Multi-modal adaptive furnace temperature control method, system and continuous annealing furnace based on spatiotemporal thermal field decoupling

Abstract

The application discloses a kind of multi-modal adaptive furnace temperature control method, system and continuous annealing furnace based on space-time thermal field decoupling, multiple independent heating zones are provided in the continuous annealing furnace, multiple groups of staggered arrangement burners are arranged in each heating zone, four-stage adaptive control strategy based on temperature ratio segmentation and thermal field space-time distribution collaborative control, including: fast response heating zone, proportional regulation transition zone, pulse cross uniform zone, dynamic thermal field maintenance zone. By decoupling furnace temperature control and thermal field spatial distribution, using the mode of spatial grouping pulse activation + time staggered control, the rapid response, accurate regulation and uniform maintenance of furnace temperature are realized.The application effectively solves the technical problems of temperature overshoot, response lag, thermal field unevenness, high energy consumption and other technical problems in the traditional control mode, significantly improves the quality of strip steel heat treatment and energy utilization efficiency.

Description

Technical Field

[0001] This invention relates to the field of heat treatment technology for metallic materials, specifically to a multimodal adaptive furnace temperature control method, system, and continuous annealing furnace based on spatiotemporal thermal field decoupling. Background Technology

[0002] The continuous annealing furnace is the core equipment of the cold-rolled strip heat treatment production line. Its function is to heat the cold-rolled strip to above the recrystallization temperature, and through controlling the heating, holding, and cooling processes, eliminate work hardening, restore plasticity, and obtain the desired microstructure and mechanical properties. The accuracy, stability, and uniformity of furnace temperature control directly affect the microstructure uniformity, strip shape quality, surface quality, and energy consumption level of the production line.

[0003] Currently, the furnace temperature control technology widely used in this field is mainly based on the gas supply control of the gas burners. Early continuous annealing furnaces mostly adopted a pure on / off control mode. Its working principle is: when the furnace temperature is lower than the set value, the natural gas solenoid valve is fully opened, and the burner operates at maximum power; when the temperature reaches or exceeds the set value, the valve is fully closed, and the burner stops working. This "all-on, all-off" binary control mode, although simple in structure and low in cost, inevitably suffers from significant temperature overshoot (exceeding the set value) and hysteresis (below the set value) due to the discontinuous control action. This causes the furnace temperature to oscillate continuously around the set value, making it difficult to stabilize. This fluctuation directly affects the uniformity of the strip heat treatment process, potentially leading to uneven product hardness and decreased surface quality. Furthermore, when approaching the set temperature, the burner continues to burn at maximum power until temperature overshoot occurs, resulting in excessive natural gas consumption. Simultaneously, frequent start-ups and shutdowns cause significant heat loss through the flue gas, resulting in low overall thermal efficiency.

[0004] To overcome the shortcomings of pure on / off control in high-temperature zones, existing technology proposes an improved scheme that divides the control process into two intervals: when the furnace temperature is significantly lower than the set value (e.g., 30% below the set value), on / off control is used to rapidly increase the furnace temperature; when the furnace temperature enters the range above 30% of the set value, it switches to proportional control mode. The principle of proportional control is that it linearly adjusts the opening of the natural gas valve according to the deviation between the measured temperature and the set temperature, thereby providing heating power that matches the current heat demand. Theoretically, this can achieve smoother and more precise temperature regulation and improve gas utilization. However, when the temperature approaches the set value range, this control method, due to its inherent "steady-state error" characteristic, cannot completely eliminate residual deviations. At this time, the system response slows down, and its ability to resist heat disturbances caused by changes in production rhythm (such as changes in strip speed and specifications) is weak, still resulting in temperature drift and decreased uniformity.

[0005] Therefore, the present invention proposes a new control scheme that can penetrate the entire heating-up, heat preservation, and dynamic compensation processes, achieving rapid response, precise temperature control, and high energy efficiency. Summary of the Invention

[0006] The object of the present invention is to provide a furnace temperature control method for a continuous annealing furnace that can penetrate the entire heating-up, heat preservation, and dynamic compensation processes, achieving rapid response, precise temperature control, and high energy efficiency.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows: A multi-modal adaptive furnace temperature control method based on spatio-temporal thermal field decoupling, the multi-modal adaptive furnace temperature control method is applied to a continuous annealing furnace, M independent heating zones are provided in the continuous annealing furnace, and N burners are provided in each heating zone, where M≥1, N≥2, and each heating zone independently executes the following control steps: Step S1: Real-time collect the furnace temperature T of the current heating zone, obtain the preset target temperature T_set of this heating zone, and calculate the temperature ratio r = T / T_set; Step S2: Dynamically select the current control strategy from four preset control modes according to the threshold interval where r is located: The first control mode: When r≤R1, execute full-power switching control, and the burners work continuously at the maximum heat load; The second control mode: When R1 < r < R2, execute proportional control, and linearly adjust the opening of the burner gas valve according to the temperature deviation e = T_set - T; The third control mode: When R2≤r≤R3, execute pulse cross control, divide the N burners in the heating zone into K working groups according to the spatial distribution, the burners in each working group are staggered in the furnace, and activate a single working group in a preset order in a cyclic manner, and each group of burners works intermittently in a switching mode; The fourth control mode: When r > R3, execute dynamic thermal field maintenance control, and selectively activate some working groups according to the furnace temperature change trend and thermal field distribution feedback to maintain the furnace temperature within the target range; Where, 0 < R1 < R2 < R3, R3≥1, and R1, R2, and R3 are preset parameters.

