Experiment and Analysis of Film-Soil Separation Motion Characteristics of a Chain Drive Residual Film Recovery Mechanism for the Tillage Layer

Abstract

The working principle and key components of a chain drive residual film recovery machine were studied. A kinematic analysis of the chain drive soil separation mechanism was completed by applying ADAMS software to obtain the trajectory, displacement, velocity and acceleration of the center of mass of the chain plate link_1 in the x- and y-directions within the effective shaking displacement. A field test of the chain drive separation mechanism was carried out. When the shaking roller was in contact with the chain, the change in speed of the chain in the x- and y-directions was not significant, but the force in the y-direction was conducive to breaking the soil pieces and improving the rate of collecting the residual film. The change in the speed of link_1 in the y-direction speed with x-direction speed explained the action of the separation mechanism on conveying and throwing of the film-soil mixture in the horizontal and vertical directions, which revealed the mechanism of the chain drive film-soil separation equipment. The field test showed that the film collection rate of the chain drive separation mechanism was 68%, and the surface residue was 6%. The test results meet the relevant national and industry standards and design requirements. The results of this study provide guidance for the design and optimization of chain drive film-soil separation equipment.

1. Introduction

Mulch has been widely used in the cultivation of cotton, peanut, and corn crops because of its significant effects on soil warming, moisture retention, soil structure maintenance, and weed growth inhibition [1,2]. Mulch is a polyethylene hydrocarbon organic polymer compound, which is extremely difficult to degrade under natural conditions and can remain in the soil for 200–400 years. A large amount of mulch is buried in the soil tillage layer and, over time, the amount of mulch residue increases, reducing soil quality, affecting crop growth and even death [3,4,5,6], resulting in lower crop yields and reduced farm income, and also causing serious “white pollution” to the agroecological environment. In addition, the buried residual film decomposes into fine particles in the soil, polluting groundwater and seriously threatening human health, so it is urgent to study the problem of residual film pollution in the cultivated layer.

Mulching technology is widely used in countries such as the United States and Japan, which started to develop mulch-back machinery in the early 1960s with the use of a mulch thickness of ≥ 0.02 mm, high tensile strength of the mulch, ease of mechanical recovery, and high recovery rate [7,8,9]. In addition, these countries have made important progress in research on biodegradable mulch, so there is less deep burial of soil tillage mulch and less serious pollution. The thickness of the mulch used in China is 0.008 mm and its tensile strength is lower, resulting in incomplete recycling of the mulch, causing a large amount of mulch to be buried in the soil layer and causing serious “white pollution” to the agro-ecological environment. In China, there are some areas where the problem of residual film pollution is particularly prominent, with the average amount of residual film on farmland being about 206.46 kg/hm² and the average value of residual film in some seriously polluted areas exceeding 275.63 kg/hm², which far exceeds the limit value for residual film on farmland (GB/T 25413-2010) of the the limit value of 75 kg/hm² in GB/T 25413-2010 [10]. Therefore, the research focus of tillage layer residual film recycling machinery is concentrated in China. Due to the differentiation of the residual film, the tensile property is reduced and easily broken, and it is mixed with crop roots, stems and soil after tillage operations, which makes mechanized recovery difficult and seriously restricts the pollution management of the residual film in the farmland tillage layer.

