Wheat field weeding actuator design method and device based on operation power consumption model

Abstract

The invention discloses a wheat field hoeing actuator design method and device based on an operation power consumption model, the hoeing actuator comprises hobs and rollers, a plurality of hobs are connected to the rollers, and the whole hoeing process is divided into four working conditions: soil touching, soil cutting, grass chopping and soil raising by taking the contact of the end points of the blades of the hobs of the actuator with soil as the initial position. A power consumption model is adopted when the hob type weeding actuator works, wherein W = sigma i1 (W1 + W2 + W3 + W4); the wheat field weeding device is mainly composed of a hob, a roller, a driving motor, a controller and an auxiliary mechanism. The actuator adopts a weeding wheel type structure, the robot-soil-weed interaction relation in the wheat field hoeing process is analyzed, a hob type hoeing robot actuator power consumption model is constructed, structural parameters with the lowest power consumption in operation are determined, the working breadth is wide, the operation resistance is small, the hoeing efficiency is high, and the hoeing efficiency is high. And the problem of high seedling damage rate during weeding of small-row-spacing crops is effectively solved.

Description

Technical Field

[0001] The present invention relates to a design method and device for a wheat field weeding actuator based on an operation power consumption model, and belongs to the technical field of smart agricultural equipment. Background Art

[0002] Smart agriculture is an advanced form of modern agricultural production, and weed control is one of the most important tasks in smart agriculture. According to statistics, uncontrolled weeds can reduce wheat yields by about 40-50%. The peak period of wheat field weeds is during the tillering period. During this period, wheat plants are small, and weeds interfere with normal tillering of wheat, resulting in reduced wheat yields. At present, wheat field weeding technologies mainly include chemical methods and mechanical methods. Chemical methods have been widely used due to their high weed control efficiency, but large-scale spraying of herbicides has caused serious environmental pollution and affected the safe production of wheat. In recent years, mechanical weeding methods have received increasing attention due to their advantages such as being environmentally friendly, increasing soil permeability, and improving soil moisture.

[0003] The weeding actuator is the core and most important structural component of the weeding robot. The principle of its selection is to minimize the operating cost while ensuring the weeding rate and not harming the crops. According to statistics, the power system used to match the power consumption of the weeding machinery accounts for about 60% of the total operating cost. Therefore, the power consumption of the weeding actuator should be minimized to control the weeding cost. The actuator mechanism most commonly used for weeding in wheat fields is the rake-tooth actuator, which is mainly composed of a support device and elastic tines. When working, the weeding force and working depth can be changed by adjusting the tension of the elastic tines, and the weeding force and working depth can be removed from the early stage of seedling emergence to the early stage of tillering. This actuator has a simple structure and is not easy to be damaged in harsh outdoor environments. However, the operation mode of dragging the rake-tooth actuator leads to large travel resistance and high power consumption. It is usually towed by large agricultural machinery. When this actuator is operating, the wheat will be subjected to the same rake-tillage intensity as the weeds, which may cause damage to the wheat crop. In order to reduce the power consumption of weeding, Rueda-Ayala V et al. installed spectral cameras on agricultural machinery to monitor the density of weeds between crop rows, and only targeted weeding in the inter-row area, effectively avoiding the power consumption waste caused by "blind raking". Peteinatos GG et al. proposed a decision-making system based on ultrasonic sensors, which adjusts the raking intensity in real time according to weed and crop information, reducing the seedling injury rate of the rake tooth actuator during operation. However, due to the certain distance between the rake teeth of the rake tooth actuator, the phenomenon of missing hoeing is serious during operation, and the weeding rate is low. The rotary tillage actuator uses a rolling forward method to remove weeds between rows. This operation form is simple to enter the soil and can adapt to soils with different compaction degrees. However, the rotary tillage actuator throws a lot of soil during operation, resulting in high power consumption. In addition, due to the large range of soil disturbance, the row spacing is required to be 40cm-75cm, and the commonly used row spacing for wheat is 20cm. Therefore, the rotary tillage actuator is very easy to damage the seedlings when applied to wheat rows. Brush actuators can also be used for weeding between rows in wheat fields. The actuator is a polypropylene brush mounted on an axis, which tears or pulls up weeds by rotating. The advantage of this actuator is that it is not easy to adhere to the soil and can be used in more humid soil environments. Rabcewicz J et al. compared and analyzed the shallow tillage and weeding effects of brush actuators and rake-tooth actuators at an operating depth of 2-4 cm. The results showed that the brush actuator could only remove annual weeds (white mustard (Sinapis alba L.)), and the weeding rate was only 44%. In order to improve the weeding rate, it is necessary to increase the working intensity of the brush actuator (the ratio between the robot's forward speed and the brush head's rotation speed), but due to the contact between the brush head and the crop, it will also lead to a higher seedling injury rate, and a higher working intensity also requires greater power consumption. Therefore, the current wheat field weeding machinery has the problem that power consumption, weeding rate, and seedling injury rate cannot be taken into account at the same time. It is necessary to develop an intelligent weeding robot actuator with low power consumption, high weeding rate, and low seedling injury rate to ensure operation stability and machine reliability.