[0008] In one embodiment, the value range of R1 is 20% - 40%, the value range of R2 is 90% - 98%, and the value range of R3 is 100% - 105%.

[0009] In one embodiment, R1 is 30%, R2 is 95%, and R3 is 102%.

[0010] In one embodiment, in the third control mode, the burners in each working group are controlled by pulse width modulation. The single activation time t_on of each working group is inversely proportional to the furnace temperature deviation e, and the rest time t_off is directly proportional to the furnace temperature stability index.

[0011] In one embodiment, in the fourth control mode, the controller calculates the thermal field uniformity index U based on the furnace temperature distribution data fed back by multi-point temperature sensors. When U is lower than a preset threshold, the burner working group corresponding to the low-temperature region is activated to achieve local heat compensation.

[0012] In one embodiment, each heating zone is provided with two sets of burners arranged opposite each other, and each set of burners is staggered along the running direction of the strip; the working group is formed by cross-combination of burners from different sets.

[0013] In one embodiment, each heating zone is equipped with eight burners. These eight burners are divided into two groups, spaced apart against the direction of the strip's movement. One group of burners, arranged against the direction of the strip's movement, is designated as burner 1, burner 3, burner 5, and burner 7, respectively. The other group of burners, arranged against the direction of the strip's movement, is designated as burner 2, burner 4, burner 6, and burner 8, respectively. The eight burners are divided into four working groups, specifically grouped as follows: Working Group A: Burners No. 1 and No. 6; Group B: Burners No. 3 and No. 8; Working Group C: Burners No. 5 and No. 4; Working Group D: Burners No. 7 and No. 2; In the third control mode, the burners of the corresponding work groups are activated cyclically according to the control sequence of work group A, work group B, work group C and work group D, and the activation time interval Δt between adjacent work groups is dynamically adjusted according to the furnace temperature change rate.

[0014] In one embodiment, the second control mode adopts a proportional-feedforward composite control algorithm, where the burner gas valve opening P = Kp × e + Kf × F, and Kp is the proportional coefficient, Kf is the feedforward coefficient, and F is the feedforward variable composed of strip specifications and travel speed.

[0015] The present invention also provides a multimodal adaptive furnace temperature control system based on spatiotemporal thermal field decoupling, the system comprising: Multiple high-precision temperature sensors are used to collect the furnace temperature at multiple points in each heating zone in real time; Multiple burners and their corresponding gas regulating valves and solenoid valves; The thermal field distribution monitoring module is used to calculate the thermal field uniformity index based on multi-point temperature data; The controller incorporates the multimodal adaptive furnace temperature control method described in any of the preceding items, and has mode switching logic, workgroup scheduling algorithm, and pulse width modulation function; The human-machine interface is used to display real-time furnace temperature, thermal field distribution, and control modes, and supports online adjustment of threshold parameters R1, R2, and R3.

[0016] The present invention also provides a continuous annealing furnace, characterized in that it includes the multimodal adaptive furnace temperature control system as described above, as well as the furnace body and strip conveying device.

[0017] The present invention, by adopting the above-described technical solution, has the following beneficial effects: 1. Through pulse cross control and dynamic thermal field maintenance control, the furnace temperature fluctuation during the heat preservation stage can be controlled within ±5℃, which is far superior to the ±30℃ of traditional switch control and the ±15~25℃ of two-stage control.

[0018] 2. Through the staggered arrangement and cyclic activation of working groups, heat is spatially evenly distributed within the furnace. Simultaneously, the thermal uniformity monitoring and compensation mechanism can correct local temperature deviations in real time, reducing the maximum temperature difference within the furnace from the traditionally controlled 30-40℃ to less than 10℃.

[0019] 3. The low-temperature section employs full-power switching control, increasing the heating rate by over 30% compared to pure proportional control. The feedforward compensation mechanism reduces the system's response time to load changes by over 40%.

[0020] 4. Pulse cross-control ensures the burner operates in the high-efficiency combustion zone, avoiding prolonged low-load operation. Simultaneously, improved thermal uniformity reduces heat loss, resulting in 8%–12% lower fuel consumption compared to traditional control methods.

[0021] 5. Improved temperature control accuracy and thermal uniformity directly enhance the microstructure uniformity, mechanical property consistency, and strip shape quality of the strip. This is particularly evident in high-value-added products such as grain-oriented silicon steel, where magnetic properties are significantly improved.

