Production control system for impermeable concrete pipes

Abstract

The present application relates to the technical field of building materials, and discloses a production control system for anti-permeation concrete pipes, comprising a collection module for collecting three groups of temperature data at the upper, middle and lower parts inside a steam curing cover and condensate temperature data, and a data processing module for sequentially running four control units in stages during the curing process, wherein the standing control unit is used to determine whether the steam curing cover is in a thermal equilibrium state, if yes, the temperature control unit is entered, if not, the circulating fan speed is adjusted until the thermal equilibrium state is reached, the temperature control unit calls the optimal steam valve opening to drive the steam valve to increase the temperature, the thermal capacity of each node of the four heat paths is weighted and combined, and is uniformly included in the state equation and the output equation, the optimal valve opening increment sequence is solved in each control cycle, and through rolling optimization and online parameter refreshing, the precision of the whole steam curing process of the anti-permeation concrete pipe is realized.

Description

Technical Field

[0001] This invention relates to the technical field of building materials, specifically to a production control system for impermeable concrete pipes. Background Technology

[0002] Impermeable concrete pipes are used in municipal drainage, water conservancy projects, and sewage treatment. During production, active admixtures such as mineral powder, silica fume, or bentonite are added to enhance the concrete's impermeability, and high-temperature steam oxidation accelerates the hydration reaction. Traditional steam curing processes typically place the pipes in a sealed curing enclosure, creating a warm environment through high-temperature steam.

[0003] In the existing steam curing process of impermeable concrete pipelines, the temperature distribution inside the steam curing hood is uneven, resulting in differences in the hydration reaction rate and degree in different parts of the pipeline. This leads to inconsistent overall impermeability of the pipeline, affecting subsequent safety and reducing its service life. To address this, a production control system for impermeable concrete pipelines is proposed. Summary of the Invention

[0004] Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a production control system for impermeable concrete pipes, which has the advantages of monitoring and adjusting the heat distribution inside the steam curing hood, thus solving the problem of uneven temperature inside the steam curing hood.

[0005] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: a production control system for impermeable concrete pipes, comprising a data acquisition module for acquiring three sets of temperature data (upper, middle, and lower) inside the steam curing hood, as well as condensate temperature data, and receiving product model codes. The system retrieves the corresponding geometric parameters, process parameters, and model basic parameters for the pipe model from a formula database, including: The data processing module is used to sequentially run four control units in stages during the curing process. The static control unit is used to determine whether the steam curing hood is in a state of thermal equilibrium. If so, it enters the heating control unit; if not, it adjusts the speed of the circulating fan until thermal equilibrium is reached. The predictive control module is used for parameter calculation to obtain the residual hydration heat power and the posterior equivalent heat dissipation coefficient after fusion, and based on this, it builds a predictive model to solve for the optimal steam valve opening. The heating control unit calls the optimal steam valve opening to drive the steam valve to heat up. The constant temperature control unit is used to stabilize the temperature at the constant temperature target temperature. The cooling control unit is used to stop heating and control the heat dissipation of the pipeline.

[0006] Preferably, the process of the static control unit determining the thermal equilibrium state includes: receiving real-time acquisition values ​​of three sets of temperature data inside the steam curing hood (upper, middle, and lower) according to a preset analysis period and generating temperature time series for the upper, middle, and lower parts; calculating the maximum vertical temperature difference by taking the average value of each analysis period; if the maximum vertical temperature difference for three consecutive analysis periods does not exceed the preset temperature difference threshold, it is determined that the thermal equilibrium state has been entered, and the heating control unit is executed; otherwise, the circulating fan speed is calculated according to the proportional control algorithm and adjusted to meet the temperature difference condition for three consecutive analysis periods.

[0007] Preferably, the calculation process for the circulating fan speed includes: determining the type of concrete pipe; if it is a standard straight pipe, the actual inner diameter is substituted into the proportional control algorithm formula; if it is a concrete pipe with a sealed bottom and a through hole in the outer wall, the equivalent inner diameter is used instead of the actual inner diameter; the corresponding expressions are as follows:

[0008] Among these steps, the pipe type is identified; if it is a standard diameter pipe with openings at both ends, its actual inner diameter d is calculated. inner =D-2δ, where D represents the pipe's outer diameter and δ is the wall thickness, and this value is used as the pipe diameter parameter d in the proportional gain formula. For pipes with a bottom-sealed design and an open hole in the outer wall, the actual inner diameter d needs to be... inner Replace with equivalent inner diameter d eff Then the equivalent inner diameter d eff As the pipe diameter parameter d in the proportional gain formula,

[0009] For a standard straight pipe, d = d inner For a pipe with a sealed bottom and an open hole in the outer wall, d=d eff K p0 This is the reference gain.

[0010] When the cross-sectional area of ​​the through-hole in the side wall of the concrete pipe is smaller than the cross-sectional area of ​​the top air inlet, the proportional gain is adaptively adjusted by the back pressure compensation coefficient. The corresponding expression is:

[0011] in, This represents the back pressure compensation coefficient. The proportional gain is multiplied by the effective deviation between the current vertical temperature difference and the fan's starting temperature threshold to obtain the speed command. The corresponding expression is:

[0012] Where, n fan This indicates the fan speed command, in revolutions per minute (rpm); K p This represents the proportional gain of the current pipeline, expressed in revolutions per minute (rpm) per degree Celsius (°C); ΔTvert This represents the maximum vertical temperature difference between the upper, middle, and lower sets of temperature sensors; △T th This represents the temperature threshold for starting the fan; in this embodiment, it is set to 4°C.