[0004] The weeding wheel (basket actuator) is a weeding tool composed of multiple blade rollers. This actuator can remove weeds growing in shallow soil without transferring soil to the crop row. Therefore, when used between crop rows with a row spacing of about 20 cm, it can reduce the seedling injury rate while increasing the operating width to ensure weeding stability. However, due to the large area of ​​the blade roller touching the soil, the weeding wheel is prone to excessive resistance during operation, resulting in slippage and "idling", resulting in a low weeding rate during operation. Han Tang et al. replaced the blade roller of the weeding wheel with rake teeth, and increased the weeding rate to more than 80% by changing the weeding depth, forward speed and operating speed. Zhang Y et al. studied the relationship between the installation angle of the weeding wheel blade and the cutting resistance, and conducted a weeding wheel performance test. The analysis found that the operating resistance was the smallest when the blade was installed perpendicular to the soil, and the seedling injury rate could be controlled within 4.4%. However, current research mainly focuses on optimizing the installation and working parameters of the weeding wheel, while ignoring the impact of the actuator structure parameters on the operation quality and power consumption. As a result, the current weeding wheel has high power consumption and is mainly used in humid soil environments containing a small amount of clay. Summary of the invention

[0005] The purpose of the present invention is to provide a design method and device for a wheat field weeding actuator based on an operation power consumption model. By analyzing the robot-soil-weed interaction relationship during wheat field weeding, a power consumption model of a roller-type weeding robot actuator is constructed, and the structural parameters with the lowest power consumption during operation are determined. This method not only has a wide working width, small operation resistance, and high weeding efficiency, but also effectively solves the problem of high seedling injury rate when weeding crops with small row spacing.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] On the one hand, the present invention provides a design method of a wheat field weeding actuator based on an operation power consumption model, wherein the weeding actuator comprises a roller cutter and a roller, a plurality of roller cutters are connected to the roller, and the structural parameters of the roller cutter and the roller that are related to the operation quality are set as: roller radius r, roller cutter blade angle α, roller cutter width l, roller cutter thickness B, and roller cutter quantity i; and taking the blade end point of the actuator roller cutter part contacting the soil as the initial position, the entire weeding process is divided into four working conditions: touching the soil, cutting the soil, crushing the grass, and throwing the soil, and then the roller cutter weeding actuator adopts the following power consumption model when operating:

[0008]

[0009] Among them, W1 is the power consumption under the soil-touching condition, W2 is the power consumption under the soil-cutting condition, W3 is the power consumption under the grass-chopping condition, and W4 is the power consumption under the soil-lifting condition;

[0010] The roller radius r, hob edge angle α, hob thickness B, and hob number i are optimized according to the following constraints:

[0011] The roller radius r satisfies:

[0012] 2r 2 ≥(r+35) 2

[0013] The hob edge angle α satisfies:

[0014] 20°≤α≤90°

[0015] The thickness of the hob B meets the following requirements:

[0016] 2≤B≤6

[0017] Number of hobs i:

[0018]

[0019] Furthermore, under the soil-touching condition, the power consumption W1 is 0W.

[0020] Furthermore, in the soil cutting condition, the power consumption W2 is the work done by the cutter to overcome the friction F1 and normal pressure F2 on the blade from the soil, the normal pressure F3 and friction F4 on the blade, that is:

[0021]

[0022] Where, r is the roller radius of the hob actuator, m; d is the operating depth of the hob actuator, m; ω is the angular velocity of the hob, rad / s; α—roll cutter edge angle, °; t1—roll cutter contact soil time, s; t2—roll cutter leave soil time, s.

[0023] Furthermore, in the grass-chopping condition, the power consumption W3 is the work done by the blade part to overcome the normal resistance F3 and friction F4 from the weed stems, that is:

[0024]

[0025] Among them, δ s —weed shear strength, MPa; ρ—weed density per unit area, plants / m 2 .

[0026] Furthermore, in the grass-chopping condition, the angular velocity ω of the reel cutter satisfies the relationship:

[0027]

[0028] Among them, m a —Roller mass, kg; A—cross-sectional area of ​​weed roots, mm2 ; τ—root strength limit, MPa.

