Design method for trafficability crawler system of combine harvester in wet and soft rice field

Abstract

The invention relates to the technical field of crossing of agricultural machinery design and terramechanics, and discloses a design method of a trafficability track system of a combine harvester in a wet and soft rice field. Firstly, a track-ground coupling system model is established, system stress is calculated based on a force balance equation by dividing a track system and utilizing a joint simulation technology, and a constraint mechanism of wet and soft soil on track trafficability is disclosed; then, based on a crawler-ground coupling system model, a three-dimensional model is introduced to analyze crawler-ground interaction, and crawler tooth structure parameters are optimized to improve traction performance; finally, a micro-nano composite bionic super-hydrophobic self-cleaning structure simulating the lotus leaf surface is designed on the surface of the track shoe, a prototype is manufactured through 3D printing, the surface gas film characteristics and the soil contact angle of the prototype are analyzed through electron microscope scanning, and the desorption effect of the prototype is verified through a traction force test. The problems that the combine harvester sinks, slides and rotates and adheres to soil in a wet and soft rice field are effectively solved, and the trafficability and the operation efficiency are remarkably improved.

Description

TECHNICAL FIELD

[0003] The present application relates to the field of agricultural machinery design and ground mechanics, in particular to a design method and manufacturing method of a track system of a combine harvester for passing in a wet and soft paddy field. Specifically, the present application aims to solve the problems of severe sinking, high slip ratio, soil adhesion leading to loss of traction, etc. of the tracked combine harvester in the wet and soft paddy field with high water content and low bearing capacity. BACKGROUND

[0005] The tracked walking mechanism is widely used in combine harvesters and other agricultural machinery due to its small ground contact pressure and large traction. However, in the rice production areas in southern China, the soil in the paddy field is often wet and soft or even saturated during the harvesting period, with extremely low bearing capacity and strong adhesion, which causes the tracked combine harvester to sink, slip and idle, and be severely attached by wet mud, greatly affecting the operation efficiency and reliability, and even causing the machine to be trapped and unable to work, resulting in economic losses.

[0006] In the field of vehicle dynamics, in order to improve the driving smoothness and dynamic performance of vehicles on off-road surfaces, some studies have focused on the coupling relationship between the track and the road surface. For example, Chinese invention patent CN111597639B discloses a track and off-road surface coupling analysis method. By establishing a track-road surface shaping filter model, the actual road surface elevation excitation composed of the ground contact section of the track is obtained, thereby providing guidance for the suspension design and power transmission device parameter design of the tracked vehicle, and the core purpose is to improve the dynamic performance and driving smoothness of the vehicle on off-road surfaces.

[0007] However, such tracked walking mechanisms cannot be adapted to the field of combine harvesters and other agricultural machinery, specifically:

[0008] Firstly, the existing tracked walking mechanism is mainly focused on solving the problem of vehicle vibration caused by road unevenness, and its goal is to improve the driving smoothness and reliability of parts. However, when the combine harvester is working in a wet and soft paddy field, the primary and fatal threat it faces is the passing problem, which is manifested as follows: 1. Severe sinking, the bearing capacity of wet and soft soil is extremely low, causing the machine body to sink. 2. High slip ratio, the adhesion between the track and the soil is insufficient, leading to slipping and idling, and the traction cannot be effectively exerted. 3. Soil adhesion, wet and soft soil is easily attached to the surface of the track, further deteriorating the traction conditions and possibly causing rubber track rupture and other failures. These problems directly lead to low operation efficiency, machine failure to work normally, and even cause delay of agricultural time and economic loss.

[0009] Secondly, the existing tracked vehicle coupling theory model does not match the soil mechanics characteristics of agriculture. The tracked road shaping filter model established is essentially a kinematic coupling, which focuses on the transmission and filtering of rigid or semi-rigid road elevation excitation through the tracked system, and the core is to analyze the vibration response. However, in the wet and soft rice field, the interaction between the tracked vehicle and the soil is a typical soil mechanics coupling problem. The core is the pressure-shear-failure process of the soil under the tracked vehicle ground pressure. The soil is regarded as a viscoelastic medium with cohesion and internal friction, and its mechanical properties change dramatically with water content. The model fails to cover these key soil mechanics behaviors, and therefore cannot be used to predict and improve the key indicators that determine the passability: traction, travel resistance and sinkage.