In response to the problem of residual film pollution in agricultural fields, research institutes, universities and enterprises have conducted a lot of research and developed hundreds of residual film recycling machines. According to the working principle, these residual film recovery machines can be classified as pop-tine, nail-tine, clamping, chain-tine, and telescopic rod-tine machines [6,11,12,13]. At present, machines suitable for residual film recovery in the tillage layer mainly include the rotating tillage tine residual film recovery machine researched by Zhang et al. (2018), which can recover residual film at 150 mm depth in the tillage layer [14,15]; however, the residual film easily accumulates on the tines, and the unloading effect is not ideal. Jin et al. researched an automatic unloading residual film recovery machine with an operating depth of 80 mm [16], but it does not reach the operating depth needed for residual film recovery in the tillage layer. Shi et al. analyzed the motion of nail tines gathering residual film, the critical speed of collecting residual film and the effective picking area [17]. Zhen researched and designed a comb tine tillage machine for the recovery of residual film and optimized the operating parameters, but the performance of film gathering and film-soil separation was unstable due to the complex soil environment and considerable fragmentation of residual film [18]. The average gathering rate in field tests was 55.04% [19,20], and the collecting effectiveness was low. The Zhang team developed a chain drive tillage machine for residual film recycling that can recover residual film buried 150 mm deep in tillage and which is suitable for recycling residual film before spring sowing after tillage [21,22,23]. The quality of the tillage operation and the operating parameters of chain driven tines have a great influence on the performance of film-soil separation, which causes the problem of difficult separation of soil and residual film. Zhang et al. (2019a) studied a chain-driven harrow tillage machine for residual film recovery, which can crush, loosen and turn soil in the tillage layer to a depth of 150 mm by using a mechanism for loosening and turning deep soil and complete the residual film collection operation to tillage depths of 80–100 mm [24,25].

The chain drive mechanism for residual film recovery is more widely used in research of tillage machinery for recovery of layers of residual film, and it has been more widely used in conveyors in machines for the recovery of surface layers of residual film and residual film balers [26,27]. At present, research on chain drive residual film recovery mechanisms mainly focuses on structural design, force analysis of popping teeth on residual films, and experimental research on field operation performance. Li studied the key mechanism and parameters of a chain drive rake-type residual film recovery machine and analyzed the operating speed characteristics of chain drive rakes using ADAMS software; however, the study used a belt drive instead of a chain drive, which failed to reflect the jitter characteristics of chain drive movement [28]. Present studies of the chain drive residual film recovery mechanism do not provide a theoretical analysis of the separation mechanism in the film-soil separation process and, in particular, they do not include an analytical study of the jitter characteristics of the chain drive mechanism.

To this end, by analyzing the motion characteristics of the film shovel and the tines of a chain drive soil-separation mechanism and studying the shaking characteristics of the mechanism with ADAMS software, we provide a theoretical reference and technical basis for further research on tillage film recovery machines.

2. Machine Structure and Working Principle

2.1. Machine Structure

The chain drive tillage machine with tines for residual film recovery consists of a frame, shovel, chain drive tine mechanism for film and soil separation, shaking roller, spring teeth, support wheel, secondary film and soil separation device, and film box, among other components. Its structure is shown in Figure 1.

2.2. Working Principle

A tractor pulls the whole machine forward, the rear output shaft of the tractor provides power for the chain drive mechanisms with tines for the film and soil separation mechanism and shaking roller, and the hydraulic output system of the tractor provides power for the secondary film and soil separation device.

During operation, the tractor pulls the chain drive tillage film recovery mechanism forward, and the shovel enters the soil to gather a mixture of film, soil and root stubble, lifting the mixture and moving it backward along the shovel surface, and pushing it to the chain drive tine film-soil separation mechanism. With the movement of the chain drive tine mechanism for soil-film separation, the film catches on the spring teeth on the chain bar while the soil pieces and root stubble smaller than the chain bar spacing fall off under the action of gravity, and the large pieces of soil and film move along the chain drive tines. Under the action of the shaking roller, the soil blocks and residual film are tossed upward, and the small soil blocks fall down again, while the residual film catches on the spring teeth and continues to move backward to separate the soil blocks and residual film. As the chain teeth rotate to the position of the brush roller, the bullet teeth on the connecting rod turn downward, and the residual film falls from the bullet teeth under the combing action of the brush roller and into the film box under the action of gravity. The residual film not caught by the teeth and mixed in the soil is thrown backward under the action of the chain drive soil-film separation mechanism and falls into the secondary film-separation device for separation, completing the recovery of the residual film from the whole tillage layer.

2.3. Soil Angle of Repose Experiment and Power Train for the Separation Mechanism

The power transmission principle of the chain drive film-soil separation mechanism is shown in Figure 2. The output shaft of the tractor transmits power to the gearbox, through which a belt drive transmits power from the output shaft to drive the rotation of the active chain, and thus realizes the rotation of the chain gear film-soil separation mechanism. The active chain gear shaft drives the shaking roller shaft to rotate via the chain drive, and the shaking roller shaft drives the shaking of the chain rod.

