A PLC-based automatic control method and system for dry powder rollers

Abstract

This invention belongs to the field of automatic control and relates to a PLC-based automatic control method and system for dry powder pressure rollers. The method includes: collecting the main motor current, real-time roller pressure, roller gap, and feed screw speed of the pressure roller; calculating state parameters based on the changes in real-time roller pressure and real-time roller gap; using a reference pressure as the target roller pressure, setting a current threshold based on the state parameters; when the main motor current exceeds the limit, calculating the pressure reduction using a nonlinear attenuation function to correct the target roller pressure; based on the deviation between the target roller pressure and the actual roller pressure and the state parameters, obtaining PID control parameters from a preset multidimensional gain surface for calculation to obtain the basic control quantity; simultaneously, combining the feed screw speed with feedforward calculation to obtain the pressure fluctuation prediction compensation quantity; judging the system stability based on the real-time roller pressure change rate; and executing hydraulic control commands by the PLC to achieve precise roller pressure adjustment. This invention can achieve stable roller pressure control, meeting the precision control requirements of high-quality production.

Description

Technical Field

[0001] This invention belongs to the field of automatic control, and in particular relates to an automatic control method and system for dry powder rollers based on PLC. Background Technology

[0002] Dry powder press rollers are key equipment in industries such as metallurgy, chemicals, and building materials. Their function is to compress powdery materials using a pair of counter-rotating rollers, forming block or sheet-like finished products with specific density and strength for subsequent transportation, storage, and processing. During the pressing process, the pressure between the rollers (referred to as roller pressure) is the core process parameter that determines the quality of the finished product, such as density, strength, and uniformity.

[0003] Current control systems for dry powder press rollers typically use a programmable logic controller (PLC) as their core, adjusting the roller position and thus controlling the roller pressure via a hydraulic system. This control system detects real-time roller pressure using pressure sensors, compares it to a target pressure, and uses a PID algorithm to calculate the deviation to drive the hydraulic valves. However, fluctuations in the physical properties of the material, such as particle size, moisture content, and flowability, as well as uneven feeding speed, can significantly disrupt the pressing process. When faced with these operational disturbances, the aforementioned control methods often result in slow system response, large overshoot, and oscillations, affecting the stability of the pressing process and the quality of the finished product.

[0004] To improve control performance, existing technologies have been modified based on PID control, for example, by introducing feedforward control based on the feed screw speed to compensate for pressure disturbances caused by feed fluctuations. However, when material characteristics change, the accuracy of the model decreases, and the compensation effect is limited. During start-up, shutdown, or strong disturbances, the roller pressure changes drastically, and the integral element of the PID controller is prone to saturation, leading to severe control overshoot and system instability, and may even cause main motor current overload, threatening equipment safety. Existing control strategies often lack the ability to identify the actual compression state of the material within the roller gap online, and fail to automatically switch control modes based on steady-state and transient processes. This makes it difficult to ensure both rapid response and stability and safety, and thus cannot meet the precision control requirements of high-quality production. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a PLC-based automatic control method and system for dry powder rollers, in order to solve the technical problem that existing technologies are unable to ensure both rapid response and stability and safety, and thus cannot meet the precision control requirements of high-quality production.

[0006] To solve the above problems, the present invention provides a technical solution for an automatic control method for dry powder pressure rollers based on PLC: A PLC-based automatic control method for dry powder pressure rollers includes the following steps: The main motor current, real-time roller pressure, real-time roller gap, and feed screw speed of the pressure roller are obtained; based on the changes in real-time roller pressure and real-time roller gap over two consecutive sampling periods, the state parameters representing the material flow and compression characteristics are calculated. A reference pressure is obtained as the target roll pressure, and a current threshold is determined based on the state parameters. When the main motor current is greater than the current threshold, the pressure reduction amount is calculated based on the excess difference and the nonlinear decay function, and the target roll pressure is corrected to the difference between the reference pressure and the pressure reduction amount. Based on the deviation between the target roll pressure and the real-time roll pressure, and the state parameters, a set of PID control parameters is obtained from a table in a preset multidimensional gain surface. The selected set of PID control parameters is used to perform PID calculation on the deviation to obtain the basic control quantity. Based on the state parameters, a preset first-order transfer function is selected, and feedforward calculation is performed in combination with the feed screw speed to obtain the pressure fluctuation prediction compensation quantity. Calculate the rate of change of real-time roller pressure; when the absolute value of the rate of change is less than a stability threshold, add the basic control quantity and the pressure fluctuation prediction compensation quantity to obtain a hydraulic control command; when the absolute value of the rate of change is greater than or equal to the stability threshold, apply a ramp limit to the integral term in the basic control quantity, use the processed basic control quantity as the hydraulic control command, and discard the pressure fluctuation prediction compensation quantity; the PLC executes the hydraulic control command to adjust the hydraulic system to control the real-time roller pressure.

