An intelligent management and control system for the whole process of an environment-friendly aluminum material coating production line

Abstract

The present application relates to the technical field of industrial automation control, and discloses an environmental protection type aluminum material coating production line whole process intelligent management and control system, which comprises an industrial control program module and a temperature sensing array, the module obtains a control mode mark and a target workpiece temperature according to formula information; the module judges the mark to adopt a preset speed in an open loop mode or to perform minimum value operation on a plurality of actual workpiece temperatures obtained from the array in a closed loop mode, to obtain a unique process variable, and to adjust the conveying chain speed based on the error of the process variable and the target temperature, the control target of the present application is changed from the ambient temperature to the workpiece body temperature, and the chain speed is adjusted to adapt to different heat capacity workpieces autonomously, so that the under-baking and over-baking problems caused by the fixed chain speed in multi-variety production are solved.

Description

Technical Field

[0001] This invention relates to an intelligent control system for the entire process of an environmentally friendly aluminum coating production line, belonging to the field of industrial automation control technology. Background Technology

[0002] Currently, in the curing process of aluminum coating production lines, industrial control systems, such as programmable logic controllers (PLCs), typically control heating elements to ensure that the air temperature in the curing tunnel remains stable at a preset process value. This approach is based on the assumption that the workpiece will complete curing as long as it stays in the environment for a sufficient amount of time. However, as the industry shifts towards flexible production methods with multiple varieties and small batches, workpieces with vastly different heat capacities, such as thin aluminum panels and heavy industrial profiles, will continuously pass through the same conveyor chain. To balance efficiency, the control system usually sets the conveyor chain speed to a compromise fixed value. This operating mode exposes the limitations of existing control logic, namely, the separation between its control objective (air temperature) and the actual process objective (curing state of the workpiece coating). The control system is unaware of the actual temperature changes of the workpiece, resulting in over-curing of workpieces with low heat capacity and severe under-curing of workpieces with high heat capacity at a fixed chain speed, creating an operational conflict between quality and efficiency.

[0003] Those skilled in the art have attempted to alleviate this problem by simply increasing or decreasing the setpoint of the drying tunnel temperature or by simply reducing the chain speed. However, these adjustments cannot resolve the aforementioned conflict and may even exacerbate energy waste or affect the quality of thin sheet workpieces. The core issue is that the system still lacks perception and feedback on the actual state of the workpiece itself, and remains an open-loop control based on preset parameters. This control logic, which relies on fixed process parameters, is still prevalent in existing automated production lines. For example, the method disclosed in patent announcement number CN208612830U discloses an environmentally friendly coating production line. Although it describes setting a drying device after painting, its control device can only set the drying temperature and drying time. This method essentially still presets a fixed dwell time, allowing the workpiece to pass through slowly. This solution does not consider the different heating curves caused by the difference in heat capacity of different workpieces, nor does it establish real-time feedback on the temperature of the workpiece itself. Therefore, when facing mixed production of multiple varieties, it also cannot resolve the conflict between over-drying of workpieces with small heat capacity and under-drying of workpieces with large heat capacity.

[0004] Therefore, the technical problem to be solved by this invention is how to construct an industrial control system that transforms the control target from indirect environmental parameters to the actual physical state of the workpiece, and dynamically adjusts the key process parameters in the production process based on the feedback of this actual state, so as to ensure the curing quality of each workpiece and reasonably control energy consumption under dynamic working conditions of multiple varieties. Summary of the Invention

[0005] This invention provides an intelligent control system for the entire process of an environmentally friendly aluminum coating production line. Its main purpose is to solve the problem that existing control systems cannot perceive the true state of the workpiece due to the separation of control objectives and process objectives. This results in the inability to adjust the residence time according to the heat capacity difference of the workpiece in flexible production of multiple varieties, thus causing the coexistence of over-baking and under-baking.

[0006] To achieve the above objectives, the present invention provides an intelligent control system for the entire process of an environmentally friendly aluminum coating production line. The system includes a temperature sensor array and an industrial control program module located at the outlet of the drying tunnel.

[0007] The industrial control program module is used to: obtain the target workpiece temperature and the flag characterizing the control mode based on the current workpiece's recipe information;

[0008] The actual workpiece temperature is obtained from multiple locations using a temperature sensor array;

[0009] Determine the control mode flag: If the flag indicates open-loop control mode, suspend the subsequent closed-loop control logic, obtain the preset open-loop speed value according to the recipe information, and use the preset open-loop speed value as the final control output signal; if the flag indicates closed-loop control mode, run the decision logic, perform a minimum value calculation on the actual workpiece temperature at multiple locations, use the minimum value of the calculation as the unique process variable, and generate a closed-loop control output through the control logic based on the error between the target workpiece temperature and the unique process variable, and use the closed-loop control output as the final control output signal.

[0010] The speed of the conveyor chain in the painting production line is adjusted using the final control output signal.