[0022] 6. The threshold parameters of the four control modes can be adjusted online, and the feedforward variables can be flexibly configured, enabling the system to adapt to changes in different specifications, varieties, and working conditions, and has strong versatility and scalability. Attached Figure Description

[0023] Figure 1 This is an example diagram showing the distribution of burners in one of the heating zones of a continuous annealing furnace.

[0024] Figure 2 This is an example diagram showing the distribution of thermocouples in one of the heating zones of a continuous annealing furnace. Detailed Implementation

[0025] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so as to more clearly understand the purpose, features and advantages of the present invention. It should be understood that the embodiments shown in the drawings are not intended to limit the scope of the present invention, but are only for illustrating the essential spirit of the technical solution of the present invention.

[0026] In the following description, certain specific details are set forth for the purpose of illustrating various disclosed embodiments in order to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments may be practiced without one or more of these specific details. In other instances, well-known apparatuses, structures, and techniques associated with this application may not have been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0027] Unless the context requires otherwise, throughout the specification and claims, the word “comprising” and its variations, such as “including” and “having”, shall be understood to have an open, inclusive meaning, that is, to be interpreted as “including, but not limited to”.

[0028] Throughout this specification, references to "an embodiment" or "an embodiment" indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Therefore, the appearance of "in an embodiment" or "an embodiment" in various places throughout the specification does not necessarily refer to the same embodiment. Furthermore, a particular feature, structure, or characteristic may be combined in any manner in one or more embodiments.

[0029] The singular forms “a” and “the” used in this specification and the appended claims include plural references unless otherwise expressly stated herein. It should be noted that the term “or” is generally used to mean “and / or” unless otherwise expressly stated herein.

[0030] In the following description, in order to clearly demonstrate the structure and operation of the present invention, a number of directional terms will be used. However, terms such as "front", "back", "left", "right", "outside", "inside", "outward", "inward", "up", and "down" should be understood as convenient terms and not as limiting terms.

[0031] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0032] In the description of this application, it should also be noted that unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "link" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific situations.

[0033] The present invention provides a multi-modal adaptive furnace temperature control method based on spatio-temporal thermal field decoupling, which is applied to a continuous annealing furnace. There are M independent heating zones in the continuous annealing furnace, M≥1, and there are N burners in each heating zone, N≥2. Each heating zone is equipped with an independent temperature sensor, a controller, and an actuator to achieve independent control of each zone.

[0034] The controller collects the current furnace temperature T of the heating zone in real time, obtains the preset target temperature T_set of this heating zone, and calculates the temperature ratio r = T / T_set. According to the threshold interval where r is located, the current control strategy is dynamically selected from four preset control modes: The first control mode is the fast-response heating-up mode: when r≤R1, full-power switching control is executed, and all burners work continuously at the maximum heat load. The goal of this mode is to raise the furnace temperature to the controllable range in the shortest time, shorten the heating-up time, and improve production efficiency.

[0035] The second control mode is the proportional-regulation transition mode: when R1 < r < R2, proportional control is executed, and the opening of the burner gas valve is linearly adjusted according to the temperature deviation e = T_set - T. The goal of this mode is to achieve a smooth transition of the furnace temperature, avoid temperature overshoot, and prepare for entering the heat preservation stage.

[0036] The third control mode is the pulse-crossing uniform mode: when R2≤r≤R3, pulse-crossing control is executed. The N burners in the heating zone are divided into K working groups according to the spatial distribution, and the burners in each working group are staggered in the furnace. The controller cyclically activates a single working group in the preset order, and each group of burners works intermittently in the switching mode. The goal of this mode is to achieve spatial uniform distribution of heat and precise time control in the heat preservation stage.

[0037] The fourth control mode is the dynamic thermal field maintenance mode: when r > R3, dynamic thermal field maintenance control is executed. The controller calculates the thermal field uniformity index U according to the temperature distribution data in the furnace feedback by the multi-point temperature sensors. When U is lower than the preset threshold, the burner working group corresponding to the low-temperature area is activated to achieve local heat compensation. The goal of this mode is to maintain the thermal field uniformity in the case of over-temperature and avoid local overheating.

[0038] Where R1, R2, and R3 are preset parameters, and their value range is: R1: 20%~40%, preferably 30%; R2: 90%~98%, preferably 95%; R3: 100%~105%, preferably 102%; The threshold setting can be determined by comprehensively considering factors such as furnace structure, burner characteristics, and strip steel specifications, and can be determined through on-site debugging or simulation optimization.

[0039] Taking an example where each heating zone has 8 burners, the burner arrangement is as follows: Figure 1 As shown. Two sets of burners are arranged opposite each other, staggered along the strip running direction. The eight burners are divided into four working groups: Working Group A: Burners No. 1 and No. 6; Group B: Burners No. 3 and No. 8; Working Group C: Burners No. 5 and No. 4; Working Group D: Burners No. 7 and No. 2; The control sequence is A→B→C→D, executed cyclically. The activation time interval Δt between adjacent working groups is dynamically adjusted according to the furnace temperature change rate. The single activation time t_on of each working group is inversely proportional to the furnace temperature deviation e, and the pause time t_off is directly proportional to the furnace temperature stability index. This dynamic pulse width modulation (PWM) method enables fine-tuning of heat.