[0007] Furthermore, the calculation method for the state parameters representing the material flow and compressibility characteristics is as follows: Real-time roll pressure and real-time roll gap are recorded in two consecutive sampling periods, respectively; Calculate the real-time roll pressure change and real-time roll gap change between these two sampling periods; The state parameter is the absolute value of the ratio of the real-time roll pressure change to the real-time roll gap change, and a very small positive number is added in the calculation to prevent the denominator from being zero.

[0008] Furthermore, methods for correcting the target roll pressure include: Obtain the main motor current and determine the current threshold corresponding to the main motor current based on the status parameters; Calculate the difference between the main motor current and the current threshold. The pressure reduction is calculated by using a function that decays non-linearly in an exponential manner, combined with a preset maximum compensation pressure value and a preset decay coefficient. Subtracting the pressure reduction amount from the reference pressure yields the corrected target roll pressure.

[0009] Furthermore, methods for obtaining a set of PID control parameters from a pre-defined multidimensional gain surface include: Establish a three-dimensional lookup table with pressure deviation and state parameters as input axes and proportional, integral, and derivative control parameters as output values; The ranges of pressure deviation and state parameters are each divided into multiple intervals to form a grid; Based on the calculated pressure deviation and state parameters, determine their corresponding grid index positions in the three-dimensional lookup table, and extract the preset proportional parameters, integral parameters, and derivative parameters from these grid index positions as the PID control parameters for the current control cycle.

[0010] Furthermore, when the current values ​​of pressure deviation and state parameters fall at the corresponding grid index positions in the three-dimensional lookup table, a set of PID control parameters applicable to the current control cycle is calculated using a two-dimensional interpolation algorithm.

[0011] Furthermore, the PID calculation employs an incremental PID algorithm.

[0012] Furthermore, the steps to obtain the pressure fluctuation prediction compensation amount include: Multiple first-order transfer function models are pre-defined. Each first-order transfer function model is defined by a gain and a time constant, and each corresponds to a range of values ​​for a state parameter. Select the corresponding first-order transfer function model based on the current state parameter values; The change in the feed screw speed is used as the input of the selected first-order transfer function model. The discretized difference equation of the selected first-order transfer function model is used to solve the problem and predict the future trend of roller pressure change. The predicted value is then converted proportionally to obtain the pressure fluctuation prediction compensation amount.

[0013] Furthermore, when the absolute value of the rate of change is greater than or equal to the stability threshold, the method for obtaining the hydraulic control command is as follows: apply a preset change limit value to the increment of the integral term in the basic control quantity within a sampling period to perform ramp limiting processing; add the integral term after ramp limiting processing back to the proportional term and the derivative term to obtain the processed basic control quantity, and use the basic control quantity as the final hydraulic control command, while no longer using the pressure fluctuation prediction compensation quantity.

[0014] Furthermore, the ramp limiting process for the increment of the integral term is implemented through a saturation function, which restricts the increment of the integral term within the positive and negative range of a preset change limit value.

[0015] The technical solution of the automatic control system for dry powder rollers based on PLC provided by this invention is as follows: A PLC-based automatic control system for dry powder rollers includes a memory and a processor; the memory stores a computer program, and when the processor executes the computer program, it implements one of the above-mentioned PLC-based automatic control methods for dry powder rollers.

[0016] The beneficial effects of this invention are as follows: This invention calculates state parameters that represent the flow and compression characteristics of materials, enabling the control system to grasp the actual working conditions within the roller gap. Based on these state parameters, on the one hand, effective protection of the main motor is achieved. When the material properties cause a sharp increase in load, the target roller pressure can be actively corrected, reducing motor overload and equipment impact, and improving operational safety. On the other hand, by consulting multidimensional gain surfaces to obtain PID control parameters that match the current working conditions, and selecting appropriate models for feedforward compensation, the accuracy of control and the ability to suppress feeding disturbances are improved.

