A real-time monitoring and control system for temperature difference between inner and outer walls of a bent pipe

Abstract

The present application relates to the technical field of pipe bending processing, and discloses a system for real-time monitoring and controlling temperature difference between inner and outer walls of a bent pipe, comprising an outer wall temperature real-time monitoring module, an inner wall temperature real-time monitoring module, a data real-time transmission module, a data processing module and an execution module, wherein the inner wall temperature real-time monitoring module adopts a temperature measuring trolley loaded with a non-contact miniature infrared temperature measuring probe, the data processing module calculates the temperature difference ΔT between the inner and outer walls in real time and compares it with a preset threshold ΔTmax, and an asymmetric decoupling control algorithm is built in the data processing module, according to the determination results of inner wall overheating or outer wall overheating, the pushing speed of the oil cylinder, the medium-frequency heating power, the cooling water flow rate of the induction coil and the air cooling air volume are respectively adjusted in a closed loop in a coordinated manner, so that the temperature difference is controlled within a safety threshold. The present application realizes multivariable adaptive decoupling control, can effectively avoid defects such as wrinkles, bulges on the inner side of the bent pipe and tensile cracking and thinning on the outer side, and significantly improves the product forming quality and production safety.

Description

Technical Field

[0001] This invention relates to the fields of pipe bending processing and automated industrial control technology, specifically to an intelligent control system for fully automatic real-time monitoring, online analysis, and multi-parameter closed-loop linkage control of the temperature difference between the inner and outer walls of pipes during the processing of large-diameter, thick-walled, large-angle medium-frequency pipe bending. Background Technology

[0002] Medium-frequency induction pipe bending machines are core equipment for heavy-duty bending of large pipelines (such as oil and gas pipelines and high-pressure steam pipelines for power plants). In the process of using a medium-frequency induction coil to locally heat the pipeline and then using a hydraulic cylinder to drive the bending, the deformation mechanism of the fibers in each layer inside the pipeline is extremely complex.

[0003] For example, invention patent (CN101539459A) discloses a temperature detection and control system for a medium-frequency hydraulic pipe bending machine, which addresses the problem of temperature difference changes between the inner and outer arcs during the pipe bending process affecting the bending process. The proposed solution is to monitor the temperature of the inner and outer arcs during the bending process and adjust the distance between the induction coil and the steel pipe to ensure that the temperature difference between the inner and outer arcs is within a set range.

[0004] However, practical manufacturing experience shows that the temperature distribution and real-time temperature difference control of the inner and outer walls of the pipe are equally decisive factors in determining the quality of the final product. If the temperature difference between the inner and outer walls exceeds the process standards required by the material, it can easily lead to serious product defects: when the inner wall temperature is too high or the outer wall temperature difference is too large, it will cause a significant decrease in the yield strength of the material on the inner side of the bend, and under the action of propulsion force, macroscopic geometric defects such as local wrinkling, bulging, or excessive ellipticity and waviness will easily occur on the inner side of the pipe; conversely, if the outer wall temperature is too high, under bending tensile stress, it is easy to cause excessive thinning of the outer wall, microcrack initiation, or even macroscopic tensile cracking, resulting in a serious over-limit of wall thickness reduction and scrapping.

[0005] To avoid the aforementioned quality defects, strict real-time monitoring and intervention of the temperature difference between the inner and outer walls during the pipe bending process are essential. However, traditional temperature measurement methods mostly rely on manual handheld infrared thermometers for intermittent measurements outside the equipment. Since medium-frequency pipe bending operations involve high-temperature radiation of several hundred degrees Celsius, strong electromagnetic interference, and cooling vapors, manual monitoring faces significant safety hazards. Furthermore, due to slow reaction times and low sampling frequencies, real-time continuous monitoring is difficult to achieve. In addition, while manual temperature measurement can be partially implemented when bending pipes at small angles, it is completely obstructed by the bending and deformation of the pipe as it extends deeper, making it impossible to detect the temperature at processing points deep within the pipe wall.