[0011] Preferably, the control logic is a PID control logic. The PID control logic generates a closed-loop control output based on the proportional, integral, and derivative operations of the error. The industrial control program module is also used to suspend the integral operation of the PID control logic simultaneously when the indicator indicates open-loop control mode, thus suspending the subsequent closed-loop control logic.

[0012] Preferably, the temperature sensing array includes multiple non-contact infrared thermometers, which are arranged in an array at the outlet of the drying tunnel in a vertical or horizontal direction to cover different cross-sectional positions of the workpiece at the outlet of the drying tunnel.

[0013] Preferably, the industrial control program module is also used to: obtain the workpiece type identifier from the host computer or barcode scanner, and according to the workpiece type identifier, query and obtain the corresponding target workpiece temperature, the flag characterizing the control mode, and the preset open-loop speed value in the recipe lookup table.

[0014] Preferably, the industrial control program module is also used to: before adjusting the conveyor chain speed of the coating production line, compare the maximum value of the actual workpiece temperature at multiple locations with a preset effective workpiece temperature threshold; if the maximum value is lower than the effective workpiece temperature threshold, it is determined to be a workpiece gap, the industrial control program module suspends the operation of the control logic and the decision logic, and keeps the value of the final control output signal unchanged.

[0015] Preferably, the system also includes a heating controller for maintaining the air temperature inside the drying tunnel. The industrial control program module is also used to: monitor the control output signal of the heating controller in real time, generate a feedforward control quantity based on the changing characteristics of the control output signal, and superimpose the feedforward control quantity with the closed-loop control output to serve as the final control output signal.

[0016] Preferably, the system further includes heating control logic for controlling the heating of the drying tunnel, and the industrial control program module is also used to: take the final control output signal or the conversion value based on the final control output signal as a feedforward signal, and provide the feedforward signal to the heating control logic to pre-compensate for thermal load disturbances caused by changes in workpiece heat capacity or chain speed adjustment.

[0017] Preferably, the industrial control program module is also used to: run a monitoring logic module in parallel outside of the control logic, the monitoring logic module is used to perform a long-cycle integration operation on the error; when the result of the long-cycle integration operation exceeds the preset calibration threshold, a calibration offset is generated, and the calibration offset is used to automatically correct the target workpiece temperature used by the control logic.

[0018] Preferably, the industrial control program module is used to generate feedforward control quantities in the following manner: during the current control cycle Obtain the control output signal of the heating controller Obtain the control output signal from the previous control cycle. Calculate the rate of change of the control output signal between two control cycles. ,in rate of change Through a preset feedforward gain Processing is performed to generate feedforward control input. ,in .

[0019] Preferably, the decision logic is also used to: before performing the minimum value operation on the actual workpiece temperature at multiple location points, compare each actual workpiece temperature with a preset effective workpiece temperature threshold, and only use actual workpiece temperatures that are not lower than the effective workpiece temperature threshold to participate in the minimum value operation.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. By acquiring the actual temperature of the workpiece at the outlet of the drying tunnel and comparing it with the set target workpiece temperature, the speed of the conveyor chain is dynamically adjusted using the generated error signal. This method establishes a control loop with the workpiece body temperature as the direct control target and the dwell time in the drying tunnel as the actual adjustment quantity. This transforms the system control logic from maintaining the ambient temperature to actively ensuring the curing state of each workpiece. As a result, it has the ability to autonomously adapt to workpieces with different heat capacities and avoids the problem of under-drying or over-drying caused by a fixed chain speed in the mixed production of multiple varieties.

[0022] 2. By adding a control mode flag to the workpiece recipe information and configuring a control arbitration logic, the control program can pre-determine whether the current workpiece is suitable for closed-loop control based on the flag. When a workpiece type with unreliable sensor readings is identified, the program will actively suspend the error-based closed-loop speed regulation logic and instead execute the safe open-loop speed preset in the recipe. This multi-modal control method uses prior process knowledge to manage the timing of intervention of real-time control logic, avoiding the uncontrolled operation of the control system due to inaccurate sensor signals under specific working conditions.

[0023] 3. By using a set of sensors to obtain the actual temperature of multiple locations on the workpiece, and adding a decision module to the control program, this module performs a minimum value calculation on multiple temperature readings before sending the signal into the closed-loop speed control logic, and uses this single minimum value as the only process variable on which the closed-loop control is based. This method of reconstructing the control input changes the goal of the control logic from ensuring that the temperature of a certain point meets the standard to ensuring that the temperature of the coldest point of the entire workpiece meets the standard. Thus, even when facing workpieces with complex shapes and uneven heat capacity, the curing quality of the most difficult-to-heat parts can be guaranteed. Attached Figure Description

[0024] Figure 1 This is a flowchart of the speed control logic based on mode arbitration of the present invention;

[0025] Figure 2 This is a diagram illustrating the dynamic temperature control effect of the system of the present invention on workpieces with different heat capacities.

[0026] Figure 3 This is a diagram showing the hardware composition and interaction architecture of the intelligent control system of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the scope of protection of the invention.

