Kiln glass liquid level control method and system based on sliding mode control

Abstract

The invention relates to a kiln glass liquid level control method and system based on sliding mode control, the system comprises a liquid level measuring unit, a sliding mode controller and a feeder, and the method comprises the following steps: S1, detecting the actual glass surface height h in a kiln in real time through the liquid level measuring unit, and transmitting the actual glass surface height h to the sliding mode controller; a liquid level height error delta h between the liquid level and a set liquid level height and a derivative thereof are selected as basic variables of the system; s2, designing a sliding mode surface and setting a corresponding reaching law; S4, deducing a control law u of a glass surface according to the sliding mode surface s and the reaching law s'; and S5, based on the control law u, controlling the feeding speed of a feeder into the kiln.

Description

Technical Field

[0001] This invention relates to the field of glass production technology, and specifically to a method and system for controlling the liquid glass level in a kiln based on sliding mold control. Background Technology

[0002] Glass, a crucial material widely used in construction, automotive, electronics, and many other fields, relies heavily on the precision and stability of its production process for product quality. The glass production process begins with mixing various glass raw materials according to a specific formula, which are then transported by a feeding machine to a high-temperature melting furnace. Inside the furnace, the raw materials undergo complex physicochemical reactions, gradually melting into a homogeneous molten glass. The quality of the molten glass largely depends on the process conditions within the furnace, with the stable control of the molten glass level being particularly critical. A stable level not only ensures uniform heating of the molten glass within the furnace and promotes complete chemical reactions, but also has a profound impact on the thickness uniformity, optical properties, and mechanical properties of the glass in subsequent glass forming processes. For example, excessive fluctuations in the molten glass level can lead to defects such as thickness deviations and stress concentration in the glass products, reducing the yield rate.

[0003] In existing technologies, the control methods used by feeding machines during material feeding often reveal numerous limitations when faced with the complex thermal environment inside the melting furnace, changes in raw material properties, and external disturbances. Their control precision is insufficient to meet the stringent requirements of modern glass production for high quality and efficiency, easily causing significant fluctuations in liquid level, which in turn affects the consistency and stability of glass products. Furthermore, traditional control methods have poor adaptability; when production process parameters or operating conditions change, extensive manual adjustments and interventions are required, which not only increases labor costs but also reduces production efficiency. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the technical problem to be solved by the present invention is to provide a method and system for controlling the glass melt level in a furnace based on sliding mode control, which can achieve precise and automatic control of the glass melt level in the furnace and improve the automation level of the glass production process.

[0005] To achieve the above objectives, the present invention provides a method for controlling the glass melt level in a furnace based on sliding mode control. A control system is set up to control the glass melt level in the furnace. The control system includes a level measurement unit, a sliding mode controller, and a feeder. The method for controlling the glass melt level in the furnace includes the following steps:

[0006] S1. The actual glass surface height h in the furnace is detected in real time by the liquid level measurement unit and transmitted to the sliding mold controller; the liquid level height error Δh = h is selected. set -h and its derivative As a fundamental variable of the system, hset To set the liquid level;

[0007] S2, Design the sliding surface Where c is a coefficient;

[0008] S3. Set the corresponding convergence law. Where k1 and k2 are coefficients, k1>0, k2>0, and sign(s) is the sign function, defined as follows:

[0009] S4. Derive the control law u of the glass surface based on the sliding surface s and the reaching law s′: The liquid level height h changes over time. A is the cross-sectional area of ​​the furnace, u is the feeding rate into the furnace, which serves as the control rate of the glass surface control system, q is the furnace discharge rate, and r is the melting rate of the glass raw material, which is related to the glass liquid level height h and time t, r = mh + nt + o, then we have Substituting s′=-k1s-k2sign(s) into the equation, we get...

[0010] S5. Based on the control law u, control the feeding rate of the feeder into the kiln.

[0011] Furthermore, in step S2, c1 and c2 are set, and c2 < c1. During normal operation, when the liquid level error Δh is less than a specific threshold, the coefficient c is set to c1. When the liquid level error Δh is greater than or equal to the specific threshold, the coefficient c is set to c2.