[0006] Although the inventor had previously applied for a utility model patent (CN219776915U) entitled "A Device for Monitoring the Inner Wall Temperature of Medium-Frequency Pipe Bending," which disclosed a hardware structure for measuring the temperature inside a pipe using a trolley carrying a contact thermometer, this existing technology still has significant limitations in industrial applications. Firstly, the movement of the trolley relies on an independent remote control or manual button control. The trolley's movement and the progress of the main cylinder of the pipe bending machine are logically and spatially disconnected, making it impossible to guarantee that the trolley probe always accurately corresponds to the external heating and bending point, easily resulting in spatial blind spots where the temperature measurement position is lagging or ahead. Secondly, the device only has a single temperature data display function (transmitting data to a monitor for workers to view), essentially remaining a "passive measuring instrument" and unable to achieve closed-loop linkage with the pipe bending machine's control system. When the temperature difference between the inner and outer walls changes abruptly or exceeds the standard, it is still necessary to rely on the on-site operators to manually adjust the power of the medium frequency power supply, the speed of the hydraulic cylinder, the air volume of the air cooling system, or the flow rate of the cooling water in the induction coil based on their personal experience. The response time is usually as long as tens of seconds or even minutes. Often, before the adjustment takes effect, the pipeline has already suffered irreversible bulging or cracking defects.

[0007] Furthermore, there is a strong coupling among industrial variables affecting the temperature difference between the inner and outer walls of medium-frequency induction heating pipes. These variables include the cylinder propulsion speed, medium-frequency heating current and voltage, external wall cooling airflow, and water cooling flow rate within the induction coil. Adjusting a single parameter often triggers a chain reaction in other variables. Therefore, the industry urgently needs an intelligent closed-loop control system capable of precise spatial temperature measurement, intelligent data analysis, and fully automatic decoupled linkage adjustment of multiple variables to address temperature differences exceeding limits in different directions. Summary of the Invention

[0008] This invention aims to solve the technical problems in existing medium-frequency induction bending pipe processing, such as the difficulty in accurately and continuously monitoring the temperature difference between the inner and outer walls, the spatial blind spots in internal temperature measurement of large-angle bends, and the harsh and inefficient manual temperature measurement environment. More importantly, it aims to address the fundamental technical pain point in existing technologies where temperature measurement data is disconnected from the processing equipment control system, making it unable to handle strongly coupled process variables, thus leading to quality defects such as wrinkling, bulging, excessive thinning, and cracking in the bent pipes. This invention provides a spatially responsive, dynamically decoupled multi-parameter closed-loop real-time monitoring and control system.

[0009] To achieve the above objectives, the present invention provides a real-time monitoring and control system for the temperature difference between the inner and outer walls of a bend, the core architecture of which includes: a real-time monitoring module for the outer wall temperature, a real-time monitoring module for the inner wall temperature, a real-time data transmission module, a data processing module, and an execution module; The real-time external wall temperature monitoring module is located behind the external induction coil of the pipe. It uses an infrared temperature sensor to collect the continuous temperature signal of the heated outer wall of the pipe in real time. The real-time internal wall temperature monitoring module includes a movable temperature measuring trolley installed inside the pipe, equipped with a miniature infrared temperature probe. The motion control logic of this trolley is strictly bound to the encoder pulse of the main propulsion cylinder of the pipe bending machine, realizing the follow-up mapping of axial spatial position and collecting the internal wall temperature at the position corresponding to the outer wall processing point in real time. The real-time data transmission module uses an industrial-grade wireless communication protocol (such as 2.4GHz) to transmit the outer wall temperature and inner wall temperature data to the data processing module in real time and synchronously at a frame rate of no less than 1Hz. The data processing module uses a central PLC controller to calculate the absolute value of the real-time temperature difference between the inner and outer walls. ΔT and compare it with the preset process safety threshold. ΔTmax Perform continuous comparisons; The execution module includes a real-time control module for the cylinder propulsion speed (connected to a proportional servo valve), a real-time control module for the medium-frequency heating power (connected to the main control terminal of the medium-frequency power supply), a real-time control module for the water flow rate in the induction coil (connected to an electric flow regulating valve), and a real-time control module for the air volume (connected to the frequency converter of the cooling fan). The data processing module incorporates an asymmetric closed-loop decoupling linkage control algorithm. When the temperature difference exceeds the standard ( ΔT>Δ Tmax When the inner wall or outer wall is overheated, the hydraulic cylinder propulsion speed, medium frequency power, cooling water speed and air volume are dynamically adjusted according to the different physical properties of the overheating, so as to bring the temperature difference between the inner and outer walls back to the safe range with the fastest response speed.