[0010] In addition, the lack of key soil parameters in the existing tracked vehicle coupling theory model makes the model unsuitable for agricultural applications, such as: soil cohesion coefficient and internal friction angle: these two factors together determine the shear strength of the soil and are the core of calculating the maximum thrust of the tracked vehicle. Soil cone index: this is a general index that directly represents the bearing capacity and shear resistance of the soil, and is widely used in the field for rapid assessment of the passability of agricultural machinery. Soil moisture content, density, etc.: these are the fundamental factors that cause the dynamic changes of soil mechanics parameters. Due to the lack of perception and modeling of these key soil parameters, the existing tracked vehicle coupling theory model cannot adapt to the large spatial and temporal differences of the rice field soil, and it is difficult to accurately evaluate and predict the passability of the combine harvester in the wet and soft rice field.

[0011] In addition, the output and application orientation of the existing tracked vehicle coupling theory model cannot directly improve the passability of agricultural machinery. The model output is mainly used to guide the parameter design of the suspension system and the power transmission device, aiming to optimize the ride comfort of the vehicle. However, the passability of the combine harvester in the wet and soft rice field ultimately depends on the interaction between the tracked vehicle system and the soil. Even if the suspension and transmission system performs well, if the tracked vehicle continues to sink, slip or is wrapped in mud, the machine will still be unable to move. Therefore, the optimization direction of the existing technology does not touch the root cause of the poor passability of agricultural machinery in wet and soft working conditions. Its technical solution cannot guide how to optimize the geometry of the tracked teeth such as height, thickness and pitch to enhance the grip and reduce resistance, and cannot provide any design basis for solving the soil adhesion problem. SUMMARY

[0013] The problem to be solved by the present application is that the existing track-ground coupling model mainly focuses on vibration response and cannot effectively solve the problem of soil subsidence, slip and adhesion in wet and soft paddy fields, and the present application provides a track system design method special for combine harvesters. By establishing a track-ground coupling system model integrating soil mechanical properties, optimizing the track structure parameters, and introducing a biomimetic super-hydrophobic self-cleaning surface, the traction performance, detachment ability and overall passability of the combine harvester in wet and soft paddy fields are significantly improved.

[0014] To solve the above problems, the present application provides a track system design method for the passability of a combine harvester in wet and soft paddy fields, comprising the following steps: S1, track-ground coupling system modeling: establishing a track-ground coupling system model, the model divides the track system into a track portion between the drive wheel and the load wheel, a track portion under the load wheel, and a track portion between each load wheel, and uses multi-body dynamics software and control analysis software for joint simulation, calculates the system stress based on the force balance equation, to reveal the constraint mechanism of wet and soft soil on track passability; S2, track structure parameter optimization: based on the track-ground coupling system model, and referring to the three-dimensional model for three-dimensional spatial analysis of track-ground interaction, the structure parameters of the track teeth on the track plate are optimized to maximize the traction performance and passability of the track in wet and soft soil; S3, super-hydrophobic self-cleaning structure design and verification: designing a biomimetic super-hydrophobic self-cleaning structure on the working surface of the track plate, and manufacturing a prototype through 3D printing, analyzing the surface air film characteristics and soil contact angle through electron microscope scanning, and verifying the detachment effect through traction test.

[0015] As a preferred embodiment, in the track-ground coupling system modeling step, when establishing the sub-model of the track portion between the drive wheel and the load wheel, the deformation amount of the track micro-element from state 1 to state 2 of the track-ground coupling system drive wheel is calculated as , according to the force balance equation, the tension of the i-th element is as shown in formula (1):

[0016] (1)

[0017] In the formula, is the tension of the i-th micro-element, is the included angle between the i-th element and the horizontal line, is the angle change amount of the i-th element from the initial value to the i-th element, and , , , the angle of the selection of the arbitrary microelement relative to the horizontal plane, and respectively, the normal pressure and the shear force. The microelement tension of the track is accurately quantified by the force balance equation formula 1, realizing high-precision simulation of the dynamic stress of the track system. Unlike the existing technology which only focuses on the vibration response of the road surface elevation excitation, the present application can accurately reveal the internal tension distribution and dynamic change of the track when driving in wet and soft soil by solving the force balance of each microelement under the joint action of the normal pressure and the shear force. The accurate tension calculation provides key mechanical input parameters for the coupled system, and is the basis for subsequent analysis of track slip, evaluation of traction limit and optimization of driving system load, thereby overcoming the defects of the existing model that cannot accurately predict the passability due to the lack of internal mechanical state analysis.