[0013] Preferably, the parameter calculation process of the predictive control module includes: based on three sets of temperature time series from three consecutive compliance analysis periods, dividing the total average temperature difference between adjacent analysis periods by the analysis duration to obtain the residual temperature rise rate, and multiplying it by the equivalent heat capacity of the current pipeline retrieved from the formula database to calculate the residual hydration heat power; calculating the difference between the comprehensive average temperature of the three sets of temperature time series and the ambient temperature of the workshop to obtain the average temperature difference inside and outside the steam curing hood, and dividing the residual hydration heat power by this temperature difference to obtain the observed equivalent heat dissipation coefficient. The expression corresponding to the prior equivalent heat dissipation coefficient stored in the formula database is as follows:

[0014] Where U0 represents the a priori equivalent heat dissipation coefficient, This indicates the heat dissipation baseline value of the steam curing cover 1 itself, which is determined by experimental calibration. This represents the contribution coefficient of the pipe's outer surface area to heat dissipation, where D represents the pipe's outer diameter and L represents the pipe's length. This represents the current outer surface area of ​​the pipe. The adoption ratio of the prior equivalent heat dissipation coefficient and the observed equivalent heat dissipation coefficient is dynamically adjusted by confidence weights, and the weighted fusion yields the fused posterior equivalent heat dissipation coefficient. The corresponding expression is:

[0015] Where w represents the data confidence weight, △T enu T represents the average temperature difference between the inside and outside of steam curing hood 1; min This represents the minimum temperature difference threshold, which is 2℃ in this embodiment; T max The maximum temperature difference threshold is represented, which is 15℃ in this embodiment; based on the confidence weight w, the confidence weight represents the degree of adoption of the prior equivalent heat dissipation coefficient and the observed equivalent heat dissipation coefficient in the calculation of the final equivalent heat dissipation coefficient.

[0016] Preferably, the process of constructing the prediction model by the prediction control module includes: using the average of three sets of temperature data (upper, middle, and lower) of the steam curing hood and the condensate temperature to form a state vector, the corresponding expression of which is:

[0017] Using the steam regulating valve opening as the sole manipulated variable, and taking the residual hydration heat power and workshop ambient temperature as external disturbance inputs, the state equation and output equation are constructed based on the weighted combination of the heat capacity of each node through four heat paths: steam heating, fan convection, hydration heat release, and ambient heat dissipation.

[0018] Preferably, the state equation mainly consists of five matrices: A1, A2, B, F, and G, as follows:

[0019] Matrix A1 and A2 are determined individually by the scaling factor and the fused posterior equivalent heat dissipation coefficient, with the fused equivalent coefficient refreshed every analysis period. Matrix B is determined by the influence of steam valve opening on the temperature of each node. Matrix F is determined by the residual hydration heat power and workshop ambient temperature. Matrix G is quantitatively determined by the effect of circulating fan speed changes on convective heat transfer at each node. Matrix B, F, and G are all pre-obtained through offline calibration experiments and stored in the formula database. The output equation mainly consists of matrix C, used to extract the upper, middle, and lower temperature groups from the state vector as control targets. The expression of the output equation is:

[0020] Here, vector y(k) represents the output vector, containing the temperatures of the upper, middle, and lower regions. Matrix C represents the output matrix, which is used to select the temperature components to be controlled from x(k). Although the condensate temperature participates in the state evolution calculation and is monitored, it is not included in the control objective and therefore is not in the output vector y(k). Preferably, the process of the predictive control module calculating the scaling factor includes: using the total equivalent heat capacity of the reference pipeline retrieved from the recipe database as a benchmark, comparing the equivalent heat capacity of the current pipeline with the reference pipeline to obtain the scaling factor, multiplying the benchmark heat capacity values ​​of the upper, middle and lower nodes by the scaling factor respectively, and calculating the actual heat capacity adapted to the thermal inertia of the current pipeline.

[0021] Preferably, the predictive control module uses the total average of the three sets of temperature data (upper, middle, and lower) of the current steam curing hood as a starting point, and combines the heating rate retrieved from the formula database with the constant temperature target temperature to generate a reference trajectory. The prediction module uses the weighted sum of the deviation between the future predicted temperature and the reference trajectory, as well as the change in valve action, as the optimization objective to solve for the optimal valve opening increment sequence. The corresponding expression is:

[0022] Where Q represents the tracking error weight matrix; R represents the control action penalty weight matrix; N p N represents the prediction time domain; c This represents the number of valve actions that need to be optimized in the future within the control time domain. The first term aims to make the predicted temperature of the three nodes within a certain number of future cycles as close as possible to the target temperature at the corresponding moment on the reference trajectory; the greater the deviation, the greater the cost. The second term aims to minimize the change in valve opening between adjacent cycles; the more drastic the change, the greater the cost. The predictive control module seeks the valve action sequence that minimizes the total cost.

[0023] Preferably, the heating control unit receives the optimal valve opening increment sequence output by the prediction module to drive the steam regulating valve. When the total average temperature of the three sets of temperature data (upper, middle, and lower) of the steam curing hood enters the allowable deviation of the constant temperature target temperature, the vertical temperature difference meets the standard for three consecutive control cycles, and the condensate temperature does not exceed the limit, the system switches to the constant temperature control unit. After the constant temperature control unit detects that the constant temperature duration has reached the standard, it switches to the cooling stage. The cooling control unit stops the steam supply and maintains the operation of the circulating fan. When the total average temperature of the three sets of temperature data drops to the safe temperature, the curing ends.