[0040] Multiple thermocouples are arranged in each heating zone to collect furnace temperature data at different locations in real time. The controller calculates the thermal field uniformity index U: U = 1 - (T_max - T_min) / T_avg Where T_max is the highest temperature, T_min is the lowest temperature, and T_avg is the average temperature. The closer the U value is to 1, the better the uniformity of the thermal field.

[0041] When U is below a preset threshold (e.g., 0.97), the controller identifies the burner working group corresponding to the low-temperature region and prioritizes activating the working group in the next pulse cycle, or extends the activation time of the working group to achieve local heat compensation.

[0042] See Figure 2 , Figure 2According to the arrangement of the burners, the heating zone is divided into a total of 8 sub-regions A - H. Each region corresponds to one of the burners, and the burner is set at approximately the central axis perpendicular to the direction of strip travel in the corresponding sub-region. At the same time, a thermocouple TC is set in each sub-region. A total of 8 thermocouples TC1 - TC8 in each sub-region are arranged staggered on the same height plane in the heating zone. The height where the thermocouple is located is determined according to the position of the strip, usually set at 50 - 100 mm from the strip surface to measure the temperature that best represents its true state. At the same time, the position of the thermocouple also needs to avoid being directly impacted by the burner flame, and the distance from all side walls, the bottom surface and the top of the furnace should usually be not less than 450 mm, and the insertion depth should not be less than 8 - 10 times the outer diameter of its protection tube to ensure measurement accuracy. The thermocouple is usually installed vertically to prevent deformation at high temperatures.

[0043] See Figure 2 , the thermocouples in each sub-region are placed outside the cross-interference zone of the two flames, and the thermocouples in the relatively two side sub-regions are arranged staggeredly in the strip travel direction. For example, the thermocouples TC1 - TC8 in the A - H regions are all located near the center of the strip, but the thermocouples in the A, C, E, G regions are set in the upper section near the strip travel direction (i.e., Figure 2 the lower right side of the corresponding region in Figure 2 ), while the thermocouples in the B, D, F, H regions are set in the lower section near the strip travel direction (i.e.,

[0044] the upper left side of the A region in

[0045] The specific algorithm for low-temperature region identification and workgroup activation is as follows: Step T1: Real-time collect the furnace temperature T_j of each thermocouple (j = 1 - 8), and calculate the temperature deviation e_j = T_set - T_j of each sub-region (when T_j < T_set, e_j is positive, otherwise it is 0).

[0046] Step T2: Calculate the thermal field uniformity index U = 1 - (T_max - T_min) / T_avg. When U is lower than the preset threshold (such as 0.97), trigger local heat compensation.

[0047] Step T3: Identify the thermocouple with the lowest temperature and its corresponding sub-region, denoted as TC_min in sub-region X. According to the above mapping table, determine the main control burner corresponding to this sub-region and its affiliated workgroup.

[0048] Step T4: In the next pulse cycle, the working group is activated first, and its activation time is extended. The extension time Δt_comp is proportional to the temperature deviation e_min: Δt_comp = k_comp × e_min, where k_comp is the compensation coefficient. The compensation coefficient k_comp usually depends on the specific architecture and accuracy requirements of the control system. It is the additional activation time that needs to be compensated for per unit temperature difference. Its value range is preferably 0.1~2.0s / ℃, and in this embodiment, it is taken as 0.5s / ℃.

[0049] Step T5: When the thermocouple temperature of the compensated area exceeds the average temperature T_avg of the heating area, or the continuous compensation time exceeds the preset maximum duration t_comp_max (e.g., 30 seconds), or U recovers to above the threshold, compensation is stopped and the normal working group polling sequence is restored.

[0050] For example, when TC1 detects the lowest temperature, it determines that sub-region A is a low-temperature zone, and its corresponding main control burner is burner number 1, belonging to work group A (burners 1 and 6). In the next pulse cycle, the controller prioritizes activating work group A to achieve local heat compensation for sub-region A.

[0051] Through the aforementioned spatial mapping relationship and judgment algorithm, the controller can clearly and uniquely determine the burner work group that needs to be activated based on the data from multiple temperature sensors, thereby achieving precise local heat compensation.

[0052] When the thermal field uniformity index U is higher than a preset threshold (e.g., 0.97) in the third and fourth control modes, the activation time interval Δt between adjacent working groups is dynamically adjusted according to the furnace temperature change rate. The single activation time t_on of each working group is inversely proportional to the furnace temperature deviation e, and the rest time t_off is directly proportional to the furnace temperature stability index. Specifically: The stability of the furnace temperature in the current heating zone is quantified by the furnace temperature stability index S, and its calculation formula is as follows: S = 1 - |dT / dt| / (dT / dt)_max in: dT / dt is the rate of change of the average temperature measured by all thermocouples in the current heating zone over time (unit: ℃ / s), which can be calculated by first-order difference or linear regression using temperature data from the most recent N sampling periods. (dT / dt)_max is the preset maximum allowable rate of change (unit: ℃ / s), which is determined according to the thermal inertia of the furnace body and process requirements. The preferred value range is 0.5~5.0℃ / s, and in this embodiment, it is taken as 2.5℃ / s. The value of S is within the range of [0,1], indicating that the furnace temperature is within the allowable range. The closer the S value is to 1, the more stable the furnace temperature is; the closer the S value is to 0, the greater the fluctuation range of the furnace temperature. When the calculated value is less than 0, S=0 is taken, indicating that the furnace temperature change rate has exceeded the maximum allowable range and is in an unstable state.

