Constant flow control method for tobacco feeding machine climbing

Abstract

This invention relates to a constant flow control method for an inclined conveyor belt of a tobacco feeder. The constant flow control system for the inclined conveyor belt includes a main controller module, a tobacco pre-filling module, a redundant high / low position detection module, and a speed regulation module. This invention models and analyzes the relationship between the motor frequency and mass flow rate of the inclined conveyor belt; then, it proposes a reasonable frequency regulation control logic for the inclined conveyor belt; finally, it verifies the model and control logic using actual production data, and further improves and refines it. This invention meets the production requirements of stable, constant flow control. Simultaneously, the operational stability of the inclined conveyor belt motor is significantly improved, and equipment wear and energy consumption are effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of control system technology, specifically to a constant flow control method for an inclined zone of a tobacco feeder. Background Technology

[0002] like Figure 1 As shown, the constant flow control system of a tobacco production line typically consists of main equipment such as a feeder bin, a feeder bottom belt, a feeder inclined belt, a leveling roller, a metering tube (equipped with multiple photoelectric detection devices), and an electronic belt scale. The feeder bin, as a large buffer device, buffers a certain amount of tobacco for the constant flow control system. The inclined belt transports the tobacco to the metering tube, and then to the electronic belt scale. The metering tube, as a small-scale tobacco buffer device, helps improve the stability of the tobacco supply to the electronic belt scale, thus achieving the purpose of constant flow control.

[0003] Currently, the speed control of the inclined belt conveyor mainly depends on the photoelectric tube signal on the metering tube. There are three main control modes: ① The metering tube has photoelectric tubes for high, medium, and low material levels, corresponding to low, medium, and high speed control modes for the inclined belt motor, respectively. This control mode has poor flexibility, resulting in frequent start-stop of the inclined belt motor. ② The metering tube has photoelectric tubes for high, medium, and low material levels, using PID algorithms and fuzzy control to control the operating speed of the inclined belt motor. However, this method has a certain degree of lag because it requires statistically analyzing and collecting the photoelectric tube blocking and conduction time signals. ③ The metering tube only has high and low material level photoelectric tube signals. The on / off state of the photoelectric tube signal controls the start and stop of the inclined belt. Its operating frequency is determined by the operating frequency of the electronic belt scale. This method results in a high number of start-stop cycles and low reliability for the inclined belt motor. Summary of the Invention

[0004] This invention addresses the problems of mismatch between the speed control of the ramp belt in a tobacco feeder and the demand for tobacco feed flow, resulting in frequent motor starts and stops, high equipment wear and tear, and high energy consumption. It proposes an improved method for controlling the speed of the ramp belt.

[0005] The technical solution of the present invention:

[0006] A constant flow control method for an inclined belt of a tobacco feeder, wherein the constant flow control system for the inclined belt of the tobacco feeder includes a main controller module, a tobacco pre-filling module, a redundant high / low position detection module, and a speed regulation module;

[0007] The main controller module includes a PLC controller, which receives signals from redundant high / low level detection modules, and judges different material levels in the quantitative tube based on the specified high / low level light transmission and light blocking judgment conditions. According to the judgment result, it outputs control commands to the speed regulation module to reduce or increase the speed, and adjusts the speed of the climbing belt motor to achieve the purpose of controlling the tobacco flow. At the same time, the speed regulation result of the speed regulation module is also fed back to the main controller module in real time.

[0008] During the stabilization stage, the tobacco pre-filling module, based on the analysis and establishment of the constant flow control system model and the mass flow rate required by the process, calculates the theoretical frequency value of the ramp belt motor. According to this frequency value, the quantitative tube is pre-filled with tobacco. After the pre-filling is completed, the electronic belt scale starts running after the high-level light blocking signal is triggered. Subsequently, the actual operating frequency value of the ramp belt motor is finely adjusted near the theoretical frequency value to keep the height of the tobacco in the quantitative tube between the second high-level phototube and the first low-level phototube, i.e., within the ideal height range.

[0009] Preferably, the stabilization phase is the first five minutes after production begins.

