed has a significant effect on the leakage digging rate, the tool speed p < 0.0001, indicating that the tool speed has a highly significant effect on the leakage digging rate, the breaking angle p < 0.0001, which indicates that the breaking angle has a highly significant effect on the leakage digging rate, and the forward speed p < 0.0001, which indicates that the forward speed has a highly significant effect on the leakage digging rate. The BC interaction term p < 0.05, indicating a significant effect, proving that there is an interactive effect of tool speed and breaking angle on the leakage rate.

From

Table 8. Analysis of variance of the net harvest rate regression equation.

Source	Sum of Square	Df	Mean Square	F-Value	p-Value
Model	34.66	14	2.48	120.16	<0.0001	significant
A: Conveying speed	2.40	1	2.40	116.25	<0.0001
B: Tool speed	0.2349	1	0.2349	11.40	0.0045
C: Groundbreaking angle	28.22	1	28.22	1369.90	<0.0001
D: Forward	3.54	1	3.54	171.90	<0.0001
AB	2.500 × 10−7	1	2.500 × 10−7	0.0000	0.9973
AC	2.500 × 10−7	1	2.500 × 10−7	0.0000	0.9973
AD	2.500 × 10−7	1	2.500 × 10−7	0.0000	0.9973
BC	0.1726	1	0.1726	8.38	0.011
BD	2.500 × 10−7	1	2.500 × 10−7	0.0000	0.9973
CD	2.500 × 10−7	1	2.500 × 10−7	0.0000	0.9973
A2	0.0077	1	0.0077	0.3185	0.549
B2	0.0313	1	0.0313	1.52	0.2381
C2	0.0313	1	0.0313	1.52	0.2381
D2	0.0077	1	0.0077	0.3757	0.5498

, it can be seen that the p < 0.0001 quadratic regression model for the net harvest rate of the single-row harvesting and cutting integrated handheld garlic harvester indicated that the regression model was highly significant. The analysis of variance shows that the conveying speed p < 0.0001, indicating that the conveying speed has a highly significant effect on the net harvesting rate; groundbreaking angle p < 0.0001, indicating that the breaking angle has a highly significant effect on the net harvesting rate; forward speed p < 0.0001, indicating that the forward speed has a highly significant effect on the net harvesting rate; and tool speed p < 0.05, indicating that the tool speed has a significant effect on the net harvesting rate. The BC interaction term p < 0.05, indicating a significant effect, proves that there is an interactive effect of the tool speed and breaking angle on the missed digging rate.

3. Results

3.1. Sideswipe Threshold Analysis Results

The single-row harvesting and cutting integrated handheld garlic harvester works in a field with a rugged road surface and complex road conditions. To ensure that the garlic harvester can operate normally, it must be analyzed for rollover. The analysis was carried out considering the low operating speed of the machine, ignoring the operating speed of the machine as well as the elastic deformation of the tires, and assuming it to be an ideal form for the analysis of the machine.

It is now assumed that the machine travels in a field where a raised stone makes the wheel landing point at an angle to the ground, a simplified diagram of which is shown in Figure 9.

The angle generated between the landing point of the wheels and ground was α. Now, assume that this angle is small and can be considered sinα ≈ α and cosα ≈ 1. The black dot in the figure is the center of mass of the machine, and the calculation equations are derived from the automobile theory as follows:

$${ma}_y{h}_g-mg\alpha h_g+F_{Zi}B-\frac{1}{2}mgB=0$$

(11)

$$\frac{a_y}{g}=\frac{\frac{1}{2}B+\alpha h_g-\frac{F_{Zi}}{mg}B}{h_g}=\left(\frac{1}{2}-\frac{F_{Zi}}{mg}\right)\frac{B}{h_g}+\alpha$$

(12)

On a horizontal road, the two wheels share the gravitational force of the vehicle mg equally. The horizontal road α = 0 and a_y = 0, and the vertical reaction force on the inside of the wheel in contact with the ground is F_Zi = mg/2. When encountering a protruding stone in a horizontal field, α increases instantaneously and F_Zi decreases when a_y increases. When F_Zi decreases to zero, the machine cannot maintain its original equilibrium, and rollover occurs.

The conclusion from the test above is that when the slope is 0°, the threshold value of the rollover is B/h_g. The center distance between the two wheels, B = 400 mm, h_g = 450 mm, is measured by calculating the threshold value B/h_g = 400/450 ≈ 0.89. By checking the data, we found that the rollover threshold value of a car is 1.1~1.6, that of a passenger and cargo vehicle is 0.8~1.1, and that of a medium-sized truck is 0.6~0.8. The rollover threshold value of this machine is moderate, which ensures the stability of the machine.

