A temperature self-adaptive control method for a paperboard drying production line based on PID

Abstract

The present application belongs to the technical field of temperature control, and particularly relates to a temperature self-adaptive control method for a paperboard drying production line based on PID, which comprises the following steps: collecting the oven temperature and the production line speed, and obtaining a smooth speed through filtering; then, the speed disturbance intensity is calculated by combining the speed change rate, the basic inertia constant and the logarithmic weighting factor, and the thermal response lag sensitivity representing the system vulnerability is constructed according to the temperature deviation; subsequently, the adaptive feedforward compensation flux is generated by fusing the basic linear compensation and the dynamic nonlinear compensation based on the lag sensitivity; finally, the adaptive feedforward compensation flux is superimposed with the PID feedback output to drive the heating mechanism. By quantifying the nonlinear impact of the speed change rate and the thermal lag characteristics of the system, the present application solves the lag and overshoot problems of the traditional control under the variable speed working condition, and improves the temperature control precision and stability of the production line.

Description

Technical Field

[0001] This invention relates to the field of temperature control technology. More specifically, this invention relates to a PID-based adaptive temperature control method for a cardboard drying production line. Background Technology

[0002] In modern corrugated cardboard production processes, the drying stage is one of the key processes determining the quality of the finished product. This stage typically consists of a series of hot plates or ovens, whose main function is to remove excess moisture absorbed by the cardboard during the bonding process through heat transfer, and to promote the rapid curing of the starch adhesive at high temperatures, thereby giving the cardboard sufficient bonding strength, flatness, and edge crush strength. The stability of the temperature inside the oven directly affects the final forming quality of the cardboard. Too low a temperature will lead to weak adhesive bonding, resulting in delamination and bubbling; too high a temperature will cause the cardboard to become overly dry, brittle, and even cause the base paper to scorch, resulting in waste of raw materials. Existing control systems typically employ classic PID closed-loop control algorithms, supplemented by simple linear feedforward compensation based on real-time speed. When an increase in speed is detected, the heating power is increased by a fixed proportion, pre-adjusting the energy output before the speed change causes fluctuations in heat load to maintain temperature stability.

[0003] However, the aforementioned conventional control methods have certain limitations when dealing with complex production line conditions. First, the drying process exhibits hysteresis and thermal inertia, making the ability of PID feedback to suppress rapid disturbances limited and prone to hysteresis. Simultaneously, existing feedforward strategies often focus only on the absolute value of speed, treating it as a linear disturbance while ignoring the nonlinear impact of the rate of speed change on the thermal load. In reality, the heat carried away by the cardboard is not a simple linear relationship; at different base speeds, the disruptive force of the same speed fluctuation on thermal equilibrium varies significantly, and the system's thermal response sensitivity differs under different temperature differences. Existing algorithms cannot dynamically perceive this nonlinear energy demand gradient caused by the rate of speed change and the system's current thermal vulnerability, resulting in severe temperature fluctuations during acceleration and deceleration, making it difficult to meet the control precision requirements for high-quality production. Summary of the Invention

[0004] To address the technical problem of poor temperature control in the aforementioned paperboard drying production line, this invention provides a PID-based adaptive temperature control method for a paperboard drying production line, comprising: The system acquires the actual temperature inside the oven, the set target temperature, and the real-time speed of the production line; smooths the real-time speed to obtain a smoothed speed; acquires the speed disturbance intensity at each moment, which is positively correlated with the time derivative of the smoothed speed at the current moment, the basic inertial constant, and the product of the current smoothed speed and the rated reference speed; acquires the thermal response hysteresis sensitivity at each moment, which is positively correlated with the absolute value of the speed disturbance intensity at the corresponding moment and the target temperature, and negatively correlated with the absolute value of the difference between the target temperature and the actual temperature; acquires the adaptive feedforward compensation flux, which includes basic linear and dynamic nonlinear compensation; the basic linear compensation is positively correlated with the product of the smoothed speed and the basic speed proportional coefficient; the dynamic nonlinear compensation is positively correlated with the dynamic compensation gain coefficient, the sign of the rate of change of speed, and the saturation function of the thermal response hysteresis sensitivity; acquires the PID control output based on the target temperature and the actual temperature; adds the PID control output to the adaptive feedforward compensation flux to obtain the final control quantity, and controls the heating actuator based on the final control quantity.