[0010] Preferably, the analysis and establishment of the constant flow control system model includes the following steps:

[0011] The volumetric flow rate of the metering tube is denoted as flow(v0), the volume of tobacco shreds stored in the metering tube is denoted as v0, the density of tobacco shreds stored in the metering tube is denoted as ρ, and the mass flow rate of the electronic belt scale is denoted as flow(m). The mass flow rate control relationship between the electronic belt scale and the metering tube is shown in formula (1):

[0012] flow(m)=ρ*flow(v0) (1)

[0013] A uniform roller is installed above the feeder's inclined belt. The thickness and height of the tobacco shreds conveyed by the inclined belt are uniform. The height of the tobacco shreds is h, the width of the inclined belt is a, the running speed of the inclined belt is v, and the volumetric flow rate of the tobacco shreds conveyed by the inclined belt is flow(v). The relationship between the volumetric flow rate of the metering tube and the volumetric flow rate of the tobacco shreds conveyed by the inclined belt is shown in formula (2):

[0014] flow(v0)=flow(v)=v*a*h(2)

[0015] Substituting formula (2) into formula (1) yields the constant flow control system model between the feeder's ramp belt operating frequency and the electronic belt scale's mass flow rate, as shown in formula (3):

[0016] flow(m)=ρ*flow(v0)=ρ*flow(v)=ρ*v*a*h(3)

[0017] The frequency converter controls the motor to run, and the motor drives the reducer to rotate according to the reduction ratio. The reducer drives the inclined belt to transport tobacco through chain drive. According to professional theoretical knowledge, the speed n of the reducer is as shown in formula (4):

[0018] n=60*f / (p*k) (4)

[0019] f represents the motor operating frequency; p represents the number of pole pairs of the motor; k represents the speed ratio of the reducer.

[0020] From formula (4), we know that the length of tobacco shreds conveyed per second on the climbing belt is denoted as L, where L = v * 1s, as shown in formula (5):

[0021] L=2*π*r*n / 60=2*π*r*f / (p*k) (5)

[0022] r represents the radius of the main drive shaft;

[0023] Substituting formula (5) into formula (3), we obtain the constant flow control system model transformation formula between the operating frequency of the ramp motor and the mass flow rate of the electronic belt scale, as shown in formula (6):

[0024] flow(m)=ρ*v*a*h=ρ*[2*π*r*f / (p*k)]*a*h(6)

[0025] During the production process, based on the changes in the mass flow rate data flow(m) of the electronic belt scale as required by the process, the motor frequency f is controlled accordingly to ensure that the system achieves the purpose of constant flow control.

[0026] Preferably, the actual operating frequency of the motor for the climbing belt is finely adjusted near the theoretical frequency, with the adjustment range being 0.2-0.8Hz, that is, Δf1, Δf2, Δf3, and Δf4 are all between 0.2-0.8Hz;

[0027] The ideal height range is 30cm-80cm, which is between the second highest phototube and the first lowest phototube.

[0028] Preferably, the constant flow system control logic includes the following steps: After the tobacco pre-filling is completed, the system proceeds to the material level judgment stage. The material level in the metering tube is divided into five states, and the judgment is made according to the different material level judgment conditions of the redundant high / low level photoelectric detection device. Different material levels correspond to different speed regulation modes:

[0029] The first material level corresponds to a speed reduction Δf1, the second material level corresponds to a speed reduction Δf2, the third material level corresponds to constant speed control, the fourth material level corresponds to a speed increase Δf3, and the fifth material level corresponds to a speed increase Δf4, where Δf1 > Δf2 and Δf3 < Δf4. Within a single scan cycle, frequency adjustment is performed once. After frequency adjustment, it is determined whether the production of this batch has ended. If there is an end signal, the control logic ends; otherwise, the control logic for the next scan cycle is performed, which involves cyclically judging the material level status. This process continues until the production of this batch ends.