[0024] (III) Beneficial Effects Compared with the prior art, the present invention provides a production control system for impermeable concrete pipes, which has the following beneficial effects: 1. This invention actively eliminates the vertical temperature difference within the steam curing hood through a circulating fan proportional control algorithm. The deviation between the current vertical temperature difference and the preset temperature difference threshold is used as a driving signal to adaptively adjust the fan speed, so that the hot air at the top of the hood circulates along the inner cavity of the pipe to the bottom, thereby ensuring uniform temperature within the hood and providing a data basis for subsequent judgment of the thermal balance state. This avoids the problem of inconsistent starting conditions during the heating stage due to excessive initial temperature difference, which affects subsequent control.

[0025] 2. This invention combines the heat capacity of each node in four heat paths—steam heating, fan convection, hydration heat release, and environmental heat dissipation—with weighted summaries and incorporates them into the state equation and output equation. Based on this, the predictive control module uses the reference trajectory as the tracking target and solves for the optimal valve opening increment sequence that satisfies the vertical temperature difference, heating rate, condensate temperature, and valve physical constraints in each control cycle. Through rolling optimization and online parameter refresh, it effectively suppresses frequent valve actions while ensuring temperature tracking accuracy, thus achieving precise steam curing of anti-seepage concrete pipelines throughout the entire process.

[0026] 3. This invention re-identifies the equivalent heat dissipation coefficient and merges it with the prior value at every analysis period to obtain the merged posterior equivalent heat dissipation coefficient, thereby dynamically tracking the real-time changes in the insulation performance of the steam curing hood. At the same time, the reference heat capacity of the three nodes is uniformly corrected by the scaling factor to obtain the actual heat capacity that adapts to the current thermal inertia of the pipeline. This enables the prediction model to automatically identify different pipeline models, reducing the debugging cost and switching time for multi-variety production. Attached Figure Description

[0027] Figure 1 This is a connection diagram of the system modules of the present invention.

[0028] Figure 2 This is a schematic diagram of the steam circulation of the present invention. Figure 1 ; Figure 3This is a schematic diagram of the steam circulation of the present invention. Figure 2 ; In the picture: 1. Steam curing hood; 2. Concrete pipe. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] As attached Figure 1 As shown, this embodiment provides a production control system for impermeable concrete pipes, including a data acquisition module, a data processing module, and a predictive control module, specifically including: The data acquisition module connects to a temperature sensor group and a condensate temperature sensor via an analog input channel. The temperature sensor group is deployed inside the steam curing hood, with at least three groups arranged vertically at the top, middle, and bottom. These sensors collect temperature data at three different heights within the steam curing hood 1 during steam curing of the impermeable concrete pipe 2, providing information on the vertical temperature field distribution within the steam curing hood 1. The condensate temperature sensor collects the temperature data of the condensate gathered during the steam process.

[0031] Before maintenance begins, the data acquisition module obtains the current pipeline model information and retrieves the corresponding process and model parameters, specifically including: The process involves obtaining the product model code of the currently generated pipeline, along with its corresponding geometric parameters, process parameters, and model base parameters. It's important to note that the product model code is obtained by the operator selecting the desired product model code through a human-machine interface (HMI). Based on this code, the system retrieves and loads the corresponding geometric, process, and model base parameters from the formula database. Geometric parameters include the pipeline's outer diameter, length, and wall thickness. Process parameters include the target isothermal temperature, heating rate, cooling rate, and upper limit of condensate temperature. Model base parameters include concrete density, specific heat capacity, equivalent heat capacity, total mass, and hydration decay coefficient. These three parameters are used throughout the entire process, from the static setting stage calculations to the heating stage control, automatically adapting to the differences in thermal characteristics between different pipeline models. The hydration decay coefficient is a characteristic parameter obtained by fitting an exponential decay function to the hydration heat release curve of the concrete used in the current concrete pipeline under laboratory conditions.

[0032] The data processing module includes a static control unit, a heating control unit, a constant temperature control unit, and a cooling control unit. These units are used for the static, heating, constant temperature, and cooling phases of the pipeline steam curing process, respectively. Specifically, they include: The static control unit presets an analysis period, which is set to 10 minutes in this embodiment. At the start of curing, the static phase begins. The static control unit processes temperature data from three elevations within the analysis period to determine whether to enter the heating phase, specifically including: The system receives real-time data from three sets of temperature sensors within the steam curing hood 1, generating upper, middle, and lower temperature time series respectively. It calculates the average of these three temperature time series within the current analysis period to assess the maximum vertical temperature difference between different locations. If the maximum vertical temperature difference within all three analysis periods is less than or equal to a preset temperature difference threshold, the steam curing hood 1 enters a thermal equilibrium state, triggering the temperature rise module and predictive control module. If the maximum vertical temperature difference exceeds the preset temperature difference threshold, the circulating fan speed is calculated using a proportional control algorithm based on the temperature difference deviation value until the maximum vertical temperature difference within the three analysis periods is less than or equal to the preset temperature difference threshold, at which point the system determines that a thermal equilibrium state has been reached. The calculation process for the circulating fan speed is as follows: Identify the type of pipe. If it is a standard diameter pipe with openings at both ends, calculate its actual inner diameter d. inner =D-2δ, where D represents the pipe's outer diameter and δ is the wall thickness, and this value is used as the pipe diameter parameter d in the proportional gain formula. For pipes with a bottom-sealed design and an open hole in the outer wall, the actual inner diameter d needs to be... inner Replace with equivalent inner diameter d eff Then the equivalent inner diameter d eff As the pipe diameter parameter d in the proportional gain formula, to account for the influence of the inner diameter of the concrete pipe 2 and the cross-sectional area of ​​the side wall through-hole on the airflow capacity, the expression for the equivalent inner diameter is:

[0033] Among them, A side This is the sum of the cross-sectional areas of all through holes on the two side walls of the concrete pipe; When the cross-sectional area of ​​the through-hole on the second side wall of the concrete pipe is not less than the cross-sectional area of ​​the top air inlet, the exhaust is unobstructed, and the proportional gain K is calculated based on the equivalent inner diameter. p The specific calculation formula is as follows:

[0034] For a standard straight pipe, d = d inner For a pipe with a sealed bottom and an open hole in the outer wall, d=d eff K p0As the reference gain, d ref For the reference pipe's inner diameter: In this embodiment, the reference gain K p0 The setup is as follows: the reference pipe is placed inside the steam curing hood 1. After establishing a stable initial vertical temperature difference during the static stage, the speed of the circulating fan is gradually increased until the temperature difference converges to the allowable range. Multiple sets of temperature difference-stable speed data are recorded, and the ratio coefficient of temperature difference to speed is obtained by least squares fitting. If the cross-sectional area of ​​the through-hole on the second side wall of the concrete pipe is smaller than the cross-sectional area of ​​the top air inlet, the back pressure compensation coefficient needs to be multiplied in the formula. The proportional gain K is calculated. p The expression is:

[0035] in, The back pressure compensation coefficient is represented, and in this embodiment, its value ranges from [1.15, 1.25]. The specific value is estimated linearly based on the ratio of the area of ​​the through-hole in the side wall of the concrete pipe 2 to the area of ​​the air inlet; the smaller the area ratio, the greater the compensation magnitude. Finally, based on the calculated proportional gain K... p The speed of the circulating fan is determined by the following formula:

[0036] Where, n fan This indicates the rotational speed of the circulating fan, in revolutions per minute (rpm); K p This represents the proportional gain of the current pipeline, expressed in revolutions per minute (rpm) per degree Celsius (°C); ΔT vert This represents the maximum vertical temperature difference between the upper, middle, and lower sets of temperature sensors; △T th The temperature threshold for fan startup is represented; in this embodiment, it is set to 4°C. The proportional gain K in the expression... p The adjustment is adaptive based on the actual inner diameter of the concrete pipe 2. For example... Figure 2 As shown, the circulating fan draws hot steam from the top of the steam curing hood 1 through the hollow of the concrete pipe 2. For a standard straight pipe open at both ends, the hot steam axially penetrates the pipe cavity to the other end, flows into the lower space outside the pipe, and finally returns to the top of the steam curing hood 1, forming an axial circulation loop; as shown... Figure 3 As shown, for a concrete pipe 2 with a sealed bottom and at least two through holes on its outer wall, a circulating fan delivers air into the pipe cavity from the top opening. The hot air flows down the pipe cavity, turns back after reaching the sealed bottom, and exits through the through holes on the side wall of the pipe into the lower space of the steam curing hood 1. It mixes with the hot air inside the hood and naturally rises to the top, thus forming a circulation. When the standard deviation and the maximum vertical temperature difference remain stable within their respective preset temperature difference thresholds for three consecutive analysis periods, it is determined that the temperature field inside the steam curing hood 1 has reached the standard and is in thermal equilibrium. Then, the heating control unit and predictive control module are executed.

[0037] The predictive control module calculates the residual hydration heat power and the posterior equivalent heat dissipation coefficient after fusion sequentially based on three analysis periods under thermal equilibrium conditions. It then adaptively initializes the matrix parameters of the MPC prediction model using a scaling factor obtained from the formula database. Specifically, this includes: Based on three analysis periods under the compliant thermal equilibrium state, all temperature values ​​within the three temperature time series included in any analysis period are summed and divided by three times the total number of collection times within that analysis period to obtain the total average temperature for that analysis period. The total average temperature for each of the three consecutive compliant analysis periods is then calculated to obtain three total average temperatures. The total average temperature of the second compliant analysis period is subtracted from the total average temperature of the third compliant analysis period to obtain the temperature change between adjacent periods. If the temperature change is negative, the absolute value is taken. The temperature change is then divided by the analysis period duration to obtain the residual temperature rise rate, representing the magnitude of the increase in average temperature due to the concrete's own hydration reaction within the analysis period. Finally, the residual temperature rise rate is multiplied by the equivalent heat capacity of concrete pipe 2 to obtain the residual hydration heat power. The residual hydration heat power reflects the weak heat power continuously released by the hydration reaction of concrete pipe 2 at the end of the static stage. This is used as a feedforward term of the internal heat source input to the MPC prediction model, enabling the predictive control module to actively deduct the contribution of concrete self-heating when calculating the steam valve opening, thereby reducing excess steam. The equivalent heat capacity of concrete pipe 2 is calculated online based on the total mass and specific heat capacity of the pipe in the formula database to obtain the equivalent heat capacity of the current pipe. In this embodiment, multiple data collections are performed at preset fixed time intervals within each analysis period. The time of each data collection is defined as a data collection time. An analysis period contains several sampling times.