[0010] Compared with the prior art, the present invention has the following significant technical advancements and beneficial effects: By logically binding the cylinder encoder pulses with the trolley stepper drive motor, the blindness of traditional manual remote control of the trolley is eliminated, and perfect spatial follow-up of processing progress and temperature measurement position is achieved; every time the cylinder pushes forward, the trolley automatically follows and aligns, completely eliminating the spatial blind zone for temperature measurement of the inner wall of large-angle, long-distance bends.

[0011] This invention transcends the stage of "simple instrument measurement" by seamlessly integrating the temperature measuring carriage into the core control loop of the entire pipe bending machine, establishing an intelligent decoupled linkage closed loop for multiple process variables. The PLC can call different asymmetric control strategies to address the two completely different defect formation mechanisms of "inner wall overheating" and "outer wall overheating," and coordinately fine-tune the push speed, power, water cooling, and air cooling, achieving adaptive decoupling of strongly coupled variables, and significantly shortening the response time compared to traditional adjustment methods.

[0012] By using millisecond-level early warning and precise intervention for temperature differences, stubborn process defects such as inner wrinkling, local bulging, excessive ovality, and outer tearing and thinning caused by excessive temperature differences can be completely eliminated, significantly improving product molding quality and pass rate.

[0013] The fully closed-loop automated operation completely keeps front-line operators away from the harsh radiation environment of high temperature, strong magnetic field, high pressure and water vapor, realizing intelligent and inherently safe production, greatly improving production safety and reducing labor intensity. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the overall structure of a medium-frequency pipe bending machine; Figure 2 This is the overall control logic diagram of the system described in this invention; Figure 3 This is a schematic diagram showing the linkage between the temperature measuring trolley and the hydraulic cylinder's propulsion distance.

[0015] The following are the labels in the diagram: 1. Hydraulic cylinder; 2. Clamping mechanism; 3. Intermediate frequency coil mechanism; 4. Rocker arm; 5. Temperature measuring carriage. Detailed Implementation

[0016] To enable those skilled in the art to better understand and implement the technical solution of the present invention, the operating mechanism and implementation steps of the present invention will be described in detail below with reference to typical embodiments and control parameters in actual production.

[0017] Example: Figure 1 As shown, the medium-frequency pipe bending machine used in this invention mainly includes a hydraulic cylinder 1, a clamping mechanism 2, a medium-frequency coil mechanism 3, and a rocker arm 4. The clamping mechanism 2 is mounted on a horizontally movable railcar and is pushed by the hydraulic cylinder 1 to move horizontally along the railcar. The clamping mechanism 2 clamps and fixes the tail end of the pipe. The front end of the pipe is fixed by the chuck of the rocker arm 4. The rocker arm 4 rotates around its central axis. Under the combined action of the continuous pushing of the hydraulic cylinder 1 and the rotational constraint of the rocker arm 4, the high-temperature plastic section of the pipe undergoes plastic bending along the set radius of the rocker arm. The induction coil is located at the outlet position of the medium-frequency coil mechanism 3, and the heating zone on the outer wall of the pipe is located at the axial position of the induction coil.

[0018] The invention patent (CN101539459A) discloses a temperature detection and control system for a medium-frequency hydraulic pipe bending machine, which solves the problem of temperature difference between the inner and outer arcs in the pipe bending process by detecting the temperatures at points a and b. This invention, however, addresses the problem of controlling the temperature difference between points d and d' inside the pipe and points c and c' outside the pipe, as shown in the diagram.

[0019] This embodiment is applied to a heavy-duty medium-frequency pipe bending unit for processing high-pressure alloy steel pipes for power plants with an outer diameter of 508mm and a wall thickness of 25mm. For example... Figure 2 As shown, the overall control logic of the system described in this invention includes a real-time outer wall temperature monitoring module and a real-time inner wall temperature monitoring module, which respectively collect the outer wall temperature. Tout and inner wall temperature Tin The data is transmitted to the data processing module (PLC) via the real-time data transmission module, and the PLC calculates the absolute value of the temperature difference. ΔTand with preset threshold ΔTmax After comparison, the corresponding process parameter adjustment instructions are output to the execution modules (cylinder propulsion speed control module, medium frequency heating power control module, water flow rate control module in induction coil and real-time air volume control module) through the asymmetric closed-loop linkage control algorithm, forming a full closed-loop control loop with temperature difference as the feedback quantity.

[0020] For monitoring the external wall temperature, a high-precision fixed infrared temperature sensor is mounted on a rigid bracket outside the induction coil of the pipe bending machine. Its optical lens focuses on the centerline 75mm behind the heated wire on the outer wall of the pipe. This sensor has a 4-20mA standard analog output interface and is directly connected to the analog input module of the PLC in the main control cabinet via a shielded cable. The acquisition frequency is set to 1Hz, and the measured external wall temperature value is output in real time. Tout .