[0030] Preferably, the redundant high / low photoelectric detection device includes four sets of photoelectric detection devices installed on the quantitative tube, namely a first high-level phototube and a second high-level phototube, which form a high-level tobacco redundant detection signal; and a first low-level phototube and a second low-level phototube, which form a low-level tobacco redundant detection signal.

[0031] The condition for determining high-level light blocking is that both high-level phototubes 1 and 2 are blocked by materials, thus the high-level light blocking condition is triggered.

[0032] The criteria for determining high-level light transmission: High-level phototubes 1 and 2. If either phototube detects light transmission and there is no material obstruction, the high-level light transmission condition is considered to be triggered.

[0033] The criteria for low-level light transmission are: low-level phototubes 1 and 2. If either phototube detects light transmission and there is no material obstruction, the low-level light transmission condition is considered to be triggered.

[0034] The criteria for determining low-level light obstruction are as follows: both low-level phototubes 1 and 2 are blocked by material, only then is the low-level light obstruction condition considered triggered. Preferably, the ramp belt adjusts its frequency based on the following five material level determination conditions, as shown below:

[0035] (1) Conditions for determining material level 1: Within a scanning cycle, the conditions for determining high-level light blocking and low-level light blocking are continuously triggered.

[0036] (2) Conditions for determining material level 2: Within one scanning cycle, the judgment conditions for high-level light blocking and high-level light transmission are triggered alternately, and the judgment condition for low-level light blocking is always triggered.

[0037] (3) Conditions for material level 3 judgment: Within one scanning cycle, the judgment conditions of high-level light transmission and low-level light blocking are continuously triggered.

[0038] (4) Material level 4 judgment condition: Within one scanning cycle, the low-level light blocking and low-level light transmission judgment conditions are triggered alternately, while the high-level light transmission judgment condition is triggered continuously.

[0039] (5) Material level 5 judgment condition: Within one scanning cycle, the low-level light transmission and high-level light transmission judgment conditions are continuously triggered.

[0040] The beneficial effects of this invention are:

[0041] This invention models and analyzes the relationship between the frequency and mass flow rate of a ramp conveyor motor; then, it proposes a reasonable frequency modulation control logic for the ramp conveyor; finally, it verifies the model and control logic using actual production data, and further improves and refines them. This invention reduces the average number of start-stop cycles of the ramp conveyor motor by 98.61%, the average number of high-frequency triggers by 96.48%, and the average flow rate range at the feed head stage by 75.778%. While improving the stability of the tobacco mass flow rate, the operational stability of the ramp conveyor motor is also significantly improved, eliminating the risks of material shortage and blockage, and reducing equipment wear and energy consumption. Attached Figure Description

[0042] Figure 1 A diagram of the constant flow control system for an existing tobacco production line;

[0043] Figure 2 This is a schematic diagram of the installation of redundant high / low position photoelectric detection devices;

[0044] Figure 3 This is a block diagram of the constant flow control system of the present invention;

[0045] Figure 4 This is a flowchart of the control logic of the constant flow control system of the present invention;

[0046] Figure 5 This is a statistical chart showing the operation of the motor on the incline before and after the improvement of this embodiment of the invention;

[0047] Figure 6 This is a data record query diagram of the operation status of the motor on the incline belt before the improvement of this embodiment of the invention;

[0048] Figure 7 This is a data record query diagram of the operation status of the climbing belt motor after the improvement of the embodiment of the present invention;

[0049] Figure 8 This is a statistical chart showing the stability of material flow rate for each batch before the improvement of this embodiment of the invention;

[0050] Figure 9 This is a statistical chart of the stability data of material flow rate for each batch after the improvement of this embodiment of the invention;

[0051] In the attached diagram: 1. Feeder bottom belt, 2. Feeder bin, 3. Equalizing roller, 4. Feeder ramp belt, 5. First high-position photocell, 6. Second high-position photocell, 7. First low-position photocell, 8. Second low-position photocell, 9. Quantitative tube, 10. Electronic belt scale. Detailed Implementation

[0052] To verify the effectiveness of the improvement, a production test was conducted using our company's Grade A tobacco shreds. The relevant equipment and other production parameters during the production process are as follows: flow(m) = 4800 kg / h, ρ = 90 kg / m 3 , r=0.13m, p=2, k=66.67, a=1.3m, h=0.1m. According to the constant flow control model analysis, combined with formula (6), the theoretical production frequency of the ramp belt motor can be calculated to be 18.61Hz. This value is used as the pre-filling frequency value. In the production process, the frequency is adjusted using this frequency as the reference value, which can play a role in quickly stabilizing the material flow and ensuring its stability.

