A feedforward control method and system for improving the control accuracy of a heating furnace

Abstract

This invention provides a feedforward control method and system for improving the control accuracy of a heating furnace. The method includes: periodically collecting the temperature of the heating furnace at preset time intervals to obtain the temperature at the previous moment and the actual temperature at the current moment; determining a feedforward temperature based on the temperature at the previous moment and the actual temperature; processing the feedforward temperature using a furnace temperature PID control method to obtain a furnace temperature control quantity; and adjusting the gas supply to the heating furnace according to the furnace temperature control quantity to adjust the temperature of the heating furnace towards a preset target temperature.

Description

Technical Field

[0001] This invention relates to the field of precise temperature control of industrial heating furnaces, and in particular to a feedforward control method and system for improving the control accuracy of heating furnaces. Background Technology

[0002] The heating furnace operates under a large lag control system. Its energy conversion process involves the following steps: upon receiving a temperature adjustment command, the gas regulating valve is activated to establish a corresponding gas flow. The gas enters the furnace and, after combustion, is converted into temperature. The temperature change is then fed back through heating detection elements. This process typically takes 40–60 seconds. Therefore, by the time temperature feedback is received, the actual situation inside the furnace is already significantly delayed, resulting in excessive overshoot and hindering precise furnace control. Consequently, the automatic control accuracy of conventional heating furnaces is typically ±15–20℃.

[0003] To address the problem of excessive overshoot, according to the principles of automatic control, we typically reduce the regulation speed to slow down the temperature change rate of the heating furnace, which can effectively reduce overshoot. However, this method comes at the cost of sacrificing the furnace's regulation speed. If the steel grade in the furnace varies significantly, multiple temperature ranges are required, and frequent temperature changes are needed in different sections of the furnace, this method will not meet production requirements.

[0004] In the process of developing this invention, the applicant discovered at least the following problems in the prior art:

[0005] Without sacrificing the furnace temperature regulation speed, the temperature overshoot is significantly reduced. Summary of the Invention

[0006] This invention provides a feedforward control method and system for improving the control accuracy of a heating furnace, solving the problem of significantly reducing temperature overshoot without sacrificing the furnace temperature regulation speed.

[0007] To achieve the above objectives, in a first aspect, embodiments of the present invention provide a feedforward control method for improving the control accuracy of a heating furnace, comprising:

[0008] The temperature of the heating furnace is collected periodically at preset time intervals to obtain the temperature at the previous moment and the actual temperature at the current moment.

[0009] The feedforward temperature is determined based on the temperature at the previous moment and the actual temperature.

[0010] The feedforward temperature is processed by the furnace temperature PID control method to obtain the furnace temperature control quantity.

[0011] The gas supply to the heating furnace is adjusted according to the furnace temperature control quantity to adjust the temperature of the heating furnace towards the preset target temperature.

[0012] Further, determining the feedforward temperature based on the temperature at the previous moment and the actual temperature includes:

[0013] Determine the absolute value of the temperature difference between the actual temperature and the target temperature;

[0014] Determine the absolute value of the temperature difference and the magnitude of the preset feedforward temperature threshold;

[0015] When the determination result is that the absolute value of the temperature difference is greater than the feedforward temperature threshold, the actual temperature is taken as the feedforward temperature.

[0016] When the determination result is that the absolute value of the temperature difference is less than or equal to the feedforward temperature threshold, the feedforward temperature is determined based on the temperature at the previous moment, the actual temperature, the absolute value of the temperature difference, and the target temperature.

[0017] Further, determining the feedforward temperature based on the temperature of the previous moment, the actual temperature, the absolute value of the temperature difference, and the target temperature includes:

[0018] The actual temperature change trend of the heating furnace at the current moment is determined based on the temperature at the previous moment and the actual temperature.

[0019] The desired temperature rise / fall direction of the heating furnace at the current moment is determined based on the actual temperature and the preset target temperature.

[0020] Determine the direction of the desired temperature rise / fall;

[0021] If it is determined that the expected temperature rises or falls in an upward direction, then the actual temperature change trend is judged.

[0022] If it is determined that the actual temperature change trend is upward, then the feedforward temperature is determined according to the following formula (1):

[0023] T_use=T_IN+T_delta*gain; (1)

[0024] If it is determined that the actual temperature change trend is decreasing, then the feedforward temperature is determined according to the following formula (2):

[0025] T_use=T_IN-T_delta*gain; (2)

[0026] Where T_use is the feedforward temperature in degrees Celsius; T_IN is the actual temperature in degrees Celsius; T_delta is the absolute value of the temperature difference in degrees Celsius; and gain is the preset scaling factor.

[0027] The actual temperature change trend includes both decreasing and increasing; the expected temperature rise and fall direction includes both decreasing and increasing.

[0028] Furthermore, after determining the direction of the desired temperature rise and fall, the method further includes:

[0029] If it is determined that the expected temperature rise and fall direction is downward, then the actual temperature change trend is judged.

[0030] If it is determined that the actual temperature change trend is upward, then the feedforward temperature is determined according to formula (1);

[0031] If it is determined that the actual temperature change trend is downward, the feedforward temperature is determined according to the following formula (2).

[0032] In a second aspect, embodiments of the present invention provide a feedforward control system for improving the control accuracy of a heating furnace, comprising:

[0033] A temperature sampling device is used to periodically collect the temperature of the heating furnace at preset time intervals to obtain the temperature at the previous moment and the actual temperature at the current moment.

[0034] A feedforward temperature determination device is used to determine the feedforward temperature based on the temperature at the previous moment and the actual temperature.

[0035] A furnace temperature control device is used to process the feedforward temperature using a furnace temperature PID control method to obtain the furnace temperature control quantity.

[0036] A gas supply device is used to adjust the gas supply to the heating furnace according to the furnace temperature control quantity, so as to adjust the temperature of the heating furnace towards a preset target temperature.

[0037] Furthermore, the feedforward temperature determination device includes:

[0038] The absolute temperature difference determination unit is used to determine the absolute temperature difference between the actual temperature and the target temperature.