[0053] For example, the current heating zone has 8 thermocouples TC1-TC8, and the controller's temperature sampling period is Δt_sample = 1 second. At time t = 10 seconds, the measured temperature values ​​of the 8 thermocouples are [815, 818, 812, 816, 814, 817, 813, 819] (unit: ℃), and the average temperature T_avg(10) is calculated to be 815.5℃. At the previous sampling time t = 9 seconds, the temperature values ​​of the 8 thermocouples are [812, 814, 812, 813, 814, 813, 813, 815] (unit: ℃), and the average temperature T_avg(9) is calculated to be 813.3℃. Taking T_set = 820℃ as an example.

[0054] Calculated using the first-order finite difference method: dT / dt=[T_avg(10)-T_avg(9)] / Δt_sample=(815.5-813.3) / 1=2.2℃ / s; S = 1 - 2.2 / 2.5 = 1 - 0.92 = 0.12; This indicates that although the rate of change in furnace temperature is still below the maximum allowable value, it is close to the upper limit, and the furnace temperature stability is poor.

[0055] t_on is inversely proportional to the temperature deviation e = T_set - T (unit: °C), specifically using a linear inverse relationship, with upper and lower limits set: t_on=max(t_on_min,min(t_on_max,t_on_base×(1-e / e_max))) in: t_on_base is the baseline activation time (the theoretical activation time when e=0), preferably ranging from 5 to 30 seconds, and is set to 15 seconds in this embodiment.

[0056] e_max is the maximum deviation at the start of the third control mode, i.e., e_max=(R3-R2)×T_set. For example, when T_set=820℃, R2=95%, and R3=102%, e_max=(0.102-0.095)×820=5.74℃.

[0057] t_on_min is the minimum activation time to ensure normal ignition of the burner. It is preferably 2 to 5 seconds, and 3 seconds is used in this embodiment.

[0058] t_on_max is the maximum activation time to prevent local overheating. It is preferably 20 to 40 seconds, and 30 seconds is used in this embodiment.

[0059] Assuming T_set = 820℃, and the current T = 815.5℃, then e = 820 - 815.5 = 4.5℃. e_max = 5.74℃.

[0060] t_on = 15 × (1 - 4.5 / 5.74) = 15 × (1 - 0.784) = 15 × 0.216 = 3.24 seconds, which is not lower than the lower limit of 3 seconds, so we take 3.24 seconds.

[0061] t_off is directly proportional to the furnace temperature stability index S, specifically using a linear proportional relationship: t_off=max(t_off_min,min(t_off_max,t_off_base×(1+k_s×S))) in: t_off_base is the baseline pause time (the theoretical pause time when S=0), preferably 5~20 seconds, and 10 seconds is used in this embodiment.

[0062] k_s is a proportionality coefficient that controls the sensitivity of the pause time to the stability index. It is preferably 0.5 to 2.0, and is 1.0 in this embodiment.

[0063] t_off_min and t_off_max are the minimum and maximum pause times, respectively, preferably 5 seconds and 40 seconds.

[0064] Taking S=0.12 as an example: t_off = 10 × (1 + 1.0 × 0.12) = 10 × 1.12 = 11.2 seconds, which is within the allowable range, so we take 11.2 seconds.

[0065] The activation time interval Δt between adjacent working groups is inversely proportional to the absolute value of the furnace temperature change rate |dT / dt|, specifically using an inverse proportional function with upper and lower limits set: Δt=max(Δt_min,min(Δt_max,Δt_base / (1+k_t×|dT / dt|))) in: Δt_base is the base interval time, preferably 1 to 5 seconds, and 2 seconds is used in this embodiment.

[0066] k_t is an adjustment coefficient, preferably 1.0~4.0, and is 2.0 in this embodiment.

[0067] Δt_min and Δt_max are the minimum and maximum interval times, respectively, preferably 1 second and 5 seconds.

[0068] Again, taking |dT / dt|=2.2℃ / s as an example: Δt = 2 / (1 + 2.0 × 2.2) = 2 / (1 + 4.4) = 2 / 5.4 ≈ 0.37 seconds, which is lower than the lower limit of 1 second, so we take Δt = 1 second. Therefore, the activation time interval between adjacent working groups is 1 second.

[0069] Based on the example of S=0.12 above, at time t=10s, when e=4.5℃, the system uses a shorter activation time t_on (3.24s) to quickly replenish heat, and a shorter rest time t_off (11.2s). The inter-group switching interval Δt is limited to the lower limit (1s) to enhance the heating response.