[0005] This invention introduces an adaptive feedforward compensation mechanism that incorporates both basic linearity and dynamic nonlinearity, enabling real-time sensing of speed disturbance intensity and the system's current thermal response hysteresis sensitivity. This strategy, which deeply integrates feedforward and feedback, not only preserves the steady-state accuracy of the PID controller but also proactively offsets the nonlinear thermal shock caused by the rate of speed change through dynamic compensation, thereby improving the system's dynamic response speed and temperature control stability under complex variable speed conditions.

[0006] Preferably, the smoothing process for the real-time speed to obtain a smoothed speed includes: The real-time speed is processed using a moving average filtering algorithm to filter out high-frequency noise above 10Hz, resulting in a smooth speed.

[0007] Preferably, obtaining the rated reference speed includes: Obtain the diameter of the drive roller, the rated maximum speed on the motor nameplate, and the reduction ratio of the reducer; the rated reference speed is directly proportional to the product of the drive roller diameter and the rated maximum speed, and inversely proportional to the reduction ratio of the reducer.

[0008] Preferably, the acquisition of the fundamental inertial constant includes: Apply a unit velocity step at the lowest stable velocity to obtain the maximum magnitude of temperature drop; the ratio of the maximum magnitude to the unit velocity step, and the sum of the system's inherent minimum turbulence coefficient, are denoted as the basic inertial constant.

[0009] Preferably, the velocity disturbance intensity satisfies the expression: ; In the formula, This represents the intensity of the velocity disturbance at time t; Represents the rate of change of velocity at time t; Represents the fundamental inertia constant; This represents the velocity at time t after smoothing. Indicates the rated reference speed of the production line; This represents the natural logarithm function.

[0010] This invention utilizes a logarithmic function to construct a velocity disturbance intensity model, overcoming the shortcomings of traditional linear models in numerical divergence or fitting distortion during high-speed operation. It also utilizes a logarithmic weighting factor to establish a nonlinear impact effect model of cardboard on heat load at different speed bases, that is, assigning higher weights at high speeds and with acceleration, thereby more accurately quantifying the actual heat energy gap under high dynamic conditions and solving the technical problem of temperature instability at high speeds.

[0011] Preferably, the thermal response hysteresis sensitivity satisfies the expression: ; In the formula, This represents the thermal response hysteresis sensitivity at time t; This represents the intensity of the velocity disturbance at time t; Indicates the set target temperature; This represents the actual temperature at time t; Indicates a tiny positive value; Represents the absolute value symbol.

[0012] This invention constructs a thermal response hysteresis sensitivity index that includes the reciprocal of the temperature difference term, linking the control gain to the current equilibrium state of the system. When the actual temperature approaches the target temperature, the sensitivity value increases nonlinearly, enabling the system to make more proactive predictions and adjustments to small speed disturbances, thereby providing stronger anti-interference capabilities in steady state and preventing the steady-state equilibrium from being easily disrupted by external disturbances.

[0013] Preferably, the dynamic compensation gain coefficient is positively correlated with the width, basis weight, specific heat capacity of the currently produced paperboard, and the difference between the target temperature and the ambient temperature, and the dynamic compensation gain coefficient satisfies the expression: ; In the formula, This represents the dynamic compensation gain coefficient at time t; This represents the control conversion gain corresponding to unit linear energy density. Indicates the width of the paperboard currently being produced; This indicates the basis weight of the paperboard currently being produced; Indicates the specific heat capacity of cardboard; Indicates the set target temperature; Indicates ambient temperature.