[0039] The feedforward logic enable judgment unit is used to determine the magnitude of the absolute value of the temperature difference and the preset feedforward temperature threshold.

[0040] The first feedforward temperature determination unit is used to take the actual temperature as the feedforward temperature when the determination result is that the absolute value of the temperature difference is greater than the feedforward temperature threshold.

[0041] The second feedforward temperature determination unit is used to determine the feedforward temperature based on the temperature at the previous moment, the actual temperature, the absolute value of the temperature difference, and the target temperature when the judgment result is that the absolute value of the temperature difference is less than or equal to the feedforward temperature threshold.

[0042] Furthermore, the second feedforward temperature determination unit includes:

[0043] The actual temperature change trend determination module is used to determine the actual temperature change trend of the heating furnace at the current moment based on the temperature at the previous moment and the actual temperature.

[0044] The desired temperature rise / fall direction determination module is used to determine the desired temperature rise / fall direction of the heating furnace at the current moment based on the actual temperature and the preset target temperature.

[0045] A desired temperature rise / fall direction determination module is used to determine the desired temperature rise / fall direction;

[0046] The first temperature actual change trend judgment module is used to judge the actual temperature change trend if it is determined that the expected temperature rises or falls in an upward direction.

[0047] The first feedforward temperature determination module is used to determine the feedforward temperature according to formula (1) if it is determined that the actual temperature change trend is upward.

[0048] The second feedforward temperature determination module is used to determine the feedforward temperature according to formula (2) if it is determined that the actual temperature change trend is decreasing.

[0049] The actual temperature change trend includes both decreasing and increasing; the expected temperature rise and fall direction includes both decreasing and increasing.

[0050] Furthermore, the second feedforward temperature determination unit also includes:

[0051] The second temperature actual change trend judgment module is used to judge the actual temperature change trend if it is determined that the expected temperature rise and fall direction is downward.

[0052] The third feedforward temperature determination module is used to determine the feedforward temperature according to formula (1) if it is determined that the actual temperature change trend is upward.

[0053] The fourth feedforward temperature determination module is used to determine the feedforward temperature according to formula (2) if it is determined that the actual temperature change trend is decreasing.

[0054] The above technical solution has the following beneficial effects: A feedforward temperature is generated based on continuously sampled furnace temperatures. When the generated feedforward temperature differs from the actual furnace temperature, the furnace temperature PID control method is adjusted using this feedforward temperature. This allows the furnace temperature to rapidly adjust towards the target temperature while reducing overshoot. When the feedforward temperature equals the actual temperature, the actual temperature is input to the furnace temperature PID control method, and no further feedforward adjustment is performed. The system then returns to normal adjustment, achieving the effect of early intervention. Specifically, when the absolute value of the furnace temperature difference is less than or equal to the feedforward temperature threshold, a feedforward temperature is generated based on the proportional coefficient, and the system is adjusted accordingly to rapidly adjust towards the target temperature while reducing overshoot. When the absolute value of the furnace temperature difference is adjusted to be greater than the feedforward temperature threshold, the actual temperature is output as the feedforward temperature. The actual temperature is then input to the furnace temperature PID control method, and no further feedforward adjustment is performed. The system then returns to normal adjustment, achieving the effect of early intervention. With the help of feedforward compensation, the control accuracy of the system has been greatly improved. It can accurately control the temperature changes of the first, second, and third heating sections of the heating furnace within ±5 degrees Celsius, and the temperature changes of the soaking section within ±10 degrees Celsius. Attached Figure Description

[0055] To more clearly illustrate the technical solutions 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.

[0056] Figure 1 This is a flowchart of a feedforward control method for improving the control accuracy of a heating furnace, one of the embodiments of the present invention;

[0057] Figure 2 This is an architecture diagram of a feedforward control system for improving the control accuracy of a heating furnace, as one embodiment of the present invention.

[0058] Figure 3 This is a diagram illustrating the effect of feedforward compensation in one embodiment of the present invention. Detailed Implementation

[0059] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] Firstly, such as Figure 1 As shown, this embodiment of the invention provides a feedforward control method for improving the control accuracy of a heating furnace, comprising:

[0061] Step S100: Periodically collect the temperature of the heating furnace at preset time intervals to obtain the temperature at the previous moment and the actual temperature at the current moment;

[0062] Step S101: Determine the feedforward temperature based on the temperature at the previous moment and the actual temperature;

[0063] Step S102: The feedforward temperature is processed by the furnace temperature PID control method to obtain the furnace temperature control quantity;

[0064] Step S103: Adjust the gas supply to the heating furnace according to the furnace temperature control amount to adjust the temperature of the heating furnace towards the preset target temperature.

[0065] In some embodiments, before step S102 of the conventional furnace temperature PID control method, a step S101 is added to generate a feedforward temperature. This causes the input of the furnace temperature PID control method to be the actual temperature under some conditions and not the actual temperature under others. By adjusting the feedforward temperature, the output of the furnace temperature PID control method is activated earlier, solving the problem of significantly reducing temperature overshoot without sacrificing the furnace temperature regulation speed. The furnace temperature is periodically collected at preset time intervals to obtain the temperature at the previous moment and the actual temperature at the current moment. The feedforward temperature is determined based on the previous moment's temperature and the actual temperature, wherein the feedforward temperature is equal to, less than, or greater than the actual temperature. The feedforward temperature is processed by the furnace temperature PID control method to obtain the furnace temperature control quantity.

[0066] PID control is a traditional analog temperature control method. Its principle is to use the difference between the input temperature value and the target temperature value to adjust the PID parameters and upper and lower limits. In existing furnace temperature control systems, the actual furnace temperature collected from the heating furnace is directly input to the PID control method. The core of PID control lies in comparing the actual furnace temperature with the set temperature to obtain seven judgment results: too high, high, slightly high, normal, slightly low, low, and extremely low. For each judgment result, different levels of compensation are applied to the PID upper and lower limits, allowing the PID output to quickly follow temperature changes and effectively meet the requirement of rapidly reaching the set furnace temperature when the furnace temperature fluctuates significantly.