[0029] Furthermore, under the soil-throwing condition, the power consumption W4 is the work done to overcome the resistance of the soil and weeds. Assuming that the end time of the scattering is t3 and the mass of the scattering soil and weeds is m, the power consumption of the roller is:

[0030]

[0031] Here, t3 is regarded as the end time of a single operation cycle, that is:

[0032] Furthermore, the power consumption model of the rotary blade weeding actuator during operation is:

[0033]

[0034] On the other hand, the present invention provides a wheat field weeding device based on an operation power consumption model, wherein the weeding actuator of the wheat field weeding device is designed using the method of the above scheme.

[0035] Furthermore, the wheat field weeding device also includes a power device, a suspension device, a connecting support, a driving motor and a controller. The power device pulls the suspension device, a connecting support is arranged at the end of the suspension device, the weeding actuator is mounted on the connecting support, and is driven by the driving motor through a chain.

[0036] Furthermore, the roller in the weeding actuator is vertically mounted on the roller, and the structural parameters of the roller and the roller are: roller radius 85 mm, roller blade angle 20°, roller thickness 2 mm, and the number of rollers 8.

[0037] The beneficial effects of the present invention are as follows:

[0038] The actuator of the present invention adopts a weeding wheel structure. By analyzing the interaction between the robot, soil and weeds during the weeding process in the wheat field, a power consumption model of the roller-type weeding robot actuator is constructed, and the structural parameters with the lowest power consumption during operation are determined. Not only does it have a wide working width, small operating resistance and high weeding efficiency, but it also effectively solves the problem of high seedling injury rate when weeding crops with small row spacing.

[0039] The actuator of the weeding device of the present invention tends to disturb the soil in the surface working space, forming an inverted trapezoidal cross-sectional shape of the working area. Since the compaction degree of soil is proportional to the depth, the power consumption required to cut the surface soil is relatively small. Therefore, compared with the shallow loose straight rotary tiller under the same working conditions, the actuator effectively reduces power consumption and increases the working width. The accumulation thickness caused by the roller weeding robot after the operation does not exceed 20mm, which is much smaller than the height of the wheat plant and will not affect the normal photosynthesis of the crop. The weeding rate is calculated by statistically analyzing the ratio of green pixels before and after the operation through image processing methods. The results show that the roller weeding device of the present invention can effectively remove weeds in the inter-row area of ​​the wheat field. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a structural schematic diagram of the rotary cutter weeding device of the present invention.

[0041] The markings in the figure are: 1. flange; 2. roller; 3. hob; 4. lock edge cover; 5. drive motor; 6. chain; 7. connecting support; 8. controller; 9. suspension device; 10. power unit; 10. camera.

[0042] Figure 2 It is a structural schematic diagram of the rotary blade wheat field weeding actuator of the present invention.

[0043] Figure 3 It is an analysis of the motion process of the weeding actuator operation; among which: a. soil contact condition; b. soil cutting condition; c. grass breaking condition; d. soil throwing condition; the red line is the motion trajectory of the actuator; F1—soil friction force on the blade; F2—soil normal pressure on the blade; F3—normal force on the blade; F4—friction force on the blade; F5—throwing resistance on the blade.

[0044] Figure 4 It is the force diagram of the weeding actuator micro-segment; among which: a. the force on the blade micro-segment; b. the force on the blade micro-segment.

[0045] Figure 5 It is a simulation of the weed-soil-actuator interaction process; among which: a. the roller-type actuator is at the initial position; b. the roller-type actuator reaches the starting point of the operation; c. the roller-type actuator operation process; d. the roller-type actuator reaches the end point of the operation.

[0046] Figure 6 It is a schematic diagram of actuator test indicators.

[0047] Figure 7 Test point settings for actuator simulation test; TP: Test Point; the red box is the Slices area.

[0048] Figure 8is the result of actuator motion simulation; among them: a. Weeding effect diagram within the actuator working width, the green particles in the red circle are broken weeds; b. Soil profile diagram after weeding; c. Soil scattering diagram after weeding, the white particles are soil particles scattered to both sides.

[0049] Fig. 9 is the dynamic change diagram of actuator test indicators; among them: aW a Simulation result diagram, where the red circle represents the velocity vector diagram of soil particles on both sides of the roller cutter; b. Velocity diagram of soil thrown on both sides, where the red circle represents the soil that has not remained stationary after accumulation, resulting in D b1 Data fluctuations; main. Dynamic changes in various test indicators. DETAILED DESCRIPTION

[0050] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] like Figure 1 As shown, a wheat field weeding device based on an operation power consumption model is mainly composed of a roller 3, a roller 2, a driving motor 5, a controller 8 and auxiliary mechanisms.

[0052] The reel 3 is the main weeding actuator. In this embodiment, a right-angle blade is used to replace the rake blade originally equipped on the weeding wheel structure. The roller is a structural component used to fasten the reel and transmit the output driving force of the hub motor. The reel rotation radius can affect the actuator torque and the contact time between the reel and the soil, thereby affecting the actuator power consumption and weeding effect. In this embodiment, the reel rotation radius is adjusted by changing the roller radius.