[0028] This invention provides an intelligent control system for the entire process of an environmentally friendly aluminum coating production line. Its core lies in constructing an industrial control closed loop with the actual temperature of the workpiece as the control target. This system operates within an industrial control system, such as a programmable logic controller (PLC) or edge controller. It mainly includes an industrial control program module and a temperature sensor array located at the oven tunnel outlet. The industrial control program module dynamically adjusts the speed of the key actuators on the production line, namely the conveyor chain, by acquiring the real-time status and formula information of the workpiece, thereby proactively adapting to the differences in heat capacity of different workpieces. In the oven tunnel curing process of aluminum coating, traditional control systems only use the air temperature inside the oven tunnel as the control target. In flexible production with multiple varieties and small batches, when facing workpieces with vastly different heat capacity characteristics, such as thin aluminum sheets and thick profiles, a fixed conveyor chain speed leads to a severe separation between the control target (air temperature) and the actual process target (the cured state of the workpiece), resulting in quality issues caused by both over-curing and under-curing. The system of this invention achieves the transformation from controlling the environment to controlling the workpiece itself through the following technical solution: The system needs to obtain the target and actual state of the workpiece. The industrial control program module includes a recipe lookup table, which stores the process parameters corresponding to different workpiece types. When the workpiece enters the production line, the system obtains the workpiece type identifier of the current workpiece through a host computer or barcode scanner. Based on this identifier, the industrial control program module queries the recipe lookup table to obtain the target workpiece temperature and the flag representing the control mode. The target workpiece temperature is the setpoint for subsequent closed-loop control. At the same time, in order to obtain the actual state of the workpiece, a temperature sensing array is set at the outlet of the drying tunnel. In a specific implementation, the array includes multiple non-contact infrared thermometers. These thermometers can be arranged in an array along the vertical or horizontal direction to cover different positions of the workpiece at the outlet section, thereby providing the industrial control program module with the actual workpiece temperature at multiple positions.

[0029] After acquiring the target and actual states, the industrial control program module executes a core control arbitration and speed adjustment logic. Its primary task is to determine the flag indicating the control mode. This design is intended to address specific working conditions, such as scenarios where high-reflectivity workpieces cause inaccurate infrared thermometer readings. If the flag indicates an open-loop control mode, the industrial control program module will actively suspend subsequent closed-loop control logic and obtain a preset open-loop speed value for that specific workpiece from the formula information. This preset open-loop speed value is used as the final control output signal to directly set the conveyor chain speed. If the flag indicates a closed-loop control mode, the industrial control program module runs the arbitration logic to process multiple actual workpiece temperature readings from the temperature sensor array. Given the complex shape of the workpiece, such as heat dissipation profiles, where the temperature rises unevenly and the curing quality depends on the coldest point, the core of this arbitration logic is to perform a minimum value calculation. In a preferred embodiment, before performing the minimum value calculation, the arbitration logic compares each actual workpiece temperature with a preset effective workpiece temperature threshold, which can be set, for example, to 150. This value is higher than the oven background temperature but lower than the normal curing temperature, and only the actual workpiece temperature, not lower than the effective workpiece temperature threshold, is used in the minimum value calculation. This step effectively eliminates invalid low-temperature interference caused by occasional sensor failure or background readings. The result of this minimum value calculation, i.e., the coldest point temperature of the workpiece cross-section, is determined as the unique process variable by the industrial control program module. The industrial control program module runs a control logic, which in a preferred embodiment is a PID proportional-integral-derivative control logic. Based on the error between the target workpiece temperature and the unique process variable, this PID control logic generates a closed-loop control output through a standard proportional, integral, and derivative operation. This closed-loop control output serves as the final control output signal, which is used by the industrial control program module to adjust... The conveyor chain speed in the coating production line; when the workpiece is under-cured, the process variable is lower than the target temperature, and the error is positive. The output of the PID control logic will automatically reduce the chain speed, extending the residence time of the workpiece in the drying tunnel, and vice versa, so that the curing state of each workpiece approaches its target temperature; when the industrial control program module suspends the closed-loop control logic in open-loop mode, in order to prevent the PID integrator from saturating due to continuous error accumulation, the program will synchronously suspend the integral calculation of the PID control logic, ensuring the smoothness of control mode switching; in addition, to deal with the inevitable gaps on the conveyor chain, the industrial control program module also includes a gap judgment logic; before executing speed adjustment, this logic compares the maximum value of the actual workpiece temperature at multiple locations with a preset effective workpiece temperature threshold, such as 150. The comparison is performed; if even the maximum value is lower than the effective temperature threshold of the workpiece, the industrial control program module determines that the current sensor coverage area is the workpiece gap; at this time, the industrial control program module will suspend the operation of the control logic and the decision logic, and keep the value of the final control output signal unchanged.