[0067] This invention relates to a feedforward control method. Before the furnace temperature PID control method, a feedforward temperature is provided to the furnace temperature PID control method without altering the PID control method itself. This feedforward temperature can be greater than, less than, or equal to the actual furnace temperature, depending on the specific conditions. Therefore, this invention, through the cooperation of the feedforward temperature and the furnace temperature PID control method, achieves a significant improvement over the traditional method that relies solely on the furnace temperature PID control method to adjust the furnace temperature. In this invention, the feedforward temperature is generated based on continuously sampled furnace temperatures. When the generated feedforward temperature differs from the actual furnace temperature, the furnace temperature PID control method is adjusted using the feedforward temperature. This reduces overshoot and controls the furnace temperature to quickly adjust towards the target temperature. When the feedforward temperature equals the actual temperature, the actual temperature is input to the furnace temperature PID control method, and no further feedforward adjustment is needed. The system returns to normal adjustment, thus achieving the effect of early intervention. With the help of feedforward compensation, the control accuracy of the system has been greatly improved. It can accurately control the temperature changes of the first, second, and third heating sections of the heating furnace within ±5 degrees Celsius of the preset target temperature of the corresponding heating section. For the heat soaking section, the furnace temperature fluctuation will be larger due to the frequent opening and closing of the furnace door. In this embodiment of the invention, the temperature change of the heat soaking section can be controlled within ±10 degrees Celsius of the preset target temperature of the heat soaking section.

[0068] Further, determining the feedforward temperature based on the temperature at the previous moment and the actual temperature includes:

[0069] Determine the absolute value of the temperature difference between the actual temperature and the target temperature;

[0070] Determine the absolute value of the temperature difference and the magnitude of the preset feedforward temperature threshold;

[0071] When the determination result is that the absolute value of the temperature difference is greater than the feedforward temperature threshold, the actual temperature is taken as the feedforward temperature.

[0072] When the determination result is that the absolute value of the temperature difference is less than or equal to the feedforward temperature threshold, the feedforward temperature is determined based on the temperature at the previous moment, the actual temperature, the absolute value of the temperature difference, and the target temperature.

[0073] The inventors discovered that in existing furnace temperature control technology, when the actual temperature exceeds the target temperature, the gas flow rate needs to be reduced to lower the actual temperature. Since the furnace is a large inertial system and its temperature cannot change abruptly, reducing the gas flow rate will cause the temperature to continue rising for a period due to the furnace's significant inertia. During this temperature rise, the gas flow rate is continuously reduced via a PID controller. When the flow rate decreases to a certain value, the temperature stops rising and slowly reverses direction (i.e., the temperature inflection point, at which point the temperature begins to decrease). However, in the temperature decrease range, the actual temperature is still higher than the target temperature. Therefore, according to the traditional furnace temperature PID control method, the gas flow rate will continue to be reduced in this region. Even without reducing the gas flow rate, the furnace system temperature can quickly drop to the target temperature during this period. Therefore, reducing the gas flow rate during this time does not benefit the system; instead, it increases the system's temperature overshoot.

[0074] In some embodiments of the present invention, the obtained feedforward temperature is used as the input to the furnace temperature PID control method, thereby improving the speed and accuracy of the furnace temperature PID control method. The method in this embodiment involves control over the direction of temperature change, i.e., the absolute value Δt of the temperature difference between the target temperature value and the actual temperature value; when Δt is greater than the dead zone value (i.e., the feedforward temperature threshold), it represents a control direction; when Δt is less than or equal to the dead zone value (i.e., the feedforward temperature threshold), the control direction changes. In traditional PID control, the direction of Δt cannot be changed regardless of the method used; therefore, traditional PID control can only adjust the control speed and accuracy by controlling the PID parameters and limiting the amplitude. The feedforward temperature threshold is determined using the following method: The furnace temperature fluctuation range under traditional PID control is -Tf to +Tf, and the peak value of the furnace temperature fluctuation under traditional PID control is Tf. Temperature values ​​(in degrees Celsius) within the range of Tf-5 to Tf-3 are used as the priority test value range for the feedforward temperature threshold. Actual debugging is performed on the system applying this embodiment of the invention, and temperature values ​​within the priority test value range are selected as the feedforward temperature threshold. The furnace temperature fluctuation range of the furnace temperature control system based on this embodiment of the invention is tested. When the obtained furnace temperature fluctuation range is within the expected furnace temperature fluctuation range, the current feedforward temperature threshold is determined to be used. The above method for determining the feedforward temperature threshold can limit the possible values ​​to a smaller range, thereby quickly determining the usable feedforward temperature threshold value. During periods when the actual temperature is lower than the target temperature and the actual temperature is decreasing, or during periods when the actual temperature is higher than the target temperature and the actual temperature is increasing, setting the feedforward temperature threshold too high will result in more time spent in feedforward temperature regulation, with a significantly larger regulation amplitude than traditional PID regulation based solely on the actual temperature, easily leading to overshoot. Conversely, setting the feedforward temperature threshold too low will fail to achieve the desired regulation effect. During periods when the actual temperature is lower than the target temperature and the actual temperature is increasing, or during periods when the actual temperature is higher than the target temperature and the actual temperature is decreasing, setting the feedforward temperature threshold too high will cause feedforward temperature regulation to intervene too early, resulting in the actual temperature approaching the target temperature at a slower rate, prolonging the furnace temperature stabilization time. Conversely, setting the feedforward temperature threshold too low will cause feedforward temperature regulation to intervene too late, by which time the actual temperature is already very close to the target temperature, and the effective time of feedforward temperature regulation is already very short. In this case, overshoot is easily caused by the excessive amplitude of pure PID regulation before the feedforward temperature regulation intervenes. Therefore, the feedforward temperature threshold needs to be determined by combining the theoretically preferred test value range and the measured value.