[0012] Furthermore, in step S2, c1 is 5 and c2 is 1.

[0013] Furthermore, in step S3, during initial operation, both coefficients k1 and k2 are set to an initial value. During continuous operation, k1 and k2 are adjusted according to the following method: an adaptive adjustment strategy based on fuzzy logic is used, with the overshoot δ of the liquid level height and the adjustment time t... s and steady-state error e ss These real-time performance metrics serve as inputs for fuzzy control, setting fuzzy adjustment rules and adjusting subsequent coefficients k1 and k2.

[0014] Furthermore, in step S3, the fuzzy adjustment rule includes: setting the overshoot δ and the adjustment time t. s and steady-state error e ss The criteria for judging the magnitude of the overshoot are as follows: when the overshoot δ is large and the settling time t is long... s When δ is large, increase k1; when δ is large and e ss When the value is large, decrease k1 and increase k2.

[0015] This invention also provides a furnace glass liquid level control system based on sliding mode control, used to control the liquid level height of glass liquid in a furnace. The system includes a liquid level measuring unit for detecting the glass level height in the furnace, a feeder for conveying glass liquid into the furnace, and a sliding mode controller. The sliding mode controller is communicatively connected to the liquid level measuring unit and receives the liquid level height signal from the liquid level measuring unit. The sliding mode controller is also connected to the feeder control system to control the feeding action and rate of the feeder. The sliding mode controller includes a storage medium storing a computer program, which, when executed, implements the aforementioned furnace glass liquid level control method.

[0016] Furthermore, the drive unit for the feeding action of the feeder includes a motor and a corresponding motor driver. The sliding mode controller is communicatively connected to the motor driver and outputs a signal to the motor driver, which then drives the motor to operate.

[0017] Furthermore, the liquid level measuring unit includes an image liquid level gauge.

[0018] As described above, the furnace glass liquid level control method and system based on sliding mode control of the present invention has the following beneficial effects:

[0019] 1. It can achieve precise and automatic control of the liquid level of molten glass in the melting furnace, improve the automation level of the glass production process, reduce errors and fluctuations caused by human factors, and thus significantly improve the quality and production efficiency of glass products.

[0020] 2. Employing the sliding mode control principle, in the closed-loop control circuit of the entire system, the feeder changes its feeding state according to the instructions of the sliding mode controller. Its feeding behavior directly affects the liquid level of the molten glass in the melting furnace. The change in liquid level is sensed by the liquid level measurement unit and fed back to the sliding mode controller, forming a continuous and dynamically adjusted control loop. In this way, the system can effectively overcome various internal and external interference factors, accurately control the liquid level of the molten glass within the set range, effectively ensure the stability of the glass production process and the consistency of product quality, and significantly improve the automation level and production efficiency of glass production.

[0021] 3. In the design of the sliding surface, different coefficients can be switched to obtain different sliding surfaces according to the working conditions of the system, so as to realize the flexible switching of the sliding surface and ensure that the system can operate stably and efficiently under different working conditions. Attached Figure Description

[0022] Figure 1 This is a simplified flowchart of the furnace glass liquid level control method based on sliding mode control according to the present invention. Detailed Implementation

[0023] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0024] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, provided they do not affect the effectiveness or purpose of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0025] See Figure 1 This invention provides a method for controlling the glass melt level in a furnace based on sliding mode control. A control system is set up to control the glass melt level inside the furnace. The control system includes a level measurement unit, a sliding mode controller, and a feeder, among other structures. The method for controlling the glass melt level in a furnace includes the following steps:

[0026] S1. The actual glass surface height h in the furnace is detected in real time by the liquid level measurement unit, converted into an electrical signal, and transmitted to the sliding mold controller; the liquid level height error Δh = h is selected. set -h and its derivative As a fundamental variable of the system, h set To set the liquid level height, that is, to control the target value that the liquid level of the glass melt should reach.