[0030] To further improve the responsiveness of the industrial control system, this system can also integrate a feedforward control strategy to overcome the lag of pure feedback control. In one embodiment, the system also includes a heating controller for maintaining the air temperature inside the drying tunnel, such as an independent PID loop controlling the burner; the industrial control program module monitors the control output signal of the heating controller in real time. When a high-heat-capacity workpiece enters the drying tunnel, it causes a sharp increase in heat load, leading to... The signal immediately rises; the industrial control program module calculates the signal's changing characteristics, i.e., its position in the current control cycle. Acquired control output signal Compared with the previous control cycle Acquired control output signal rate of change between ,in and pass it through a preset feedforward gain. Process the data to generate a feedforward control variable. ,in The industrial control module superimposes the feedforward control quantity with the closed-loop control output generated by the PID control logic to form the final control output signal. This allows the speed control logic to anticipate heat load disturbances as soon as the workpiece enters the drying tunnel, enabling early chain speed adjustment and shortening response lag. In another embodiment, the industrial control module can also use information from the speed control loop for feedforward compensation of the heating loop. The system also includes a heating control logic for controlling the heating of the drying tunnel. The industrial control module uses the final control output signal (i.e., the chain speed command) or a converted value based on the final control output signal (e.g., a lower chain speed indicates a higher heat load and a larger feedforward signal) as the feedforward signal and provides this feedforward signal to the heating... The thermal control logic pre-compensates for thermal load disturbances caused by changes in workpiece heat capacity or chain speed adjustments. Finally, to address long-term, systematic control deviations due to sensor contamination or process drift, the industrial control program module may include a self-calibration mechanism. In addition to the control logic, a monitoring logic module runs in parallel. This monitoring logic module performs a long-cycle integral operation on the difference between the target workpiece temperature and the unique process variable to detect whether the error has a persistent non-zero mean deviation. When the result of the long-cycle integral operation exceeds a preset calibration threshold, the monitoring logic module generates a calibration offset and uses this offset to automatically correct the target workpiece temperature used by the control logic.

[0031] Example 1: This example illustrates the specific operation of the technical solution in a particular industrial application scenario. In an industrial control system upgrade project for an aluminum coating production line, a challenging flexible production condition is encountered. This condition requires the continuous mixing and processing of two workpieces with drastically different heat capacities and surface conditions on the same conveyor chain: the first is a thin-walled aluminum single plate (workpiece A) with a wall thickness of only 0.8mm and a high-gloss mirror coating; the second is a heavy-duty industrial aluminum profile (workpiece B) with a substrate thickness of up to 15mm. Workpiece A has extremely low heat capacity and heats up rapidly, but its high-gloss surface greatly interferes with the emissivity of the infrared thermometer, making the readings highly unreliable. Workpiece B has a large heat capacity and heats up slowly, and its I-shaped cross-section causes uneven heating rates between the web and flanges, easily resulting in under-baking at the coldest point. After the first batch of workpieces A is identified by the barcode scanner, the industrial control program module retrieves its process information from the formula lookup table. This information includes a target workpiece temperature of 185°C. A flag representing the control mode is set to open-loop control mode. Based on the judgment logic of this flag, the industrial control program module actively suspends the PID control logic and its integral calculation based on the outlet temperature feedback, and instead extracts a preset open-loop speed value from the recipe, such as a safe speed of 2.2 m / min determined based on offline process calibration. This speed can ensure that workpiece A is neither under-baked nor over-baked. The industrial control program module uses this 2.2 m / min as the final control output signal to drive the conveyor chain frequency converter.

[0032] When the temperature sensing array passes through the gap between workpiece A and workpiece B at the oven tunnel outlet, the actual workpiece temperature at multiple locations acquired by the array is the maximum value among the oven tunnel background temperatures, which is lower than the preset 150°C. When the effective temperature threshold of the workpiece is reached, the gap judgment logic of the industrial control program module is triggered, actively suspending all speed regulation-related decision-making and control logic operations, and maintaining the final control output signal at 2.2 m / min unchanged. This avoids unnecessary violent oscillations in the chain speed caused by the low temperature signal of the workpiece gap in the control system. When the following workpiece B is identified, the industrial control program module obtains its formula information, including the target workpiece temperature of 190°C. And the closed-loop control mode flag; at this time, the industrial control program module activates the closed-loop control logic; workpiece B, as a huge heat load source, enters the drying tunnel, and the control output signal of the heating controller used to maintain the air temperature... A sudden surge; the monitoring logic of the industrial control program module detected this. The rapid positive rate of change is immediately converted into a feedforward control quantity, which is superimposed on the current PID closed-loop control output. This results in the final control output signal proactively reducing the conveyor chain speed, for example, from 2.2 m / min to 1.5 m / min, before workpiece B reaches the outlet. When workpiece B reaches the oven outlet, the industrial control program module obtains the actual workpiece temperature at three locations from the vertically arranged temperature sensor array: upper flange 188.2... Web plate 186.5 Lower flange 186.1 The decision logic of the industrial control program module has three values ​​all exceeding 150. The effective temperature threshold of the workpiece is determined, and the minimum value is calculated from these three readings, resulting in 186.1. The coldest point temperature of the workpiece is used as the sole process variable; the PID control logic of the industrial control program module is based on the target workpiece temperature of 190°C. With the process variable 186.1 The error between the two is used to generate a closed-loop control output. This output, superimposed with the attenuated feedforward control quantity, further reduces the final control output signal, stabilizing the conveyor chain speed at 1.3 m / min. Under the chain speed dynamically optimized by this system, the coldest point temperature at the outlet of subsequent workpiece B is stably maintained at 190°C. It is near the target value.