[0053] The driving motor 5 and the roller 2 are driven by a chain 6. A plurality of roller cutters 3 are welded to the outside of the roller. An extended sleeve is embedded at the axis of the roller 2 and fixed to the connecting support 7 by a thread. A locking cover plate 4 is installed on the outside to prevent reverse rotation when the driving motor 5 is stopped. The overall actuator structure is fixed to the rear of the suspension device 9 by connecting supports 7 on both sides.

[0054] When weeding, the driving motor 5 drives the reel 3 to rotate into the soil to a certain depth, disturbing the weeds and soil in the working area. After weeding, the reel 3 is lifted off the ground, and the soil is mainly thrown backwards to protect the crops on both sides from being covered by the soil, thereby reducing the robot's seedling injury rate.

[0055] like Figure 2As shown in the figure, the key component of the weeding device is the actuator, which mainly includes two parts: the roller and the roller. Among them, multiple rollers are connected to the roller by welding. The roller mainly performs the actions of loosening the soil, cutting or pulling out the weeds in the working area. The important structural parameters that determine its working quality include the roller blade angle α, the roller width l, the roller thickness B, the number of rollers i and the angle of entry into the soil; the roller is used to limit the roller rotation radius and maintain the stability of the weeding depth. Its important structural parameter is the roller radius r.

[0056] In the design, the roller cutter actuator has a large soil contact width during operation, so it is necessary to minimize the working resistance to prevent slipping and "idling" when operating in dryland crops such as wheat. Secondly, due to the narrow row spacing in wheat fields, it is necessary to minimize the soil spreading on both sides while ensuring the weeding rate. In order to clarify the impact of various structural parameters on the operating resistance and soil throwing, this embodiment analyzes the operation process of the roller cutter actuator.

[0057] During the weeding process, the robot, soil, and weeds form a force balance system. Taking the end point of the actuator blade touching the soil as the initial position, the entire operation process can be divided into four working conditions: touching the soil, cutting the soil, breaking the grass, and throwing the soil. Figure 3 shown.

[0058] a. Touching the soil: The end of the blade touches the soil plane, and the position of the roller at this time is set to the initial position, that is, the roller rotation angle θ is 0°; the normal pressure F2 and friction F1 on the roller blade are both 0N, and the friction F4 on the blade gradually increases from 0N. When the driving force is greater than the maximum static friction of the soil on the blade, the roller cuts into the soil and starts working. Since weeding has not started, the power consumption W1 is 0W under this working condition.

[0059] b. Soil cutting: After the roller cutter enters the working area, it will squeeze, push and cut the soil. The blade angle α can determine the sharpness of the roller cutter and affect the resistance of the actuator to soil cutting during operation. The roller cutter width l can determine the width of soil disturbance during operation and change the operating width of the actuator. The roller radius r can determine the working time of the roller cutter in the soil and affect the cumulative power consumption of the actuator. Under this working condition, the actuator mainly overcomes the friction force F1 and normal pressure F2 on the blade body from the soil, and the normal pressure F3 and friction force F4 on the blade to do work. The forces on each micro-segment of the roller cutter are as follows: Figure 4 As shown in the figure, the soil friction force on the blade micro-segment dH under this working condition is:

[0060] dF1=N1fdH (1)

[0061] Among them, N1 = EBl; E—soil compaction, MPa; l—roller width, m; f—soil-actuator friction coefficient; B—blade thickness, m. Field test was used to determine E=0.4658±0.1725MPa; since the current wheat field row spacing is generally 200mm, l=0.16m was set to avoid the actuator from hurting the seedlings; and f=0.5 was determined through reference and analysis.

[0062] Soil normal pressure on blade micro-segment dH:

[0063] dF2=N1dH (2)

[0064] Overcoming normal force on the hob blade micro-segment dS:

[0065] dF3=N2ldS (3)

[0066] Where, N2 = (EB + δb); b - blade thickness, m; δ - soil shear strength, MPa;

[0067] Overcoming friction on the micro-segment dS of the hob blade:

[0068] dF4=(EB+δb)lfdS (4)

[0069] The power consumption calculation method of the hob actuator is the work done by the various resistances in the direction of the rotating radius of the hob. The total work of each part of the hob is calculated by integration. Under this working condition, the power consumption W2 is the work done by the hob to overcome F1, F2, F3, and F4, that is:

[0070]

[0071]

[0072] Wherein, r is the roller radius of the roller cutter actuator, m; d is the operating depth of the roller cutter actuator, m; generally, the depth of weeds in wheat fields is 0-35 mm, so d=35 mm is set; ω is the angular velocity of the roller cutter, rad / s. α—Roller blade angle, °. t1—Roller contact soil time, set to 0s; t2—Roller leave soil time, s; Zhang Y et al. found that the power consumption is lowest when the tool is installed at an angle of 90°. Therefore, this paper chooses to install the roller vertically on the roller. According to the geometric relationship,

[0073] c. Grass cutting: During operation, the reel cuts or breaks the weeds in the inter-row area. The weeds are mainly removed and cut by the reel blade, so the blade angle α is a key structural parameter affecting this working condition. When the thickness B of the reel is different, the length of the blade part is also different, which in turn affects the grass cutting resistance of the reel. At this time, the actuator mainly overcomes the normal resistance F3 and friction F4 from the weed stems at the blade part.