3. Analysis Key Components

3.1. Analysis of the Film-Lifting Mechanism

The film-lifting mechanism is the component that lifts the mixture of soil, film and root stubble from the 150 mm tillage layer, and its performance is directly related to the traction and power consumption of the machine. Therefore, a reasonable design of the structure and parameters of the film-lifting mechanism is the key to ensure the reliable operation of the chain drive residual film recovery mechanism. It is also an important part of the process of effectively pushing the soil and film mixture into the chain drive film-soil separator to achieve soil separation.

3.1.1. Structure of the Film-Raising Mechanism

The structure of the film-lifting mechanism is shown in Figure 3 and consists of a shovel, shovel frame and frame. To lift the residual film, soil and root stubble of the tillage layer together and smoothly transport the film-soil mixture to the chain drive film-soil separation mechanism, the film shovel and the driven chain roller are mounted on the shovel frame, the tail of the film shovel is 15 mm from the chain drive film-soil separation device, and the vertical height between the shovel tip and the center of the driven chain roller is 160 mm to ensure that the chain drive film-soil separation mechanism is always behind the shovel during operation and reduces resistance to operation.

According to design requirements [29], the vertical distance from the shovel tip to the center of the driven chain roller, $\mathrm{H}=160 \mathrm{mm}$, and the angle of entry, $\alpha =24°$, give an effective shovel length of $\mathrm{L}=393.37 \mathrm{mm}$, which is rounded to 395 mm.

3.1.2. Force Analysis of the Spade

After the shovel lifts the mixture of tillage residue, soil and root stubble, the forces on the mixture are shown in Figure 4.

For ease of analysis, the soil mixture gathered by the shovel is considered to be a mass, and a force analysis is carried out to establish the equation shown in Equation (1):

$$\{\begin{array}{c}F\hspace{0.17em}cos\hspace{0.17em}\alpha -F_f-G\hspace{0.17em}sin\hspace{0.17em}\alpha =0\\ F_N-G\hspace{0.17em}cos\hspace{0.17em}\alpha -F\hspace{0.17em}sin\hspace{0.17em}\alpha =0\end{array}$$

(1)

$$F_f=\mu F_N=F_N\hspace{0.17em}tan\varphi$$

(2)

$\mu$ is the coefficient of friction of the shovel against the soil and $\varphi$ is the angle of friction of the soil against the steel (°).

The traction force is calculated as shown in Equation (3) when the film-raising mechanism is connected to the tractor via the frame [29]:

$$F_Q=SL\rho g\hspace{0.17em}tan(\alpha +\varphi )+KS+K_P{G}_2$$

(3)

Among these:

$$F=G\hspace{0.17em}tan(\alpha +\varphi )=SL\rho g\hspace{0.17em}tan(\alpha +\varphi )$$

(4)

where $L$ is the effective length of the shovel (m), $S$ is the sink cut area of the soil (m²), g is the acceleration of gravity (m/s²), $\rho$ is the density of the soil (kg/m³), $K$ is the specific resistance of the soil (N/m²), $K_p$ is the drag coefficient of the tractor-driven machine (N/m²), $G_2$ is the gravity of the soil-film mixture on the shovel surface during machine operation (N), and $K_P G_2$ is the resistance to overcome during machine operation (N).

According to Equations (3) and (4) [30,31], the force $F$ required to lift the film-soil mixture with the film-raising shovel is 1770.79 N, and the traction force $F_Q$ is 8083.82 N.

3.2. Analysis of the Chain Drive Film-Soil Separation Mechanism

3.2.1. Structure of the Soil Separation Mechanism

The chain drive film separation mechanism is a key component of the tillage layer film recovery machine, and it mainly consists of active chain rollers, driven chain rollers, carrier rollers, chain, shaking rollers, chain rods and spring teeth. Its structure is shown in Figure 5. The chain and tooth film separation device consist of four 24 A chains and two rows of chain rods forming two sets of parallel chain-and-tooth devices. The ends of the chain rods are mounted on two customized 24 A chains and fixed to the chains by bolts. The spring teeth are mounted on the two adjacent chain rods to achieve the radial limit of the spring teeth around the chain rod axis, and the axial positioning of the spring teeth on the chain rods is achieved by a positioning sleeve.