[0033] Example 2: The test platform was a standard aluminum coating production line, whose drying tunnel had its air temperature stabilized at 200°C by an independent control loop. At the outlet of the drying tunnel, three non-contact infrared thermometers, named S1, S2, and S3, were installed at equal intervals along the vertical direction, with a measurement accuracy of 0.1. Together, they form a temperature sensing array, whose signals are connected to an industrial control system (PLC) running the industrial control program module of this invention. The control output signal of the PLC is connected to the frequency converter (VFD) of the conveyor chain. Two workpieces with different thermal properties and morphologies were selected for the experiment: workpiece A is a 1.0mm thin-walled aluminum plate with low heat capacity, and the target workpiece temperature set in its formula is 190°C. Workpiece B is a 12mm thick C-shaped aluminum profile with high heat capacity and irregular shape. The target workpiece temperature set in its formula is 190°C. The experiment included one sample group and two control groups. Workpieces A and B were mixed and continuously produced in the same batch, and the system state and workpiece temperature were recorded when the workpieces exited the drying tunnel. Control group 1 simulated an existing system that only controlled air temperature; its industrial control program module disabled closed-loop speed regulation logic, and the conveyor chain speed was set to a fixed compromise value of 1.8 m / min. Control group 2 simulated closed-loop control using only single-point temperature measurement; its industrial control program module activated PID control logic, but the only process variable was taken from the reading of the intermediate sensor S2, ignoring S1 and S3. The sample group of this invention adopted the complete scheme of this invention; its industrial control program module activated PID control logic and ran a decision logic, determining that the readings of S1, S2, and S3 were all higher than 150. After the effective temperature threshold of the workpiece is reached, the minimum value calculation is performed, and this minimum value is used as the only process variable. During the test, the industrial control system automatically adjusts or maintains the chain speed, and records and analyzes the workpiece outlet temperature and system status. The test results are compared as follows.

[0034] During the experiment in Example 2, the gap judgment logic of the industrial control program module was constantly running. When the gap between workpiece A and workpiece B passed through the drying tunnel outlet, the system (sample group of this invention) monitored that the readings of S1, S2, and S3 instantly dropped to 110.1. 109.5 108.8 The industrial control program module extracts the maximum value of 110.1 from this set of readings. and compared it with the already labeled 150 Comparison of effective temperature thresholds for workpieces, due to 110.1 Below 150 The industrial control program module determines that there is a gap between the workpieces and actively suspends the calculations of the control logic and the decision logic, maintaining the conveyor chain speed output by the system unchanged until the subsequent workpiece B enters the sensor array, at which point its maximum reading (e.g., 188.9) is reached. (Above 150) Only after the industrial control program module is unsuspended and the closed-loop control logic resumes operation; comparative test results show that: in control group 1, at a fixed chain speed, the system cannot sense the actual temperature of the workpiece, causing the outlet temperature of workpiece A to exceed 210°C. The workpiece was severely over-baked, and the coldest point of workpiece B, namely the S2 reading, was only 172.5. far below 190 The target material was severely under-baked, exhibiting a state of both over-baking and under-baking; although control group 2 used closed-loop speed regulation, its control logic was based solely on the S2 reading. When workpiece B passed, the system accelerated at 173.9... Or 180.1 Adjusting the chain speed to 1.4 m / min was insufficient to bring its coldest point to 190 degrees Celsius. At the same time, this speed is too slow for the flange edges (S1, S3), causing the flange temperature to reach 198.8°C. Localized over-baking occurred, and the control logic could not account for temperature differences at different locations on the workpiece. In this invention's sample unit, the industrial control program module automatically increased the chain speed to approximately 2.5 m / min when processing workpiece A, ensuring it met requirements. When processing workpiece B, its decision logic adjusted the three readings from 188.9... 172.1 With 187.4 In the middle, the minimum value operation was performed, locking 172.1. The root reading is used as the sole process variable. The PID control logic, therefore, receives the error signal indicating severe under-drying at the coldest point and responds by drastically reducing the chain speed from 2.5 m / min for workpiece A to 1.2 m / min. After the system automatically adjusts and stabilizes, the outlet coldest point temperature of subsequent workpiece B stabilizes at 189.4 °C at this chain speed. Meanwhile, the wing temperature is 190.6°C. The system also achieves good control, realizing overall curing quality control for workpieces with complex shapes. The combination of temperature sensing array and decision logic in the industrial control system of this invention establishes a monitoring mechanism at the industrial control system level. This mechanism enables the PID control logic to be unaffected by the complex shape of the workpiece and to focus solely on the coldest temperature that determines the curing quality for closed-loop adjustment. Thus, under dynamic working conditions with multiple varieties and complex shapes, adaptive optimization of curing quality and production efficiency for different workpieces is achieved.