[0014] This invention directly maps the physical specifications of cardboard, such as width, weight, and specific heat capacity, to dynamic compensation gain coefficients, solving the problem of control model mismatch when switching between different production orders using traditional single-parameter PID controllers. This invention can automatically scale the feedforward compensation intensity according to the actual heat absorption capacity of the object being heated, ensuring that the control system can output energy compensation that matches the physical properties of both heavy and light weight cardboard, thus reducing the scrap rate during order changeover.

[0015] Preferably, the adaptive feedforward compensation flux satisfies the expression: ; In the formula, Let represent the adaptive feedforward compensation flux at time t; Indicates the base speed proportionality coefficient; This represents the velocity at time t after smoothing. This represents the dynamic compensation gain coefficient at time t; Represents a symbolic function; Represents the rate of change of velocity at time t; This represents the thermal response hysteresis sensitivity at time t; Represents the natural constant.

[0016] This invention uses an exponential decay function as a nonlinear adjustment factor to achieve a smooth and controlled output of adaptive feedforward compensation flux. When the rate of change of velocity is large and the system sensitivity is high, it utilizes saturation characteristics to provide compensation quickly, while maintaining linear following under normal conditions. This soft switching mechanism not only ensures rapid suppression of severe disturbances, but also prevents system overshoot oscillations caused by sudden changes in compensation, thus achieving a unity of steady-state support and dynamic disturbance rejection.

[0017] Preferably, obtaining the basic speed proportionality coefficient includes: In the calibration experiment, the average values ​​of the stable control quantities at high speed and low speed, as well as the corresponding high speed and low speed values, are obtained; the basic speed proportional coefficient is equal to the ratio of the difference between the average values ​​of the control quantities at high speed and low speed to the difference between the high speed and low speed values, where high speed and low speed are preset values.

[0018] Preferably, obtaining the actual temperature inside the oven, the set target temperature, and the real-time speed of the production line includes: Temperature sensors are installed inside the oven to collect the actual temperature; the set target temperature is received through a human-machine interface; and a rotary encoder is installed on the main drive shaft to collect the real-time speed of the production line.

[0019] The beneficial effects of this invention are as follows: This invention constructs a logarithmically weighted speed disturbance intensity model to evaluate the nonlinear thermal shock during the speed change process, especially during high-speed acceleration and deceleration; at the same time, it introduces a thermal response hysteresis sensitivity index and uses the reciprocal characteristic of temperature difference to dynamically adjust the system's anti-disturbance gain, enabling it to have high sensitivity protection capability in steady state; this invention also combines adaptive mapping of paperboard physical specification parameters to achieve a smooth switch of control strategy from steady-state support to dynamic anti-disturbance, solving the problem of temperature fluctuation in large hysteresis drying systems under complex speed change conditions. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating a temperature adaptive control method for a cardboard drying production line based on PID according to the present invention; Figure 2 This is a schematic diagram illustrating the comparison of the temperature response effects of the present invention and pure PID control; Figure 3 This is a schematic diagram illustrating the comparison between the temperature deviation quantification of the present invention and pure PID control. Detailed Implementation

[0021] This invention discloses a temperature adaptive control method for a cardboard drying production line based on PID control, referring to... Figure 1 This includes steps S1-S5: S1: Real-time acquisition of the current actual temperature, set target temperature, and real-time operating speed of the cardboard drying production line's oven; noise reduction processing of the real-time operating speed using a low-pass filtering algorithm to obtain a smoothed speed signal.

[0022] It should be noted that the operating environment of a cardboard drying production line is complex, and the collected signals are often mixed with high-frequency noise. Therefore, the raw speed data must first be cleaned to lay a data foundation for constructing accurate kinetic indicators.

[0023] Specifically, the system collects real-time data on the current actual temperature inside the drying oven of the cardboard drying production line, the set target temperature, and the real-time operating speed of the production line, including: The actual temperature is collected by a temperature sensor placed inside the oven; the set target temperature is obtained from the human-machine interface; and the real-time operating speed of the production line is collected by a rotary encoder installed on the main drive shaft. For example, the target temperature is 115℃, and the sampling frequency is set to 50Hz.