[0017] Furthermore, this invention can distinguish between steady-state and transient processes. When pressure fluctuates drastically, it limits the PID integral term and suspends feedforward compensation, reducing control overshoot and oscillation, and ensuring stable convergence under strong disturbances. Overall, this invention achieves smooth control of the roller pressing without increasing hardware costs, ensuring the uniformity of finished product quality and enhancing equipment reliability. Attached Figure Description

[0018] Figure 1 This is a flowchart of the steps of an automatic control method for dry powder rollers based on PLC according to the present invention; Figure 2 This is a structural block diagram of a PLC-based automatic control system for dry powder rollers according to the present invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0020] A specific embodiment of the automatic control method for dry powder pressure rollers based on PLC provided by the present invention: like Figure 1 As shown, the PLC-based automatic control method for dry powder rollers includes the following steps: S1: Obtain the main motor current, real-time roller pressure, real-time roller gap, and feed screw speed of the pressure roller; calculate the state parameters representing the material flow and compression characteristics based on the changes in real-time roller pressure and real-time roller gap within two consecutive sampling periods.

[0021] Specifically, this step involves acquiring the main motor current signal through a current transformer installed in the main motor circuit, measuring the real-time roller pressure through a pressure sensor installed on the hydraulic cylinder, measuring the real-time roller gap through a displacement sensor installed on the movable roller bearing housing, and obtaining the feeding screw speed by reading the frequency feedback from the feeding screw drive frequency converter or by a rotary encoder installed on the screw shaft. The displacement sensor uses a grating ruler or a wire encoder. The PLC controller cyclically acquires the instantaneous values ​​of the above four process variables at a fixed sampling period through a high-speed input module and an analog input module.

[0022] In this step, the calculation method for the state parameters representing the material flow and compressibility characteristics is as follows: Real-time roll pressure and real-time roll gap are recorded in two consecutive sampling periods, respectively; Calculate the changes in real-time roll pressure and real-time roll gap between these two sampling periods; The state parameter is the ratio of the change in real-time roll pressure to the change in real-time roll gap, and a very small positive number is added to the calculation to prevent the denominator from being zero.

[0023] More specifically, let the current sampling period be... The real-time rolling pressure is Real-time roller gap is The real-time rolling pressure of the previous sampling period was Real-time roller gap is The state parameters are The change in real-time roller pressure is The real-time change in roller gap is State parameters for: ,in, It is a very small positive number to prevent the denominator from being zero. State parameters. In a sense, it is similar to the compressive modulus of the material within the roller gap. A large value indicates that the material is hard or has poor flowability. A smaller value indicates that the material is soft or has good flowability.

[0024] S2, obtain the reference pressure as the target roll pressure, and determine the current threshold based on the state parameters; when the main motor current is greater than the current threshold, calculate the pressure reduction amount based on the excess difference and the nonlinear decay function, and correct the target roll pressure to the difference between the reference pressure and the pressure reduction amount.

[0025] This step is an intelligent safety protection mechanism. Its purpose is not to passively shut down the machine after the main motor is overloaded, but to proactively and smoothly adjust the target roller pressure when an overload risk is detected, thus avoiding equipment damage and ensuring production continuity and safety. When the actual main motor current exceeds its corresponding current threshold, the system performs the following operations: First, the system calculates how much the actual main motor current exceeds its corresponding current threshold. Then, based on this excess current, the system calculates the amount of reduction required for the target roller pressure using a preset non-linear decay function. This non-linear decay function is characterized by a small reduction in target roller pressure when the actual main motor current only slightly exceeds the threshold; when the actual main motor current significantly exceeds the threshold, the reduction in target roller pressure increases significantly, but not indefinitely, tending towards a preset maximum reduction limit. Finally, the system subtracts this calculated pressure reduction from the initially set reference pressure to obtain a corrected, lower target roller pressure. By proactively reducing the production pressure target, the load on the main motor can be directly reduced, restoring its current to a safe range.

[0026] Specifically, in this step, the nonlinear decay function is an exponential decay function. The main motor current is defined as... According to the state parameters Determined main motor current The corresponding current threshold is Pressure reduction amount is The reference pressure is The corrected target roll pressure is Reference pressure This is obtained by the operator according to process requirements. Current threshold. With state parameters Relatedly, in this embodiment, through a linear relationship It is confirmed that, among them, and This is a preset coefficient, representing the allowable current threshold as the material becomes harder. The higher the real-time main motor current. Greater than When the difference is exceeded, calculate the value. .