[0038] Based on the residual heat of hydration, the equivalent heat dissipation coefficient of the steam curing hood 1 is calculated, providing accurate heat dissipation parameters for the subsequent MPC prediction model. Specifically, this includes: Based on the three analysis periods under the compliant thermal equilibrium state, the total average temperature of the three analysis periods is calculated respectively. The three values ​​are added together and divided by three to obtain the comprehensive average temperature. Then, the average temperature is subtracted from the ambient temperature of the workshop to obtain the average temperature difference inside and outside the steam curing hood 1. Finally, the calculated residual hydration heat power is divided by this average temperature difference to obtain the observed equivalent heat dissipation coefficient based on the real-time data of the current concrete pipe 2. The corresponding expression is as follows:

[0039] Among them, U obs p represents the observed equivalent heat dissipation coefficient of the current batch of real-time data; hyd Represents residual hydration heat power; ΔT envThis represents the average temperature difference between the inside and outside of the steam curing hood 1. However, during the static stage, the temperature difference between the inside and outside of the hood is not significant. Relying solely on the observed equivalent heat dissipation coefficient calculated at this time results in a low signal-to-noise ratio. To improve the robustness of the extrapolation results, a priori equivalent heat dissipation coefficient is used, and its corresponding expression is as follows:

[0040] Where U0 represents the a priori equivalent heat dissipation coefficient, This indicates the heat dissipation baseline value of the steam curing cover 1 itself, which is determined by experimental calibration. This represents the contribution coefficient of the pipe's outer surface area to heat dissipation, where D represents the pipe's outer diameter and L represents the pipe's length. This represents the current outer surface area of ​​the pipe, where the heat dissipation base value of the steam curing hood 1 is included. The basis for this calculation is as follows: The air heat capacity inside the steam curing hood 1 is obtained by multiplying the air volume by the air density and then by the air specific heat capacity. This air heat capacity is then multiplied by an empirical coefficient to obtain the equivalent heat capacity encompassing the heat storage effect of the insulation layer of the steam curing hood 1. In this embodiment, the empirical coefficient is greater than one, and the specific value is determined by back-calculation based on the insulation layer material and metal structure of the steam curing hood 1 during the empty hood calibration experiment. In this embodiment, the value is 1.3. A linear segment on the natural cooling curve of the empty hood is selected, and the cooling rate is obtained by dividing the temperature drop within this segment by the time span. The equivalent heat capacity is multiplied by the cooling rate to obtain the heat loss power during this period. Finally, the heat loss power is divided by the average temperature difference between the inside and outside of the hood during this period to obtain the heat dissipation baseline value of the steam curing hood 1 itself. The calculated a priori equivalent heat dissipation coefficient is stored in the formula database and bound to this type of concrete pipe for subsequent use in the production of the same type of pipe.

[0041] Based on the prior equivalent heat dissipation coefficient, the adoption ratio of the prior equivalent heat dissipation coefficient and the observed equivalent heat dissipation coefficient is dynamically adjusted by a confidence weight. This confidence weight is determined by the average temperature difference between the inside and outside of the steam curing hood 1. The corresponding expression is as follows:

[0042] Where w represents the data confidence weight, △T enu T represents the average temperature difference between the inside and outside of steam curing hood 1; min This represents the minimum temperature difference threshold, which is 2℃ in this embodiment; T maxThe maximum temperature difference threshold is represented by a value of 15℃ in this embodiment. Based on the confidence weight w, which characterizes the degree to which the prior equivalent heat dissipation coefficient and the observed equivalent heat dissipation coefficient are adopted in calculating the final equivalent heat dissipation coefficient, specifically, the weight is zero when the average temperature difference is below the minimum temperature difference threshold, and the prior equivalent heat dissipation coefficient is adopted; the weight is one when the average temperature difference is above the maximum temperature difference threshold, and the observed equivalent heat dissipation coefficient is adopted. A weighted average of the prior equivalent heat dissipation coefficient and the observed equivalent heat dissipation coefficient is performed to obtain the fused posterior equivalent heat dissipation coefficient, which reflects the true change in the thermal insulation performance of the steam curing hood 1. The corresponding expression is:

[0043] Where U represents the fused posterior equivalent heat dissipation coefficient; the fused posterior equivalent heat dissipation coefficient is input into the subsequent MPC prediction model to make the modeling of the heat dissipation term correspond to the current insulation level.

[0044] During the heating phase, to achieve precise predictive control of the steam valve opening, the predictive control module constructs an MPC predictive model reflecting the steam curing hood 1. Specifically, this includes: When determining the structure of the prediction model, the prediction model uses the temperatures of three temperature measuring points deployed at the top, middle, and bottom of the steam curing hood 1, along with the condensate temperature, to form a state vector. The corresponding expression is:

[0045] Where k represents the control cycle index, T up (k), T mid (k), T low (k) represents the temperature at three temperature measuring points at the top, middle, and bottom of the steam curing hood 1, respectively, T coud (k) represents the condensate temperature; before the prediction model runs, the initial state value is determined; the prediction control module extracts the mean of three temperature time series for each of the last compliant analysis period based on the compliant thermal equilibrium state, and simultaneously takes the mean of the condensate temperature time series for that analysis period. These four values ​​together constitute the initial state vector of MPC, serving as the current state starting point of the prediction model during the heating stage. This reflects the initial temperature distribution of concrete pipe 2 at the start of steam curing.