[0075] The embodiments of this invention have the following technical effects: When the absolute value of the temperature difference in the heating furnace is less than or equal to the feedforward temperature threshold, a feedforward temperature is generated according to the proportional coefficient, and the system is adjusted accordingly. This allows the system to quickly adjust towards the target temperature while reducing overshoot. When the absolute value of the temperature difference in the heating furnace is adjusted to be greater than the feedforward temperature threshold, the actual temperature is output as the feedforward temperature. At this point, the actual temperature is input to the furnace temperature PID control method, and no further feedforward adjustment is performed. The system returns to normal adjustment, thus achieving the effect of early intervention. With the help of feedforward compensation, the control accuracy of the system is greatly improved. It can accurately control the temperature changes of the first, second, and third heating stages of the heating furnace within ±5 degrees Celsius of the preset target temperature of the corresponding heating stage. For the soaking stage, due to the frequent opening and closing of the furnace door, the furnace temperature fluctuation will be larger. The embodiments of this invention can control the temperature changes of the soaking stage within ±10 degrees Celsius of the preset target temperature of the soaking stage.

[0076] Further, determining the feedforward temperature based on the temperature of the previous moment, the actual temperature, the absolute value of the temperature difference, and the target temperature includes:

[0077] The actual temperature change trend of the heating furnace at the current moment is determined based on the temperature at the previous moment and the actual temperature.

[0078] The desired temperature rise / fall direction of the heating furnace at the current moment is determined based on the actual temperature and the preset target temperature.

[0079] Determine the direction of the desired temperature rise / fall;

[0080] If it is determined that the expected temperature rises or falls in an upward direction, then the actual temperature change trend is judged.

[0081] If it is determined that the actual temperature change trend is upward, then the feedforward temperature is determined according to formula (1);

[0082] If it is determined that the actual temperature change trend is decreasing, then the feedforward temperature is determined according to formula (2);

[0083] The actual temperature change trend includes both decreasing and increasing; the expected temperature rise and fall direction includes both decreasing and increasing.

[0084] Furthermore, after determining the direction of the desired temperature rise and fall, the method further includes:

[0085] If it is determined that the expected temperature rise and fall direction is downward, then the actual temperature change trend is judged.

[0086] If it is determined that the actual temperature change trend is upward, then the feedforward temperature is determined according to formula (1);

[0087] If it is determined that the actual temperature change trend is downward, then the feedforward temperature is determined according to formula (2).

[0088] In some embodiments, the actual temperature change trend of the heating furnace at the current moment is determined based on the temperature at the previous moment and the actual temperature. Specifically, the temperature difference is obtained by subtracting the actual temperature from the temperature at the previous moment. If the temperature difference is less than a first temperature difference threshold and the first temperature difference threshold is less than 0, the actual temperature change trend is upward; if the temperature difference is greater than a second temperature difference threshold and the second temperature difference threshold is greater than 0, the actual temperature change trend is downward. Preferably, the absolute value of the first temperature difference threshold is equal to the absolute value of the second temperature difference threshold. The desired temperature rise / fall direction of the heating furnace at the current moment is determined based on the actual temperature and a preset target temperature. Specifically, when the target temperature is greater than the actual temperature, the desired temperature rise / fall direction is upward; when the target temperature is less than or equal to the actual temperature, the desired temperature rise / fall direction is downward. By detecting the inflection point of the actual temperature, when the actual temperature reaches the temperature inflection point, a false, disguised abrupt temperature change (i.e., feedforward temperature) is generated, and the furnace temperature PID control method is used to perform the opposite operation using the abrupt temperature change. That is, after the actual temperature reaches the inflection point of decline, a reverse high temperature is generated, causing the furnace temperature PID control method to increase the gas flow rate in advance to prepare for heating when the actual temperature is higher than the target temperature; conversely, when the actual temperature reaches the inflection point of rise, it reduces the gas flow rate in advance to prepare for cooling. The advantage of the feedforward control method in this embodiment of the invention is that it can significantly reduce the overshoot of temperature control and reduce temperature oscillation, thus significantly improving the accuracy of temperature control. Here, gain is a preset proportional coefficient, preferably ranging from 1.5 to 3.0 or 2.0 to 2.5, which determines the... Figure 3 The slope of the feedforward temperature curve 302 shown determines the rate of increase or decrease of the feedforward temperature. The larger the gain setting, the steeper the slope of the feedforward temperature change, and the faster the feedforward temperature will deviate from the actual temperature. A larger gain setting also results in a larger feedforward action amplitude, which can easily cause furnace temperature oscillations.

[0089] The embodiments of this invention have the following technical effects: When the absolute value of the temperature difference in the heating furnace is less than or equal to the feedforward temperature threshold, a feedforward temperature is generated according to the proportional coefficient, and the system is adjusted accordingly. This allows the system to quickly adjust towards the target temperature while reducing overshoot. When the absolute value of the temperature difference in the heating furnace is adjusted to be greater than the feedforward temperature threshold, the actual temperature is output as the feedforward temperature. At this point, the actual temperature is input to the furnace temperature PID control method, and no further feedforward adjustment is performed. The system returns to normal adjustment, thus achieving the effect of early intervention. With the help of feedforward compensation, the control accuracy of the system is greatly improved. It can accurately control the temperature changes of the first, second, and third heating stages of the heating furnace within ±5 degrees Celsius of the preset target temperature of the corresponding heating stage. For the soaking stage, due to the frequent opening and closing of the furnace door, the furnace temperature fluctuation will be larger. The embodiments of this invention can control the temperature changes of the soaking stage within ±10 degrees Celsius of the preset target temperature of the soaking stage.

[0090] Secondly, such as Figure 2 As shown, an embodiment of the present invention provides a feedforward control system for improving the control accuracy of a heating furnace, comprising:

[0091] Temperature sampling device 200 is used to periodically collect the temperature of heating furnace 204 at preset time intervals to obtain the temperature at the previous moment and the actual temperature at the current moment;

[0092] The feedforward temperature determination device 201 is used to determine the feedforward temperature based on the temperature at the previous moment and the actual temperature.

[0093] The furnace temperature control device 202 is used to process the feedforward temperature using a furnace temperature PID control method to obtain the furnace temperature control quantity.