[0027] Pressure reduction The calculation method is as follows: ;in, The preset maximum compensation pressure value, This is the preset attenuation coefficient.

[0028] The corrected target roll pressure is The calculation formula is: ;like Not greater than ,but Keep as .

[0029] S3. Based on the deviation between the target roll pressure and the real-time roll pressure and the state parameters, a set of PID control parameters is obtained from a table in a preset multidimensional gain surface. The selected set of PID control parameters is used to perform PID calculation on the deviation to obtain the basic control quantity. Based on the state parameters, a preset first-order transfer function is selected and fed forward calculation is performed in combination with the feed screw speed to obtain the pressure fluctuation prediction compensation quantity.

[0030] This step includes two core algorithms: adaptive PID feedback control and adaptive feedforward compensation. These algorithms can overcome the shortcomings of traditional fixed-parameter PID controllers, such as slow response, large overshoot, and oscillation when operating conditions change. At the same time, they can compensate for pressure disturbances caused by fluctuations in feeding speed in advance, thus achieving more stable and precise roller pressing control.

[0031] This invention no longer uses a fixed set of PID control parameters. Instead, it searches for the most suitable PID control parameters for the current operating conditions in real time within a preset multidimensional gain surface based on two dimensions: pressure deviation and state parameters. This allows the PID controller to adjust in real time; that is, when the material hardens and the deviation is large, one set of PID control parameters is used; when the material softens and the deviation is small, another set of PID control parameters is used, thereby achieving real-time optimization of the control loop and obtaining a precise basic control quantity. Furthermore, this invention also utilizes state parameters to select a first-order transfer function from multiple preset models that best describes the relationship between the current feed rate change and the roller pressure change. Taking the real-time feed screw speed change as input, the selected model is used for calculation to predict the upcoming pressure fluctuation and generate a pressure fluctuation prediction compensation quantity.

[0032] Specifically, methods for obtaining a set of PID control parameters from a pre-defined multidimensional gain surface include: Establish a three-dimensional lookup table with pressure deviation and state parameters as input axes and proportional, integral, and derivative control parameters as output values; The ranges of pressure deviation and state parameters are each divided into multiple intervals to form a grid; Based on the calculated pressure deviation and state parameters, determine their corresponding grid index positions in the three-dimensional lookup table, and extract the preset proportional parameters, integral parameters, and derivative parameters from these grid index positions as the PID control parameters for the current control cycle.

[0033] Define pressure deviation as The scaling parameter is The integral parameter is The differential parameter is The basic control quantity is .in, The three-dimensional lookup table stores the optimal proportional parameters under different combinations of operating conditions. Integral parameters and differential parameters The PLC is based on the current and The value is calculated using a two-dimensional interpolation algorithm in a three-dimensional lookup table to find the most suitable set of values. , , Values. Incremental PID calculations are performed using this set of parameters. In one embodiment, the basic control quantity is calculated as follows: ,in, , , This represents the pressure deviation between the current sampling period, the previous sampling period, and the sampling period before that.

[0034] In addition, step S3, the step of obtaining the pressure fluctuation prediction compensation amount, includes: Multiple first-order transfer function models are pre-defined. Each first-order transfer function model is defined by a gain and a time constant, and each corresponds to a range of values ​​for a state parameter. Select the corresponding first-order transfer function model based on the current state parameter values; The change in the feed screw speed is used as the input of the selected first-order transfer function model. The discretized difference equation of the selected first-order transfer function model is used to solve the problem and predict the future trend of roller pressure change. After proportional conversion, the predicted value is used to obtain the pressure fluctuation prediction compensation amount.

[0035] S4, calculate the rate of change of real-time roller pressure; when the absolute value of the rate of change is less than the stability threshold, add the basic control quantity and the pressure fluctuation prediction compensation quantity to obtain the hydraulic control command; when the absolute value of the rate of change is greater than or equal to the stability threshold, apply a ramp limit to the integral term in the basic control quantity, use the processed basic control quantity as the hydraulic control command, and discard the pressure fluctuation prediction compensation quantity; the PLC executes the hydraulic control command to adjust the hydraulic system to control the real-time roller pressure.