[0024] Preferably, the real-time running speed is denoised using a low-pass filtering algorithm to obtain a smoothed speed signal, including: A moving average filtering algorithm is used to process the real-time operating speed, filtering out high-frequency interference above 10Hz to obtain a smoothed speed signal. It should be noted that if the cutoff frequency is set too low, such as 1Hz, the speed signal will lag, causing subsequent feedforward compensation to miss its optimal timing; if the cutoff frequency is set too high, such as 50Hz, it will not effectively filter out power frequency interference.

[0025] At this point, the smoothed velocity signal has been obtained.

[0026] S2: Obtain the rated reference speed and basic inertia constant of the production line; perform time differentiation calculation on the smoothed speed signal to obtain the speed change rate; obtain the speed disturbance intensity based on the speed change rate, the basic inertia constant, and the nonlinear ratio of the current real-time speed to the rated reference speed.

[0027] It should be noted that existing technologies often neglect the impact of velocity change rate on heat load, adjusting only proportionally based on velocity magnitude. However, as a heat-absorbing medium, the rate at which cardboard passes through the oven directly corresponds to changes in mass flow. Furthermore, the thermal shock effect of this change at different reference velocities is nonlinear; fluctuations at high speeds have a greater disruptive effect on thermal equilibrium than fluctuations at low speeds. Therefore, this invention constructs a velocity disturbance intensity model, using the velocity change rate as a nonlinear weighting factor to characterize the energy demand gradient under the current operating conditions.

[0028] Specifically, the rated reference speed and basic inertia constant of the production line are obtained, including: It should be noted that, in order to ensure the accuracy of the speed disturbance intensity calculation, it is necessary to calibrate the physical limits and basic disturbance immunity of the production line.

[0029] Obtain the diameter of the drive roller, the rated maximum speed on the motor nameplate, and the reduction ratio of the reducer. For example, the diameter of the drive roller is 0.6m, the rated maximum speed on the motor nameplate is 1800rpm, and the reduction ratio of the reducer is 25.

[0030] The rated reference speed of the production line is obtained based on the diameter of the drive roller, the rated maximum speed, and the reduction ratio of the reducer. The rated reference speed is used to normalize the speed data to ensure that the logarithmic terms are within a reasonable mathematical range under any operating conditions.

[0031] The rated reference speed of the production line satisfies the expression: ; In the formula, Indicates the rated reference speed of the production line; Indicates the diameter of the drive roller; This indicates the rated maximum speed on the motor nameplate; Indicates the reduction ratio of the speed reducer; It represents pi (π).

[0032] Obtain the unit velocity step, the maximum amplitude of the temperature drop after applying the unit velocity step at the lowest stable velocity, and the minimum turbulence coefficient. For example, the unit velocity step is 0.3 m / s, the maximum amplitude is 3.2 °C, and the minimum turbulence coefficient is 0.42.

[0033] The fundamental inertial constant is obtained based on the unit velocity step, the maximum amplitude, and the minimum turbulence coefficient. This fundamental inertial constant characterizes the basic thermal disturbance caused by mechanical transmission and air convection at the production line's minimum operating speed.

[0034] The fundamental inertial constant satisfies the following expression: ; In the formula, Represents the fundamental inertia constant; This represents the maximum temperature drop after a unit velocity step is applied at the lowest stable velocity. Indicates a unit velocity step jump; This represents the system's inherent minimum turbulence coefficient, for example, .

[0035] In the formula, This reflects the system's initial sensitivity to sudden rate changes. If If the value is too large, it will lead to an artificially high base value for the shock index, causing the system to generate excessive feedforward compensation during low-speed, small fluctuations, thus triggering oscillations; if... If the value is too small, it will lead to an underestimation of the basic thermal disturbance, resulting in a slow compensation response.