[0094] The gas supply device 203 is used to adjust the gas supply of the heating furnace 204 according to the furnace temperature control quantity, so as to adjust the temperature of the heating furnace 204 towards the preset target temperature.

[0095] Further, the feedforward temperature determination device 201 includes:

[0096] The absolute temperature difference determination unit is used to determine the absolute temperature difference between the actual temperature and the target temperature.

[0097] The feedforward logic enable judgment unit is used to determine the magnitude of the absolute value of the temperature difference and the preset feedforward temperature threshold.

[0098] The first feedforward temperature determination unit is used to take the actual temperature as the feedforward temperature when the determination result is that the absolute value of the temperature difference is greater than the feedforward temperature threshold.

[0099] The second feedforward temperature determination unit is used to determine the feedforward temperature based on the temperature at the previous moment, the actual temperature, the absolute value of the temperature difference, and the target temperature when the judgment result is that the absolute value of the temperature difference is less than or equal to the feedforward temperature threshold.

[0100] Furthermore, the second feedforward temperature determination unit includes:

[0101] The actual temperature change trend determination module is used to determine the actual temperature change trend of the heating furnace at the current moment based on the temperature at the previous moment and the actual temperature.

[0102] The desired temperature rise / fall direction determination module is used to determine the desired temperature rise / fall direction of the heating furnace at the current moment based on the actual temperature and the preset target temperature.

[0103] A desired temperature rise / fall direction determination module is used to determine the desired temperature rise / fall direction;

[0104] The first temperature actual change trend judgment module is used to judge the actual temperature change trend if it is determined that the expected temperature rises or falls in an upward direction.

[0105] The first feedforward temperature determination module is used to determine the feedforward temperature according to formula (1) if it is determined that the actual temperature change trend is upward.

[0106] The second feedforward temperature determination module is used to determine the feedforward temperature according to formula (2) if it is determined that the actual temperature change trend is decreasing.

[0107] The actual temperature change trend includes both decreasing and increasing; the expected temperature rise and fall direction includes both decreasing and increasing.

[0108] Furthermore, the second feedforward temperature determination unit also includes:

[0109] The second temperature actual change trend judgment module is used to judge the actual temperature change trend if it is determined that the expected temperature rise and fall direction is downward.

[0110] The third feedforward temperature determination module is used to determine the feedforward temperature according to formula (1) if it is determined that the actual temperature change trend is upward.

[0111] The fourth feedforward temperature determination module is used to determine the feedforward temperature according to formula (2) if it is determined that the actual temperature change trend is decreasing.

[0112] The feedforward control system for improving the control accuracy of the heating furnace provided in this embodiment corresponds one-to-one with the aforementioned feedforward control method for improving the control accuracy of the heating furnace. The embodiments of this invention can be understood based on the aforementioned feedforward control method for improving the control accuracy of the heating furnace, and will not be repeated here.

[0113] The embodiments of this invention have the following technical effects: A feedforward temperature is generated based on continuously sampled furnace temperatures. When the generated feedforward temperature differs from the actual furnace temperature, the furnace temperature PID control method is adjusted using the feedforward temperature to rapidly adjust the furnace temperature towards the target temperature while reducing overshoot. When the feedforward temperature equals the actual temperature, the actual temperature is input to the furnace temperature PID control method, and no further feedforward adjustment is performed. The system returns to normal adjustment, thus achieving the effect of early intervention. Specifically, when the absolute value of the furnace temperature difference is less than or equal to the feedforward temperature threshold, a feedforward temperature is generated based on a proportional coefficient, and the system is adjusted accordingly to rapidly adjust towards the target temperature while reducing overshoot. When the absolute value of the furnace temperature difference is adjusted to be greater than the feedforward temperature threshold, the actual temperature is output as the feedforward temperature. The actual temperature is then input to the furnace temperature PID control method, and no further feedforward adjustment is performed. The system returns to normal adjustment, thus achieving the effect of early intervention. With the help of feedforward compensation, the control accuracy of the system has been greatly improved. It can accurately control the temperature changes of the first, second, and third heating sections of the heating furnace within ±5 degrees Celsius of the preset target temperature of the corresponding heating section. For the heat soaking section, the furnace temperature fluctuation will be larger due to the frequent opening and closing of the furnace door. In this embodiment of the invention, the temperature change of the heat soaking section can be controlled within ±10 degrees Celsius of the preset target temperature of the heat soaking section.

[0114] The technical solutions of the present invention will be described in detail below with reference to specific application examples. For technical details not described in the implementation process, please refer to the relevant descriptions above.

[0115] This invention embodiment performs feedforward processing on the feedback temperature (i.e., the actual temperature sampled from the heating furnace). Specifically, it converts the actual temperature into a feedforward temperature based on preset conditions, ensuring that the resulting feedforward temperature may be greater than, less than, or equal to the actual temperature under different conditions. Specifically, a feedforward temperature threshold is set. When the actual temperature is less than or equal to the feedforward temperature threshold, the actual temperature rise / fall status (i.e., the actual temperature change trend) and the required temperature rise or fall (i.e., the desired temperature rise / fall direction) are determined. The temperature difference (absolute value) is then proportionally amplified, thereby enabling the feedforward-adjusted furnace temperature control system or PID control system (furnace temperature PID control method) to perform proactive actions, achieving better control performance. The specific method is as follows:

[0116] First, let's explain the parameters involved:

[0117] The absolute value of the temperature difference, T_delta, is the absolute value of the target temperature minus the actual temperature.

[0118] Feedforward adjustment range or feedforward temperature threshold T_step: is used to compare with the absolute value of the temperature difference to determine how the feedforward temperature is calculated;

[0119] Furnace gas temperature or actual temperature T_IN: This is the furnace gas temperature feedback value or the sampled furnace temperature of the self-heating furnace;

[0120] The proportional gain coefficient is used to calculate the feedforward temperature and reflects the degree of feedforward adjustment. The larger the coefficient, the higher the feedforward adjustment rate, the larger the feedback temperature difference received by the system, and the faster the system response speed.