[0053] The storage-type feeder is model WCL15A, with a rated production capacity of 6400Kg / h; the incline belt motor has a speed of 1380r / min and a power of 3.3Kw; the reducer has a power of 3.3Kw and a speed ratio of 66.67; the incline belt motor drive frequency converter is model FC-302; the electronic belt scale is model K64E, with a flow range of 4000-8000Kg / h.

[0054] Experimental Results Analysis

[0055] Due to the lack of a precise quantitative relationship between the operating frequency of the inclined belt motor and the mass flow rate of the electronic belt scale, based on experience, the "optimal frequency" for the inclined belt motor is set to 13Hz. Considering the need for rapid replenishment when material is low, the high-frequency value of the inclined belt motor is set to 35Hz. To prevent material blockage in the metering tube, the low-frequency value is set to 0Hz. A certain grade A product weighs approximately 7500 kg, the electronic belt scale's process flow rate requirement is 4800 kg / h, and the production time is 90 minutes. (See Table 1 and...) Figure 5 As shown, before the improvement, the production data of grade A (10 batches) was collected and analyzed. The average number of motor start-stop cycles was as high as 143 times per batch, and the average number of high-frequency triggers was as high as 142 times per batch.

[0056] Based on the constant flow control system model analysis, when the process flow requirement of the electronic belt scale is 4800 kg / h, the theoretical frequency value of the ramp belt is 18.61 Hz, which is very close to the "optimal frequency". From the volumetric flow rate of the ramp belt and the rapid replenishment time requirement of the metering tube, it can be seen that setting the safe replenishment frequency to 30 Hz, which exceeds the theoretical frequency value by 60%, is sufficient to meet the needs of rapid and timely replenishment. Similarly, to prevent metering tube blockage, the low-frequency value is set to 0 Hz. (See Table 1 and...) Figure 5 As shown, after the improvement, the production data of grade A (10 batches) was collected and analyzed. The average number of motor start-stop cycles was reduced to 2 times per batch, a reduction of 98.61%; the average number of high-frequency triggers was reduced to 5 times per batch, a reduction of 96.48%.

[0057] Table 1. Statistics on the operation of the uphill belt motor before and after improvement.

[0058]

[0059] InTouch supervisory control and data acquisition (SCADA) software is widely used in industrial production. This software can completely record the entire process data of the motor's operating frequency during incline belt operation, such as... Figure 6 and Figure 7 As shown, the actual operating frequency data of the motors before and after the improvement are recorded respectively, which more intuitively shows the number of times the entire batch of motors started and stopped, the number of times high-frequency triggers, and other related data.

[0060] The fluctuations in the flow rate of tobacco shreds during the initial feeding stage (first 5 minutes) are statistically analyzed, as shown in Table 2 and... Figure 6 As shown, before the improvement, the average maximum value of material flow fluctuation was 4823.691 kg / h, the average minimum value was 4779.951 kg / h, and the average range was 41.062 kg / h; after the improvement, the average maximum value of material flow fluctuation was 4804.305 kg / h, the average minimum value was 4794.359 kg / h, and the average range was 9.946 kg / h, with the range reduced by 75.778%.

[0061] Table 2. Statistics on Fluctuations in Tobacco Material Flow Rate Before and After Improvement in the Feeding Stage

[0062]

[0063] Production data shows that, after the improvement, based on the precise constant flow control system model analysis and through scientific methods of adjusting the operating frequency of the inclined belt motor, the requirements for rapid, timely, stable, and constant flow feeding can be met, especially in the initial feeding stage, where the effect is more significant. After the improvement, the average number of start-stop cycles of the inclined belt motor decreased by 98.61%, the average number of high-frequency triggers decreased by 96.48%, and the average flow range difference in the initial feeding stage decreased by 75.778%. While improving the stability of tobacco mass flow rate, the operational stability of the inclined belt motor has also been greatly improved, eliminating the risks of material shortage and blockage, and reducing equipment wear and energy consumption.