The chain drive film and soil separation device are designed to separate the soil and film residue from a 150 mm deep layer of tillage by shaking the chain rods and pulling the tines together. The minimum clearance between the chain rods is 55 mm, and the distance between adjacent teeth is 100 mm, with the last row of teeth being installed centrally in relation to the previous row.

The projectile tooth structure is shown in Figure 6. The teeth are machined from 65 Mn spring steel of φ4 mm, the tip of each tooth is 30 mm long, the distance between adjacent tips is 80 mm and the center distance of the winding circle is 80 mm, which creates a minimum gap of 4 mm and a maximum gap of 13 mm when the teeth are installed on the chain stays with a minimum distance of 55 mm to increase the shaking of the teeth in the unloading area and improve the unloading rate.

To obtain a better screening capacity for the chain drive membrane-soil separation mechanism, a speed of 2.2 m/s was used for the chain operation [29], and the theoretical speed of the active chain roller was calculated to be 283.75 r/min.

3.2.2. Analysis of the Shaking Rollers

The movement characteristics of the shaking rollers and chain link shaking directly affect the performance of the film-soil separation. The structure of a shaking roller is shown in Figure 7 and consists of a drive shaft, a shaking frame and a roller wheel. The shaking frame is composed of an equilateral triangle, and the rollers are mounted evenly on the shaking frame with a central circle φ150 at an angle of 120°. The drive shaft and the shaking frame are fixed, and the rollers rotate on the shaking frame. When working, the active chain roller drives the drive shaft to rotate through the chain drive, driving the rotation of the shaking frame, and the roller wheel comes into contact with the chain of the chain drive film-soil separation mechanism, driving the chain to shake in a rolling manner.

Based on the speed of the chain during operation, the speed of the jitter rollers is calculated according to Equation (5) as follows:

$$n_1=60\times v/\mathrm{L}=30{\omega }_1/\pi$$

(5)

where v is the speed of the chain movement (m/s), ${\mathsf{\omega }}_1$ is the angular speed of the shaking roller (rad/s), n₁ is the speed of the shaking roller (r/min), and L is the circumference of the shaking roller (mm). The theoretical speed of the shaking roller is calculated as 406.46 r/min.

3.2.3. Movement Analysis of the Chain Drive Soil Separation Mechanism

The chain drive film-soil separation mechanism relies on forced shaking by the shaking roller rotation to improve the separation performance of the chain bar and spring teeth on the film-soil mixture. To analyze the motion of the chain drive film-soil separation mechanism, the film-soil mixture on the chain is the mass point O, the line connecting the center line of the upper carrier roller and the active chain roller is the x-axis, the direction of the chain movement is in the positive direction of the x-axis, the vertical direction is the y-axis, the right angle coordinate system x-o-y is established, and the motion of the film-soil mixture on the chain rod is as shown in Figure 8. The trajectory of the film-soil mixture motion on the chain drive film-soil separation mechanism is represented by a bold line, and the velocity v_y of the film-soil mixture in the y-direction during the motion is:

$$v_y=v_0 sin\beta +v_d sin\psi$$

(6)

where v_y is the velocity of the film-soil mixture in the y-direction of the coordinate system (m/s), v₀ is the forward velocity of the machine (m/s), v_d is the velocity of the shaking roller acting on the film-soil mixture (m/s), v_t is the velocity of the chain rod acting on the film-soil mixture (m/s), β is the angle between the chain and the horizontal direction (°), and ψ is the angle between v_d and the x-axis (°).