[0121] Temperature rise requirement flag T_rise_need: When the target temperature is higher than the actual temperature, a temperature rise is required. Set this flag to 1; otherwise, set it to 0.

[0122] Temperature drop flag T_fall_need: Set this flag to 1 when the target temperature is lower than the actual temperature and cooling is required; otherwise, set it to 0.

[0123] Temperature Rising Flag T_rise_now: Set this flag to 1 when an actual temperature rise is detected, otherwise set it to 0.

[0124] Temperature is falling flag T_fall_now: Set this flag to 1 when an actual temperature drop is detected, otherwise set it to 0.

[0125] Temperature feedback output value or feedforward temperature T_use: Feedforward temperature output value.

[0126] The steps of the embodiments of the present invention are described below:

[0127] (1) Confirm the four temperature indicators: First, a self-increasing adder needs to be written, with an increment cycle of 1 second. When the adder equals 1, the current actual temperature is stored in the variable T_first (equivalent to the temperature at the previous moment); when the adder is greater than or equal to the calculation cycle (T_COUNT_n, usually T_COUNT_n = 5), the current actual temperature is stored in the variable T_second (equivalent to the actual temperature); simultaneously, the self-increasing adder is reset to zero, and a new timing cycle begins. Calculate the temperature change rate T_change_rate = T_first - T_PV (T_PV is the current temperature, i.e., T_second).

[0128] A. Temperature Required Rise Flag: When the target temperature is greater than the actual temperature, the temperature required rise flag is set to 1;

[0129] B. Temperature needs to decrease flag: When the target temperature is less than or equal to the actual temperature, the temperature needs to decrease flag is set to 1;

[0130] C. Temperature rising indicator: When the rate of temperature change T_change_rate < -0.1, the temperature rising indicator is set to 1;

[0131] D. Temperature is decreasing flag: When the rate of temperature change T_change_rate > 0.1, the temperature is decreasing flag is set to 1;

[0132] (2) Calculate the feedforward adjustment temperature (feedforward temperature)

[0133] A. When the absolute value of the temperature difference is greater than the feedforward adjustment area (or feedforward temperature threshold) T_step, directly set the furnace gas temperature (actual temperature) T_IN to the temperature feedback output value (feedforward temperature) T_use.

[0134] B. When the absolute value of the temperature difference is less than or equal to the feedforward adjustment region (or feedforward temperature threshold) T_step, and the temperature needs to rise (i.e., T_rise_need = 1),

[0135] a. If the temperature is rising at this time (i.e., T_rise_now = 1), then T_use = T_IN + T_delta * gain;

[0136] b. If the temperature is decreasing at this time (i.e., T_fall_now = 1), then T_use = T_IN - T_delta * gain;

[0137] C. When the absolute value of the temperature difference is less than or equal to the feedforward adjustment region (or feedforward temperature threshold) T_step, and the temperature needs to decrease (i.e., T_fall_need = 1),

[0138] a. If the temperature is rising at this time (i.e., T_rise_now = 1), then T_use = T_IN + T_delta * gain;

[0139] b. If the temperature is decreasing at this time (i.e., T_fall_now = 1), then T_use = T_IN - T_delta * gain.

[0140] The embodiments of this invention have the following technical effects: A feedforward temperature is generated based on continuously sampled furnace temperatures. When the generated feedforward temperature differs from the actual furnace temperature, the furnace temperature PID control method is adjusted using the feedforward temperature to rapidly adjust the furnace temperature towards the target temperature while reducing overshoot. When the feedforward temperature equals the actual temperature, the actual temperature is input to the furnace temperature PID control method, and no further feedforward adjustment is performed. The system returns to normal adjustment, thus achieving the effect of early intervention. Specifically, when the absolute value of the furnace temperature difference is less than or equal to the feedforward temperature threshold, a feedforward temperature is generated based on a proportional coefficient, and the system is adjusted accordingly to rapidly adjust towards the target temperature while reducing overshoot. When the absolute value of the furnace temperature difference is adjusted to be greater than the feedforward temperature threshold, the actual temperature is output as the feedforward temperature. The actual temperature is then input to the furnace temperature PID control method, and no further feedforward adjustment is performed. The system returns to normal adjustment, thus achieving the effect of early intervention. With the help of feedforward compensation, the control accuracy of the system has been greatly improved. It can accurately control the temperature changes of the first, second, and third heating sections of the heating furnace within ±5 degrees Celsius of the preset target temperature of the corresponding heating section. For the heat soaking section, the furnace temperature fluctuation will be larger due to the frequent opening and closing of the furnace door. In this embodiment of the invention, the temperature change of the heat soaking section can be controlled within ±10 degrees Celsius of the preset target temperature of the heat soaking section.