[0064] The design and implementation of this constant flow control system provides a scientific flow supply model. Based on this model, the speed control of the inclined belt motor can achieve a fast, timely, stable, and progressive frequency conversion response, meeting the production requirements of stable and constant flow control. At the same time, the operational stability of the inclined belt motor is also greatly improved, and equipment wear and energy consumption are effectively reduced.

Claims

1. A method for constant flow control in an inclined zone of a tobacco feeder, characterized in that, The constant flow control system of the tobacco feeder with ramp belt includes a main controller module, a tobacco pre-filling module, a redundant high / low position detection module, and a speed regulation module. The main controller module includes a PLC controller, which receives signals from redundant high / low level detection modules, and judges different material level heights in the quantitative tube based on the specified high / low level light transmission and light blocking judgment conditions. According to the judgment result, it outputs control commands to the speed regulation module to reduce or increase the speed, and adjusts the speed of the climbing belt motor to achieve the purpose of controlling the tobacco flow rate. At the same time, the speed regulation result of the speed regulation module is also fed back to the main controller module in real time. During the stabilization stage, the tobacco pre-filling module, based on the analysis and establishment of the constant flow control system model and the mass flow rate required by the process, calculates the theoretical frequency value of the ramp belt motor. According to this frequency value, the quantitative tube is pre-filled with tobacco. After the pre-filling is completed, the electronic belt scale starts running after the high-level light blocking signal is triggered. Subsequently, the actual operating frequency value of the ramp belt motor is finely adjusted near the theoretical frequency value to keep the height of the tobacco in the quantitative tube between the second high-level phototube and the first low-level phototube, i.e., within the ideal height range.

2. The method for constant flow control of an inclined belt in a tobacco feeder according to claim 1, characterized in that, The stabilization phase is the first five minutes after production begins.

3. The method for constant flow control of an inclined belt in a tobacco feeder according to claim 1, characterized in that, The analysis and establishment of a constant flow control system model includes the following steps: The volumetric flow rate of the metering tube is denoted as flow(v0), the volume of tobacco shreds stored in the metering tube is denoted as v0, the density of tobacco shreds stored in the metering tube is denoted as ρ, and the mass flow rate of the electronic belt scale is denoted as flow(m). The mass flow rate control relationship between the electronic belt scale and the metering tube is shown in formula (1): flow(m)=ρ*flow(v0) (1) A uniform roller is installed above the feeder's inclined belt. The thickness and height of the tobacco shreds conveyed by the inclined belt are uniform. The height of the tobacco shreds is h, the width of the inclined belt is a, the running speed of the inclined belt is v, and the volumetric flow rate of the tobacco shreds conveyed by the inclined belt is flow(v). The relationship between the volumetric flow rate of the metering tube and the volumetric flow rate of the tobacco shreds conveyed by the inclined belt is shown in formula (2): flow(v0)=flow(v)=v*a*h(2) Substituting formula (2) into formula (1) yields the constant flow control system model between the feeder's ramp belt operating frequency and the electronic belt scale's mass flow rate, as shown in formula (3): flow(m)=ρ*flow(v0)=ρ*flow(v)=ρ*v*a*h(3) The frequency converter controls the motor to run, and the motor drives the reducer to rotate according to the reduction ratio. The reducer drives the inclined belt to transport tobacco through chain drive. According to professional theoretical knowledge, the speed n of the reducer is as shown in formula (4): n=60*f / (p*k) (4) f represents the motor operating frequency; p represents the number of pole pairs of the motor; k represents the speed ratio of the reducer. From formula (4), we know that the length of tobacco shreds conveyed per second on the uphill belt is denoted as L, where L = v * 1s, as shown in formula (5): L=2*π*r*n / 60=2*π*r*f / (p*k) (5) r represents the radius of the main drive shaft; Substituting formula (5) into formula (3), we obtain the constant flow control system model transformation formula between the operating frequency of the ramp motor and the mass flow rate of the electronic belt scale, as shown in formula (6): flow(m)=ρ*v*a*h=ρ*[2*π*r*f / (p*k)]*a*h(6) During the production process, based on the changes in the mass flow rate data flow(m) of the electronic belt scale as required by the process, the motor frequency f is controlled accordingly to ensure that the system achieves the purpose of constant flow control.