[0036] Preferably, the smoothed velocity signal is subjected to time derivative calculation to obtain the velocity change rate; based on the velocity change rate, the fundamental inertial constant, and the nonlinear ratio of the current real-time velocity to the rated reference velocity, the velocity disturbance intensity is obtained, including: The rate of change of velocity is obtained by calculating the time derivative of the smoothed velocity signal.

[0037] It should be noted that when constructing the velocity disturbance intensity, the higher the velocity, the more mass of cardboard passes through the oven per unit time, meaning a larger system thermal load base. In this case, the same acceleration will lead to larger-scale mass flow fluctuations. Therefore, this invention uses a logarithmic function to smoothly map the baseline velocity ratio to prevent numerical explosion at high speeds, while also reflecting nonlinear gain.

[0038] The intensity of the velocity disturbance at any given time satisfies the expression: ; In the formula, This represents the intensity of the velocity disturbance at time t; Represents the rate of change of velocity at time t; Represents the fundamental inertia constant; This represents the velocity at time t after smoothing. Indicates the rated reference speed of the production line; This represents the natural logarithm function.

[0039] In the formula, It reflects the direct rate of load change; The term is a logarithmic weighting factor, which means that when the production line is running at high speed, even with the same acceleration, the calculated speed disturbance intensity will be greater than the value when running at low speed. This indicates that the rate of change of velocity at time t is weighted by a logarithmic weighting factor and a fundamental inertial constant, representing the degree of severe disruption to the system's thermal balance caused by heat load fluctuations at a high reference velocity.

[0040] Thus, the velocity disturbance intensity at any given time has been obtained.

[0041] S3: Based on the intensity of the velocity disturbance and the degree of deviation of the smoothed velocity data relative to the target temperature, obtain the thermal response hysteresis sensitivity.

[0042] It should be noted that obtaining the physical-level velocity disturbance intensity cannot be directly used for control; it must be analyzed in conjunction with the system's current thermodynamic state. Due to the oven's large hysteresis characteristic, the system's sensitivity to external shocks depends on the deviation between the current temperature and the target temperature. When the actual temperature is very close to the setpoint, the system is in a fine equilibrium state, and any small external disturbance can easily disrupt the steady state; in this case, the system requires close monitoring. Conversely, when the temperature difference is large, the system is already in a stressed symmetry state, and its sensitivity to additional shocks is relatively reduced. Therefore, this invention maps the velocity disturbance intensity into the system's error space to construct a thermal response hysteresis sensitivity index.

[0043] Specifically, based on the intensity of the velocity disturbance and the degree of deviation of the smoothed velocity data relative to the target temperature, the thermal response hysteresis sensitivity is obtained, including: The thermal response hysteresis sensitivity at any given time satisfies the expression: ; In the formula, This represents the thermal response hysteresis sensitivity at time t; This represents the intensity of the velocity disturbance at time t; Indicates the set target temperature; This represents the actual temperature at time t; This indicates a small positive value, used to avoid a denominator of 0. For example, ; Represents the absolute value symbol.

[0044] In the formula, Characterizing the vulnerability of the system's current thermal state, as the actual temperature approaches the target temperature, the denominator approaches... As this value increases, the influence weight of the velocity disturbance intensity is amplified; Transforming kinetic shocks into thermodynamic response requirements: When the system is in equilibrium, the response to velocity fluctuations should be more sensitive to prevent the steady state from being disrupted.

[0045] Thus, the thermal response hysteresis sensitivity at each moment was obtained.

[0046] S4: Based on the physical specifications and ambient temperature of the current paperboard being produced, obtain the dynamic compensation gain coefficient; based on the smoothed speed, the dynamic compensation gain coefficient, the direction of the speed change rate, and the thermal response hysteresis sensitivity, obtain the adaptive feedforward compensation flux.