When the film-soil mixture is in the AB arc position, the velocity in the y-direction by the chain drive film-soil separation mechanism is composed of the sum of the velocities of v₀ and v_d in the y-direction. At point B, the velocity of the film-soil mixture in the y-direction is the velocity of v₀ in the y-direction. At the BC arc position, the velocity of the film-soil mixture in the y-direction is the velocity of v₀ in the y-direction minus the velocity of v_d in the y-direction. For the film-soil mixture in the process from A to B and then to C, the velocity of the mixture in the y-direction from the initial point A gradually decreases to point C to reach the minimum value.

According to Equation (5), we obtain:

$${\omega }_1=2\times \frac{v}{L\pi }=\frac{2v}{3\sqrt{3}R\pi }$$

(7)

$$v_d={\mathsf{\omega }}_1\times R=\frac{2v}{3\sqrt{3}\pi }$$

(8)

R is the maximum dithering radius of the dithering roller (mm). Combined with Equations (6) and (8), the result is:

$$v_y=v_0 sin\beta + v\frac{2}{3\sqrt{3}\pi }sin\psi$$

(9)

According to Equation (9), the angle β between the chain and the horizontal direction can be ignored due to the change in the angle caused by jitter, and the forward speed v₀ can also be regarded as a constant value during actual operation, so Equation (9) can be simplified as follows:

$$v_y=a+vbsin\psi$$

(10)

where a and b are constants. As a result, the velocity v_y of the chain drive film-soil separation mechanism acting on the film-soil mixture in the y-direction represents the change in the jitter characteristics and separation capacity of the separation mechanism. From Equation (10), it can be approximated that the jitter performance of the chain drive membrane-soil separation mechanism varies with the sine curve of the chain motion velocity v and the angle ψ. This shows that the chain speed v and the angle between v_d and the x-axis are the key parameters affecting the soil separation performance of the chain drive mechanism.

4. Simulation Analysis of the Chain-Drive Film-Soil Separation Mechanism

4.1. Model and Simplification

The chain module of ADAMS software was used to model and analyze the chain drive soil separation mechanism. In the operation toolbox of ADAMS/View, components such as the frame, driven chain roller, upper carrier roller, chain and shaking roller were created, and constraints were added between the components [32,33]. The model built in this study is shown in Figure 9.

To accurately simulate the actual movement of the film-soil separation mechanism, the material properties of the components were added to each of its parts according to the actual situation. To improve the speed of the simulation and to facilitate the analysis of the Chain module, the separation mechanism was suitably simplified by removing the lower carrier rollers and replacing the upper carrier rollers and the rollers of the shaking frame with sprockets of different tooth numbers.

The translation drive speed added to the frame was calculated to be 700 mm/s, the rotational drive acting on the active chain roller was 29.7 rad/s, and the rotational drive acting on the shaking frame was 42.5 rad/s.

4.2. Calculations

When performing the ADAMS solution calculations, the simulation was set to 1.0 s and 100 steps.

4.3. Simulation Studies

To shorten the simulation analysis time of the chain drive film-soil separation mechanism, it is necessary to focus on the movement of the chain teeth in the part above the shaking roller. As the chain drive film-soil separation mechanism has multiple chain sections, the chain plate was selected as the research object during the analysis. After the simulation, the chain plate link_1 was selected as the object from the post-processor, and a series of simulation results were output. Figure 10 shows the displacement graph of link_1 vs. time, and Figure 11 shows the displacement of link_1 in the y-direction on the vertical axis vs. the displacement in the x direction on the horizontal axis, to obtain the trajectory curve of the link_1 mass point.

Figure 12 and Figure 13 show the velocity and acceleration graph of the chain plate link_1 center of mass.

Figure 14 and Figure 15 show the variation of the link_1 mass in the y-direction (vertical axis) vs. the displacement of the link_1 mass in the x-direction (horizontal axis).