[0018] As a preferred, the track-ground coupling system modeling step further comprises a ground drivability measurement step: according to the Bekker ground mechanics theory, the approximate effective traction provided by the unit load area soil under the action of uniform pressure is used to measure the drivability of the ground, and the calculation formula is shown as formula (2); (2)

[0019] In the formula, , Wherein, p, W, b, L, h are design parameters of the track, , Z, C, , , are soil mechanical property parameters. By applying the Bekker ground mechanics theory and using formula (2) to calculate the effective traction, a direct quantitative correlation between the track design parameters and the soil mechanical properties is established. This method places the design parameters p, W, b, L, h of the track and the key mechanical property parameters Z, C, φ of the soil in the same model, so that the designer can quantitatively predict the passability of different track design schemes in a specific wet and soft soil. An objective and quantitative index for measuring the drivability of the ground is provided, and by calculating the effective traction DP per unit area, a unified and scientific criterion is provided for evaluating the passability of different wet and soft paddy soil, overcoming the blindness of the existing technology which relies solely on experience.

[0020] As preferred, the track structure parameter optimization step specifically comprises: setting multiple track shoe schemes with different widths b, different pitches t, and different track shoe heights h; performing track shoe soil shearing tests, analyzing the forces of the track shoe on three shearing planes: the forces of the lower edge of the track shoe on the first plane parallel to the track shoe, and the forces of the two side edges of the track shoe on the two side planes perpendicular to the track shoe; based on the test data, drawing a characteristic curve of the hitch traction force with respect to the track shoe height and the track shoe thickness ratio, so as to select the optimal parameter combination.

[0021] The lower edge of the track shoe is parallel to the first plane of the track shoe, and the two side edges of the track shoe are perpendicular to the two side planes of the track shoe; based on the test data, a characteristic curve of the hitch traction force with respect to the track shoe height and the track shoe thickness ratio is drawn, so as to select the optimal parameter combination.

[0022] The shearing action of the track shoe on the soil is analyzed by decomposing it into three planes, and a characteristic curve is drawn,

[0023] The internal mechanism of the track shoe structure and the traction performance is revealed, and the mechanism of the track shoe generating traction force can be more comprehensively understood by analyzing the shearing action of the lower edge and the two side edges of the track shoe on the three different planes, thereby providing a theoretical basis for precise optimization of the track shoe structure. The scientific optimization of the track shoe geometric parameters is realized, and the "hitch traction force-track shoe height-track shoe thickness ratio" characteristic curve is drawn through systematic tests, which can directly and accurately determine the optimal track shoe parameter combination that can generate the maximum traction force under specific soil conditions, avoiding the disadvantages of relying on experience and trial and error in traditional design.

[0024] As preferred, in the track structure parameter optimization step, the soil failure angle is back calculated according to formula (3) to establish a track shoe traction force prediction model: F = (γ·z·N_γ + c·N_c + q·N_q) · B · L · (1 + δ / B) · K (3) wherein F is the traction force, γ is the soil density, z is the settlement, c is the soil cohesion, q is the additional load, B is the track shoe width, L is the track shoe pitch, δ is the track shoe thickness, K is the deformation modulus, and N_γ, N_c, N_q are bearing capacity factors related to the soil failure angle φ and the internal friction angle θ.

[0025] The three-dimensional traction force prediction model shown in formula (3) realizes precise prediction of the track shoe traction force: the model comprehensively considers multiple factors such as soil density, cohesion, settlement, additional load, and track shoe geometric parameters, can more realistically simulate the extrusion and shearing process of the track shoe on the soil in three-dimensional space, and has much higher prediction accuracy than traditional empirical formulas or simplified models. The model provides a core tool for fine design of the track structure, and back calculation of key state parameters such as the soil failure angle can guide the design of a track shoe structure that best matches specific wet and soft soil conditions, thereby significantly improving traction efficiency and reducing driving resistance.

[0026] Preferably, in the design and verification step of the superhydrophobic self-cleaning structure, the biomimetic superhydrophobic self-cleaning structure is a composite micro-roughness model that mimics the surface of a lotus leaf, featuring nipple-like micron-level protrusions and nano-level secondary structures. By designing a micro-nano composite roughness model that mimics the surface of a lotus leaf, soil adhesion is effectively suppressed at its source. The biomimetic structure significantly increases the soil contact angle by forming a stable air film between the track plate and the wet soil, making it difficult for soft, wet soil to spread and adhere to the track surface. This fundamentally solves the technical problem in existing technologies where tracks are easily covered by wet mud, leading to loss of traction. It endows the track with continuous self-cleaning ability; even when operating in sticky soil, the structure can easily remove adhering substances through vibrations or simple movements during operation, keeping the track surface clean and ensuring continuous and effective traction output.