[0074] Overcoming normal force on the hob blade micro-segment dS:

[0075] dF3=N3ldS (6)

[0076] Where N3 = δ s ρb;δ s —weed shear strength, MPa; ρ—weed density per unit area, plants / m 2 By consulting the literature, δ s =1.24MPa

[27] , ρ=133 plants / m 2 .

[0077] Overcoming friction on the micro-segment dS of the hob blade:

[0078] dF4=δ s ρblfdS (7)

[0079] In this working condition, the power consumption W3 is the work done by the hob to overcome F3 and F4, that is:

[0080]

[0081] In this working condition, when ω is too low, weeds cannot be removed and the relationship should be satisfied:

[0082]

[0083] Among them, m a —Roller mass, kg; A—cross-sectional area of ​​weed roots, mm 2 ; τ—root strength limit, MPa; through field measurement and reference, A=2mm 2 ,τ=5.301MPa.

[0084] d. Throwing soil: At this time, the reel is separated from the soil in the working area, and some soil and weed mixture remain on the reel. These mixtures are finally thrown inside or on both sides of the working area as the actuator rotates. Among them, when the roller radius r changes, the kinetic energy generated by the actuator when it rotates is also different, which can determine the final throwing position of the mixture remaining on the reel. In this working condition, the main work is to overcome the resistance of the thrown soil and weeds. Assuming that the throwing end time is t3, and the mass of the thrown soil and weeds is m, the power consumption of the reel is:

[0085]

[0086] Since it is difficult to define the specific time t3, and the reset condition is no-load rotation, which has little impact on the overall power consumption, t3 is regarded as the end time of a single operation cycle, that is:

[0087] The power consumption during the hob movement is the sum of the work done by the hob resistance in each stage, that is:

[0088] W h =W1+W2+W3+W4 (11)

[0089] Therefore, the power consumption model of the hob actuator during operation can be determined:

[0090]

[0091] The design optimization variables of the hob actuator are the roller radius r, the hob blade angle α, the hob thickness B, and the number of hobs i. Substituting the known parameters into the established power consumption model, the objective function is:

[0092]

[0093] Constraints include: To ensure that the actuator cutter can be inserted vertically into the soil, r must satisfy:

[0094] 2r 2 ≥(r+35) 2 (14)

[0095] To ensure structural strength, the tool edge angle is usually greater than 20°, but too large an angle will lead to too high resistance to soil penetration, so its maximum should not exceed 90°, that is, α should ensure:

[0096] 20°≤α≤90° (15)

[0097] The thickness of the blade mainly affects the structural strength and operating performance of the actuator and should be ensured

[32]

[33] :

[0098] 2≤B≤6 (16)

[0099] i should satisfy the formula:

[0100]

[0101] fmincon is a function used to solve the minimum value of nonlinear multivariate functions and can solve constrained optimization problems. This embodiment applies it to solve the objective function in a numerical analysis environment. The results show that when r = 85, α = 20, B = 2, and i = 7.13, the objective function achieves the minimum value, f(r, α, B, i) = 178.3983. When i is rounded to 8, the optimal structural parameters of the hob-type actuator with the lowest power consumption are finally determined: roller radius 85mm, hob blade angle 20°, hob thickness 2mm, and hob number 8. The overall height of the weeding device is adjustable to ensure a soil penetration depth of 35mm. Substituting the structural parameters into formula (9), it is calculated that ω≥23.5306rad / s. Since ω is proportional to power consumption, in order to ensure the lowest power consumption during operation, ω=23.5306rad / s.

[0102] The following is a motion simulation analysis of the hob-type actuator of the present invention.