According to Figure 10, the maximum amplitude of the motion of link_1 is 64.45 mm in the x-direction and 81 mm in the y-direction. According to Figure 11, the amplitude of the trajectory of link_1is 63.67 mm in the x-direction, and its maximum amplitude in the y-direction is 81 mm. According to Figure 11, link_1 effectively jerks in the x-direction between 27 mm and 726 mm in the chain tensioning section during the analysis time of 1 s. In combination with Figure 10, the effective jerks of link_1 are between 0.19 s and 0.74 s. Therefore, the time period 0.19–0.74 s was used for the analysis of the movement of link_1 in the chain tensioning section. Using the Animation Control function, the contact time between link_1 and the jitter rollers was found to be between 0.52 s and 0.56 s. According to Figure 10, when link_1 and the jitter rollers are in contact, their displacements are 426 mm and 462.35 mm in the x-direction and 554.59 mm and 545.73 mm in the y-direction, respectively.

According to Figure 12 and Figure 13, the start time of the action of the jitter roller on link_1 is 0.52 s and the end time is 0.56 s, corresponding to when the maximum and minimum velocities of the center of mass of link_1 in the x-direction, are 3256.58 mm/s and −973.82 mm/s, and the maximum and minimum accelerations are 1.1 × 10⁷ mm/s² and −9.74 × 10⁵ mm/s², respectively. The velocities in the x- and y-directions are 524.39 mm/s and −919.06 mm/s, respectively, with accelerations of 1.03 × 10⁷ mm/s² and −3.71 × 10⁶ mm/s², respectively. The maximum and minimum velocities of the link_1 center of mass in the x- and y-directions at other times outside the jitter roll action are 4744.18 mm/s and −1207.34 mm/s, respectively, corresponding to times of 0.34 s, 0.36 s. The maximum and minimum accelerations in the x-direction were 1.69 × 10⁷ mm/s² and −8.27 × 10⁶ mm/s²,corresponding to 0.45~0.62 s; the maximum and minimum velocities of the link_1 center of mass in the y-direction were 7038.6 mm/s, −4841.26 mm/s, corresponding to 0.59 s, 0.34 s. The maximum and minimum accelerations in the y-direction are 1.03 × 10⁷ mm/s² and 9.73 × 10⁶ mm/s², corresponding to 0.53 s and 0.73 s, respectively.

According to Figure 14 and Figure 15, the maximum velocities of the center of mass of link_1 in the x-direction and y-direction are 4744.72 mm/s and 7308.59 mm/s, respectively, and the minimum velocities are −1270.34 mm/s and −4841.26 mm/s, respectively, for the displacement of link_1 in the x-direction effective jitter section from 27 mm to 726 mm; when the displacement of link_1 in the x-direction moves from 426 mm to 462.35 mm, link_1’s center of mass in the x-direction changes from 2312.93 to 489.75 with a more drastic change and a larger magnitude. The y-direction velocity changes from −411.08 mm/s to −6.79 mm/s with a smaller overall change.

Figure 14 and Figure 15 show that in the displacement band from 123.47 mm to 264.40 mm, after a minimum in the x- and y-directions for the same x-direction displacement, the velocity starts to increase, while the displacement in the x-direction moves in the opposite direction, with a maximum movement of 12.2 mm.

4.4. Analysis of the Results

The simulation analysis showed that the shaking displacement of link_1 in the tensioning zone of the chain was in the range of 27–726 mm in the x-direction, and the trajectory of link_1 in this zone basically varied in a cosine curve, indicating that the results of the kinematic analysis of the theoretical analysis of the chain drive film-soil separation mechanism were consistent with the results of the simulation analysis.

The maximum and minimum values of the velocity of the link_1 center of mass in the x-direction and y-direction did not appear in the time period of 0.52–0.56 s when the jitter rollers were in contact with link_1 for the displacement of link_1 in the x-direction in the range of 27–726 mm. In the time period of 0.52–0.56 s, the velocity changes in the x-direction and y-direction were flat. However, when the shaking roller and link_1 were not in contact, the flexible characteristics of the chain were used to drive its movement in the x- and y-directions, and the movement speed in the y-direction was faster than that in the x-direction, which was conducive to the shaking separation of the film-soil mixture.