[0021] For monitoring the internal wall temperature, a wireless intelligent temperature measurement vehicle 5 powered by a built-in high-capacity lithium battery pack is used. The chassis of the temperature measurement vehicle is equipped with two sets of high-temperature resistant running wheels independently driven by high-precision stepper motors, and integrates a miniature rotary encoder to realize closed-loop vehicle displacement feedback.

[0022] A miniature non-contact infrared temperature probe is mounted on the top of the temperature measurement cart via a shock-absorbing spring support frame. The probe's optical field of view is focused on the top of the inner wall of the pipe. The core control board inside the cart is connected to a 2.4GHz industrial-grade wireless communication transceiver module. The outer surface of the cart is wrapped with a ceramic fiber heat insulation protective layer to ensure its continuous and stable operation in the high-temperature airflow inside the pipe, ranging from 300°C to 500°C.

[0023] On the pipe bending machine's propulsion mechanism, a high-resolution industrial rotary encoder is coaxially mounted at the tail of the piston rod of the main hydraulic cylinder. With each forward step of the piston rod, the encoder synchronously outputs a pulse signal of a certain proportion. The core processing unit inside the main control cabinet uses a Siemens S7-1500 series industrial-grade programmable logic controller (PLC). This PLC is expanded with a wireless communication gateway module, specifically designed to establish a high-speed, bidirectional industrial wireless link with the temperature measurement trolley inside the pipe.

[0024] The specific connection relationships of the digital transformation of the pipe bending machine actuator are shown in Table 1: Hydraulic cylinder propulsion speed control module High-precision proportional servo valve 4-20mA analog current Hydraulic oil flow rate and thrust speed of main cylinder Medium frequency heating power control module Medium frequency power inverter trigger board 0-10V analog voltage Heating current, voltage and output power Water flow rate control module within the induction coil Electric sleeve regulating valve Modbus-RTU bus commands Volumetric flow rate of cooling water circuit Real-time air volume control module High-power fan frequency converter 4-20mA analog current Fan speed and air volume of pipe cooling During the bending process of a medium-frequency induction coil, the position of the external medium-frequency induction coil remains relatively fixed in space, while the pipe continuously passes forward through the induction coil and bends under the push of the hydraulic cylinder. Therefore, in order to ensure that the internal temperature measuring carriage is always aligned with the external induction coil heating band, the carriage must adopt a reverse follow-up synchronous stepping motion within the pipe cavity.

[0025] like Figure 3As shown, the axial displacement of the temperature measuring trolley 5 inside the pipe maintains a strict follow-up mapping relationship with the advancing distance of the hydraulic cylinder 1. The hydraulic cylinder 1 advances one set step... δL The temperature measuring cart 5 moves precisely along the inside of the pipe in the opposite direction by the corresponding mapped distance. δx ( δx = δL This ensures that the miniature infrared temperature probe mounted on the trolley is always axially aligned with the heating area of ​​the outer wall induction coil, thereby eliminating the spatial blind spot for inner wall temperature measurement during large-angle pipe bending.

[0026] In this embodiment of the invention, the PLC calculates the current absolute thrust displacement ΔL of the hydraulic cylinder in real time by counting the number of pulses input from the rotary encoder of the main hydraulic cylinder. cylinder In this process, the trigger step size is set to δL = 100 ext{mm}. The control timing of the servo mapping mechanism is as follows: When the pipe bending machine starts, the piston rod of the hydraulic cylinder moves forward, and the PLC accumulates the displacement. When the displacement increment is detected to reach 100mm, the PLC immediately sends an action command packet to the temperature measuring trolley inside the pipe through the 2.4GHz wireless gateway. The command includes the target forward stroke δx=100ext{mm}.

[0027] After receiving the command packet, the temperature measuring trolley immediately drives the trolley to move precisely 100mm deeper into the pipe (i.e., against the direction of the hydraulic cylinder's thrust) according to the preset acceleration curve. The miniature encoder inside the trolley performs closed-loop verification of the movement distance, with the error controlled within ±0.5mm.

[0028] Once the trolley is in position, it immediately sends a "position confirmation" flag signal back to the PLC via the wireless module.

