Conveying pressure control method and device of powder and particle pneumatic conveying system

Abstract

The invention relates to the technical field of material transportation, in particular to a conveying pressure control method and device of a powder and particle pneumatic conveying system. The method comprises the steps that the material humidity, the conveying pressure and the air speed of a frequency conversion fan are obtained; determining a humidity adjusting coefficient; in the pressurization stage, a suppression coefficient is determined according to the current wind speed and the target wind speed; according to the humidity adjustment coefficient and the inhibition coefficient, inhibiting the proportionality item to obtain a target proportionality coefficient; enhancing the differential term in combination with the humidity adjustment coefficient and the pressure deviation to obtain a target differential coefficient; in the pressure reduction stage, the standard humidity is compared with the air speed and the conveying pressure under the material humidity at the current sampling moment and the humidity adjusting coefficient, the integral item is adjusted, and a target integral coefficient is obtained; and adjusting the conveying pressure based on the adjusted PID coefficient. The problem of asymmetry of bidirectional adjustment of pressurization and depressurization can be solved, the adjustment logic is optimized, and the conveying efficiency and stability of pneumatic conveying of powder and particle materials are improved.

Description

Technical Field

[0001] This invention relates to the field of material transportation technology, specifically to a method and device for controlling the conveying pressure of a pneumatic conveying system for powder and granular materials. Background Technology

[0002] Pneumatic conveying systems for powder and granular materials are core material handling equipment in chemical, grain, power, and pharmaceutical industries. Leveraging their advantages of being enclosed, environmentally friendly, and flexible in layout, they are widely used for long-distance or multi-point conveying of materials such as cement, pulverized coal, grain, and lithium battery cathode materials. However, the stability of this system is highly susceptible to fluctuations in material humidity: in high-humidity environments, hygroscopic materials such as lactose and lithium iron phosphate are prone to agglomeration and adhesion, leading to a sharp increase in pipeline resistance and a decrease in material flowability; in low-humidity environments, fine powder materials, due to their excessive suspension, are prone to loss of conveying speed control.

[0003] Currently, pressure control in pneumatic conveying systems for powder and granular materials mostly adopts the traditional single-loop PID scheme. This scheme achieves closed-loop control by detecting the deviation between the pipeline pressure and the target value and adjusting the speed of the variable frequency fan. It has a mature application foundation in stable operating scenarios. However, humidity can cause changes in material properties, which the single-loop PID scheme cannot effectively adapt to. Especially under high humidity conditions, the "resistance hysteresis" caused by material residue during depressurization will significantly reduce the PID regulation effect. On the other hand, during pressurization, insufficient parameter adaptation may lead to overshoot, resulting in asymmetry in the two-way regulation of pressurization and depressurization, leading to poor conveying efficiency and stability of pneumatic conveying of powder and granular materials. Summary of the Invention

[0004] To address the technical problems of poor conveying efficiency and stability in pneumatic conveying of powder and granular materials in related technologies, this invention provides a method and device for controlling the conveying pressure of a pneumatic conveying system for powder and granular materials. The specific technical solution adopted is as follows: This invention proposes a method for controlling the conveying pressure of a pneumatic conveying system for powder and granular materials. The method involves configuring a variable frequency fan, a humidity detection module, and a pressure detection module within the pneumatic conveying system for powder and granular materials. The system acquires the material humidity from the humidity detection module, the conveying pressure from the pressure detection module, and the wind speed of the variable frequency fan at different sampling times; and determines the humidity adjustment coefficient based on the different preset humidity ranges in which the material humidity is located. During the pressurization phase, based on the current wind speed and the target wind speed to be adjusted, a suppression coefficient is determined to avoid large-scale wind speed adjustments; based on the humidity adjustment coefficient and the suppression coefficient, the proportional term of the delivery pressure is suppressed to obtain the target proportional coefficient; combined with the humidity adjustment coefficient and the deviation between the delivery pressure and the target pressure, the differential term is enhanced to obtain the target differential coefficient. During the depressurization phase, the values ​​of wind speed and conveying pressure under standard humidity and material humidity at the current sampling time are compared with the humidity adjustment coefficient. The integral term is then adjusted to obtain the target integral coefficient. The conveying pressure is regulated based on the adjusted PID coefficients.