The maximum and minimum values of acceleration in the x-direction of link_1 occurred before 0.52 s, while the maximum and minimum values of acceleration in the y-direction occurred exactly between 0.52 s and 0.56 s. The overall acceleration in the x-direction was greater than that in the y-direction. According to Newton’s second law, when the shaking roller is in contact with link_1, the force in the y-direction is the greatest, which has an upward impact on the soil clods to break them and increase the film collection rate. When the shaking roller is not in contact with link_1, the force in the x-direction is the greatest, which has a stronger effect on the backward transport of the soil mixture and is less likely to produce film congestion.

To further the film-soil separation performance of the chain drive film-soil separation mechanism, the data in Figure 14 and Figure 15 were exported using the table function of Export to form a velocity variation graph with the velocity of link_1 in the y-direction as the vertical axis vs. the velocity of link_1 in the x-direction on the horizontal axis, as shown in Figure 16.

To analyze the velocity variation of link_1 within the effective jitter band between 27 mm and 726 mm, combined with the fact that the velocity variation is divided into two trends, upward and downward, as shown in Figure 16, the velocity variation Equation (11) was constructed as shown in Figure 17.

$$\{\begin{array}{c}{v}_x{}^{\prime }-v_x=\nabla v_x\\ v_y{}^{\prime }-v_y=\nabla v_y\end{array}$$

(11)

where $\left(v_x,v_y\right)$ is the velocity at any point on the velocity change curve (mm/s), $\left(v_x{}^{\prime },v_y{}^{\prime }\right)$ is the velocity at the point on the velocity change curve after the relative $\left(v_x,v_y\right)$ (mm/s), $C=\frac{m_2}{m_1}\times 100$ is the velocity difference in the y-analysis, (mm/s), and $\nabla v_x$ is the velocity difference in the x-direction (mm/s).

When $\frac{\nabla v_y}{\nabla v_x}=1$, the chain drive film-soil separation mechanism has the same effect on the horizontal and vertical transport of the film-soil mixture.

When $\frac{\nabla v_y}{\nabla v_x}>1$, the chain drive film soil separation mechanism has a greater effect on the vertical transport of the film-soil mixture than the horizontal one.

When $\frac{\nabla v_y}{\nabla v_x}<1$, the conveying effect of the chain drive film-soil separation mechanism on the film-soil mixture in the horizontal direction is greater than that in the vertical direction.

After analysis, the maximum value of $\frac{\nabla v_y}{\nabla v_x}$ was 93.65, corresponding to a velocity difference of 30.2 mm/s in the x-direction and 2.83 × 10³ mm/s in the y-direction. The minimum value of $\frac{\nabla v_y}{ \nabla v_x}$ was 0.15, corresponding to a velocity difference of −1.48 × 10³ mm/s in the x-direction and −2.25 × 10² mm/s in the y-direction; the positive and negative values of $\frac{\nabla v_y}{\nabla v_x}$ cross. This shows that the chain drive film-soil separation mechanism is useful for transporting and throwing the film-soil mixture in the horizontal and vertical directions and that the alternating positive and negative velocity differences during its motion are not only beneficial to the continuous backward transport of the film-soil mixture but also beneficial to the shaking separation of the film-soil mixture, revealing the film-soil separation mechanism and the change of the chain drive film-soil separation mechanism and providing theoretical guidance for the design and optimization of the chain drive film-soil separation mechanism. This study provides theoretical guidance for the design and optimization of the chain drive soil separation mechanism.

5. Field Trials

To verify the operational performance of the chain drive film-soil separation mechanism, a physical prototype of the complete machine was tested. In June 2020, operational performance tests were carried out in a test field of the 6th Mission in Wensu County, Aksu, Xinjiang [34,35]. This is shown in Figure 18. The test field was selected from a flat cotton field after plowing. The equipment was powered by a John Deere 754 tractor operating at a speed of 2.5–3.0 km/h. The speed of the active chain roller of the chain tine tiller was 283.75 r/min, and the speed of the shaking roller was 406.5 r/min.