[0103] The motion simulation of the hob-type actuator in this embodiment is analyzed on the discrete element software EDEM2.7. The soil particles are represented by spherical particles with a radius of 5 mm. The particles are generated in a soil box composed of five planes. The box size is 1000 mm long × 350 mm wide × 300 mm high, ensuring that the actuator has enough motion range within a certain simulation time and does not produce any edge effect with the soil box. The final number of soil particles generated is 50,000, and the soil density is 1280 kg / m 3 . The Hertz-Mindlin with Bonding model is used between particles. This model introduces a "force chain" effect between soil particles so that there is a certain adhesion between particles to simulate the bonding force of real soil. The morphology and mechanical parameters of weeds are shown in Table 1. The discrete element model of weeds is established through the EDEM particle replacement function, and the particle radius is set to 0.65 mm. According to the weed density, 32 weed models are evenly set above the soil model. The actuator-related parameter settings refer to 65Mn steel, and the Hertz-Mindlin model is used to model the interaction between soil, weeds and actuators. The model uses a nonlinear elastic method to predict the interaction between soil, weeds and actuators. All discrete element setting related parameters are shown in Table 2.

[0104] Table 1 Basic parameters of weed simulation model

[0105]

[0106] Before starting the simulation, the established roller cutter actuator model is positioned above the weed and soil model to ensure that the roller cutter actuator will not destroy the force chain generated between the soil and weeds. The roller cutter actuator operating depth is consistent with the power consumption model, d = 35mm. After the soil and weed models are completely still, the actuator slowly descends to the set operating depth; during the descent, it is accompanied by slow rotation (10r / min) to avoid rigid extrusion between the roller cutter and soil particles when the actuator contacts the soil layer, resulting in inaccurate simulation values.

[0107] Table 2 Basic parameters of soil model

[0108]

[0109] Set the actuator forward speed to 0.5m / s. According to the ω value, the speed is converted to n = 225r / min. Set the operation time to 1.5s. The simulation process is as follows: Figure 5 As shown. After the hob actuator slowly reaches the starting point of the operation from the initial position ( Figure 5 b) The weeds and soil in the working area are disturbed by rotating the roller around the axis of the roller ( Figure 5 c) Due to the soil and weeds being thrown backwards in the soil-raising condition, they are intercepted by the box and piled up behind the starting point of the operation. The actuator stops working after reaching the end point, and the simulation ends when the soil and weeds in the model are completely still ( Figure 5 d).

[0110] In order to test the soil disturbance range of the designed roller cutter actuator during field operation, a simulation study was conducted on its motion process. The test indicators include the operating width (W a , W b )、Operation depth (D a )、Spreading width (W t ), stacking thickness (D b ) and average power (P a ),like Figure 6 As shown in the figure, since the row spacing of wheat fields is generally about 200 mm, the areas on both sides 100 mm (TP A) and 150 mm (TP B) away from the axis of the working area are taken as potential crop areas, and the accumulation thickness at these two points is tested to analyze the interference caused by the actuator to the wheat during operation.

[0111] After the simulation is completed, the model is post-processed and analyzed to obtain the performance index values ​​of the actuator. Five test points are set for data collection, such as Figure 7As shown. Since there is soil accumulation at the starting and ending positions of the actuator operation, in order to ensure the accuracy of the collected data, the test area is taken in the middle of the soil model, and the distance between each test point is 125mm. Each time the data is collected, the Slices function in the Clipping module is used to intercept the soil profile at each test point, and the thickness is set to 50mm. The Ruler function is used for data collection for each performance indicator. Among them, when testing the operating width, in order to eliminate the data anomalies caused by the actuator throwing soil back into the operating area, the soil model at the time step when the roller just left each test point is selected for statistics. When testing other performance indicators, data collection is carried out 3s after the operation is completed to ensure that the soil particles are completely still during the test.

[0112] The motion simulation results of the weeding robot actuator are as follows: Figure 8 , and statistically analyze the data of the test indicators at each test point in a single operation cycle, and analyze the dynamic changes of each test indicator during the operation process ( Fig. 9 ). The details are as follows:

[0113] The operating width can directly affect the weeding effect. When the root depth of the weeds in this range is greater than the working depth of the actuator, they will be cut up and taken out of the soil or buried in the soil. When the root depth of the weeds is less than the working depth of the actuator, they will be directly pulled out by the actuator. Figure 8 a. The dynamic change of the operating width of the extraction test point position in a single operating cycle (t0-t1) ( Fig. 9 ), it can be seen from the figure that under the soil contact condition, W a , W b are all 0mm. As the hob moves, W a Rapidly increases, and finally stabilizes at around 200mm; W b There was no significant change during the operation cycle, which was about 160 mm. The operation width values ​​at each test point were counted and the average was taken, W b 160.25mm, which is close to the actuator width; W a 205.34mm, significantly larger than W b This may be because the soil compaction is positively correlated with the depth. The bonding bonds in the lower layer of the soil model are more difficult to break. Therefore, when the force is the same, the upper soil disturbance area is large, and the operating width is wider than the actuator itself. The soil profile formed is as follows: Fig. 9 As shown in b. Considering that the row spacing of wheat fields is generally about 200 mm, the rotary cutter actuator can cover the entire inter-row area during operation, and because of the small bottom width, it can protect the roots of wheat crops that spread to the inter-row area from being damaged.