[0047] It should be noted that after obtaining the thermal response hysteresis sensitivity, it needs to be converted into a specific energy control increment. Conventional feedforward control usually only performs linear compensation based on speed, which cannot cope with the nonlinear thermal inertia during acceleration and deceleration. Therefore, this invention adopts a strategy of combining basic linear support with dynamic nonlinear adjustment. By using the thermal response hysteresis sensitivity index and adjusting the dynamic gain through an exponential decay function, it ensures that the compensation amount not only follows the speed but also follows the system's ability to withstand speed changes in the current state.

[0048] Specifically, based on the physical specifications and ambient temperature of the currently produced paperboard, the dynamic compensation gain coefficient is obtained, including: It should be noted that feedforward compensation includes two parts: steady-state support and dynamic compensation, which correspond to different physical parameters.

[0049] Obtain the base velocity proportionality coefficient, which is used to describe the slope of the static linear relationship between velocity and heat load under steady state.

[0050] The basic speed proportional coefficient satisfies the following expression: ; In the formula, Indicates the base speed proportionality coefficient; , These represent the high speed and low speed during the calibration experiment, respectively. , These represent the average control outputs of the PID controller at high and low speeds during the calibration experiment, respectively. For example, , .

[0051] The physical specifications and ambient temperature of the currently produced paperboard are obtained. These physical specifications include the control conversion gain per unit linear energy density, the width of the paperboard, its basis weight, its specific heat capacity, and the ambient temperature. For example, the control conversion gain per unit linear energy density is 0.78% / (J / m), the width of the paperboard is 1.5m, and the basis weight is 0.22. The specific heat capacity of the currently produced cardboard is 1250 J / (kg). The ambient temperature was 23.5℃.

[0052] Obtain the dynamic compensation gain coefficient, which represents the upper limit of the additional maximum energy compensation required to offset thermal inertia at the moment of speed change.

[0053] The dynamic compensation gain coefficient at any given time satisfies the following expression: ; In the formula, This represents the dynamic compensation gain coefficient at time t; This represents the control conversion gain corresponding to unit linear energy density. Indicates the width of the paperboard currently being produced; This indicates the basis weight of the paperboard currently being produced; Indicates the specific heat capacity of cardboard; Indicates the set target temperature; Indicates ambient temperature.

[0054] In the formula, This indicates the total energy required to heat the current specification of cardboard from ambient temperature to the set temperature, ensuring that the dynamic compensation force automatically increases when producing thick or wide cardboard at the same acceleration.

[0055] It should be noted that, The dimension of is [%]. The dimensions are [% / (J / m)]. The dimension of is m. The dimensions are , The dimension is J / (kg) ℃), and The dimension of is ℃, and the dimensions of the left and right sides of the equation are consistent.

[0056] Preferably, the adaptive feedforward compensation flux is obtained based on the smoothed velocity, the dynamic compensation gain coefficient, the direction of the velocity change rate, and the thermal response hysteresis sensitivity, including: It should be noted that, to prevent overcompensation, the thermal response hysteresis sensitivity needs to be mapped to a finite interval, and the sign of the compensation is determined by the velocity direction. Simultaneously, a sign function is used to extract the direction of the rate of change of velocity.

[0057] The adaptive feedforward compensation flux at any given time satisfies the following expression: ; In the formula, Let represent the adaptive feedforward compensation flux at time t; Indicates the base speed proportionality coefficient; This represents the velocity at time t after smoothing. This represents the dynamic compensation gain coefficient at time t; Represents a symbolic function; Represents the rate of change of velocity at time t; This represents the thermal response hysteresis sensitivity at time t; Represents the natural constant.

[0058] In the formula, Combining the smoothed velocity at time t with the base velocity ratio coefficient provides basic linear thermal support; The term uses an exponential decay function to map the thermal response hysteresis sensitivity to the (0,1) interval, which serves as a dynamic gain adjustment factor. When the acceleration increases, the impact is large and the system is in equilibrium. The compensation increases to near the saturation value and determines whether to increase or decrease heating based on the direction of acceleration, thereby offsetting thermal inertia.

[0059] Thus, the adaptive feedforward compensation flux at any given time has been obtained.