[0005] Furthermore, determining the humidity adjustment coefficient based on the different preset humidity ranges in which the material's humidity falls includes: Under fixed operating conditions, the same material with different humidity levels is conveyed, and the pressure fluctuation index of the conveying pressure and the response time of PID regulation are obtained. As the material humidity is traversed in order from low to high, when the pressure fluctuation index first exceeds the preset fluctuation threshold, the corresponding material humidity is taken as the first humidity threshold H1; the response time under the first humidity threshold H1 is taken as the first analysis time. As the material humidity increases, when the first analysis time exceeds a preset multiple, the corresponding material humidity is used as the second humidity threshold H2, where the preset multiple is 1.5 times. Based on the first humidity threshold H1 and the second humidity threshold H2, the overall humidity is divided into three preset humidity ranges: [0,H1], (H1,H2] and (H2,Hmax], where Hmax represents the maximum value of the material humidity. Each preset humidity range is assigned a different humidity adjustment coefficient. The higher the material humidity in each preset humidity range, the smaller the value of the humidity adjustment coefficient.

[0006] Furthermore, determining the suppression coefficient to avoid large-scale wind speed adjustments based on the current wind speed and the target wind speed to be adjusted includes: Calculate the wind speed difference between the target wind speed and the current wind speed, and normalize the wind speed difference as the suppression coefficient.

[0007] Furthermore, the step of suppressing the proportional term of the delivery pressure based on the humidity adjustment coefficient and the suppression coefficient to obtain the target proportional coefficient includes: The difference between the real number 1 and the suppression coefficient is calculated and used as the wind speed proportional adjustment index. The initial proportional coefficient of the proportional term is multiplied by the wind speed control index and the humidity adjustment coefficient, and the target proportional coefficient is used as the product of these factors.

[0008] Furthermore, the differential term is enhanced by incorporating the humidity adjustment coefficient and the deviation between the delivery pressure and the target pressure to obtain the target differential coefficient, including: Calculate the sum of the real number 1 and the humidity adjustment coefficient, and use it as the differential humidity adjustment index; The difference between the target pressure and the delivery pressure is taken as the pressure deviation. The pressure deviation is normalized, and the normalized value is added to the real number 1 to obtain the pressure differential adjustment index. The product of the initial differential coefficient of the differential term and the differential adjustment index of humidity and pressure is calculated as the target differential coefficient.

[0009] Furthermore, the values ​​of wind speed and conveying pressure under the standard humidity and the material humidity at the current sampling time, as well as the humidity adjustment coefficient, are used to adjust the integral term to obtain the target integral coefficient, including: Based on the comparison between the current material humidity at the sampling time and the wind speed and conveying pressure under standard humidity, the wind pressure error of the material humidity at the current sampling time is determined; Calculate the product of the humidity regulation coefficient and the wind pressure error, and use the sum of the real number 1 and the product as the humidity integral regulation index; The product of the initial integral coefficient of the integral term and the humidity integral adjustment index is used as the target integral coefficient.

[0010] Furthermore, determining the wind pressure error of the material humidity at the current sampling time based on a comparison of the wind speed and conveying pressure under standard humidity conditions includes: The delivery pressure and wind speed are normalized respectively. The sum of the normalized delivery pressure and the preset parameter adjustment coefficient is used as the denominator, and the normalized wind speed is used as the numerator to calculate the wind pressure ratio. The difference between the wind pressure ratio under standard humidity and the current material humidity at the sampling time is normalized and used as the wind pressure error.

[0011] Furthermore, the method of regulating the delivery pressure based on the adjusted PID coefficients includes: During the boosting phase, PID control is performed based on the target proportional coefficient, initial integral coefficient, and target derivative coefficient at the current sampling time.

[0012] Furthermore, the method of regulating the delivery pressure based on the adjusted PID coefficients also includes: During the step-down phase, PID control is performed based on the initial proportional coefficient, target integral coefficient, and initial derivative coefficient at the current sampling time.

[0013] On the other hand, a conveying pressure control system for a pneumatic conveying system for powder and granular materials is also provided. The system includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of the method as described in any of the foregoing.

[0014] The present invention has the following beneficial effects: In this embodiment of the invention, a variable frequency fan, a humidity detection module, and a pressure detection module are configured in the pneumatic conveying system for powder and granular materials to acquire humidity and pressure data, and the pressure is adjusted based on the variable frequency fan. Furthermore, considering the different characteristics of the pressurization and depressurization stages, the traditional PID control method, which uses a uniform control approach, is abandoned. This avoids asymmetry in the two-way adjustment of pressurization and depressurization, leading to adjustment oscillations during pressurization and lag during depressurization. By adjusting different PID control parameters for the pressurization and depressurization stages, the conveying pressure regulation is improved. The stability of the pneumatic conveying system is improved. Specifically, during the pressurization stage, the target proportional coefficient is determined by suppressing the proportional term based on the difference between the target wind speed and the humidity. The target differential coefficient is determined by the deviation between the conveying pressure and the target pressure and the humidity. During the depressurization stage, the integral term is adjusted by comparing the wind speed and conveying pressure with those under standard humidity and combining the humidity adjustment coefficient to obtain the target integral coefficient. Thus, the pressurization stage can effectively suppress regulation oscillations, and the depressurization stage can effectively avoid pressure regulation lag, thereby optimizing the regulation logic and improving the conveying efficiency and stability of the pneumatic conveying of powder and granular materials. Attached Figure Description