[0114] The working depth of the rotary cutter actuator is set to 35 mm, but due to the disturbance between the rotary cutter and the soil during operation, the working depth (Da ) is often greater than the set working depth. The root system of weeds in the field during the tillering period of wheat is shallow, generally less than 35mm; when the working width is similar, a deeper working depth means more deep soil is disturbed and the required power consumption is also higher, so D a It is also an important performance indicator of the hob actuator. The dynamic change of the operating depth in a single cycle (t0-t1) at the test point is derived ( Fig. 9 ), the working depth in the soil contact condition is 0 mm, as the cutter reaches the deepest working position in the soil cutting condition, D a Gradually increase to the set working depth (35mm), due to the adhesion between particles, the final stable D a Slightly larger than 35mm. The Ruler tool was used to count the operating depth at each test point. The analysis showed that the average operating depth in the simulation model was 36.53mm, indicating that the designed roller cutter actuator did not disturb the deeper soil during operation, resulting in less ineffective power consumption. Combined with the operating width, the roller cutter actuator tends to disturb the soil in the lateral operating space during operation, reducing the operating power consumption while ensuring the weeding effect.

[0115] When the rotary cutter actuator is working in the wheat field, the soil between the rows and the chopped weeds will adhere to the rotary cutter and be scattered inside or on both sides of the working area as the rotary cutter rotates. Studies have shown that the height of wheat plants during the tillering period is generally greater than 120 mm. When the thickness of the soil accumulated on both sides exceeds the height of the wheat plants, it may affect the photosynthesis of the crop and cause seedling damage. Figure 8 As shown in c, soil particles larger than the initial model height are marked in white. Analysis shows that the soil height on both sides of the actuator has increased. The dynamic change of the spreading width in a single operation cycle (t0-t1) at the test point position is derived ( Fig. 9 ), the analysis found that after the cutter reaches the soil-throwing condition, W t It starts to increase from 0mm, and the farthest distance of the scattered particles is about 300mm. Statistics of the scattering situation at each test point, after the hob actuator is operated, W t The average value is 308.36 mm. The soil particles can reach the crop area. It is necessary to further analyze the accumulation thickness and potential damage to the seedlings. The dynamic accumulation thickness of a single cycle (t0-t1) is as follows: Fig. 9 As shown, D b1 After the scattered particles hit the ground, they gradually increase to 18.92 mm. Due to inertia, the particles roll to a wider position. b1 Finally, it stabilizes at around 13 mm. When the scattered particles reach TP B, D b2 It starts from 0mm and eventually reaches 6.8mm. Statistics of different test points, at TP A position D b1The average value is 12.86 mm, TP B position D b2 The average value is 7.10mm, and each test point is much smaller than 120mm. Therefore, the rotary cutter actuator can protect the crops on both sides from damage when weeding in the wheat field.

[0116] The power consumption of the actuator under the same working parameters should be used as an important indicator of the performance of the actuator. After the simulation is completed, the power required for the hob actuator to complete the task in the working area is exported through the Export Results Data function. The operating power (P) ( Fig. 9 ), when the actuator cuts into the soil, the particle bonding bond in the model is a whole, resulting in a large operating power in the early stage, and gradually fluctuates around 200W in the later stage. The average of the derived power is taken, and the result shows that the average power of the hob actuator is 209.41W, which is 17.38% different from the power value calculated in the power consumption model established in the early stage, indicating that the established interactive simulation model can accurately predict the power consumption of the machine operation.

[0117] In summary, the present invention is based on a weeding wheel structure, establishes the robot-soil-weed interaction relationship during wheat field weeding, analyzes the resistance from soil and weeds to the actuator during operation, constructs a power consumption model of a roller-type weeding robot, determines the actuator structural parameters with the lowest power consumption, and designs a roller-type wheat field weeding device with low operating resistance and high weeding efficiency. The present invention uses a discrete element method to conduct a motion simulation test of a roller-type actuator, analyzes the dynamic changes of soil and weeds during operation, and conducts field tests at the experimental base of Nanjing Agricultural University. The test indicators include operating width, operating depth, spreading width, stacking thickness, average power and weeding rate. The results show that the designed weeding robot actuator tends to disturb the soil in the surface working space, forming an inverted trapezoidal cross-sectional shape of the working area. Since soil compaction is proportional to depth, the power consumption required to cut the surface soil is relatively small. Therefore, compared with the shallow loose straight rotary tiller under the same working conditions, the actuator effectively reduces power consumption and increases the working width. The thickness of the accumulation caused by the rotary weeding robot after operation does not exceed 20mm, which is much smaller than the height of the wheat plant and will not affect the normal photosynthesis of the crop. The weeding rate is calculated by statistically analyzing the ratio of green pixels before and after the operation through image processing. The results show that the rotary weeding robot can effectively remove weeds in the inter-row area of ​​the wheat field. The simulation test results are consistent with the trend of the field verification test results, indicating that the designed robot can weed the inter-row area of ​​the wheat field with low power consumption and high efficiency.