[0060] S5: Based on the set target temperature and the actual temperature, obtain the feedback output of the conventional PID controller; based on the feedback output and the adaptive feedforward compensation flux, obtain the final control quantity, and use the final control quantity to drive the actuator to complete the adaptive temperature control of the paperboard drying production line.

[0061] It should be noted that the adaptive feedforward compensation flux of this invention is a precise prediction of speed fluctuations as a specific disturbance source, while PID feedback control is a correction for model errors and other unknown disturbances. Combining the two preserves the stability of PID control while giving the system a rapid response capability to variable speed conditions.

[0062] Specifically, based on the set target temperature and the actual temperature, the feedback output of a conventional PID controller is obtained, including: Using a conventional PID control algorithm, the feedback output at time t is obtained based on the deviation between the set target temperature and the actual temperature at time t. For example, the proportional gain of the PID controller is 5.8, the integral gain is 0.12, and the derivative gain is 1.1.

[0063] Preferably, based on the feedback output and the adaptive feedforward compensation flux, a final control quantity is obtained, and the actuator is driven using the final control quantity to complete the adaptive temperature control of the paperboard drying production line, including: The final control quantity at any given time satisfies the expression: ; In the formula, This represents the final control quantity at time t; This represents the feedback output at time t; Let represent the adaptive feedforward compensation flux at time t.

[0064] In the formula, The final superimposed control commands are used to directly drive the opening of the steam regulating valve or the power of the electric heater, thereby achieving precise control of the oven temperature.

[0065] It should be noted that, as Figure 2 This diagram illustrates the temperature response performance comparison between the present invention and pure PID control, used to verify the control accuracy advantage of the present invention. The horizontal axis represents time, and the vertical axis represents temperature; the target temperature represents the set drying process temperature, 115℃; the pure PID control temperature curve represents the temperature response adjusted solely by PID feedback, showing a temperature drop during the acceleration phase (10-20 seconds) and a significant temperature rise during the deceleration phase (45-55 seconds); the PID + feedforward control temperature curve represents the temperature response of the present invention's composite control strategy.

[0066] like Figure 3 This diagram illustrates a quantitative comparison of temperature deviation between the present invention and pure PID control, used to quantitatively verify the technical advantages of the present invention. The horizontal axis represents time, and the vertical axis represents temperature deviation. The pure PID control deviation curve represents the absolute difference between the actual temperature and the target temperature under pure PID control, showing that the deviation increases during acceleration and deceleration, and the average deviation is relatively large during the steady-state phase. The PID+feedforward control deviation curve represents the temperature deviation of the present invention's composite control strategy, with an overall amplitude smaller than that of pure PID control. The two filled areas represent the cumulative deviation areas of the two control strategies, reflecting the deviation optimization effect of the present invention.

[0067] Thus, the temperature adaptive control of the cardboard drying production line based on PID was completed.

[0068] 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 method for temperature self-adaptive control of a paperboard drying production line based on PID, characterized in that, include: The actual temperature inside the oven, the set target temperature, and the real-time speed of the production line are obtained. The real-time speed is smoothed to obtain a smoothed speed; the speed disturbance intensity at each moment is obtained, and the speed disturbance intensity is positively correlated with the time derivative of the smoothed speed at the current moment, the fundamental inertial constant, and the ratio of the current smoothed speed to the rated reference speed. The thermal response hysteresis sensitivity at each moment is obtained. This sensitivity is positively correlated with the absolute value of the velocity disturbance intensity and the target temperature at the corresponding moment, and negatively correlated with the absolute value of the difference between the target temperature and the actual temperature. The adaptive feedforward compensation flux is obtained, comprising basic linear compensation and dynamic nonlinear compensation. The basic linear compensation is positively correlated with the product of the smoothing velocity and the basic velocity proportionality coefficient. The dynamic nonlinear compensation is positively correlated with the dynamic compensation gain coefficient, the sign of the velocity change rate, and the saturation function of the thermal response hysteresis sensitivity. The dynamic compensation gain coefficient is positively correlated with the width, basis weight, specific heat capacity of the currently produced cardboard, and the difference between the target temperature and the ambient temperature. The dynamic compensation gain coefficient satisfies the following: ； denotes a dynamic compensation gain coefficient at the t-th moment; denotes a control amount conversion gain corresponding to a unit line energy density; denotes a width of the currently produced paperboard; denotes a grammage of the currently produced paperboard; denotes a specific heat capacity of the paperboard; denotes a set target temperature; denotes an ambient temperature; Obtain PID control output based on the target temperature and the actual temperature; The PID control output is added to the adaptive feedforward compensation flux to obtain the final control quantity, and the heating actuator is controlled based on the final control quantity.