[0036] This step enables the system to automatically distinguish between stable and transient operating conditions and adopt different control strategies to balance fast response and stable convergence. It solves the problem that the PID integral term is prone to saturation, leading to serious overshoot and oscillation when the system is in a transient process such as starting, stopping or encountering strong disturbances.

[0037] This step calculates the rate of change of real-time roller pressure and compares it with a stability threshold to determine whether the system is currently in a stable or highly fluctuating state. If the absolute value of the rate of change of real-time roller pressure is less than the stability threshold, it indicates that the system is in a stable or slightly fluctuating state. The system then employs a composite control strategy, adding the basic control quantity calculated by PID control to the pressure fluctuation prediction compensation quantity calculated by feedforward. The sum of these two values ​​serves as the final hydraulic control command, which is output to the actuator. This approach ensures both accurate tracking of the target and rapid compensation for minor disturbances.

[0038] If the absolute value of the rate of change of real-time roller pressure is greater than or equal to the stability threshold, it indicates that the system is in a state of severe fluctuation, at which point the system will switch control modes. First, the system will temporarily abandon the use of the pressure fluctuation prediction compensation amount obtained by feedforward calculation, because the accuracy of the prediction model will decrease when the system is in a state of severe fluctuation, and incorrect prediction compensation may exacerbate instability. At the same time, the system will apply a ramp limit to the integral term in the PID controller, that is, limit the increment of the integral term to within the positive and negative range of the preset change limit value through a saturation function, and do not allow it to increase too quickly in each control cycle. This can effectively prevent integral saturation caused by long-term accumulation of errors, thereby greatly suppressing control overshoot. Finally, the integrated term after the limitation process is added to the proportional term and the derivative term to obtain a smoother basic control quantity as the hydraulic control command, ensuring the stability of the control process.

[0039] During execution, the PLC converts the calculated digital hydraulic control commands into standard current or voltage signals via an analog output module. These analog signals are then sent to the amplifiers of the electro-hydraulic proportional valves or servo valves in the hydraulic station, controlling the valve core opening and direction. This precisely regulates the flow and pressure of hydraulic oil entering or leaving the hydraulic cylinder, driving the movable pressure roller to move and ensuring that the real-time roller pressure between the movable and fixed pressure rollers quickly and stably tracks the target roller pressure.

[0040] In an optional embodiment, the increment of the integral term is defined as The limit value for the change of the integral term is ,but ,in, For integration parameters, For the pressure deviation during the sampling period, The sampling period is defined. The increment of the integral term is limited to obtain the corrected increment. , ,in, It is a saturated function. The corrected integral term is: .

[0041] This invention significantly improves the accuracy, stability, and safety of roller pressing control without increasing hardware costs by calculating the state parameters of the material in real time, adaptively adjusting PID control parameters, feedforward compensation, and motor protection strategies, and automatically switching control modes according to system stability. Ultimately, it ensures the uniformity of finished product quality.

[0042] A specific embodiment of the automatic control system for dry powder rollers based on PLC provided by the present invention: like Figure 2 As shown, the PLC-based automatic control system for dry powder rollers includes a processor and a memory. The memory stores a computer program. When the processor executes the computer program, it implements the PLC-based automatic control method for dry powder rollers in any of the above embodiments.

[0043] The PLC-based automatic control system for dry powder rollers also includes other components well known to those skilled in the art, such as communication buses and communication interfaces. Their settings and functions are known in the art and will not be described in detail here.

[0044] While various embodiments of the invention have been shown and described in this specification, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will occur to those skilled in the art without departing from the spirit and essence of the invention.