[0070] At time t=20s, the average temperature T_avg(20) is 818.0℃, the furnace temperature rise rate slows down (dT / dt=0.5℃ / s), S=0.80, and the stability is significantly improved. The deviation decreases (e=2.0℃), the activation time t_on is extended to 9.78s, the rest time t_off is extended to 18.0s, and the interval time Δt remains 1s.

[0071] At time t=30s: the furnace temperature is very close to the set value (e=0.5℃), the rate of change is very low (dT / dt=0.2℃ / s), S=0.92>0.9, and the furnace temperature is stable. The activation time t_on is further extended to 13.7s (close to the reference value), the pause time t_off is extended to 19.2s, the interval time Δt automatically increases to 1.43s, the pulse cycle slows down, and precise heat preservation is achieved.

[0072] In addition, to avoid overcompensation causing new local overheating, the controller is equipped with one or more of the following anti-overadjustment mechanisms: (1) The maximum activation time for a single compensation is t_comp_max (30 seconds) to prevent the single compensation time from being too long.

[0073] (2) The cumulative compensation time of the same working group in two consecutive pulse cycles shall not exceed t_comp_max.

[0074] (3) After each compensation activation, the thermal field uniformity index U and local temperature are recalculated. If the improvement is insufficient (U is still below the threshold or the lowest temperature area has not changed), the next compensation is started instead of a one-time compensation.

[0075] (4) Set the compensation stop threshold U_stop=U_threshold+δ, where δ is the hysteresis amount, preferably 0~0.02. In this embodiment, δ=0, that is, when U recovers to above 0.97, the compensation stops to avoid frequent switching near the threshold.

[0076] (5) When any of the following conditions are met, immediately terminate the current compensation control for the specific low temperature region and restore the normal pulse cycle sequence (A→B→C→D): Condition 1: Thermal field uniformity index U ≥ U_stop (i.e. ≥ 0.97); Condition 2: The temperature of the thermocouple in the compensated low-temperature region exceeds the current average temperature T_avg of the heating region; Condition 3: The duration of a single continuous compensation in the same work group exceeds t_comp_max (30 seconds).

[0077] For example, in the example above, the target temperature T_set=820℃, the thermal field uniformity threshold U_threshold=0.97, the compensation coefficient k_comp=0.5s / ℃, the maximum compensation time t_comp_max=30s, the hysteresis δ=0, and the compensation stop threshold U_stop=0.97.

[0078] At a certain moment, the temperatures of each thermocouple are [815, 818, 812, 816, 814, 817, 813, 819]. The calculated values ​​are: T_max = 819, T_min = 812, T_avg = 815.5, U = 1 - 7 / 815.5 ≈ 0.9914 > 0.97, so compensation is not triggered.

[0079] Assuming that under the fourth control mode (i.e., the overall furnace temperature exceeds R3, T>836.4℃ in this embodiment), due to pulse scheduling anomalies, sub-regions A and F under the responsibility of work group A experience localized high temperatures, while sub-regions D and E under the responsibility of work group C experience localized low temperatures. The thermocouple temperatures become: [850, 845, 835, 825, 815, 855, 840, 830] (unit: ℃). Among them, TC1 (850℃) and TC6 (855℃) are localized high temperatures, and TC4 (825℃) and TC5 (815℃) are relatively low temperatures. Calculations show: T_max=855℃, T_min=815℃, T_avg≈836.9℃, U=1-40 / 836.9≈0.9522<0.97, triggering compensation.

[0080] Execution of compensation: Identify the lowest temperature thermocouple: TC5 (815℃), located in sub-region E. According to the spatial mapping table, sub-region E corresponds to the main control burner No. 5, and belongs to work group C (burners No. 5 and No. 4).

[0081] Calculate the temperature deviation: e_min = T_set - T_min = 820 - 815 = 5℃.

[0082] Compensation time: Δt_comp=min(k_comp×e_min,t_comp_max)=min(0.5×5,30)=2.5 seconds.

[0083] In the next pulse cycle, the controller prioritizes activating workgroup C and extends its activation time by 2.5 seconds to increase the temperature of sub-regions D and E.

[0084] Results after compensation: Assuming that after compensation is performed, the temperature is re-collected as: [848,844,836,828,822,853,839,831]. The calculation yields: T_max=853, T_min=822, temperature difference=31, T_avg≈837.6, U=1-31 / 837.6≈0.9630, still lower than 0.97, but the minimum temperature has increased from 815 to 822, and the uniformity has improved.

[0085] According to the step-by-step compensation strategy, the controller restarts the compensation process and continues to activate workgroup C.

[0086] After the second compensation, the temperature is: [846,843,838,832,828,851,838,832]. The calculation yields: T_max=851, T_min=828, temperature difference=23, T_avg≈838.5, U=1-23 / 838.5≈0.9726, which is higher than the threshold of 0.97. Exit the compensation program and restore the normal pulse cycle sequence.