When testing the operational performance of the film gathering mechanism, the measured area was divided into two areas, before and after the operation, and the measuring points were measured using the five-point method. The samples were taken before and after the operation according to the depth of the tillage layer of 150 mm. The mass was weighed after removing the dust and moisture, and the average value was calculated. The collection rate of the tilled layer was calculated according to Equation (12):

$$J=\left(1-\frac{W}{W_0}\right)\times 100$$

(12)

where J is the gathering rate (%), W is the mass of residue in the 150 mm deep tillage layer after the operation (g), and W₀ is the mass of residue in the 150 mm deep tillage layer before the operation (g).

The extent of residual film left on the surface after film-soil separation was expressed as the surface residual rate and was calculated according to Equation (13):

$$C=\frac{m_2}{m_1}\times 100$$

(13)

where C is the residual percentage on the surface (%), m₁ is the mass of residual film in the 150 mm deep tillage layer before operation (g), and m₂ is the mass of residual film on the scattered surface after operation (g).

Residual film gathering and separation indexes were measured in accordance with the test requirements of the standard GB/T 25412-2010 “Residual Film Recycling Machine”. The results of the field tests are shown in

Table 1. Performance of the chain drive film soil separation mechanism.

Parameters	Test Value	Technical Requirements
Tillage gathering rate/%	68	≥65
Surface residual rates/%	6	/
Gathering depth/mm	150	100–150

.

6. Discussion

There has been a lot of research on tillage layer residual film recovery tools, but there are still many shortcomings, such as the actual operating depth being not up to standard, and the pick-up rate for tillage layer residual film being low. Our research optimized the mechanism for the above shortcomings and we designed a chain tine type tillage residue recovery machine tool that has a simple structure and reliable operation performance and makes up for the shortcomings of the models in existing research. While ensuring the effective working depth was maintained at 150 mm, the tillage film pick-up rate was increased from 55.04% [19,20] in the existing study to 68%. In addition, our research analyzed the working process of a chain-tooth type film recycling machine using ADAMS software. Compared with existing research in which the chain drive in the actual working condition was replaced by the belt drive in the analysis [28], the analysis process of our research was closer to the actual working condition, and the research results are more reliable. Compared with the existing related research, the analysis method in our research is more innovative and intuitively clarifies the motion characteristics and mechanism in the process of film-soil separation, which provides theoretical guidance for the design and optimization of a chain tine type tillage residual film recycling machine.

7. Conclusions

The shaking roller is a key component of the chain drive film-soil separation mechanism, and its shaking action on the chain directly determines the performance of film-soil separation. Through a kinematic analysis of the film-soil separation mechanism, the velocity v_y of the action of the separation mechanism on the mixture in the y-direction can indicate the change in the shaking characteristics and the separation capacity of the separation mechanism. The key parameters affecting the film-soil separation performance of the chain drive film-soil separation mechanism are the chain movement velocity v and the angle between v_d and the x-axis. A kinematic simulation analysis of the film-soil separation mechanism by ADAMS software provided the motion displacement, velocity, acceleration and trajectory of the chain plate. The derivation of the mechanism in the whole movement process was accurately calculated, as well as its effect on membrane soil separation, which showed that the trajectory of the center of mass of the chain plate link_1 changed in a sine curve during the jittering operation section, which is consistent with the results of the kinematic analysis for the chain drive film-soil separation mechanism.

Simulation results showed that the chain drive film-soil separation mechanism made use of the flexible characteristics of the chain, and drove the chain to both sides of the excitation point through the excitation of the shaking roller. When the velocity in the y-direction reached the maximum, the displacement along the x-direction decreased to achieve the collision and crushing of the film-soil mixture and facilitated film-soil separation. The mechanism and change of film-soil separation by the chain drive film-soil separation device were revealed, which provided theoretical guidance for the design and optimization of chain drive film-soil separation equipment.

Our research analyzed and simulated the key components of, and conducted field experiments on, the operational performance of the chain drive film-soil separation equipment. The field test showed that the collection rate of the chain drive film-soil separation mechanism reached 68% when the tillage depth reached 150 mm, and the surface residue reached 6%. The values were 3% higher than the performance index of the industry standard NY/T 1277-2006. All the test indexes met the requirements of national and industry standards, the test results met the design requirements, and the results of field experiments were basically consistent with the results of the simulation analysis. Our research objectives were met.