[0015] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a flowchart of a method for controlling the conveying pressure of a pneumatic conveying system for powder and granular materials, provided in one embodiment of the present invention. Figure 2 This is a schematic diagram of a pneumatic conveying system for powder and granular materials provided in one embodiment of the present invention. Detailed Implementation

[0017] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a pneumatic conveying system for powder and granular materials proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0019] The following description, in conjunction with the accompanying drawings, details a specific scheme for a method for controlling the conveying pressure of a pneumatic conveying system for powder and granular materials provided by the present invention.

[0020] Please see Figure 1 The diagram illustrates a flow chart of a method for controlling the conveying pressure of a pneumatic conveying system for powder and granular materials according to an embodiment of the present invention. The method includes: S101: Obtain the material humidity collected by the humidity detection module, the conveying pressure collected by the pressure detection module, and the wind speed of the variable frequency fan at different sampling times; determine the humidity adjustment coefficient according to the different preset humidity ranges in which the material humidity is located.

[0021] Pneumatic conveying systems for powder and granular materials are core material handling equipment in chemical, grain, power, and pharmaceutical industries. Leveraging their advantages of being enclosed, environmentally friendly, and flexible in layout, they are widely used for long-distance or multi-point conveying of materials such as cement, pulverized coal, grain, and lithium battery cathode materials. However, the stability of this system is highly susceptible to fluctuations in material humidity: in high-humidity environments, hygroscopic materials such as lactose and lithium iron phosphate are prone to agglomeration and adhesion, leading to a sharp increase in pipeline resistance and a decrease in material flowability; in low-humidity environments, fine powder materials, due to their excessive suspension, are prone to loss of conveying speed control.

[0022] Currently, pressure control in pneumatic conveying systems for powder and granular materials mostly employs traditional single-loop PID control schemes. These schemes achieve closed-loop control by detecting the deviation between pipeline pressure and the target value and adjusting the speed of the variable frequency fan. This approach has a mature application foundation under stable operating conditions. However, humidity can cause changes in material properties, which single-loop PID schemes cannot effectively adapt to. Especially under high humidity conditions, the "resistance hysteresis" caused by material residue during pressure reduction significantly diminishes the PID control effect, while insufficient parameter adaptation during pressure increase may lead to overshoot. Therefore, the stability and reliability of conveying pressure control in related technologies are relatively poor.

[0023] See Figure 2 , Figure 2 This is a schematic diagram of a pneumatic conveying system for powder and granular materials according to an embodiment of the present invention. It utilizes airflow at a certain pressure and speed as power and carrier to transport powdered or granular solid materials to a designated location via pipelines. In this embodiment of the invention, a variable frequency fan, a humidity detection module, and a pressure detection module are added to a traditional pneumatic conveying system for powder and granular materials.

[0024] The humidity detection module is installed at the feed inlet or upstream of the pipeline. It needs to be dust-resistant, have a response time of ≤2 seconds, collect material humidity in real time, and have a data acquisition frequency greater than 100Hz. The pressure sensor is installed at a critical node in the pipeline, such as the midpoint, while the variable frequency fan is used to generate airflows with different dynamics.

[0025] It should be noted that the sampling frequency for different types of data is the same to ensure that the data is analyzed on the same time dimension. Furthermore, for ease of calculation, all indicator data involved in the calculations in this embodiment of the invention have undergone data preprocessing to eliminate the influence of dimensions. The specific methods for removing the influence of dimensions are well-known to those skilled in the art and are not limited here.

[0026] In this embodiment of the invention, the humidity of the material itself can directly affect the pneumatic conveying effect of powder and granular materials. Therefore, in this embodiment of the invention, the influence of humidity is first analyzed, and the effect of humidity is eliminated by humidity adjustment coefficient.

[0027] Furthermore, in some embodiments of the present invention, the humidity adjustment coefficient is determined according to the different preset humidity ranges in which the material humidity is located, including: conveying the same material with different humidity levels under fixed working conditions, obtaining the pressure fluctuation index of the conveying pressure and the response time of PID adjustment; traversing the material humidity in ascending order, when the pressure fluctuation index first exceeds the preset fluctuation threshold, the corresponding material humidity is taken as the first humidity threshold H1; the response time under the first humidity threshold H1 is taken as the first analysis time; as the material humidity increases, when the first response time exceeds the first analysis time of the preset multiple, the corresponding material humidity is taken as the second humidity threshold H2, wherein the preset multiple is 1.5 times; the overall humidity is divided into three preset humidity ranges based on the first humidity threshold H1 and the second humidity threshold H2: [0,H1], (H1,H2] and (H2,Hmax], wherein Hmax represents the maximum value of the material humidity, and a different humidity adjustment coefficient is determined for each preset humidity range, wherein the higher the material humidity in each preset humidity range, the smaller the value of the humidity adjustment coefficient.