[0027] Preferably, the method further includes a model reliability verification step: by measuring the soil conic index (CI) under different soil conditions, analyzing the influence of various factors on the CI value, and comparing the trend of CI value changes with the prediction results of the tracked-ground coupled system model to verify the reliability of the model. By introducing the soil conic index (CI) for model reliability verification, a reliable bridge is established between the theoretical model and engineering practice. By comparing the model prediction results with the internationally recognized soil bearing capacity index (CI), which is rapidly measurable in the field, the credibility and practical value of the tracked-ground coupled system model are greatly enhanced. This ensures the universality and reliability of the design method under different soil conditions. The verification step guarantees that the optimized tracked system is not only suitable for ideal laboratory conditions but also adaptable to the complex soil environment with large spatiotemporal variability in actual paddy fields, improving the success rate and robustness of the design.

[0028] Preferably, given the corresponding soil parameters and track width, the soil failure angle is calculated using formula (4) based on the change in track tooth height:

[0029] (4)

[0030] In the formula, B is the track shoe width, and L is the track shoe pitch. It is the ratio of track tooth thickness to track plate pitch. Let K be the soil density and K be the deformation modulus. denoted as the soil-baffle external friction angle, h as the tooth height, c as the soil cohesion, and n as the soil deformation index. For soil cohesion, This represents the amount of soil subsidence. For the additional load, , , Respectively, the factors related to the baffle parameters, the failure angle. For the failure angle, For the internal friction angle.

[0031] According to the material properties of the track, the appropriate grousers height and grousers thickness ratio are selected, the relationship between the settlement and the grousers height is determined, and then according to the data accumulation, the characteristic curve of the hook traction force with the grousers height and the grousers thickness ratio is drawn.

[0032] The McKeys-Ali three-dimensional model is cited for the traction force prediction of the grousers track, the three-dimensional space analysis of the track-ground interaction is carried out, the optimal track structure matching is obtained according to the three-dimensional model and the related discipline theory according to the expression of the related parameters and the force under the typical wet and soft soil conditions.

[0033] Compared with the prior art, the beneficial technical effects obtained by the present application are:

[0034] The present application solves the fundamental problem of the agricultural machinery passability, the track-ground coupling system modeling is combined with the soil mechanics characteristics for the first time, the pressure-shear-failure process of the wet and soft paddy field soil is analyzed, the sinking and slip problems of the combine harvester under the wet and soft working conditions can be effectively predicted and improved, and the passability of the machinery is fundamentally improved.

[0035] The present application realizes the precise optimization design of the track structure, the mathematical model of the track-ground coupling system is established, the three-dimensional space analysis and the McKeys-Ali three-dimensional model are combined, the geometric parameters of the grousers including the height, the thickness, the pitch and the like can be accurately optimized, the traction performance of the track is significantly improved, and the driving resistance is effectively reduced.

[0036] The application innovatively adopts a biomimetic super-hydrophobic self-cleaning technology, and for the first time applies the micro-nano composite structure on the surface of a lotus leaf to the surface design of a track, significantly reduces the soil adhesion by forming an air film layer, solves the technical problem that the traditional track is easily wrapped by wet mud, and greatly improves the self-cleaning ability of the track.

[0037] The application establishes a complete and reliable reliability verification system, introduces a soil cone index (CI) as a verification index, establishes an evaluation system combining a theoretical model and experimental verification, ensures the accuracy and reliability of the design method, and provides a scientific basis for the optimal design of the track system.

[0038] The application significantly improves the operation efficiency and economy, effectively reduces the sinking rate and skidding rate of the combine harvester in the wet and soft rice field through a systematic design method, improves the operation efficiency and reliability, reduces the maintenance cost and loss of agricultural time caused by the stuck vehicle, and has significant economic benefits.

[0039] The application fills the blank of the design method of the special track for agricultural machinery, and fills the blank of the existing technology in the field through a complete design method from soil mechanics analysis, coupling system modeling to structural parameter optimization, and provides technical support for the professional design of the track system of agricultural machinery. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 A schematic diagram of a track system design method for the passability of a combine harvester in a wet and soft rice field. DETAILED DESCRIPTION

[0043] The application will be further described in detail below in combination with specific embodiments. It should be noted that these embodiments are only used to explain the application, and do not constitute a limitation on the protection scope of the application.

[0044] Embodiment 1: Track-ground coupling system modeling and parameter optimization

[0045] This embodiment details the specific implementation process of the track-ground coupling system modeling and track structure parameter optimization in the design method of the application.

[0046] Step 1: Track-ground coupling system modeling

[0047] First, the soil mechanics properties of typical wet and soft rice field soil (loam and clay) in Jiangsu are tested. The three-phase ratio of the soil is measured under different water content conditions (20%, 30%, 40%), and key parameters such as the cohesion modulus Kc, friction modulus Kφ, sinking index n, cohesion coefficient c, and internal friction angle φ of the soil are obtained.