[0027] Liquid level height error Δh and its derivative The data directly reflects the deviation in liquid level control and serves as the core basis for control. During data acquisition, high-precision sensors are used to obtain the glass surface height h and these state variables. Advanced filtering algorithms are employed to remove measurement noise, and data normalization is performed to ensure that the data input to the sliding mode controller is accurate, stable, and within a suitable numerical range, laying the foundation for subsequent precise control.

[0028] S2, Design the sliding surface Where c is a coefficient, and an appropriate value can be set according to different working conditions.

[0029] In the sliding surface function, the coefficient *c* is determined based on the system's dynamic characteristics under specific operating conditions. This constant plays a crucial role in subtly adjusting the weighting of the sliding surface on the error and its rate of change, thereby finely regulating the system's dynamic response characteristics. When *c* is large, the system is more sensitive to changes in error and can respond quickly to the trend of error changes, but this may lead to a large overshoot when the system approaches the sliding surface. Conversely, when *c* is small, the system response is relatively smooth, and the overshoot is reduced, but the response speed may be slower. Therefore, in practical applications, the optimal value can be determined through extensive experiments and theoretical analysis based on the specific requirements and characteristics of the system. Preferably, in this embodiment, the coefficients *c* and *k*... μ Different values ​​are selected based on different operating conditions to adapt to varying requirements. Based on actual needs, c1 and c2 are set, with c2 < c1. During normal operation, when the liquid level error Δh is less than a specific threshold, the coefficient c is set to c1, which can be a large value, preferably 5. This stage focuses on fine-tuning the liquid level. When the liquid level error Δh is greater than or equal to the specific threshold, the coefficient c is set to c2, preferably 1, but other suitable values ​​can be selected based on actual conditions. This stage allows for greater adjustment of the liquid level under large deviations, quickly correcting significant errors. By real-time monitoring of the liquid level error and comparison with the threshold, the coefficient c is switched to either c1 or c2, enabling flexible switching of the sliding surface and ensuring stable and efficient system operation under different conditions.

[0030] S3. Set the corresponding convergence law. Where k1 and k2 are coefficients, k1>0, k2>0, and sign(s) is the sign function, defined as follows:

[0031] In the exponential reaching law, k1 primarily determines the rate at which the system state approaches the sliding surface. A larger k1 value will cause the system state to approach the sliding surface at a faster speed, thereby shortening the system's response time, but it may also exacerbate oscillations during the approach process. Conversely, a smaller k1 value will make the approach process slower, reducing the system's response speed. The role of k2 is to effectively mitigate chattering that may occur when the system slides on the sliding surface.

[0032] Since k1>0 and k2>0, when the sliding surface s(h)>0, the approach law applies. The value is negative, thus decreasing s(h). When s(h) < 0 on the sliding surface, the approach law applies. Since the value is positive, the sliding surface s(h) increases, so both cases will cause s(t) to approach 0. When the sliding surface s(h) = 0, we obtain... Then there is ln(cΔh)=-t,cΔh=e-t According to cΔh=e -t As can be seen from the curve, the liquid level height error Δh gradually approaches 0 over time, indicating high error accuracy.

[0033] In the initial state of the control system, coefficients k1 and k2 are both set with initial values ​​as initial start-up parameters. As part of the optimal design, during continuous operation, k1 and k2 are adjusted in the following way: An adaptive adjustment strategy based on fuzzy thrust logic is employed, using the overshoot δ of the liquid level height and the adjustment time t... s and steady-state error e ss These real-time performance metrics serve as inputs to fuzzy control, setting fuzzy adjustment rules and adjusting subsequent coefficients k1 and k2. The overshoot δ refers to the peak liquid level h during the adjustment process. max With the target value h set The difference between the target value h set The percentage of the ratio, i.e., δ = (h max -h set ) / h set *100%. Adjust time t s This refers to the time it takes for the glass melt surface to reach a steady-state value from its initial state. In this embodiment, the target value h is... set 95% of the target steady-state value is taken as the desired steady-state value when the liquid level reaches the target value h. set When the value reaches 95% and the fluctuation is within the allowable error range, i.e., when a steady-state value is reached, the time taken is called the adjustment time t. s Steady-state error e ss This refers to the difference between the actual output and the expected output of the system after it reaches steady state, that is, the difference between the steady-state value and the target value h of the liquid glass surface. set The difference. Fuzzy push logic is a commonly used adjustment strategy for handling uncertain and imprecise information. After setting certain fuzzy adjustment rules, it is based on the input overshoot δ and adjustment time t. s and steady-state error e ss Adjust the subsequent coefficients k1 and k2.