[0118] The test results show that the working area of ​​the rotary blade weeding device is an inverted trapezoid, which fully covers the working area while ensuring that the wheat root system is not damaged; the working width is 202.8mm, the working depth is 36mm, and there is less soil on both sides, which can protect the wheat from being buried during weeding; the average power is 197.70W, which effectively reduces the operating cost and the weeding rate is 98.94%.

[0119] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the protection scope of the present invention in any form, and all technical solutions obtained by equivalent replacement and the like fall within the protection scope of the present invention. The parts not involved in the present invention are the same as the prior art or can be implemented by the prior art.

Claims

1. A design method for a wheat field weeding actuator based on an operation power consumption model, characterized in that: The weeding actuator includes a roller and a roller, and multiple rollers are connected to the roller. The structural parameters of the roller and the roller that are related to the work quality are set as: roller radius r, roller blade angle α, roller width l, roller thickness B, and roller number i; and the blade end of the actuator roller part contacts the soil as the initial position, and the whole weeding process is divided into four working conditions: touching the soil, cutting the soil, breaking the grass, and throwing the soil. Then, the roller-type weeding actuator adopts the following power consumption model when working: Among them, W1 is the power consumption under the soil-touching condition, W2 is the power consumption under the soil-cutting condition, W3 is the power consumption under the grass-chopping condition, and W4 is the power consumption under the soil-lifting condition; The roller radius r, hob edge angle α, hob thickness B, and hob number i are optimized according to the following constraints: The roller radius r satisfies: 2r 2 ≥(r+35) 2 The hob edge angle α satisfies: 20°≤α≤90° The thickness of the hob B meets the following requirements: 2≤B≤6 Number of hobs i:

2. The method for designing a wheat field weeding actuator based on an operation power consumption model according to claim 1, characterized in that: Under the soil-touching condition, the power consumption W1 is 0W.

3. The method for designing a wheat field weeding actuator based on an operation power consumption model according to claim 1, characterized in that: In soil cutting conditions, the power consumption W2 is the work done by the cutter to overcome the friction F1 and normal pressure F2 on the blade from the soil, the normal pressure F3 and friction F4 on the blade, that is: Where, r is the roller radius of the hob actuator, m; d is the operating depth of the hob actuator, m; ω is the angular velocity of the hob, rad / s; α—roll cutter edge angle, °; t1—roll cutter contact soil time, s; t2—roll cutter leave soil time, s.

4. The method for designing a wheat field weeding actuator based on an operation power consumption model according to claim 1, characterized in that: In the grass-chopping condition, the power consumption W3 is the work done by the blade part to overcome the normal resistance F3 and friction F4 from the weed stems, that is: Among them, δ s —weed shear strength, MPa; ρ—weed density per unit area, plants / m 2 .

5. The method for designing a wheat field weeding actuator based on an operation power consumption model according to claim 4, characterized in that: In the grass-chopping condition, the angular velocity ω of the reel cutter satisfies the relationship: Among them, m a —Roller mass, kg; A—cross-sectional area of ​​weed roots, mm 2 ; τ—root strength limit, MPa.

6. The method for designing a wheat field weeding actuator based on an operation power consumption model according to claim 1, characterized in that: In the soil-throwing condition, the power consumption W4 is the work done to overcome the resistance of the scattered soil and weeds. Assuming that the end time of the spreading is t3 and the mass of the scattered soil and weeds is m, the power consumption of the roller is: Here, t3 is regarded as the end time of a single operation cycle, that is:

7. The method for designing a wheat field weeding actuator based on an operation power consumption model according to claim 1, characterized in that: The power consumption model of the rotary blade weeding actuator during operation is:

8. A wheat field weeding device based on an operation power consumption model, characterized in that: The weeding actuator of the wheat field weeding device is designed using the method described in any one of claims 1 to 7.

9. A wheat field weeding device based on an operation power consumption model according to claim 8, characterized in that: The wheat field weeding device also includes a power device, a suspension device, a connecting support, a driving motor and a controller. The power device pulls the suspension device. A connecting support is arranged at the end of the suspension device. The weeding actuator is installed on the connecting support and is driven by the driving motor through a chain.

10. The wheat field weeding device based on the operation power consumption model according to claim 8, characterized in that: The roller in the weeding actuator is vertically mounted on the roller, and the structural parameters of the roller and the roller are: roller radius 85 mm, roller blade angle 20°, roller thickness 2 mm, and the number of rollers 8.

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