[0035] Example 3: This example combines Figures 1 to 3 This document describes a fully intelligent control system for an environmentally friendly aluminum coating production line, such as... Figure 1 As shown, the system obtains the workpiece type identifier through a host computer or barcode scanner, queries the formula lookup table to obtain the target workpiece temperature and control mode flag, and the control mode arbitration logic makes a judgment based on the flag. In open-loop control mode, the system obtains the preset open-loop speed from the formula information as the control output signal. In closed-loop control mode, the temperature sensor array set at the oven outlet obtains multiple actual workpiece temperatures. The arbitration logic performs a minimum value operation on these temperatures to obtain a unique process variable, the coldest point. The control logic PID generates a closed-loop control output based on the error between the target workpiece temperature and the process variable at the coldest point. In addition, a feedforward control logic can monitor the output signal of the heating controller used to maintain the air temperature in the oven to generate a feedforward control quantity. This feedforward control quantity is superimposed with the closed-loop control output to form the final control output signal, which is used to adjust the conveyor chain speed of the coating production line through the conveyor chain frequency converter.

[0036] like Figure 2 As shown, the horizontal axis represents time in minutes (min), and the vertical axis represents temperature in degrees Celsius (°C). The figure shows a 190 The target temperature is determined by the following: workpiece A represents a workpiece with a smaller heat capacity, which heats up rapidly, reaching the target temperature in 3.0 minutes; while workpiece B represents a workpiece with a larger heat capacity, which heats up more slowly. The system dynamically adjusts the workpiece B to reach the target temperature after 6–7 minutes, and eventually stabilizes at the same target temperature as workpiece A. Figure 3 As shown, the system includes a host computer as an input terminal for recipe management and a barcode scanner for workpiece identification, and an industrial control system PLC / edge controller as the core. The controller runs the industrial control program module of this invention. The controller interacts with the equipment in the drying tunnel, receives the actual workpiece temperature signal from the temperature sensor array at the outlet of the drying tunnel, and outputs control signals to adjust the speed of the conveyor chain including the frequency converter. In addition, the controller can selectively send feedforward signals to the heating controller in the drying tunnel and receive the status information of the heater.

[0037] Example 4: This example illustrates a reproducible engineering procedure for calibrating key gain parameters for two feedforward control logics in an industrial control program module, ensuring that dynamic coordinated control of the system can be realized on a specific production line; this procedure is performed after the basic deployment of the system has been completed, but all feedforward gains are set to zero ( , The procedure is executed in its initial state; the first phase of the procedure is used to determine the feedforward gain of the heating controller output to the speed control logic. This gain is used by the industrial control program module to generate feedforward control quantities based on the changing characteristics of the heating controller's output signal. The system operates stably in closed-loop mode, conveying a workpiece A with a small heat capacity, such as a 1.0mm thin plate. The system automatically optimizes to stabilize the conveyor chain speed at 2.5m / min. At this point, the coldest point temperature at the outlet, i.e., the only process variable, stabilizes at the target value of 190°C. At this point, the calibration program is started in the system, and three workpieces B with high heat capacity, such as 12mm thick profiles, are continuously fed onto the chain. The industrial control program module then... In the case of workpiece B entering the drying tunnel, record the control output signal of the heating controller. Maximum rate of change The minimum value of the unique process variable reached by these three workpieces B at the exit was recorded, and the average under-baking error was -17.7. The calibration program of the industrial control module automatically adjusts the feedforward gain. Set an initial value, such as 0.05, and repeat the above steps of feeding three workpieces B; This enables the G0S_B19 industrial control program module to detect... When the signal is received, that is, before the feedback action of the PID control logic, a feedforward control quantity is generated in advance. This information is then added to the final control output signal to reduce the conveyor chain speed in advance; the system records the average under-drying error at this point, such as -11.5. The calibration procedure increments by a preset step size, such as 0.05. The experiment was repeated until the system detected the minimum average under-baking error. At that time, the average under-baking error was -2.1. ,like If the value is increased further to 0.20, the average under-baking error becomes positive, such as +1.5. Then the system determines To this end, the feedforward gain of the control loop is controlled and this parameter is fixed.