[0141] like Figure 3As shown, the four curves in the figure are respectively the target temperature curve 300, the actual temperature curve 301, the feedforward temperature curve 302, and the gas supply curve 303; in stage S1, when the actual temperature curve 301 decreases and begins to deviate downward from the target temperature curve 300 (that is, the desired temperature rise and fall direction is upward and the actual temperature change trend is downward, at this time the feedforward temperature is determined by formula (2), and the feedforward temperature obtained at this time is lower than the actual temperature), the feedforward temperature curve 301 will deviate from the target temperature curve 300 by a larger margin than the actual temperature curve 300. At this time, the feedforward temperature is different from the actual temperature, as shown by the gas supply curve 303 in stage S1. The furnace temperature PID control method is based on the input In stage S2, as the actual temperature decreases, when the absolute value of the temperature difference exceeds the preset feedforward temperature threshold, the feedforward temperature curve 301 coincides with the actual temperature curve 300. At this time, the feedforward temperature equals the actual temperature, which is equivalent to directly inputting the actual temperature into the furnace temperature PID control method, executing the traditional furnace temperature PID control method, as shown by the gas supply curve 303 in stage S2. At this time, since the deviation between the actual temperature and the target temperature is large, and the actual temperature is lower than the target temperature, the gas supply continues to be adjusted rapidly to increase the gas supply, intervening in the furnace temperature and preventing the furnace temperature from overshooting towards a lower temperature. In stage S3, when the actual temperature curve 301 enters the temperature rise segment and the absolute value of the temperature difference is less than or equal to the preset feedforward temperature threshold (i.e., when the desired temperature rise and fall direction is upward and the actual temperature change trend is upward, the feedforward temperature is determined by formula (1), and the feedforward temperature obtained at this time is higher than the actual temperature and also higher than the target temperature), the feedforward temperature curve 302 jumps, and the feedforward temperature is significantly greater than the actual temperature and also greater than the target temperature, as shown by the gas supply curve 303 in stage S3. This reduces the rate of increase of gas supply in the furnace temperature PID control method, keeping the gas supply basically stable, thereby avoiding a large overshoot of the furnace temperature towards higher temperatures. As the actual temperature gradually rises and approaches the target temperature, the feedforward temperature also gradually decreases and approaches the target temperature. During this period, the furnace temperature PID control method basically maintains a stable gas supply. In stage S4, when the actual temperature continues to rise and exceeds the target temperature (that is, when the expected temperature rise and fall direction is downward and the actual temperature change trend is upward, the feedforward temperature is determined by formula (1)), the feedforward temperature will rise by a larger margin than the actual temperature, as shown by the gas supply curve 303 in stage S4. After the feedforward temperature is input to the furnace temperature PID control method, the furnace temperature PID control method will control the gas supply to decrease rapidly in order to avoid the furnace temperature from overshooting significantly towards the high temperature direction.In stage S5, when the actual temperature curve 301 enters the temperature drop segment and the absolute value of the temperature difference is less than or equal to the preset feedforward temperature threshold (that is, when the desired temperature rise and fall direction is downward and the actual temperature change trend is downward, the feedforward temperature is determined by formula (2). At this time, the feedforward temperature obtained is lower than the actual temperature and also lower than the target temperature), the feedforward temperature curve 302 jumps, the feedforward temperature is significantly lower than the actual temperature, and the feedforward temperature is also lower than the target temperature, as shown by the gas supply curve 303 in stage S5. This reduces the rate of gas supply reduction in the furnace temperature PID control method, keeps the gas supply basically stable, and avoids a large overshoot of the furnace temperature towards the low temperature direction. Based on the relationship between the temperature curves and the gas supply curve, it can be seen that within the temperature feedforward adjustment range, the feedforward temperature output value T_use adjusts the system according to the proportional coefficient. The feedforward temperature input to the furnace temperature PID control method deviates significantly from the actual temperature, and the direction of this deviation is exactly the same as the direction the system needs to adjust. Therefore, the system accelerates its adjustment. Once the system adjusts the temperature out of the feedforward adjustment range, the feedforward temperature output value T_use outputs the actual temperature, and the system returns to normal adjustment, thus achieving the effect of early intervention. With the help of the feedforward temperature determination device, the furnace temperature control accuracy of the system is greatly improved. It can accurately control the temperature changes of the first, second, and third heating sections of the furnace within ±5 degrees Celsius of the preset target temperature of the corresponding heating section. For the soaking section, due to the frequent opening and closing of the furnace door, the furnace temperature fluctuation will be larger. This embodiment of the invention can control the temperature change of the soaking section within ±10 degrees Celsius of the preset target temperature of the soaking section.

[0142] The following is a specific example to illustrate this:

[0143] This invention was tested on five heating furnaces used in two production lines for hot-rolled strip with lengths of 2032 mm and 1450 mm. Four of these furnaces were conventional heating furnaces, specifically single regenerative heat exchange furnaces, and one was a regenerative furnace. The hourly output of a single furnace was 500-600 tons, the feedforward temperature threshold was 8 degrees Celsius, the target temperature was set in the range of 1000 to 1300 degrees Celsius according to specific production requirements, and the gain ratio coefficient was 2.5. Specifically, the target temperature for the upper part of the first heating section is set to 1120 degrees Celsius, and the target temperature for the lower part of the first heating section is set to 1090 degrees Celsius. The target temperature for the upper part of the second heating section is set to 1130 degrees Celsius, and the target temperature for the lower part of the second heating section is set to 1100 degrees Celsius. The target temperature for the upper part of the third heating section is set to 1130 degrees Celsius, and the target temperature for the lower part of the third heating section is set to 1100 degrees Celsius. The target temperature for the upper part of the heat spreader is set to 1120 degrees Celsius, and the target temperature for the lower part of the heat spreader is set to 1100 degrees Celsius. The following explanation uses an input temperature of 1154.533 as an example and a target temperature of 1149.999675 as an example: When the input temperature is 1154.533 and the current actual temperature trend is downward, and the target temperature is 1149.999675, the expected temperature rise / fall direction is downward, and the actual temperature change trend is downward. This can be achieved through the formula... (2) Determine the feedforward temperature: T_use=T_IN-T_delta*gain=1154.533-4.533325*2.5=1143.1996875. The obtained feedforward temperature is less than the target temperature of 1149.999675, as shown in the gas supply curve 303 in stage S5. This allows the furnace temperature PID control method to reduce the rate of gas supply reduction and maintain a basically stable gas supply, thereby avoiding a large overshoot of the furnace temperature towards a lower temperature. It accurately controls the temperature changes of the first, second, and third heating sections of the heating furnace within ±5 degrees Celsius of the preset target temperature of the corresponding heating section. For the soaking section, due to the frequent opening and closing of the furnace door, the furnace temperature fluctuation will be larger. In this embodiment of the invention, the temperature change of the soaking section can be controlled within ±10 degrees Celsius of the preset target temperature of the soaking section. Since the measurement of slab temperature is currently mainly carried out through furnace gas temperature. The calculation of slab temperature in the secondary stage of the heating furnace is based on collecting furnace gas temperature data. Therefore, the smaller the fluctuation in furnace gas temperature, the higher the accuracy of the secondary model's calculation of the actual slab temperature. Furthermore, smaller furnace gas temperature fluctuations result in more uniform slab heating, leading to smaller watermarks on the slab and ultimately a higher thickness hit rate in the rolled slab. In practical implementation, for example, based on the test analysis of three heating furnaces on Liuzhou Steel's 2032 line, each heating furnace has four sections, totaling eight temperature control sections. The feedforward temperature thresholds are set between 8 and 12 degrees Celsius, and the gain value is set between 2.5 and 3.5. These parameters are not fixed but are adjusted periodically based on the accuracy of temperature control.Because the control precision of valves changes with their usage, and this change directly affects the control precision of PID control, adjusting the feedforward threshold and gain appropriately can correct the temperature control precision. The basis for adjusting the feedforward threshold and gain is to observe the range of actual temperature fluctuations, so that the actual temperature fluctuates around the target temperature. The smaller the temperature oscillation, the better. The temperature changes of the first, second, and third heating sections of the heating furnace are precisely controlled within ±5 degrees Celsius of the preset target temperature of the corresponding heating section. For the soaking section, the furnace temperature fluctuation will be larger due to the frequent opening and closing of the furnace door. In this embodiment of the invention, the temperature change of the soaking section can be controlled within ±10 degrees Celsius of the preset target temperature of the soaking section.