[0028] As the moisture content of the material increases, the material will stick together and clump together. This sticking effect will affect the airflow stability of the variable frequency fan, resulting in pressure fluctuations.

[0029] The pressure fluctuation index of the delivery pressure can be specifically the dispersion index of the delivery pressure itself. In this embodiment of the invention, the standard deviation can be used to calculate the standard deviation of the delivery pressure at the previous 10 sampling times, and normalize it as the pressure fluctuation index. Of course, in other embodiments of the invention, the variance can also be used to calculate the pressure fluctuation index, and there is no limitation on this.

[0030] The preset fluctuation threshold is the threshold value of the pressure fluctuation index. The specific value of the preset fluctuation threshold is 0.5. That is, when the pressure fluctuation index first exceeds 0.5, the corresponding material humidity is used as the first humidity threshold H1.

[0031] The specific logic is that, in the experimental data, when the material humidity increases to a certain value, the material humidity at which the pressure fluctuation first exceeds the low humidity stability threshold (that is, the pressure fluctuation index is greater than 0.5) is the first humidity threshold H1; when the humidity continues to increase and the adjustment response time T is significantly prolonged (50% more than H1, with a preset multiple of 1.5 times), it is the second humidity threshold H2.

[0032] In this embodiment of the invention, the first humidity threshold H1 and the second humidity threshold H2 can be obtained by averaging multiple tests.

[0033] The three preset humidity ranges can be specifically defined as a low humidity range [0, H1], a medium humidity range (H1, H2], and a high humidity range (H2, Hmax). The material's position within the preset humidity range is determined based on real-time humidity analysis.

[0034] Analysis of actual scenarios shows that in the low humidity range [0, H1], the material is roughly in the form of dust, with good fluidity, is not easy to clump, and is easily carried by airflow. At this time, dust accumulation is likely to occur. Therefore, it is necessary to quickly adjust the pressure to avoid this problem, and the humidity adjustment coefficient is at its maximum value.

[0035] In the medium humidity range (H1, H2), the material exhibits slight adhesion and moderate flowability. At this time, a medium humidity adjustment coefficient can be set to balance the response speed and stability, and avoid excessive adjustment caused by low humidity adjustment coefficient, which may lead to local accumulation.

[0036] In the high humidity range (H2, Hmax), materials are highly adhesive and prone to clumping, resulting in high pipeline resistance. In this case, slow adjustment is required to allow buffer time for material flow. For example, during the depressurization phase, the speed should be reduced slowly to avoid a sudden drop in wind speed that could cause material settling and accumulation. The humidity adjustment coefficient should be minimized in this case.

[0037] Based on the above scenario analysis, in this embodiment of the invention, as the material humidity increases, a more cautious adjustment is required, meaning the corresponding humidity adjustment coefficient value should be smaller. For example, each preset humidity range can be configured with a preset humidity adjustment coefficient; for instance, the humidity adjustment coefficient for the low humidity range [0, H1] is 1; the humidity adjustment coefficient for the medium humidity range (H1, H2) is 0.8; and the humidity adjustment coefficient for the high humidity range (H2, Hmax) is 0.6. Of course, in other embodiments of the invention, the humidity adjustment coefficient can also be directly adjusted linearly based on the material humidity, according to the actual scenario and accuracy requirements, without limitation.

[0038] In this embodiment of the invention, the two different stages of pressurization and depressurization are classified and analyzed. For details of the analysis, please refer to the following embodiments.

[0039] S102: During the pressurization stage, based on the current wind speed and the target wind speed to be adjusted, determine the suppression coefficient to avoid large-scale wind speed adjustments; based on the humidity adjustment coefficient and the suppression coefficient, suppress the proportional term of the delivery pressure to obtain the target proportional coefficient; combining the humidity adjustment coefficient and the deviation between the delivery pressure and the target pressure, enhance the differential term to obtain the target differential coefficient.

[0040] In this embodiment of the invention, during the pressurization stage, the pressure control of the conveying powder / granular material is achieved by adjusting the air velocity. Therefore, the air velocity before and after adjustment is different, and the pressurization stage is a stage where the air velocity increases. Increased air velocity leads to upward pressure adjustment. Increased air velocity causes collisions between later and earlier materials, and forces particles to adhere to the barrel wall, resulting in increased conveying pressure and overall instability. Therefore, it is crucial to suppress this instability.

[0041] In order to analyze the severity of the wind speed increase and thus assess the suppression effect, this embodiment of the invention calculates the suppression coefficient based on the current wind speed and the target wind speed to be adjusted.