[0046] The only manipulated variable of the predictive control module is the opening percentage of the steam regulating valve, denoted as μ. valve (k), Meanwhile, two external inputs that cannot be directly controlled but will continuously affect temperature changes are included in the prediction model: the residual heat of hydration P, which gradually decays exponentially during the heating phase. hyd (t) and the average temperature difference T between the inside and outside of the steam curing hood 1 env Specifically, the residual heat of hydration is updated periodically according to an exponential decay law, as expressed below:

[0047] Where, p hyd (k) represents the real-time residual hydration heat power of the concrete during the k-th control cycle; P hyd0 This represents the initial value of the residual hydration heat power calculated during the settling stage; This represents the hydration attenuation coefficient corresponding to this type of pipe in the formula database; T s This represents the duration of the control cycle. After each control cycle, the residual hydration heat power at the current moment is recalculated, and the updated value is input as the internal heat source feedforward term into the perturbation vector of the prediction model. The fused posterior equivalent heat dissipation coefficient also needs to be re-identified every analysis period to obtain the updated equivalent heat dissipation coefficient and replace the old value in the prediction model. In this embodiment, based on external inputs and manipulated variables, the following four heat paths act on each node. The prediction model extrapolates the flow of four heat streams: the first stream is the heat directly injected into the steam curing hood 1 after the steam valve is opened; the second stream is the forced convection heat transfer formed inside and outside the pipe when the circulating fan is running; the third stream is the continuous heat release from the hydration reaction of the concrete itself; and the fourth stream is the heat lost to the workshop environment through the wall of the steam curing hood 1 and the surface of the concrete pipe 2. These four heat paths act simultaneously on the upper, middle, and lower regions and the condensate node, jointly determining the rate of temperature rise and fall at each location. The four heat paths are weighted and combined according to the heat capacity of each node, and a state equation and a vector equation are updated in each control cycle. In this embodiment, the duration T of a single control cycle is... s Set to 30 seconds; the corresponding expression is as follows:

[0048]

[0049] The state equation describes how the temperature of each node evolves from the previous control cycle to the next. Vector x(k) represents the temperature state of the four nodes in the k-th cycle, while x(k+1) is the temperature predicted by the model for the next cycle. The state equation consists of five matrices. Matrix A1, determined by the scaling factor, represents the internal heat transfer between the four nodes due to temperature differences under no heat loss conditions; the thicker the pipe, the slower the temperature change reflected by matrix A1. Matrix A2, determined by the fused posterior equivalent heat dissipation coefficient U, describes the rate at which each node loses heat to the workshop environment and is refreshed every analysis period as the equivalent heat dissipation coefficient is updated. Matrix B describes the impact of changes in steam valve opening on the temperature of each node. Variable μ... valve(k) represents the percentage of steam valve opening actively adjusted by the predictive control module. Matrix F is the disturbance matrix, describing the magnitude of the impact of uncontrolled external factors on each node; vector d(k) is the disturbance vector, representing the two external inputs: residual hydration heat power and workshop ambient temperature in the current cycle. Matrix G describes the quantitative impact of circulating fan speed changes on convective heat transfer at each node. Its setting is based on the fact that the circulating fan forces airflow circulation within the steam curing hood during operation, producing varying degrees of convective heat transfer effects on each node. This physical relationship is obtained through offline calibration experiments. Under fixed circulating fan speed conditions, temperature change data at each node are recorded, and a quantitative relationship between circulating fan speed and the temperature rise rate at each node is fitted. n fan (k) represents the fan speed in the current control cycle. The output equation is responsible for extracting the target value of the predictive control module from the complete state vector. Vector y(k) represents the output vector, containing the temperatures of the upper, middle, and lower regions. Matrix C represents the output matrix, which is used to filter out the temperature components to be controlled from x(k). Although the condensate temperature participates in the state evolution calculation and is monitored, it is not included in the control target and therefore is not in the output vector y(k). The specific values ​​of matrices A1 and A2 are independently determined by the scaling factor and the fused posterior equivalent heat dissipation coefficient, respectively; the coefficients of matrices B, F, and G are obtained in advance through offline calibration experiments and fixed in the formula database, and are directly called during online operation.

[0050] The scaling factor is used to correct for differences in the thermal inertia of concrete pipe 2 in the prediction model. Different types of pipes have different equivalent heat capacities due to differences in outer diameter, wall thickness, and length. To quantify this difference, the equivalent heat capacity of the reference concrete pipe 2 is used as a benchmark, and the equivalent heat capacity of the current concrete pipe 2 is compared with it. That is, the equivalent heat capacity of the current concrete pipe 2 is divided by the equivalent heat capacity of the reference concrete pipe 2. The resulting scaling factor is denoted as the benchmark value of the scaling factor, and the corresponding expression is as follows:

[0051] in, The base value for the scaling factor, C ref The total equivalent heat capacity of the reference pipe is represented by C, obtained through experimental calibration. pie This represents the equivalent heat capacity of the current concrete pipe 2. The prediction model multiplies the baseline heat capacity values ​​corresponding to the upper, middle, and lower nodes of the pipe by a scaling factor based on different pipe sizes to obtain the actual heat capacity of the current pipe. The corresponding expression is:

[0052] Among them, C up，0 C mid，0 C low，0The reference heat capacity values ​​of the three nodes are represented by the heating experiment recording the actual temperature rise curve of the reference concrete pipe 2, and then the heat capacity values ​​of the three nodes are repeatedly adjusted by the simulation model until the simulated temperature rise curve completely coincides with the actual curve. The three values ​​determined at this time are the calibrated node heat storage capacity.