[0034] In this embodiment, preferably, the set fuzzy adjustment rules include: setting an overshoot δ and an adjustment time t. s and steady-state error e ss The criteria for judging the magnitude of the overshoot are as follows: when the overshoot δ is large and the settling time t is long... s When δ is large, increase k1; when δ is large and e ssWhen the overshoot is large, decrease k1 and increase k2. Through fuzzy reasoning and declarative processing, the values ​​of k1 and k2 are adjusted in real time. This adaptive adjustment mechanism enables the sliding mode controller to dynamically optimize the reaching law parameters according to the actual operating conditions, effectively cope with internal and external uncertainties of the system, and always maintain good control performance. The judgment condition for the magnitude of the overshoot δ can be described by a membership function, which describes the degree to which the overshoot δ belongs to the "large" or "small" category. Specifically, the performance index judgment method in existing control system principles can be adopted. By defining a membership function, calculating the membership value, and judging whether the overshoot δ belongs to "large" or "small" based on the membership value, this method quantifies the fuzzy concept through the membership function, helping the computer to automatically judge the magnitude of the overshoot. Adjustment time t s and steady-state error e ss The criteria for judging the magnitude of the parameters can all be set with a threshold. Parameters less than the threshold are judged as small, and parameters greater than or equal to the threshold are judged as large. The overshoot δ and settling time t are given above. s and steady-state error e ss Examples of criteria for judging the magnitude of overshoot, rather than specific limitations: overshoot δ, settling time t s and steady-state error e ss Other suitable methods can also be used to determine the size of the criteria. Furthermore, other methods can also be used for fuzzy adjustment rules.

[0035] S4. Derive the control law u of the glass surface based on the sliding surface s and the reaching law s′:

[0036] Let be the partial derivative matrix of the sliding surface with respect to the state vector h, reflecting the changing relationship between the sliding surface and the system state. In this invention, the liquid level height h changes with time, therefore... A is the cross-sectional area of ​​the furnace, which can be manually set in the sliding mold controller; u is the feeding rate into the furnace, serving as the control rate of the glass surface; q is the output of the furnace, which can be manually set in the sliding mold controller or acquired by a corresponding detection instrument and transmitted to the sliding mold controller; r is the melting rate of the glass raw material, which is related to the glass liquid level height h and time t, and can be expressed as r = mh + nt + o, where m, n, and o are coefficients related to the glass liquid process and can be manually set in the sliding mold controller.

[0037] in This is the general formula for the system state-space equations. The term f(h) represents the inherent dynamic characteristics of the system state h, that is, the rate of change of the system state itself when there is no external input u. It reflects the internal state transition law of the system and is the spontaneous motion trend of the system without external intervention. The term g(h)u represents the influence of the external input u on the system state h, that is, the influence of the external control input on the system state through the corresponding input channel, which determines how the system state will change under control. g(h) can be a function of h, and in some cases it can also be a constant that does not contain h.

[0038] Based on the above formula, we obtain Right now That is, at this point, g(h) is a constant that does not contain h. Substituting s′=-k1s-k2sign(s) into the equation, we can calculate...