[0048] Then, RecurDyn multi-body dynamics software and Matlab / Simulink control analysis software are used for joint simulation analysis. The track system is divided into three parts:

[0049] 1. The track part between the drive wheel and the track roller;

[0050] 2. The track part under the track roller;

[0051] 3. The track part between the track rollers;

[0052] When establishing the sub-model of the track part between the drive wheel and the track roller, the track micro-element deformation amount from state 1 to state 2 is set as According to the force balance equation, the tension of the i-th element is calculated as formula:

[0053]

[0054] In the formula, is the tension of the i-th micro-element, is the included angle between the i-th element and the horizontal line, is the angle change amount of the i-th element from the initial value to the i-th element, and , , , is the selected angle of the arbitrary micro-element relative to the horizontal plane, and are the normal pressure and shear force, respectively. Through the force balance equation formula 1, the tension of the track micro-element is accurately quantified, and high-precision simulation of the dynamic force of the track system is realized. Unlike the existing technology which only focuses on the vibration response of the road elevation excitation, the present application can accurately reveal the internal tension distribution and dynamic change of the track when driving in wet and soft soil by solving the force balance of each micro-element under the joint action of normal pressure and shear force. The present application provides key mechanical input parameters for the coupled system. Accurate tension calculation is the basis for subsequent analysis of track slip, evaluation of traction limit and optimization of drive system load, thereby overcoming the defects of the existing model that cannot accurately predict the passability due to the lack of internal mechanical state analysis. By solving the equation, the internal tension distribution of the track system is obtained, which provides accurate mechanical input for subsequent analysis.

[0055] Second step: ground drivability evaluation

[0056] Based on Bekker ground mechanics theory, the approximate effective traction provided by the unit load area soil under the action of uniform pressure is used to measure the drivability of the ground, and the calculation formula is shown in the formula;

[0057] In the formula, , Wherein, p, W, b, L, h are the design parameters of the track, respectively representing the ground pressure, vertical load, track width, ground length and grousers height; , Z, C, , , are soil mechanics parameters, respectively representing soil density, settlement, soil cohesion coefficient, soil internal friction angle and soil plastic deformation coefficient.

[0058] The specific implementation process is: selecting typical wet and soft paddy soil in Jiangsu area, the soil parameters are measured under the condition of 30% water content: soil density γ=1800 kg / m3, soil cohesion coefficient c=12kPa, internal friction angle =24°, soil plastic deformation coefficient ω=0.15. The track design parameters are taken: ground pressure p=24kPa, vertical load W=8500N, track width b=420mm, ground length L=1850mm, grousers height h=48mm.

[0059] Through calculation, the maximum traction FHmax=18.6 kN, the driving resistance R=4.2 kN, and the effective traction DP=0.82. The results show that under the current soil conditions, it has good drivability, which provides a quantitative basis for the optimization design of the track structure.

[0060] By applying Bekker ground mechanics theory and using the above complete formula to calculate the effective traction, the precise quantitative correlation between the track design parameters and the soil mechanics characteristics is established. The calculation method fully considers the enhancement effect of grousers height on traction, the influence of soil plastic deformation on traction transmission and the accurate estimation of driving resistance, so that the designer can accurately predict the passing performance of different track design schemes in specific wet and soft soil. Compared with the traditional simplified model, the evaluation method provided by the present application has higher precision and engineering practical value, and provides a unified and scientific criterion for evaluating the passability of different wet and soft paddy soil, and overcomes the blindness of the existing technology which is only judged by experience.

[0061] Third step: track structure parameter optimization

[0062] Five sets of track shoe schemes with different geometric parameters were set up:

[0063] Width b: 350mm, 400mm, 450mm

[0064] Pitch t: 90mm, 100mm, 110mm

[0065] Grouser height h: 35mm, 40mm, 45mm, 50mm, 55mm

[0066] Track shoe soil shearing tests were conducted to analyze the force of the grouser on three shearing planes:

[0067] 1. The first plane of the lower blade edge of the grouser parallel to the track shoe

[0068] 2. The side surface of the left blade edge of the grouser perpendicular to the track shoe

[0069] 3. The side surface of the right blade edge of the grouser perpendicular to the track shoe

[0070] Based on the test data, the characteristic curve of the hitch traction force with the ratio of the grouser height and the grouser thickness was drawn. The results show that when the grouser height h = 45mm and the ratio of the grouser thickness to the pitch δ / L = 0.12, the hitch traction force reaches the maximum value.