[0053] At the beginning of each control cycle, an average temperature is calculated from the current actual values ​​of the upper, middle, and lower temperature groups, serving as the starting point of the curve. Then, using the heating rate corresponding to this type of pipeline in the formula database as the slope, a smoothly rising slope is plotted from the starting point towards the constant temperature target temperature. This slope defines the temperature change trend of the three nodes over several future sampling times; this slope is the reference trajectory. Based on the reference trajectory, an optimal set of steam valve opening adjustments is found for each control cycle to minimize the deviation between the predicted temperature of the three nodes and the target temperature at the corresponding time on the reference trajectory over a future period. The corresponding expression is as follows:

[0054] Where Q represents the tracking error weight matrix; R represents the control action penalty weight matrix; i represents the step index in the prediction time domain; j represents the step index in the control time domain; N p N represents the number of cycles for predicting future temperature output; c Indicates the number of future valve opening changes; △μ valve (k+j) represents the change in valve opening in the j-th future control cycle; y(k+i|k) represents the temperature vectors of the upper, middle, and lower measuring points predicted for the i-th future cycle under the current control cycle k; and r(k+i) represents the target temperature vector of the reference trajectory at the corresponding time. The first term aims to make the predicted temperature of the three nodes within several future cycles as close as possible to the target temperature on the reference trajectory at the corresponding time; the greater the deviation, the greater the cost. The second term aims to minimize the change in valve opening between adjacent cycles; the more drastic the change, the greater the cost. The predictive control module seeks the valve action sequence that minimizes the total cost. Simultaneously, the predictive control module must adhere to five hard constraints: valve opening not exceeding physical limits, action rate not exceeding mechanical tolerance, vertical temperature difference between the three nodes always less than a preset temperature difference threshold, heating rate not exceeding the upper limit specified in the formula, and condensate temperature always below the safety threshold. In this embodiment, the control cycle is 30 seconds, with the specific value determined by the implementer. After obtaining the optimal valve opening percentage, the predictive control module converts this value into a current signal and sends it to the heating control unit to control the steam valve during the heating process to reach the corresponding opening position, thereby accurately controlling the steam flow rate entering the steam curing hood.

[0055] The temperature control unit receives the numerical value from the predictive control module and converts it into a current signal for temperature control. When the average temperature of the three sets of sensors first enters the constant temperature target temperature and the deviation from the target temperature is less than the set allowable range, the unit does not immediately switch phases. Instead, it further checks the stability of the vertical temperature difference, requiring that the temperature difference between any two of the upper, middle, and lower sets of sensors remain stable within a preset temperature difference threshold for three consecutive control cycles. Simultaneously, it confirms that the condensate temperature never exceeds the safety threshold throughout the process. Only when these three conditions are simultaneously met and remain stable for the specified number of control cycles does the temperature control unit determine that the temperature rise phase has officially ended and the constant temperature phase needs to begin, thus executing the constant temperature control unit. In this embodiment, the allowable range is 1.5℃ to 3.0℃; the safety threshold is 60℃ to 80℃.

[0056] The constant temperature control unit reads the circulating fan speed based on the constant temperature target value and updates the hydration heat power exponentially. Then, it solves for the optimal valve increment under all constraints and executes the calculation. Simultaneously, it updates the equivalent heat dissipation coefficient and refreshes matrix A every analysis period. Once the constant temperature duration reaches the target, the control unit switches to the cooling phase. During the cooling phase, no more steam heat is supplied to the steam curing hood 1; instead, slow natural cooling is used. The circulating fan continues to run at low speed, transferring internal heat from higher-temperature areas to lower-temperature areas. The curing process ends when the average temperature of the three nodes naturally drops to the safe temperature in the formula database, as detected by the cooling control unit. The operator can then remove the steam curing hood 1 and proceed to the next process. In this embodiment, the safe temperature is set between 40°C and 50°C.

[0057] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A production control system for impermeable concrete pipes, comprising a data acquisition module for acquiring three sets of temperature data (upper, middle, and lower) inside the steam curing hood, as well as condensate temperature data, and receiving product model codes; retrieving the corresponding geometric parameters, process parameters, and model foundation parameters of the pipe model from a formula database; characterized in that... Also includes: The data processing module is used to sequentially run four control units in stages during the curing process, including a static control unit, a heating control unit, a constant temperature control unit, and a cooling control unit. The static control unit is used to determine whether the steam curing hood is in a state of thermal equilibrium. If so, it enters the heating control unit; if not, it adjusts the speed of the circulating fan until thermal equilibrium is reached. The heating control unit calls the optimal steam valve opening to drive the steam valve to heat up. The constant temperature control unit is used to maintain the temperature stably at the constant temperature target temperature. The cooling control unit is used to stop heating and control the heat dissipation of the pipeline.

2. Predictive control module, used for parameter estimation, to obtain residual hydration heat power and fused posterior equivalent heat dissipation coefficient, and based on this, to build a predictive model to solve for the optimal steam valve opening.