[0042] The target wind speed to be adjusted represents the preset target wind speed value that needs to be adjusted to. For example, if the current wind speed is 1 meter per second and it needs to be adjusted to 3 meters per second, then the corresponding target wind speed to be adjusted is 3 meters per second.

[0043] Furthermore, in some embodiments of the present invention, determining a suppression coefficient to avoid large-scale wind speed adjustments based on the current wind speed and the target wind speed to be adjusted includes: calculating the wind speed difference between the target wind speed and the current wind speed, and normalizing the wind speed difference as the suppression coefficient.

[0044] In this embodiment of the invention, the greater the difference between the target wind speed and the current wind speed, the greater the wind speed that needs to be adjusted. At this time, a greater degree of suppression effect is needed to avoid directly adjusting the wind speed over a large range, which would cause a sudden increase in the collision between materials.

[0045] In one embodiment of the present invention, the normalization process can be specifically, for example, maximum and minimum value normalization. Furthermore, the normalization in subsequent steps can all adopt maximum and minimum value normalization. In other embodiments of the present invention, other normalization methods can be selected according to the specific range of the numerical values, which will not be elaborated further.

[0046] Furthermore, in high-humidity environments, powdered materials can adhere to the inner walls of pipes and valves, forming initial adhesion resistance. However, this resistance is unstable; once a change in airflow is triggered, it can cause a sudden change in resistance, leading to a mismatch between the PID control force and the system gain, resulting in regulation oscillations and lag. During pressurization, adhesion resistance can easily cause sudden changes in resistance, leading to regulation oscillations.

[0047] Because sudden changes in resistance can easily occur during pressurization, causing rapid changes in the airflow of the fan and thus oscillations, the PID parameters need to be adjusted accordingly to adapt to the pipeline conditions during pressurization.

[0048] It should be noted that the PID control has an initial proportional coefficient, initial integral coefficient, and initial derivative coefficient that have not been adjusted in this embodiment of the invention. The initial PID parameters obtained at the current sampling time are obtained by analyzing the original PID. The specific acquisition of the initial PID parameters is well known to those skilled in the art and is not limited thereto.

[0049] Based on the humidity adjustment coefficient and the suppression coefficient, the proportional term of the delivery pressure is suppressed to obtain the target proportional coefficient, including: calculating the difference between the real number 1 and the suppression coefficient as the wind speed proportional adjustment index; and taking the product of the initial proportional coefficient of the proportional term, the wind speed control index, and the humidity adjustment coefficient as the target proportional coefficient.

[0050] Among them, the wind speed proportional adjustment coefficient is the adjustment value of the corresponding proportional term after the suppression coefficient has been applied. The larger the value of the suppression coefficient, the smaller the value of the corresponding wind speed proportional adjustment index. Thus, the suppression effect is achieved by reducing the proportional term.

[0051] The larger the humidity adjustment coefficient, the lower the humidity. In this case, a larger adjustment effect can be used. Therefore, the product of the initial proportional coefficient of the proportional term and the wind speed control index and the humidity adjustment coefficient is used as the target proportional coefficient.

[0052] Understandably, the target proportional coefficient is lower than the initial proportional coefficient, which means that suppression regulation has been implemented to weaken the proportional adjustment and thus suppress overshoot.

[0053] However, while adjusting the PID parameters for boosting aims to suppress overshoot, simultaneously adjusting both the proportional and derivative terms can lead to a mismatch between their coefficients, potentially resulting in double regulation and reduced control system stability. Therefore, the proportional and derivative parameters should be adjusted in opposite directions: while decreasing the proportional term, the derivative term should be appropriately increased to improve system stability.

[0054] In this embodiment of the invention, in order to suppress the adjustment oscillation caused by the sudden change in adhesion resistance, it is also necessary to adjust the differential term in combination with the material humidity data.

[0055] Furthermore, in some embodiments of the present invention, the differential term is enhanced by combining the humidity adjustment coefficient and the deviation between the delivery pressure and the target pressure to obtain the target differential coefficient, including: calculating the sum of the real number 1 and the humidity adjustment coefficient as the humidity differential adjustment index; taking the difference between the target pressure and the delivery pressure as the pressure deviation, normalizing the pressure deviation, and adding the normalized value to the real number 1 to obtain the pressure differential adjustment index; and calculating the product of the initial differential coefficient of the differential term and the humidity differential adjustment index and the pressure differential adjustment index as the target differential coefficient.

[0056] The target pressure is the pre-set pressure information in the pipeline. Since the delivery pressure will change unstablely according to the state of the material in the pipeline, the smaller the delivery pressure is than the target pressure, the more the proportional term will overshoot, resulting in insufficient pressure in the pipeline. Therefore, it is necessary to increase the derivative term, normalize the pressure deviation, and add the normalized value to the real number 1 to obtain the pressure derivative adjustment index, which represents the influence of the delivery pressure value on the derivative term.