[0039] S5. Based on the control law u, control the feeding rate of the feeder into the kiln. In step S4 above, the control law u obtained by solving the above equation can generate a suitable control input in real time according to the current state of the system and the requirements of the sliding surface and the approach law. That is, the required amount of molten glass to be output by the feeder into the kiln is obtained. The sliding surface controller controls the feeder to operate accordingly, so that it outputs the corresponding amount of molten glass, thereby driving the system state to be flexibly and dynamically adjusted under the constraint of the sliding surface.

[0040] This adjustment and control mechanism of the furnace glass liquid level control method enables the control system to quickly and stably track the reference input (i.e., the amount of glass liquid to be output to the furnace), and it has strong robustness to uncertainties in internal system parameters and various external disturbances. For example, when the parameters of some components within the system drift or when there are random disturbances in the external environment, sliding mode control can automatically adjust the control strategy to ensure that the system output still closely tracks the reference input, maintaining system stability and control accuracy.

[0041] This invention also provides a sliding mode control system for controlling the liquid glass level in a furnace. The system includes a liquid level measuring unit for detecting the liquid glass level in the furnace, a feeder for conveying the liquid glass into the furnace, and a sliding mode controller. The sliding mode controller is communicatively connected to the liquid level measuring unit and receives the liquid level signal from the unit. It is also connected to the feeder control system to control the feeder's feeding action and rate. The sliding mode controller includes a storage medium storing a computer program, which, when executed, implements the aforementioned furnace liquid glass level control method.

[0042] In this invention, the liquid level measurement unit is a crucial component for acquiring liquid level information. A high-precision liquid level gauge suitable for the harsh, high-temperature environment of the melting furnace is selected, preferably an image-based liquid level gauge. This gauge continuously captures images of the liquid surface within the melting furnace using a high-definition industrial camera, and the liquid level height is determined based on these images. The liquid level gauge is installed at a specific location within the melting furnace, continuously measuring the liquid level height of the molten glass and converting this physical liquid level information into an electrical signal, which is then transmitted to the sliding mode controller. The accuracy and reliability of this unit are paramount, as it provides the fundamental data source for the entire control system, and its performance directly impacts the precision of subsequent control actions.

[0043] In this invention, the sliding mode controller, as the core control hub of the system, receives the liquid level height electrical signal from the liquid level measurement unit, performs data processing and control strategy calculations, and constructs the sliding surface based on this data. To ensure the real-time performance and stability of the control, the sliding mode controller preferably uses an industrial-grade high-performance processor or programmable logic controller (PLC) to build the hardware platform. This platform has powerful computing capabilities and abundant interface resources, enabling it to quickly and accurately complete complex control algorithm calculations and output control commands to the drive execution unit of the feeding machine.

[0044] In this invention, the feeding machine serves as the terminal equipment directly acting on the conveying of glass raw materials. The feeding machine includes a drive execution unit for performing the feeding action. The drive execution unit includes a motor and a corresponding motor driver. The sliding mold controller is communicatively connected to the motor driver, outputting signals to the motor driver, which then drives the motor to rotate, thereby performing the feeding action. The feeding rate of the feeding machine can be correlated with the motor speed. Based on the control law u, the sliding mold controller controls the motor to rotate at the corresponding speed, thus facilitating accurate control of the feeding rate of the feeding machine.

[0045] The furnace glass liquid level control method and system based on sliding mode control of the present invention have the following beneficial effects:

[0046] 1. It can achieve precise and automatic control of the liquid level of molten glass in the melting furnace, improve the automation level of the glass production process, reduce errors and fluctuations caused by human factors, and thus significantly improve the quality and production efficiency of glass products.

[0047] 2. Employing the sliding mode control principle, in the closed-loop control circuit of the entire system, the feeder changes its feeding state according to the instructions of the sliding mode controller. Its feeding behavior directly affects the liquid level of the molten glass in the melting furnace. The change in liquid level is sensed by the liquid level measurement unit and fed back to the sliding mode controller, forming a continuous and dynamically adjusted control loop. In this way, the system can effectively overcome various internal and external interference factors, accurately control the liquid level of the molten glass within the set range, effectively ensure the stability of the glass production process and the consistency of product quality, and significantly improve the automation level and production efficiency of glass production.