4. The method for constant flow control of an inclined belt in a tobacco feeder according to claim 3, characterized in that, The actual operating frequency of the motor for the climbing belt is finely adjusted near the theoretical frequency value, with an adjustment range of 0.2-0.8Hz, meaning that Δf1, Δf2, Δf3, and Δf4 are all between 0.2-0.8Hz. The ideal height range is 30cm-80cm, which is between the second highest phototube and the first lowest phototube.

5. The method for constant flow control of an inclined belt in a tobacco feeder according to claim 3, characterized in that, The constant flow system control logic includes the following steps: After the tobacco pre-filling is completed, the system proceeds to the material level judgment stage. The material level in the metering tube is divided into five states, and the judgment is made according to the different material level judgment conditions of the redundant high / low level photoelectric detection device. Different material levels correspond to different speed regulation modes: The first material level corresponds to a speed reduction Δf1, the second material level corresponds to a speed reduction Δf2, the third material level corresponds to constant speed control, the fourth material level corresponds to a speed increase Δf3, and the fifth material level corresponds to a speed increase Δf4, where Δf1 > Δf2 and Δf3 < Δf4. Within a single scan cycle, frequency adjustment is performed once. After frequency adjustment, it is determined whether the production of this batch has ended. If there is an end signal, the control logic ends; otherwise, the control logic for the next scan cycle is performed, which involves cyclically judging the material level status. This process continues until the production of this batch ends.

6. The method for constant flow control of an inclined belt in a tobacco feeder according to claim 5, characterized in that, The redundant high / low position photoelectric detection device includes four sets of photoelectric detection devices installed on the quantitative tube, namely the first high position photoelectric tube and the second high position photoelectric tube, which form a high position tobacco redundant detection signal; the first low position photoelectric tube and the second low position photoelectric tube form a low position tobacco redundant detection signal. The condition for determining high-level light blocking is that both high-level phototubes 1 and 2 are blocked by materials, thus the high-level light blocking condition is triggered. The criteria for determining high-level light transmission: High-level phototubes 1 and 2. If either phototube detects light transmission and there is no material obstruction, the high-level light transmission condition is considered to be triggered. The criteria for low-level light transmission are: low-level phototubes 1 and 2. If either phototube detects light transmission and there is no material obstruction, the low-level light transmission condition is considered to be triggered. The condition for determining low-level light blocking is that both low-level phototubes 1 and 2 are blocked by materials.

7. The method for constant flow control of an inclined belt in a tobacco feeder according to claim 6, characterized in that, The frequency adjustment for the ramp zone is based on the following five conditions, which are shown below: (1) Conditions for determining material level 1: Within a scanning cycle, the conditions for determining high-level light blocking and low-level light blocking are continuously triggered. (2) Conditions for determining material level 2: Within one scanning cycle, the judgment conditions for high-level light blocking and high-level light transmission are triggered alternately, and the judgment condition for low-level light blocking is always triggered. (3) Conditions for material level 3 judgment: Within one scanning cycle, the judgment conditions of high-level light transmission and low-level light blocking are continuously triggered. (4) Material level 4 judgment condition: Within one scanning cycle, the low-level light blocking and low-level light transmission judgment conditions are triggered alternately, while the high-level light transmission judgment condition is triggered continuously. (5) Material level 5 judgment condition: Within one scanning cycle, the low-level light transmission and high-level light transmission judgment conditions are continuously triggered.

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