[0144] The embodiments of this invention have the following technical effects: A feedforward temperature is generated based on continuously sampled furnace temperatures. When the generated feedforward temperature differs from the actual furnace temperature, the furnace temperature PID control method is adjusted using the feedforward temperature to rapidly adjust the furnace temperature towards the target temperature while reducing overshoot. When the feedforward temperature equals the actual temperature, the actual temperature is input to the furnace temperature PID control method, and no further feedforward adjustment is performed. The system returns to normal adjustment, thus achieving the effect of early intervention. Specifically, when the absolute value of the furnace temperature difference is less than or equal to the feedforward temperature threshold, a feedforward temperature is generated based on a proportional coefficient, and the system is adjusted accordingly to rapidly adjust towards the target temperature while reducing overshoot. When the absolute value of the furnace temperature difference is adjusted to be greater than the feedforward temperature threshold, the actual temperature is output as the feedforward temperature. The actual temperature is then input to the furnace temperature PID control method, and no further feedforward adjustment is performed. The system returns to normal adjustment, thus achieving the effect of early intervention. With the help of feedforward compensation, the control accuracy of the system has been greatly improved. It can accurately control the temperature changes of the first, second, and third heating sections of the heating furnace within ±5 degrees Celsius of the preset target temperature of the corresponding heating section. For the heat soaking section, the furnace temperature fluctuation will be larger due to the frequent opening and closing of the furnace door. In this embodiment of the invention, the temperature change of the heat soaking section can be controlled within ±10 degrees Celsius of the preset target temperature of the heat soaking section.

[0145] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0146] In the above detailed description, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, the invention is presented with fewer features than all of the features of the single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, wherein each claim stands alone as a preferred embodiment of the invention.

[0147] The disclosed embodiments have been described above to enable any person skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit and scope of this disclosure. Therefore, this disclosure is not limited to the embodiments given herein, but is consistent with the broadest scope of the principles and novel features disclosed in this application.

[0148] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations falling within the scope of the appended claims. Furthermore, the term "comprising" as used in the specification or claims is used in a manner similar to the term "including." Additionally, the use of any term "or" in the specification of the claims is intended to mean "non-exclusive or."

[0149] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A feedforward control method for improving the control accuracy of a heating furnace, characterized in that, include: The temperature of the heating furnace is collected periodically at preset time intervals to obtain the temperature at the previous moment and the actual temperature at the current moment. The feedforward temperature is determined based on the temperature at the previous moment and the actual temperature. The feedforward temperature is processed by the furnace temperature PID control method to obtain the furnace temperature control quantity. The gas supply to the heating furnace is adjusted according to the furnace temperature control value in order to adjust the temperature of the heating furnace towards the preset target temperature. The step of determining the feedforward temperature based on the temperature at the previous moment and the actual temperature includes: Determine the absolute value of the temperature difference between the actual temperature and the target temperature; Determine the absolute value of the temperature difference and the magnitude of the preset feedforward temperature threshold; When the determination result is that the absolute value of the temperature difference is greater than the feedforward temperature threshold, the actual temperature is taken as the feedforward temperature. When the determination result is that the absolute value of the temperature difference is less than or equal to the feedforward temperature threshold, the feedforward temperature is determined based on the temperature at the previous moment, the actual temperature, the absolute value of the temperature difference, and the target temperature. Determining the feedforward temperature based on the previous temperature, the actual temperature, the absolute value of the temperature difference, and the target temperature includes: The actual temperature change trend of the heating furnace at the current moment is determined based on the temperature at the previous moment and the actual temperature. The desired temperature rise / fall direction of the heating furnace at the current moment is determined based on the actual temperature and the preset target temperature. Determine the direction of the desired temperature rise / fall; If it is determined that the expected temperature rises or falls in an upward direction, then the actual temperature change trend is judged. If the actual temperature change trend is determined to be upward, the feedforward temperature is determined according to the following formula: T_use = T_IN + T_delta * gain; If it is determined that the actual temperature change trend is downward, then the feedforward temperature is determined according to the following formula: T_use = T_IN - T_delta * gain; Where T_use is the feedforward temperature in degrees Celsius; T_IN is the actual temperature in degrees Celsius; T_delta is the absolute value of the temperature difference in degrees Celsius; and gain is the preset scaling factor. After determining the direction of the desired temperature rise and fall, the method further includes: If it is determined that the expected temperature rise and fall direction is downward, then the actual temperature change trend is judged. If the actual temperature change trend is determined to be upward, the feedforward temperature is determined according to the following formula: T_use = T_IN + T_delta * gain; If it is determined that the actual temperature change trend is downward, then the feedforward temperature is determined according to the following formula: T_use = T_IN - T_delta * gain; Where T_use is the feedforward temperature in degrees Celsius; T_IN is the actual temperature in degrees Celsius; T_delta is the absolute value of the temperature difference in degrees Celsius; and gain is the preset scaling factor. The actual temperature change trend includes both decreasing and increasing; the expected temperature rise and fall direction includes both decreasing and increasing.

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