[0057] The higher the material humidity, the more necessary it is to improve the differential term in order to ensure overall stability. Therefore, in this embodiment of the invention, the sum of the real number 1 and the humidity adjustment coefficient is used as the humidity differential adjustment index to achieve the improvement effect of the differential term.

[0058] In summary, the embodiments of the present invention calculate the product of the initial differential coefficient of the differential term with the humidity differential adjustment index and the pressure differential adjustment index, and use it as the target differential coefficient. The target differential coefficient is greater than the initial differential coefficient, so as to improve the differential term and generate a mutual coupling effect with the reduction of the proportional term, making the overall adjustment process more stable.

[0059] S103: During the depressurization stage, compare the values ​​of wind speed and conveying pressure under standard humidity and material humidity at the current sampling time, as well as the humidity adjustment coefficient, and adjust the integral term to obtain the target integral coefficient.

[0060] During pressure reduction, resistance lag occurs due to adhesion resistance, leading to regulation lag. The greater the adhesion resistance, the more severe the regulation lag, thus requiring a greater adjustment force to avoid it. In other words, the PID control system, in its attempt to counteract the resistance, prevents the air pressure from decreasing on time, resulting in regulation lag.

[0061] In this embodiment of the invention, the resistance to adhesion is often caused by the accumulation of material in the conveying drum, so it can be regarded as a static error to a certain extent, and thus it can be solved by increasing the integral adjustment parameter.

[0062] Furthermore, in some embodiments of the present invention, the integral term is adjusted by comparing the values ​​of wind speed and conveying pressure under standard humidity and material humidity at the current sampling time, as well as the humidity adjustment coefficient, to obtain a target integral coefficient. This includes: determining the wind pressure error of the material humidity at the current sampling time based on the comparison between the wind speed and conveying pressure under standard humidity and material humidity at the current sampling time; calculating the product of the humidity adjustment coefficient and the wind pressure error, and using the sum of the real number 1 and the product value as the humidity integral adjustment index; and using the product of the initial integral coefficient of the integral term and the humidity integral adjustment index as the target integral coefficient.

[0063] In this embodiment of the invention, the wind pressure error is first analyzed. In this embodiment of the invention, the wind pressure error analysis process is mainly achieved through the form of wind pressure ratio.

[0064] Furthermore, in some embodiments of the present invention, the wind pressure error of the material humidity at the current sampling time is determined based on the comparison between the material humidity at the current sampling time and the wind speed and conveying pressure under standard humidity. This includes: normalizing the conveying pressure and wind speed respectively, using the sum of the normalized conveying pressure value and the preset parameter adjustment coefficient as the denominator and the normalized wind speed value as the numerator to calculate the wind pressure ratio; and normalizing the difference between the wind pressure ratio under standard humidity and the material humidity at the current sampling time as the wind pressure error.

[0065] The preset parameter adjustment coefficient is a parameter adjustment value set in the denominator position to prevent the denominator from being 0. The effect of this preset parameter adjustment coefficient on the overall analysis error can be ignored. Specifically, it can be set to 0.1. Here, the preset parameter adjustment coefficient is dimensionless data. That is to say, the delivery pressure and wind speed are normalized separately. The sum of the normalized value of the delivery pressure and 0.1 is the denominator, and the normalized value of the wind speed is the numerator. The wind pressure ratio is then calculated.

[0066] In a pneumatic material conveying system, wind speed is the driving force that propels the material flow, while wind pressure is the data representation of overcoming resistance to maintain wind speed. The more severe the material accumulation in the system, the greater the system resistance that the control system needs to overcome. Therefore, the greater the wind pressure required to maintain the same wind speed, the smaller the wind pressure ratio at the current sampling moment indicates greater resistance, and the larger the integral term coefficient should be at this time.

[0067] There is a wind pressure ratio at the current sampling time. The standard wind pressure ratio is determined under standard humidity (e.g., 50%). The difference between the wind pressure ratio under standard humidity and the wind pressure ratio under material humidity at the current sampling time is normalized and used as the wind pressure error. The larger the wind pressure error value, the smaller the wind pressure ratio value at the current sampling time, indicating that the resistance at the current sampling time is greater. When the system's wind pressure error is smaller and continues to decrease, it indicates that the system resistance is greater at this time. The integral term should be increased to achieve the effect of counteracting the influence of resistance.

[0068] The higher the humidity of the material, the more viscous it is, and the easier it is to clump together. Compared with the dusty material under low humidity, it will generate greater resistance. Therefore, it is necessary to analyze it in conjunction with the humidity adjustment coefficient.