[0048] 3. In the design of the sliding surface, different coefficients can be switched to obtain different sliding surfaces according to the working conditions of the system, so as to realize the flexible switching of the sliding surface and ensure that the system can operate stably and efficiently under different working conditions.

[0049] In summary, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0050] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for controlling the glass melt level in a furnace based on sliding mode control, comprising a control system for controlling the glass melt level in the furnace, the control system including a level measurement unit, a sliding mode controller, and a feeder, characterized in that: The method for controlling the glass liquid level in the furnace includes the following steps: S1. The actual glass surface height h in the furnace is detected in real time by the liquid level measurement unit and transmitted to the sliding mold controller; the liquid level height error Δh = h is selected. set -h and its derivative As a fundamental variable of the system, h set To set the liquid level; S2, Design the sliding surface Where c is the coefficient; S3. Set the corresponding convergence law. Where k1 and k2 are coefficients, k1>0, k2>0, and sign(s) is the sign function, defined as follows: S4. Derive the control law u of the glass surface based on the sliding surface s and the reaching law s′: The liquid level height h changes over time. A is the cross-sectional area of ​​the furnace, u is the feeding rate into the furnace, which serves as the control rate of the glass surface control system, q is the furnace discharge rate, and r is the melting rate of the glass raw material, which is related to the glass liquid level height h and time t, r = mh + nt + o, then we have Substituting s′=-k1s-k2sign(s) into the equation, we get... S5. Based on the control law u, control the feeding rate of the feeder into the kiln.

2. The furnace glass liquid level control method based on sliding mode control according to claim 1, characterized in that: In step S2, c1 and c2 are set, and c2 < c1. During normal operation, when the liquid level error Δh is less than a specific threshold, the coefficient c is set to c1. When the liquid level error Δh is greater than or equal to the specific threshold, the coefficient c is set to c2.

3. The furnace glass liquid level control method based on sliding mode control according to claim 2, characterized in that: In step S2, c1 is 5 and c2 is 1.

4. The furnace glass liquid level control method based on sliding mode control according to claim 1, characterized in that: In step S3, during initial operation, coefficients k1 and k2 are both set to initial values. During continuous operation, k1 and k2 are adjusted according to the following method: an adaptive adjustment strategy based on fuzzy logic is used, with the overshoot δ of the liquid level height and the adjustment time t... s and steady-state error e ss These real-time performance metrics serve as inputs for fuzzy control, setting fuzzy adjustment rules and adjusting subsequent coefficients k1 and k2.

5. The furnace glass liquid level control method based on sliding mode control according to claim 4, characterized in that: In step S3, the fuzzy adjustment rules include: setting the overshoot δ and the adjustment time t. s and steady-state error e ss The criteria for judging the magnitude of the overshoot are as follows: when the overshoot δ is large and the settling time t is long... s When δ is large, increase k1; when δ is large and e ss When the value is large, decrease k1 and increase k2.

6. A sliding mode control system for controlling the liquid glass level in a furnace, comprising a liquid level measuring unit for detecting the liquid glass level in the furnace, a feeder for conveying the liquid glass into the furnace, and a sliding mode controller, wherein the sliding mode controller is communicatively connected to the liquid level measuring unit and receives the liquid level signal from the liquid level measuring unit, and the sliding mode controller is connected to the feeder control system to control the feeding action and rate of the feeder, characterized in that: The sliding mode controller includes a storage medium, and the storage medium stores a computer program that, when executed, implements the furnace glass liquid level control method based on sliding mode control as described in any one of claims 1 to 5.

7. The furnace glass liquid level control system based on sliding mode control according to claim 6, characterized in that: The drive unit for the feeding action of the feeder includes a motor and a corresponding motor driver. The sliding mode controller is communicatively connected to the motor driver and outputs a signal to the motor driver, which then drives the motor to operate.

8. The furnace glass liquid level control system based on sliding mode control according to claim 7, characterized in that: The liquid level measurement unit includes an image liquid level gauge.

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