[0087] If the compensation time is too long, causing the temperatures of TC4 and TC5 to be too high, for example, if the collected temperatures are [845,842,837,845,843,850,837,831], then: TC4=845℃, TC5=843℃, average temperature is about 841℃. Both TC4 and TC5 exceed the average temperature, triggering exit condition 2 (the temperature of the compensated area exceeds the average temperature), immediately terminating compensation and restoring the normal pulse cycle sequence.

[0088] In the proportional regulation transition mode, a proportional-feedforward composite control algorithm is adopted, where the gas valve opening P = Kp × e + Kf × F. Kp is the proportional coefficient, Kf is the feedforward coefficient, and F is the feedforward variable, which may include: strip specifications (thickness, width), strip speed, strip type (thermal conductivity, specific heat capacity), and ambient temperature. Feedforward compensation can predict the impact of load changes on furnace temperature in advance, improving the system's dynamic response capability.

[0089] This invention employs full-power switching control at low temperatures, with the burner operating at maximum heat load to rapidly increase furnace temperature and shorten heating time. When the furnace temperature approaches the set value, it switches to proportional control, linearly adjusting the heat load based on temperature deviation for a smooth transition and to avoid overshoot. When the furnace temperature nears the set value, it switches to pulse cross-control, using cyclic activation of the control group to achieve uniform heat distribution in time and space. When the furnace temperature exceeds the set value, it switches to dynamic thermal field maintenance control, selectively activating the burner based on the thermal field distribution to maintain uniformity and prevent localized overheating. Through the organic combination and smooth switching of these four modes, this invention achieves optimized control across the entire operating range, simultaneously meeting the requirements of rapid response, precise temperature control, uniform heat preservation, and high energy efficiency.

[0090] Example 1: Application in a 1450mm silicon steel continuous annealing production line at a steel plant A steel plant's 1450mm continuous annealing production line for silicon steel mainly produces high-grade grain-oriented silicon steel (30Q130) and non-grain-oriented silicon steel. The production line is 320m long and has 6 heating zones, 4 soaking zones, and 5 cooling zones. Each heating zone is approximately 15m long, with burners arranged on both sides, 4 on each side, for a total of 8 burners.

[0091] Based on on-site debugging and simulation optimization, the control parameters for each heating zone are set as follows: R1=30%; R² = 95%; R3 = 102%; Kp = 0.8 (proportional coefficient) Kf = 0.2 (feedforward coefficient) Feedforward variables: strip thickness, width, speed The following is a comparison of the effects of using the control method of this invention compared to the original control method (switch + proportional two-stage): The temperature fluctuation during the heat preservation stage has been improved from ±25℃ to ±8℃, the maximum temperature difference inside the furnace has been improved from 35℃ to 10℃, the heating time (from room temperature to 800℃) has been shortened from 45 minutes to 32 minutes, and the unit consumption of natural gas has been reduced from 32m³. 3 / t decreased to 29m 3 / t, the magnetic induction of the product B800 has been increased from 1.84T to 1.86T.

[0092] Taking the third heating zone as an example, the target temperature T_set = 820℃. When the furnace temperature T = 779℃ (r = 95%), the system enters the pulse cross-control mode. The working group cycle sequence is A→B→C→D. When the furnace temperature is 815.5℃ (deviation e = 4.5℃), according to the aforementioned formula, the single activation time t_on = 3.24s, the pause time t_off = 11.2s, and the activation time interval between adjacent working groups Δt = 1s.

[0093] As the furnace temperature approaches the set value, the controller dynamically adjusts t_on, t_off, and Δt based on the temperature deviation. When the furnace temperature rises to 818.0℃ (e=2.0℃), t_on is adjusted to 9.78s, t_off to 18.0s, and Δt remains at 1s; when the furnace temperature rises to 819.5℃ (e=0.5℃), t_on is adjusted to 13.7s, t_off to 19.2s, and Δt automatically increases to 1.43s, achieving precise heat preservation.

[0094] Multi-point thermocouple feedback shows that after adopting pulse cross control, the temperature distribution in the furnace is uniform, and the temperature difference at each point is less than 8℃.

[0095] Example 2: Adaptive performance under different operating conditions 1. Operating conditions with specification changes When the strip steel specification is switched from 2.0mm×1200mm to 2.5mm×1200mm, the heat load demand increases by about 25%. The feedforward compensation module increases the proportional control output in advance according to the thickness change, so that the furnace temperature fluctuation is controlled within ±5℃ and the recovery time is less than 2 minutes.

[0096] 2. Speed ​​variation conditions When the production line speed increases from 80m / min to 100m / min, the feedforward compensation module increases the heat load in advance according to the speed change, and at the same time, the activation time of the pulse cross control working group is automatically extended to ensure furnace temperature stability.

[0097] 3. Product switching operation When switching from non-oriented silicon steel to oriented silicon steel, the target temperature increases from 780℃ to 840℃. The control mode automatically undergoes the complete process of rapid heating → proportional adjustment → pulse cross-control, with a smooth switching process and no overshoot.