[0069] In this embodiment of the invention, the product of the humidity adjustment coefficient and the wind pressure error is calculated, and the sum of the real number 1 and the product is used as the humidity integral adjustment index. The product of the initial integral coefficient of the integral term and the humidity integral adjustment index is used as the target integral coefficient.

[0070] The humidity integral adjustment index is a value greater than 1, which can improve the integral term and ensure the resistance effect. The greater the resistance, the larger the value of the humidity integral adjustment index, which makes the target integral coefficient larger, thereby increasing the adjustment force and avoiding resistance lag.

[0071] S104: Regulates the conveying pressure based on the adjusted PID coefficients.

[0072] In this embodiment of the invention, the initial proportional coefficient, initial derivative coefficient, and initial integral coefficient are used as the PID coefficients before adjustment, and the target proportional coefficient, target derivative coefficient, and target integral coefficient are used as the PID coefficients after adjustment.

[0073] Different PID coefficients are adjusted during the boost and depressurization phases, therefore, it is necessary to perform adjustment analysis by category.

[0074] During the pressurization phase, PID control is performed based on the target proportional coefficient, initial integral coefficient, and target derivative coefficient at the current sampling time. In this embodiment of the invention, during pressurization, the sudden changes in resistance and material collisions caused by rapid changes in wind speed are suppressed by "weakening the proportional term and increasing the derivative term," thus avoiding adjustment oscillations.

[0075] During the pressure reduction phase, PID control is performed based on the initial proportional coefficient, target integral coefficient, and initial derivative coefficient at the current sampling time. In this embodiment of the invention, during pressure reduction, "integral term reinforcement" is used to counteract the regulation lag caused by adhesion resistance, ensuring that the pressure decreases as expected.

[0076] This eliminates the drawbacks of asymmetrical two-way pressure increase and decrease regulation, improves control precision, and thus achieves stable conveying and improves conveying efficiency.

[0077] In summary, in this embodiment of the invention, by configuring a variable frequency fan, a humidity detection module, and a pressure detection module in the pneumatic conveying system for powder and granular materials, humidity and pressure data are acquired, and pressure is adjusted based on the variable frequency fan. Furthermore, considering the different characteristics of the pressurization and depressurization stages, the traditional PID control method, which uses a uniform control approach, is abandoned. This avoids asymmetry in the two-way adjustment of pressurization and depressurization, leading to adjustment oscillations during pressurization and lag during depressurization. By adjusting different PID control parameters for the pressurization and depressurization stages, the stability of the conveying pressure regulation is improved. Specifically, in the pressurization stage, the target proportional coefficient is determined by suppressing the proportional term based on the difference between the target wind speed and humidity, and the target derivative coefficient is determined by the deviation between the conveying pressure and the target pressure and humidity. In the depressurization stage, the integral term is adjusted by comparing the wind speed and conveying pressure with those under standard humidity conditions, combined with the humidity adjustment coefficient, to obtain the target integral coefficient. Therefore, the pressurization stage effectively suppresses adjustment oscillations, and the depressurization stage effectively avoids pressure regulation lag, thereby optimizing the adjustment logic and improving conveying efficiency and stability.

[0078] On the other hand, the present invention also provides a conveying pressure control system for a pneumatic conveying system for powder and granular materials. The system includes a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any of the aforementioned methods.

[0079] It should be noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0080] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for controlling the conveying pressure of a pneumatic conveying system for powder and granular materials, characterized in that, The method of configuring a variable frequency fan, a humidity detection module, and a pressure detection module in a pneumatic conveying system for powder and granular materials includes: The system acquires the material humidity from the humidity detection module, the conveying pressure from the pressure detection module, and the wind speed of the variable frequency fan at different sampling times; and determines the humidity adjustment coefficient based on the different preset humidity ranges in which the material humidity is located. During the pressurization phase, based on the current wind speed and the target wind speed to be adjusted, a suppression coefficient is determined to avoid large-scale wind speed adjustments; based on the humidity adjustment coefficient and the suppression coefficient, the proportional term of the delivery pressure is suppressed to obtain the target proportional coefficient; combined with the humidity adjustment coefficient and the deviation between the delivery pressure and the target pressure, the differential term is enhanced to obtain the target differential coefficient. During the depressurization phase, the values ​​of wind speed and conveying pressure under standard humidity and material humidity at the current sampling time are compared with the humidity adjustment coefficient. The integral term is then adjusted to obtain the target integral coefficient. The target proportional coefficient, target derivative coefficient, and target integral coefficient are used as the adjusted PID coefficients, and the conveying pressure is adjusted based on the adjusted PID coefficients.