Claims

1. A PLC-based automatic control method for dry powder pressure rollers, characterized in that, Includes the following steps: The main motor current, real-time roller pressure, real-time roller gap, and feed screw speed of the pressure roller are obtained. Based on the changes in real-time roller pressure and real-time roller gap over two consecutive sampling periods, state parameters representing the material flow and compression characteristics are calculated, including: recording real-time roller pressure and real-time roller gap over two consecutive sampling periods; calculating the changes in real-time roller pressure and real-time roller gap between these two sampling periods; the state parameter is the absolute value of the ratio of the changes in real-time roller pressure and real-time roller gap, and a very small positive number is added to the calculation to prevent the denominator from being zero; The reference pressure is obtained as the target roll pressure, and the current threshold is determined based on the state parameters. When the main motor current is greater than the current threshold, the pressure reduction is calculated based on the excess difference and the nonlinear decay function, and the target roll pressure is corrected to the difference between the reference pressure and the pressure reduction. Based on the deviation between the target roll pressure and the real-time roll pressure, as well as the state parameters, a set of PID control parameters is obtained from a table in the preset multidimensional gain surface. The selected set of PID control parameters is used to perform PID calculation on the deviation to obtain the basic control quantity. Based on the state parameters, a preset first-order transfer function is selected, and feedforward calculation is performed in combination with the feed screw speed to obtain the pressure fluctuation prediction compensation quantity. Calculate the rate of change of real-time roller pressure; when the absolute value of the rate of change is less than the stability threshold, add the basic control quantity and the pressure fluctuation prediction compensation quantity to obtain the hydraulic control command; when the absolute value of the rate of change is greater than or equal to the stability threshold, apply a ramp limit to the integral term in the basic control quantity, use the processed basic control quantity as the hydraulic control command, and discard the pressure fluctuation prediction compensation quantity; the PLC executes the hydraulic control command to adjust the hydraulic system to control the real-time roller pressure; when the absolute value of the rate of change is greater than or equal to the stability threshold, the method for obtaining the hydraulic control command is as follows: apply a preset change limit value to the increment of the integral term in the basic control quantity within one sampling period for ramp limiting processing; add the ramp-limited integral term, proportional term, and derivative term again to obtain the processed basic control quantity, and use this basic control quantity as the final hydraulic control command, while no longer using the pressure fluctuation prediction compensation quantity.

2. The automatic control method of the PLC-based dry powder press roller according to claim 1, characterized in that, Methods for correcting the target roll pressure include: Obtain the main motor current and determine the current threshold corresponding to the main motor current based on the status parameters; Calculate the difference between the main motor current and the current threshold. The pressure reduction is calculated by using a function that decays non-linearly in an exponential manner, combined with a preset maximum compensation pressure value and a preset decay coefficient. Subtracting the pressure reduction amount from the reference pressure yields the corrected target roll pressure.

3. The automatic control method of the PLC-based dry powder press roller according to claim 1, characterized in that, Methods for obtaining a set of PID control parameters from a pre-defined multidimensional gain surface include: Establish a three-dimensional lookup table with pressure deviation and state parameters as input axes and proportional, integral, and derivative control parameters as output values; The ranges of pressure deviation and state parameters are each divided into multiple intervals to form a grid; Based on the calculated pressure deviation and state parameters, determine their corresponding grid index positions in the three-dimensional lookup table, and extract the preset proportional parameters, integral parameters, and derivative parameters from these grid index positions as the PID control parameters for the current control cycle.

4. The automatic control method for dry powder pressure rollers based on PLC according to claim 3, characterized in that, When the current values ​​of pressure deviation and state parameters fall at the corresponding grid index position in the three-dimensional lookup table, a set of PID control parameters applicable to the current control cycle is calculated using a two-dimensional interpolation algorithm.

5. The automatic control method for dry powder pressure rollers based on PLC according to claim 4, characterized in that, The PID calculation uses an incremental PID algorithm.

6. The automatic control method of a PLC-based dry powder press roller according to claim 1, wherein, The steps to obtain the pressure fluctuation prediction compensation amount include: Multiple first-order transfer function models are pre-defined. Each first-order transfer function model is defined by a gain and a time constant, and each corresponds to a range of values ​​for a state parameter. Select the corresponding first-order transfer function model based on the current state parameter values; The change in the feed screw speed is used as the input of the selected first-order transfer function model. The discretized difference equation of the selected first-order transfer function model is used to solve the problem and predict the future trend of roller pressure change. The predicted value is then converted proportionally to obtain the pressure fluctuation prediction compensation amount.

7. The automatic control method of a PLC-based dry powder press roller according to claim 1, characterized in that, The ramp limiting of the increment of the integral term is achieved through a saturation function, which restricts the increment of the integral term within the positive and negative range of a preset change limit value.

8. A PLC-based automatic control system for a dry powder press roll, characterized by, It includes a memory and a processor; the memory stores a computer program, and when the processor executes the computer program, it implements the PLC-based automatic control method for dry powder rollers as described in any one of claims 1-7.

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