2. The temperature adaptive control method for a PID-based paperboard drying production line according to claim 1, characterized in that, The process of smoothing the real-time speed to obtain a smoothed speed includes: The real-time speed is processed using a moving average filtering algorithm to filter out high-frequency noise above 10Hz, resulting in a smooth speed.

3. The temperature adaptive control method for a cardboard drying production line based on PID control according to claim 1, characterized in that, The acquisition of the rated reference speed includes: Obtain the diameter of the drive roller, the rated maximum speed on the motor nameplate, and the reduction ratio of the reducer; the rated reference speed is directly proportional to the product of the drive roller diameter and the rated maximum speed, and inversely proportional to the reduction ratio of the reducer.

4. The temperature adaptive control method for a cardboard drying production line based on PID control according to claim 1, characterized in that, The acquisition of the fundamental inertial constant includes: Apply a unit velocity step at the lowest stable velocity to obtain the maximum amplitude of temperature drop; the ratio of the maximum amplitude to the unit velocity step, and the sum of the sum of the system's inherent minimum turbulence coefficient, are denoted as the basic inertial constant.

5. The temperature adaptive control method for a cardboard drying production line based on PID control according to claim 1, characterized in that, The intensity of the velocity disturbance satisfies the expression: ； In the formula, This represents the intensity of the velocity disturbance at time t; Represents the rate of change of velocity at time t; Represents the fundamental inertia constant; This represents the velocity at time t after smoothing. Indicates the rated reference speed of the production line; This represents the natural logarithm function.

6. The temperature adaptive control method for a cardboard drying production line based on PID control according to claim 1, characterized in that, The thermal response hysteresis sensitivity satisfies the expression: ； In the formula, This represents the thermal response hysteresis sensitivity at time t; This represents the intensity of the velocity disturbance at time t; Indicates the set target temperature; This represents the actual temperature at time t; Indicates a tiny positive value; Represents the absolute value symbol.

7. The temperature adaptive control method for a cardboard drying production line based on PID control according to claim 1, characterized in that, The adaptive feedforward compensation flux satisfies the expression: ； In the formula, Let represent the adaptive feedforward compensation flux at time t; Indicates the base speed proportionality coefficient; This represents the velocity at time t after smoothing. This represents the dynamic compensation gain coefficient at time t; Represents a symbolic function; Represents the rate of change of velocity at time t; This represents the thermal response hysteresis sensitivity at time t; Represents the natural constant.

8. The temperature adaptive control method for a cardboard drying production line based on PID control according to claim 1, characterized in that, The acquisition of the basic speed proportional coefficient includes: In the calibration experiment, the average values ​​of the stable control quantities at high speed and low speed, as well as the corresponding high speed and low speed values, are obtained; the basic speed proportional coefficient is equal to the ratio of the difference between the average values ​​of the control quantities at high speed and low speed to the difference between the high speed and low speed values, where high speed and low speed are preset values.

9. The temperature adaptive control method for a cardboard drying production line based on PID control according to claim 1, characterized in that, The acquisition of the actual temperature inside the oven, the set target temperature, and the real-time speed of the production line includes: Temperature sensors are installed inside the oven to collect the actual temperature; the set target temperature is received through a human-machine interface; and a rotary encoder is installed on the main drive shaft to collect the real-time speed of the production line.

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