3. The production control system for impermeable concrete pipes according to claim 1, characterized in that: The process by which the static control unit determines the thermal equilibrium state includes: The system receives real-time temperature data from the upper, middle, and lower parts of the steam curing hood during preset analysis periods and generates temperature time series for the upper, middle, and lower parts. The average value of each analysis period is used to calculate the maximum vertical temperature difference. If the maximum vertical temperature difference for three consecutive analysis periods does not exceed the preset temperature difference threshold, the system is determined to be in thermal equilibrium and the heating control unit is activated. Otherwise, the circulating fan speed is calculated using a proportional control algorithm and adjusted to meet the temperature difference condition for three consecutive analysis periods.

4. The production control system for impermeable concrete pipes according to claim 2, characterized in that: The calculation process for the circulating fan speed includes: To determine the type of concrete pipe, if it is a standard straight pipe, the actual inner diameter is substituted into the proportional control algorithm formula. If it is a concrete pipe with a sealed bottom and a through hole on the outer wall, the equivalent inner diameter is used instead of the actual inner diameter. When the cross-sectional area of ​​the through hole on the side wall of the concrete pipe is smaller than the cross-sectional area of ​​the top air inlet, the proportional gain is adaptively adjusted through the back pressure compensation coefficient. The proportional gain is multiplied by the effective deviation between the current vertical temperature difference and the temperature threshold for fan startup to obtain the circulating fan speed.

5. The production control system for impermeable concrete pipes according to claim 3, characterized in that: The process of parameter calculation for the predictive control module includes: Based on three temperature time series from three consecutive compliance analysis periods, the residual temperature rise rate is obtained by dividing the total average temperature difference between adjacent analysis periods by the analysis duration, and then multiplied by the equivalent heat capacity of the current pipeline retrieved from the formula database to calculate the residual hydration heat power. The average temperature difference between the inside and outside of the steam curing hood is calculated by the difference between the comprehensive average temperature of the three temperature time series and the ambient temperature of the workshop, and the residual hydration heat power is divided by this temperature difference to obtain the observed equivalent heat dissipation coefficient. The prior equivalent heat dissipation coefficient stored in the formula database is dynamically adjusted by confidence weights to determine the adoption ratio of the prior equivalent heat dissipation coefficient and the observed equivalent heat dissipation coefficient, and then weighted and fused to obtain the fused posterior equivalent heat dissipation coefficient.

6. The production control system for impermeable concrete pipes according to claim 4, characterized in that: The process of constructing the prediction model by the prediction control module includes: The state vector is constructed using the average of three sets of temperature data (upper, middle, and lower) of the steam curing hood and the condensate temperature. The steam regulating valve opening is the only manipulated variable. The residual hydration heat power and the workshop ambient temperature are used as external disturbance inputs. Based on the four heat paths of steam heating, fan convection, hydration heat release, and ambient heat dissipation, the state equation and output equation are constructed by weighted combination of the heat capacity of each node.

7. The production control system for impermeable concrete pipes according to claim 5, characterized in that: The state equation consists of five matrices: A1, A2, B, F, and G. Matrices A1 and A2 are determined individually by the scaling factor and the fused posterior equivalent heat dissipation coefficient, and the fused equivalent coefficient is refreshed every analysis period. Matrix B is determined by the degree of influence of the steam valve opening on the temperature of each node. Matrix F is determined by the residual hydration heat power and the workshop ambient temperature. Matrix G is determined by the quantitative determination of the convective heat transfer of each node by the change in the speed of the circulating fan. Matrices B, F, and G are all obtained in advance through offline calibration experiments and fixed in the formula database. The output equation consists of matrix C, which is used to extract the upper, middle, and lower three sets of temperatures from the state vector as control targets.

8. The production control system for impermeable concrete pipes according to claim 6, characterized in that: The process by which the predictive control module calculates the scaling factor includes: Using the total equivalent heat capacity of the reference pipeline retrieved from the recipe database as a benchmark, the equivalent heat capacity of the current pipeline is compared with that to obtain a scaling factor. The benchmark heat capacity values ​​of the upper, middle, and lower nodes are multiplied by this scaling factor to calculate the actual heat capacity that adapts to the thermal inertia of the current pipeline.

9. The production control system for impermeable concrete pipes according to claim 7, characterized in that: The predictive control module takes the total average of the three sets of temperature data (upper, middle, and lower) of the current steam curing hood as the starting point, and generates a reference trajectory by combining the heating rate retrieved from the formula database with the constant temperature target temperature. The prediction module uses the weighted sum of the deviation between the future predicted temperature and the reference trajectory and the change in valve action as the optimization objective to solve for the optimal valve opening increment sequence.

10. The production control system for impermeable concrete pipes according to claim 8, characterized in that: The heating control unit receives the optimal valve opening increment sequence output by the prediction module to drive the steam regulating valve. When the total average temperature of the three sets of temperature data (upper, middle, and lower) of the steam curing hood enters the allowable deviation of the constant temperature target temperature, the vertical temperature difference meets the standard for three consecutive control cycles, and the condensate temperature does not exceed the limit, it switches to the constant temperature control unit. After the constant temperature control unit detects that the constant temperature time has reached the standard, it switches to the cooling stage. The cooling control unit stops the steam supply and maintains the operation of the circulating fan. When the total average temperature of the three sets of temperature data drops to the safe temperature, the curing ends.

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