2. The method for controlling the conveying pressure of a pneumatic conveying system for powder and granular materials as described in claim 1, characterized in that, The step of determining the humidity adjustment coefficient based on the different preset humidity ranges of the material's humidity includes: Under fixed operating conditions, the same material with different humidity levels is conveyed, and the pressure fluctuation index of the conveying pressure and the response time of PID regulation are obtained. As the material humidity is traversed in order from low to high, when the pressure fluctuation index first exceeds the preset fluctuation threshold, the corresponding material humidity is taken as the first humidity threshold H1; the response time under the first humidity threshold H1 is taken as the first analysis time. As the material humidity increases, when the first analysis time exceeds a preset multiple, the corresponding material humidity is used as the second humidity threshold H2, where the preset multiple is 1.5 times. Based on the first humidity threshold H1 and the second humidity threshold H2, the overall humidity is divided into three preset humidity ranges: [0,H1], (H1,H2] and (H2,Hmax], where Hmax represents the maximum value of the material humidity. Each preset humidity range is assigned a different humidity adjustment coefficient. The higher the material humidity in each preset humidity range, the smaller the value of the humidity adjustment coefficient.

3. The method for controlling the conveying pressure of a pneumatic conveying system for powder and granular materials as described in claim 1, characterized in that, The step of determining the suppression coefficient to avoid large-scale wind speed adjustments based on the current wind speed and the target wind speed to be adjusted includes: Calculate the wind speed difference between the target wind speed and the current wind speed, and normalize the wind speed difference as the suppression coefficient.

4. The method for controlling the conveying pressure of a pneumatic conveying system for powder and granular materials as described in claim 1, characterized in that, The step of suppressing the proportional term of the delivery pressure based on the humidity adjustment coefficient and the suppression coefficient to obtain the target proportional coefficient includes: The difference between the real number 1 and the suppression coefficient is calculated and used as the wind speed proportional adjustment index. The initial proportional coefficient of the proportional term is multiplied by the wind speed control index and the humidity adjustment coefficient, and the target proportional coefficient is used as the product of these factors.

5. The method for controlling the conveying pressure of a pneumatic conveying system for powder and granular materials as described in claim 1, characterized in that, The differential term is enhanced by incorporating the humidity adjustment coefficient and the deviation between the delivery pressure and the target pressure to obtain the target differential coefficient, including: Calculate the sum of the real number 1 and the humidity adjustment coefficient, and use it as the differential humidity adjustment index; The difference between the target pressure and the delivery pressure is taken as the pressure deviation. The pressure deviation is normalized, and the normalized value is added to the real number 1 to obtain the pressure differential adjustment index. The product of the initial differential coefficient of the differential term and the differential adjustment index of humidity and pressure is calculated as the target differential coefficient.

6. The method for controlling the conveying pressure of a pneumatic conveying system for powder and granular materials as described in claim 1, characterized in that, The values ​​of wind speed and conveying pressure under the standard humidity and the material humidity at the current sampling time, along with the humidity adjustment coefficient, are used to adjust the integral term to obtain the target integral coefficient, including: Based on the comparison between the current material humidity at the sampling time and the wind speed and conveying pressure under standard humidity, the wind pressure error of the material humidity at the current sampling time is determined; Calculate the product of the humidity regulation coefficient and the wind pressure error, and use the sum of the real number 1 and the product as the humidity integral regulation index; The product of the initial integral coefficient of the integral term and the humidity integral adjustment index is used as the target integral coefficient.

7. The method for controlling the conveying pressure of a pneumatic conveying system for powder and granular materials as described in claim 6, characterized in that, The determination of the wind pressure error of the material humidity at the current sampling time based on the comparison between the material humidity at the current sampling time and the wind speed and conveying pressure under standard humidity conditions includes: The delivery pressure and wind speed are normalized respectively. The sum of the normalized delivery pressure and the preset parameter adjustment coefficient is used as the denominator, and the normalized wind speed is used as the numerator to calculate the wind pressure ratio. The difference between the wind pressure ratio under standard humidity and the current material humidity at the sampling time is normalized and used as the wind pressure error.

8. The method for controlling the conveying pressure of a pneumatic conveying system for powder and granular materials as described in claim 1, characterized in that, The method of adjusting the delivery pressure based on the adjusted PID coefficients includes: During the boosting phase, PID control is performed based on the target proportional coefficient, initial integral coefficient, and target derivative coefficient at the current sampling time.

9. The method for controlling the conveying pressure of a pneumatic conveying system for powder and granular materials as described in claim 1, characterized in that, The method of regulating the delivery pressure based on the adjusted PID coefficients also includes: During the step-down phase, PID control is performed based on the initial proportional coefficient, target integral coefficient, and initial derivative coefficient at the current sampling time.

10. A conveying pressure control system for a pneumatic conveying system for powder and granular materials, the system comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method as described in any one of claims 1 to 9.

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