[0071] Step 4: Verification of the Traction Force Prediction Model

[0072] The following formula (3) was used to establish the grouser traction force prediction model: F = (γ·z·N_γ + c·N_c + q·N_q) · B · L · (1 + δ / B) · K

[0073] Where F is the traction force, γ is the soil density, z is the settlement, c is the soil cohesion, q is the additional load, B is the track shoe width, L is the track shoe pitch, δ is the grouser thickness, K is the deformation modulus, and N_γ, N_c, N_q are bearing capacity factors related to the soil failure angle φ and the internal friction angle θ.

[0074] Where the parameter values are: soil density γ = 1800kg / m³, settlement z = 85mm, soil cohesion c = 15kPa, additional load q = 5kPa, track shoe width B = 400mm, track shoe pitch L = 100mm, grouser thickness δ = 12mm, and deformation modulus K = 1.2.

[0075] The soil failure angle φ = 26.5° was back calculated through the model, with an error within the allowable range compared to the measured value φ = 25°, verifying the accuracy of the model.

[0076] Example 2: Design and verification of super-hydrophobic self-cleaning structure

[0077] This embodiment details the specific implementation process of the design and verification of the super-hydrophobic self-cleaning structure in the present application.

[0078] First step: design of super-hydrophobic structure

[0079] By imitating the microstructure of lotus leaves, a composite micro-rough model with papillary microscale protrusions and nanoscale substructures is designed. The specific parameters are as follows:

[0080] Microscale protrusions: height 15-25 μm, diameter 8-12 μm, spacing 20-30 μm;

[0081] Nanoscale substructures: nanorod array, diameter 80-120 nm, height 1-2 μm;

[0082] Second step: 3D printing and structure characterization

[0083] A track shoe prototype with the above super-hydrophobic structure is manufactured using high-precision 3D printing technology. The printing material is wear-resistant polyurethane composite material to ensure the structural strength and service life.

[0084] The printed sample is characterized by scanning electron microscopy to confirm the size accuracy and morphology integrity of the micro-nano composite structure. The electron microscopy scanning shows that the prepared track surface successfully replicates the micro-nano hierarchical structure of lotus leaves.

[0085] Third step: air film characteristics and contact angle test

[0086] The contact angle between water droplets and the super-hydrophobic surface is measured using a contact angle meter. The test results show that the contact angle reaches 158°±3°, exhibiting excellent super-hydrophobic performance.

[0087] The interface characteristics between wet soft soil and the track surface are observed by electron microscopy scanning to confirm the formation of a continuous and stable air film layer with a thickness of about 2-5 μm.

[0088] Fourth step: verification of detachment effect

[0089] A traction test platform is set up to conduct detachment effect verification tests. The traditional track shoe and the super-hydrophobic self-cleaning track shoe of the present application are compared and tested.

[0090] Test conditions: soil moisture content 35%, test time 2 hours. The test results show that:

[0091] Traditional track shoe: soil adhesion amount reaches 3.2 kg / m², traction force decreases by 42%;

[0092] Super-hydrophobic track shoe of the present application: soil adhesion amount is only 0.8 kg / m², traction force decreases by 15%;

[0093] The super-hydrophobic self-cleaning structure of the present application significantly reduces soil adhesion and maintains stable output of traction force.

[0094] Example 3: Model reliability verification and overall optimization

[0095] First step: soil cone index test

[0096] Measure the soil cone index CI under different soil conditions:

[0097] Low water content soil (20%): CI = 650 kPa

[0098] Medium water content soil (30%): CI = 450 kPa

[0099] High water content soil (40%): CI = 280 kPa

[0100] Second step: comparison of model prediction results

[0101] Compare the prediction results of the track-ground coupling system model with the measured CI values:

[0102] Under the condition of CI = 450 kPa, the model predicts a settlement of 80 mm, and the measured settlement is 85 mm, with a relative error of 5.9%;

[0103] Under the condition of CI = 280 kPa, the model predicts a settlement of 120 mm, and the measured settlement is 125 mm, with a relative error of 4.0%;

[0104] The comparison results show that the model prediction accuracy meets the engineering requirements.

[0105] Third step: overall structure optimization matching

[0106] Reference McKeys-Ali three-dimensional model for final structure optimization, comprehensive analysis of all key parameters:

[0107] Track shoe width: 400 mm;

[0108] Track pitch: 100 mm;

[0109] Grouser height: 45 mm;

[0110] Grouser thickness: 12 mm;

[0111] Super-hydrophobic structure parameters: micro-protrusion height 20 μm, nano-structure diameter 100 nm;

[0112] Through three-dimensional space analysis, the best track structure matching scheme under typical wet and soft soil conditions is obtained.