3.2. Orthogonal Test Results

Solution optimization analysis was carried out using Design-Expert software after determining the conditions affecting the factors: 0.5 ≤ x1 ≤ 1 m/s, 120 r/min ≤ x2 ≤ 140 r/min, 15° ≤ x3 ≤ 25°, 0.4 m/s ≤ x4 ≤ 1.2 m/s. The analysis resulted in the optimal solution, i.e., the average diameter at conveying speed is 0.6 m/s, the tool speed is 125.6 r/min, the breaking angle is 19.2°, the forward speed is 0.9 m/s, the height of the clamping point from the ground is 62.15 mm, and the side-turning threshold is 0.89, the optimal solution is reached when the garlic harvester’s injury rate y1 is 0.495%, the leakage rate y2 is 1.122%, and the net harvest rate y3 is 94.163%. Taking the values at this point as the standard values, as the values change under the interaction in the response surface analysis, the response surface under the influence of each interaction can be derived, as shown in Figure 10.

From the response surface analysis in the above figure, it can be seen that the variation pattern of the factor-influenced response surface is consistent with the model and the analysis of variance results of the regression equation. The final tri-optimal index of the machine, that is, the garlic injury rate y1 of 0.495%, missed digging rate y2 of 1.122%, and net harvest rate y3 of 94.163%, was also derived.

The test methods validated in the field trials were consistent with those described in Section 3.2. The comparison test results are listed in

Table 9. Comparison test results.

Serial Number	Single-Row Harvesting and Cutting Integrated Handheld Garlic Harvester
	Garlic Injury Rate/%	Leakage Rate/%	Net Garlic Collection Rate/%
1	0.497	1.116	94.066
2	0.479	1.124	93.893
3	0.492	1.098	94.281
4	0.526	1.077	93.894
5	0.481	1.195	94.681
Average value	0.495	1.122	94.163

.

From Table 9, it can be seen that the single-row harvesting and cutting integrated handheld garlic harvester had an injury rate of 0.495%, a leakage rate of 1.122%, and a net harvest rate of 94.163%, which is 57.1% lower in injury rate, 25% lower in leakage rate, and 4.0% higher in net harvest rate than the conventional garlic harvester and can meet the needs of garlic harvesting operations.

4. Discussion

This single-row harvesting and cutting integrated handheld garlic harvester was designed based on model design, simulation experiments, and the completion of trial of key parts. To compare with manual garlic harvesting, manual garlic harvesting can only harvest 0.3 mu per day according to 12 h of work per day, but this machine can harvest 9 mu per day; the cost of manual garlic harvesting is about 1800 CNY/mu, and the cost of machine operation is about 800 CNY/mu, that is, the efficiency of this machine is 30 times of manual harvesting, the cost saving is about 1000 CNY/mu, and this machine only needs one person for operation can be completed, saving on labor at the same time as reducing costs.

Compared with the Japanese Yanmar H1Z garlic harvester, the working efficiency of the H1Z machine is 0.47 mu/hour and the working efficiency of this machine is 0.75 mu/hour, i.e., the working efficiency of this machine is faster.

Compared with the domestic 4S-6 machine, the garlic injury rate of the 4S-6 machine is 0.98%, the digging leakage rate is 1.52%, and the net harvesting rate is 92.96%, while the garlic injury rate of this machine is 0.562%, the digging leakage rate is 1.224%, and the net harvesting rate is 95.239%. In the same harvesting environment, this machine can ensure garlic harvesting efficiency to meet the requirements of the garlic harvesting operation.

5. Conclusions

In this paper, a single-row harvesting and cutting integrated handheld garlic harvester is proposed and studied based on the current situation of non-homogeneous and modular garlic cultivation in China. Its structure is mainly composed of an adjustable-height soil-breaking mechanism, a one-shaft multi-moving speed control mechanism, a multi-stage gear transmission mechanism, and an integrated harvesting and cutting mechanism. The adaptability of the soil-breaking device to different soil environments was studied using finite element simulations. The results showed that the soil-breaking device can operate on soils in different environments. The rollover threshold of the machine was investigated using rollover analysis. The results show that a rollover threshold of 0.89 can ensure the stability of the operation of the machine. Through orthogonal test analysis, the conveying speed, tool speed, rotation angle, and forward speed were used as the influencing factors for the experimental study, and the wounding rate, leakage digging rate, and net harvesting rate were determined as the experimental performance indices. The four-factor three-level quadratic term fitting and solution analysis of Design-Expert determined that the wounding rate of this machine was 0.495%, leakage cutting rate was 1.122%, and net harvest rate was 94.163%. Compared to the conventional garlic harvester, the wounded garlic rate was reduced by 51.2%, the missed cut rate was reduced by 18.2%, and the net harvest rate was increased by 5.1%, meeting the requirements of garlic harvesting operations.