[0098] The preferred embodiments of the present invention have been described in detail above. However, it should be understood that after reading the above teachings, those skilled in the art can make various alterations or modifications to the present invention. These equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A multimodal adaptive furnace temperature control method based on spatiotemporal thermal field decoupling, wherein the multimodal adaptive furnace temperature control method is applied to a continuous annealing furnace, the continuous annealing furnace having M independent heating zones, each heating zone having N burners, wherein M≥1, N≥2, characterized in that, Each heating zone independently performs the following control steps: Step S1: Real-time collect the furnace temperature T of the current heating zone, obtain the preset target temperature T_set of this heating zone, and calculate the temperature ratio r = T / T_set; Step S2: According to the threshold interval where r is located, dynamically select the current control strategy from the four preset control modes: The first control mode: When r ≤ R1, perform full-power switching control, and the burners work continuously at the maximum heat load; The second control mode: When R1 < r < R2, perform proportional control, and linearly adjust the opening of the burner gas valve according to the temperature deviation e = T_set - T; The third control mode: When R2 ≤ r ≤ R3, perform pulse cross control. Divide the N burners in the heating zone into K working groups according to the spatial distribution. The burners within each working group are staggered in the furnace, and a single working group is cyclically activated in the preset order. Each group of burners works intermittently in a switching mode; The fourth control mode: When r > R3, perform dynamic thermal field maintenance control. According to the furnace temperature change trend and the feedback of the thermal field distribution, selectively activate some working groups to maintain the furnace temperature within the target range; Among them, 0 < R1 < R2 < R3, R3 ≥ 1, and R1, R2, and R3 are preset parameters.

2. The multimodal adaptive furnace temperature control method as described in claim 1, characterized in that, The value range of R1 is 20% - 40%, the value range of R2 is 90% - 98%, and the value range of R3 is 100% - 105%.

3. The furnace temperature control method as described in claim 2, characterized in that, R1 is 30%, R2 is 95%, and R3 is 102%.

4. The multimodal adaptive furnace temperature control method as described in claim 1, characterized in that, In the third control mode, the burners within each working group are controlled by pulse width modulation. The single activation time t_on of each working group is inversely proportional to the furnace temperature deviation e, and the停歇 time t_off is directly proportional to the furnace temperature stability index.

5. The multimodal adaptive furnace temperature control method as described in claim 1, characterized in that, In the fourth control mode, the controller calculates the thermal field uniformity index U according to the temperature distribution data in the furnace feedback by the multi-point temperature sensor. When U is lower than the preset threshold, activate the burner working group corresponding to the low-temperature area to achieve local heat compensation.

6. The multimodal adaptive furnace temperature control method as described in claim 1, characterized in that, There are two groups of burners arranged oppositely in each heating zone, and each group of burners is staggered along the running direction of the strip; the working group is composed of the burners cross-combined from different groups.

7. The multimodal adaptive furnace temperature control method as described in claim 6, characterized in that, There are 8 burners in each heating zone. The 8 burners are divided into two groups and are arranged at intervals along the reverse direction of the strip's travel. One group of burners is sequentially defined as burner No. 1, burner No. 3, burner No. 5, and burner No. 7 along the reverse direction of the strip's travel, and the other group of burners is sequentially defined as burner No. 2, burner No. 4, burner No. 6, and burner No. 8 along the reverse direction of the strip's travel. The 8 burners are divided into 4 working groups, and the specific grouping method is: Working group A: Burner No. 1 and burner No. 6; Working group B: Burner No. 3 and burner No. 8; Working group C: Burner No. 5 and burner No. 4; Working group D: Burner No. 7 and burner No. 2; In the third control mode, activate the burners of the corresponding working groups in the control order of working group A, working group B, working group C, and working group D, and the activation time interval Δt between adjacent working groups is dynamically adjusted according to the furnace temperature change rate.

8. The multimodal adaptive furnace temperature control method as described in claim 1, characterized in that, The second control mode adopts a proportional-feedforward composite control algorithm, where the burner gas valve opening P = Kp × e + Kf × F, and Kp is the proportional coefficient, Kf is the feedforward coefficient, and F is the feedforward variable.

9. A multimodal adaptive furnace temperature control system based on spatiotemporal thermal field decoupling, characterized in that, The system includes: Multiple high-precision temperature sensors are used to collect the furnace temperature at multiple points in each heating zone in real time; Multiple burners and their corresponding gas regulating valves and solenoid valves; The thermal field distribution monitoring module is used to calculate the thermal field uniformity index based on multi-point temperature data; The controller incorporates the multimodal adaptive furnace temperature control method as described in any one of claims 1 to 8, and has mode switching logic, workgroup scheduling algorithm, and pulse width modulation function; The human-machine interface is used to display real-time furnace temperature, thermal field distribution, and control modes, and supports online adjustment of threshold parameters R1, R2, and R3.

10. A continuous annealing furnace, characterized in that, It includes the multimodal adaptive furnace temperature control system as described in claim 9, as well as the furnace body and strip conveying device.

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