[0113] Fourth step: comprehensive performance verification

[0114] The optimized track system is subjected to comprehensive performance test:

[0115] Passing performance: in wet soft soil with moisture content of 35%, the amount of subsidence is reduced by 35%;

[0116] Traction performance: the hook traction force is increased by 28%;

[0117] Self-cleaning performance: the amount of soil adhesion is reduced by 75%;

[0118] Work efficiency: the work efficiency of the combine harvester is increased by 22%;

[0119] The test results fully verify the effectiveness and superiority of the design method of the present application.

[0120] Example 4: grousers traction force prediction and structure optimization

[0121] Soil failure angle back calculation: the soil failure angle back calculation is carried out by using the following formula:

[0122] (4)

[0123] In the formula, B is the track shoe width, L is the track shoe pitch, is the ratio of grouser thickness to track shoe pitch, is the soil density, K is the deformation modulus, is the soil-pavement external friction angle, h is the grouser height, c is the soil cohesion, n is the soil deformation index, is the soil cohesion, is the soil subsidence, is the additional load, , , are factors related to the baffle parameters and the failure angle, respectively. is the failure angle, is the internal friction angle.

[0124] Parameter values: track shoe width B = 400 mm; track shoe pitch L = 100 mm; gullet thickness ratio λ = 0.12; soil density γ = 1750 kg / m³; deformation modulus K = 1.15; soil-shoe outer friction angle δ = 18°; gullet height h = 45 mm; soil cohesion c = 13 kPa; soil deformation index n = 0.8; soil subsidence z = 80 mm; additional load q_z = 4 kPa;

[0125] Through iterative calculation, the soil failure angle β = 52.3° and the internal friction angle φ = 25.6° are obtained.

[0126] Gullet parameter optimization:

[0127] According to the performance of track materials (wear-resistant polyurethane, tensile strength ≥ 35 MPa), three groups of gullet parameters are selected for testing:

[0128] Scheme A: h = 40 mm, λ = 0.10;

[0129] Scheme B: h = 45 mm, λ = 0.12;

[0130] Scheme C: h = 50 mm, λ = 0.14;

[0131] Through the accumulation of test data, the characteristic curve of the hook traction force with the gullet height and the gullet thickness ratio is drawn. The results show that scheme B achieves the best balance in hook traction force, driving resistance and material strength.

[0132] Three-dimensional model structure optimization:

[0133] The McKeys-Ali three-dimensional model is cited for final structure optimization:

[0134] A three-dimensional finite element model of track-soil interaction is established;

[0135] Set boundary conditions: the Drucker-Prager criterion is used for the soil constitutive model;

[0136] Analysis parameters: ground pressure distribution, stress transmission path, soil flow pattern;

[0137] Optimization objectives: maximize traction force, minimize driving resistance, and balance stress distribution;

[0138] Through three-dimensional spatial analysis, the best track structure matching parameters are obtained:

[0139] Track shoe width: 400 mm;

[0140] Track pitch: 100 mm;

[0141] Gullet height: 45 mm;

[0142] Grouser thickness: 12mm;

[0143] Grouser angle: 15°;

[0144] Grouser spacing: 60mm;

[0145] Verification test results:

[0146] Field test verification on the optimized track structure:

[0147] Traction performance: hook pull force increased by 31.5%;

[0148] Through performance: in the soil with moisture content of 35%, the amount of subsidence is reduced by 38.2%;

[0149] Detachment performance: soil adhesion is reduced by 72.8%;

[0150] Service life: fatigue life is increased by 45% based on stress analysis optimization;

[0151] This embodiment fully demonstrates the whole process from micro surface structure design to macro system optimization, and through the collaborative design method of multi-scale and multi-physical field, the significant improvement of the passability of the combine harvester in the wet and soft rice field is realized.

[0152] The above is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features described herein.

Claims

1. A method for designing a track system of a combine harvester for passing through a wet and soft paddy field, characterized in that, The method comprises the following steps: S1, track-ground coupling system modeling: a track-ground coupling system model is established, the model divides the track system into a track section between the driving wheel and the track roller, a track section under the track roller, and a track section between the track rollers, and uses multi-body dynamics software and control analysis software for joint simulation, calculates the system stress based on force balance equation, and reveals the constraint mechanism of wet soft soil on track passability; S2, track structure parameter optimization: based on the track-ground coupling system model, and referring to the three-dimensional model, the track-ground interaction is analyzed in three-dimensional space, and the structure parameters of the track shoe are optimized to maximize the traction performance and passability of the track in wet soft soil; S3, super-hydrophobic self-cleaning structure design and verification: a bionic super-hydrophobic self-cleaning structure is designed on the working surface of the track shoe, a prototype is manufactured by 3D printing, a scanning electron microscope is used to analyze the surface air film characteristics and soil contact angle, and the detachment effect is verified by traction test.