[0038] The second phase of the procedure is used to determine the feedforward gain from the speed regulation logic output to the heating control logic. This refers to the conversion value in the industrial control program module; the system retains the calibrated value. The system operates stably, and the switching test from workpiece A to workpiece B is performed again. The industrial control program module records: when workpiece B enters, and the speed regulation logic reduces the final control output signal from 2.5 m / min to 1.2 m / min, the instantaneous overshoot of the air temperature in the drying tunnel due to the reduced chain speed and extended residence time is approximately +8.5 m / min. The calibration program of the industrial control module activates the speed regulation-heating feedforward logic, which will... Set an initial value, such as 0.2; at this time, the industrial control program module will reduce the chain speed through... This is converted into a feedforward signal, which is provided to the heating control logic to pre-compensate for heat load disturbances, i.e., to actively reduce heating output as the chain speed decreases; the system records that the air temperature overshoot has dropped to +3.1. ; Incremental calibration procedure The experiment was repeated until the air temperature overshoot was suppressed within the target range, such as ±1.0. Inside, the system determines at this time. The value is set to 0.35 and fixed. This parameter calibration process ensures the stability of coordinated operation between the two independent PID loops in the control system, namely the speed regulation loop and the heating loop.

[0039] Example 5: This example illustrates the construction and filling procedure of the formula lookup table in the industrial control program module. This procedure ensures that when the system faces a new workpiece or a new coating system, the target workpiece temperature, control mode flag, and preset open-loop speed value upon which its control logic depends have reproducible engineering basis. The execution environment of the procedure is the production line already deployed in the industrial control system, utilizing the system's data recording function. The first step is to calibrate the target workpiece temperature and the preset open-loop speed value. A batch of representative reference workpieces with known reliable infrared thermometry is selected, such as a matte plate of standard thickness, and calibrated contact thermocouples are fixed at different positions on their surface. The industrial control program module is set to manual mode, and the workpiece is passed through the drying tunnel (air temperature 200°C) at a low fixed chain speed, such as 1.0 m / min. The system records thermocouple data and plots the temperature rise curve of the workpiece body; based on the curing window provided by the coating supplier, such as 190... Hold the temperature for 10 minutes to determine the required curing temperature at the oven outlet. This temperature is then determined by the system and stored in the recipe lookup table as the target workpiece temperature for that type of workpiece, such as 190°C. The system, through multiple experiments, gradually increased the chain speed until it found a point where the exit temperature of the workpiece (measured by a thermocouple) was exactly 190°C. The critical chain speed, such as 1.5 m / min, is determined by the system and stored in the recipe lookup table as the preset open-loop speed value for the workpiece.

[0040] The second step is to calibrate the control mode flag, select a new workpiece to be tested, such as a high-gloss mirror-finish workpiece, and repeat the thermocouple fixing and furnace-passing test in the first step; the system records the actual temperature of the thermocouple, such as 192.5, as the workpiece passes through the exit. Non-contact measurements from temperature sensing arrays, such as 165.3. The industrial control program module automatically compares the deviations between the two; when the absolute value of the deviation is (27.2), the deviation is considered closed. Exceeding a system-preset engineering threshold characterizing sensor reliability, such as 5 When the system determines that the workpiece falls under the condition of unreliable infrared measurement, the industrial control program module automatically sets the control mode flag corresponding to the workpiece type to open-loop control mode in the recipe lookup table; conversely, if the deviation is less than 5... If so, the system will set it to closed-loop control mode.

[0041] Example 6: Before the industrial control system is put into production operation, it is necessary to determine the effective temperature threshold of the workpiece used for workpiece gap judgment and decision logic in the industrial control program module, and heat the drying tunnel to the standard operating temperature of 200°C. The conveyor chain is then allowed to run unloaded, and the industrial control program module continuously monitors the readings of the temperature sensor array, recording the average background temperature under stable conditions, such as 108.5°C. Based on this background temperature value, the system adds a fixed safety margin, such as 40. Therefore, the effective temperature threshold for this workpiece was determined to be 148.5. This parameter is then fixed; the subsequent steps are to verify the system's sensor fault-tolerant logic and the industrial control program module's decision logic. Before performing the minimum value calculation, a pre-processing data validity verification step is included, which compares each actual workpiece temperature with a preset physical valid range, such as 100. Up to 300 For comparison, if the reading is below 100 or higher than 300 The reading was determined to be an invalid signal and was automatically removed from the minimum value calculation for this cycle. During debugging, by simulating the disconnection of sensor S1, the system log showed that the S1 reading was 0. The decision logic automatically rejects it, and only uses the readings of S2 and S3 to perform the minimum value operation, so the control system runs smoothly.

[0042] The PID control logic parameters of the industrial control program module were determined through standard tuning tests in the field of industrial control systems. A standard workpiece, a B-thickness profile, was passed through at an open-loop speed of 1.5 m / min, and the coldest point temperature at its exit was recorded as 182.0 °C. The system switched to closed-loop mode, reducing the target workpiece temperature from 182.0°C. The step size has been increased to 190.0. And only enable proportional control, gradually increase the proportional gain. The system continues until it detects a sustained, constant-amplitude oscillation in the process variable, at which point it records the critical gain. (e.g., 3.2) and oscillation period (e.g., 2.5 minutes), the system will use this as a basis. and The system calculates and fixes the proportional, integral, and derivative parameters of the PID control logic using a built-in tuning algorithm within the industrial control system. Finally, the system sets the parameters of the monitoring logic module, which performs a long-cycle integral operation on the error of the control logic in the industrial control program module. This long cycle is set to a complete production shift, such as 8 hours. The system calculates the average error over these 8 hours, and sets a preset calibration threshold of ±0.5. When the system detects the 8-hour average error, such as +0.7... If the threshold is exceeded, the monitoring logic module will automatically generate a value of -0.1 in the next cycle. The system uses this calibration offset to automatically correct the target workpiece temperature used by the control logic, from 190.0... Revised to 189.9 .

[0043] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A fully intelligent control system for an environmentally friendly aluminum coating production line, characterized in that, The system includes a temperature sensor array located at the outlet of the drying tunnel and an industrial control program module. The industrial control program module is used to: obtain the target workpiece temperature and a flag indicating the control mode based on the current workpiece recipe information; obtain the actual workpiece temperature at multiple locations from the temperature sensor array; determine the control mode flag: if the flag indicates an open-loop control mode, suspend the subsequent closed-loop control logic, obtain a preset open-loop speed value based on the recipe information, and use the preset open-loop speed value as the final control output signal. If the indicator shows closed-loop control mode, the decision logic is executed to perform a minimum value calculation on the actual workpiece temperature at multiple locations. This minimum value is used as the unique process variable. Based on the error between the target workpiece temperature and this unique process variable, a closed-loop control output is generated through the control logic, which is then used as the final control output signal. The final control output signal is used to adjust the conveyor chain speed of the coating production line. The system also includes a heating controller for maintaining the air temperature inside the drying tunnel. The industrial control program module is further used to: monitor the control output signal of the heating controller in real time; generate a feedforward control quantity based on the changing characteristics of the control output signal; and superimpose the feedforward control quantity with the closed-loop control output to form the final control output signal. The industrial control program module generates the feedforward control quantity in the following manner: during the current control cycle... Obtain the control output signal of the heating controller Obtain the control output signal from the previous control cycle. Calculate the rate of change of the control output signal between two control cycles. ,in rate of change Through a preset feedforward gain Processing is performed to generate feedforward control input. ,in .

2. The intelligent control system for the entire process of an environmentally friendly aluminum coating production line according to claim 1, characterized in that, The control logic is a PID control logic. The PID control logic generates a closed-loop control output based on the proportional, integral, and derivative operations of the error. The industrial control program module is also used to suspend the integral operation of the PID control logic simultaneously when the indicator shows open-loop control mode, thus suspending the subsequent closed-loop control logic.

3. The intelligent control system for the entire process of an environmentally friendly aluminum coating production line according to claim 1, characterized in that, The temperature sensing array includes multiple non-contact infrared thermometers, which are arranged in an array along the vertical or horizontal direction at the outlet of the drying tunnel to cover different cross-sectional positions of the workpiece at the outlet of the drying tunnel.

4. The intelligent control system for the entire process of an environmentally friendly aluminum coating production line according to claim 1, characterized in that, The industrial control program module is also used to: obtain the workpiece type identifier from the host computer or barcode scanner, and according to the workpiece type identifier, query and obtain the corresponding target workpiece temperature, the flag characterizing the control mode, and the preset open-loop speed value from the recipe lookup table.

5. The intelligent control system for the entire process of an environmentally friendly aluminum coating production line according to claim 1, characterized in that, The industrial control program module is also used to: compare the maximum value of the actual workpiece temperature at multiple locations with a preset effective workpiece temperature threshold before adjusting the conveyor chain speed of the coating production line. If the maximum value is lower than the effective temperature threshold of the workpiece, it is determined to be a workpiece gap. The industrial control program module suspends the operation of the control logic and the decision logic, and keeps the value of the final control output signal unchanged.

6. The intelligent control system for the entire process of an environmentally friendly aluminum coating production line according to claim 1, characterized in that, The system also includes heating control logic for controlling the heating of the drying tunnel. The industrial control program module is also used to: take the final control output signal or the converted value based on the final control output signal as a feedforward signal and provide the feedforward signal to the heating control logic in advance to compensate for the thermal load disturbance caused by changes in workpiece heat capacity or chain speed adjustment.

7. The intelligent control system for the entire process of an environmentally friendly aluminum coating production line according to claim 1, characterized in that, The industrial control program module is also used to: run a monitoring logic module in parallel with the control logic, the monitoring logic module is used to perform a long-cycle integration operation on the error; when the result of the long-cycle integration operation exceeds the preset calibration threshold, a calibration offset is generated, and the calibration offset is used to automatically correct the target workpiece temperature used by the control logic.

8. The intelligent control system for the entire process of an environmentally friendly aluminum coating production line according to claim 1, characterized in that, The decision logic is also used to: before performing the minimum value operation on the actual workpiece temperature at multiple locations, compare each actual workpiece temperature with a preset effective workpiece temperature threshold, and only use actual workpiece temperatures that are not lower than the effective workpiece temperature threshold to participate in the minimum value operation.

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