2. The method of designing a track system for a combine harvester to pass through a wet soft paddy field according to claim 1, wherein In the step of modeling the track-ground coupling system, when establishing the sub-model of the track part between the drive wheel and the road wheel, the force of the drive wheel of the track-ground coupling system is calculated, and the track micro-element deformation amount of the track from state 1 to state 2 is set as According to the force balance equation, the tension of the i th unit is shown in formula (1): （1） wherein, is the tension of the i-th microelement, is the angle between the i-th element and the horizontal line, is the angle change from the initial value to the i-th element, and , , , is the selected angle of any microelement relative to the horizontal plane, and are the normal pressure and shear force, respectively.

3. The method of designing a track system for a combine harvester to pass through a wet soft paddy field according to claim 1, wherein The tracked-ground coupling system modeling step further comprises a ground drivability measuring step: according to Bekker ground mechanics theory, the drivability of the ground is measured by using the approximate effective traction provided by the unit load area soil under the action of uniform pressure, and the calculation formula is shown as formula (2); (2) wherein, , wherein p, W, b, L, h are design parameters of the track, , Z, C, , are soil mechanical properties parameters.

4. The method of designing a track system for a combine harvester to pass through a wet soft paddy field according to claim 1, characterized in that, The track structure parameter optimization step specifically comprises: setting multiple track shoe schemes with different widths b, different pitches t, and different track shoe heights h; performing track shoe soil shearing test, analyzing the forces on the three shearing planes of the track shoe: the first plane parallel to the lower edge of the track shoe, and the two side planes perpendicular to the track shoe; based on the test data, a characteristic curve of the hook traction force with respect to the track shoe height and the track shoe thickness ratio is drawn, so as to select the optimal parameter combination. In the track structure parameter optimization step, the soil failure angle is back calculated according to formula (3) to establish a track shoe traction force prediction model: F = (γ·z·N_γ + c·N_c + q·N_q) · B · L · (1 + δ / B) · K (3) Wherein, F is the traction force, γ is the soil density, z is the settlement, c is the soil cohesion, q is the additional load, B is the track shoe width, L is the track shoe pitch, δ is the track shoe thickness, K is the deformation modulus, N_γ, N_c, N_q are bearing capacity factors related to the soil failure angle φ and the internal friction angle θ.

5. The method of designing a track system for a combine harvester to pass through a wet soft paddy field according to claim 4, characterized in that, In the super-hydrophobic self-cleaning structure design and verification step, the bionic super-hydrophobic self-cleaning structure is a composite micro-rough model simulating the surface of a lotus leaf, with papillary microscale protrusions and nanoscale secondary structures.

6. The method of designing a track system for a combine harvester to pass through a wet soft paddy field according to claim 1, wherein The method further comprises a model reliability verification step: by measuring the soil cone index CI under different soil conditions, analyzing the influence of various factors on the CI value, and comparing the change trend of the CI value with the prediction result of the track-ground coupling system model, the reliability of the model is proved.

7. The method of designing a track system for a combine harvester to pass through a wet soft paddy field according to claim 6, wherein Under the condition of determining the corresponding soil parameters and the track shoe width, according to the change of the track shoe height, the soil failure angle is back calculated by using the calculation formula (4):

8. The method of claim 6, wherein the track system design is adapted for the passage of the combine in a wet and soft paddy field. According to the material properties of the track, the appropriate track shoe height and track shoe thickness ratio are selected, the relationship between the settlement and the track shoe height is determined, and then according to the data accumulation, the characteristic curve of the hook traction force with respect to the track shoe height and the track shoe thickness ratio is drawn; （4） where B is the track shoe width, L is the track shoe pitch, is the ratio of the grousers thickness to the track shoe pitch, is the soil density, K is the deformation modulus, is the soil-pavement external friction angle, h is the grousers height, c is the soil cohesion, n is the soil deformation index, is the soil cohesion, is the soil settlement, is the additional load, , , are factors related to the baffle parameters, the failure angle, respectively; is the failure angle, is the internal friction angle; ​ The three-dimensional model of McKeys-Ali is cited to predict the traction of the track with the teeth, the track-ground interaction is analyzed in the three-dimensional space, the track structure under the typical wet and soft soil conditions is optimized according to the expressions of the related parameters and forces, the best track structure matching is obtained according to the three-dimensional model and the related discipline theories.

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