[0029] Upon receiving the arrival confirmation signal, the PLC immediately starts a 3-second static dwell timer. During these 3 seconds, the vehicle remains completely stationary, and its miniature infrared sensor continuously reads 150 inner wall temperature data points at an internal sampling rate of 50Hz. The vehicle's microprocessor removes the largest and smallest abrupt changes and performs an arithmetic average on the remaining data to obtain the precise inner wall temperature data Tin for the current cross-section.

[0030] The trolley packages the calculated Tin data, attaches a tag with the current mileage, and transmits it back to the PLC via a wireless link. After the transmission is complete, the trolley remains stationary and waits until the cylinder displacement accumulates to increase by another 100mm, at which point the above cycle is repeated.

[0031] Asymmetric closed-loop linkage control algorithm and adjustment example: After the PLC receives Tout and Tin aligned at the same spatial cross-section, it calculates the current real-time absolute value of the temperature difference ΔT = |Tin - Tout|. Based on the material characteristics of the high-pressure alloy steel pipe, the upper limit threshold of the allowable temperature difference ΔT is preset on the touch screen. max =15^\circ ext{C}.

[0032] The initial reference machining process parameters of the system are set as follows: initial value of cylinder propulsion speed V0=12ext{mm / s}, initial value of medium frequency heating power P0=80ext{kW}, initial value of induction coil cooling water flow velocity W0=1.5ext{m / s}, and initial operating frequency of air-cooled fan inverter F0=30ext{Hz}.

[0033] Process Adjustment Example A: Intervention in the Overheated State of the Inner Wall When the bending process reaches the fourth servo temperature measurement point, the outer wall infrared sensor transmits a temperature of Tout = 490°C, while the inner wall temperature transmitted by the servo carriage inside the pipe reaches Tin = 522°C.

[0034] Algorithm diagnosis: At this point, the calculated real-time temperature difference ΔT = |522 - 490| = 32^(-C) > 15^(-C), and satisfies Tin > Tout. The system confirms that the pipeline is in a state of severe internal overheating. Without intervention, the low yield strength of the inner wall will easily lead to severe bulging and wrinkling defects on the inner side under the propulsion force.

[0035] Linkage adjustment steps: The PLC's built-in inner wall cooling closed-loop algorithm is activated. Due to the strong coupling of various process variables, the PLC performs multi-channel dynamic decoupling output: 1) Reduce propulsion speed: Output a 4-20mA current signal to the proportional servo valve to reduce the cylinder propulsion speed by 5% from the initial 12mm / s to 11.4mm / s, so as to reduce the axial extrusion deformation rate of the high-heat inner wall.

[0036] 2) Reduce heating power: Send an analog control signal to the intermediate frequency power supply to reduce the heating power by 5% from 80kW to 76kW, thereby suppressing the deep conduction of heat to the inner wall from the source.

[0037] 3) Enhance external air cooling: Output adjustment signal to the fan inverter to significantly increase its operating frequency from the initial 30Hz to 35Hz in one go. By drastically increasing the external cold air flow, the reference temperature of the outer wall is forcibly lowered, and the heat of the inner wall is indirectly extracted by utilizing the thermal conduction effect of the steel itself.

[0038] 4) Water cooling to maintain the original state: Keep the flow rate of cooling water in the induction coil constant at 1.5m / s to prevent the cooling water from drawing away too much heat from the induction coil, causing the outer wall temperature to drop too quickly.

[0039] Stabilization Delay: After the command is issued, the PLC starts a 4-second stabilization delay timer. During this period, temperature difference comparison is disabled, allowing the hydraulic proportional valve, frequency converter, and thermal field to undergo physical transition. After 4 seconds, the delay ends, and the system rereads the temperature. At this time, Tout = 482°C, Tin = 494°C, and the absolute value of the temperature difference drops to 12°C ≤ 15°C, reaching the acceptable range.

[0040] The system stops parameter correction and continues to steadily advance while maintaining the current optimized combination of process parameters.

[0041] Process Adjustment Example B: Intervention in the Overheating State of the External Wall When the bending process reaches a large angle (the stroke is close to 800mm), the uneven electromagnetic induction caused by the local deformation of the pipe wall during bending results in the outer infrared sensor transmitting Tout=535^\circ ext{C} and the inner follow-up carriage transmitting Tin=502^\circext{C}.

[0042] Algorithm diagnosis: At this point, the calculated real-time temperature difference ΔT = |502 - 535| = 33^(-15°C) > 15^(-15°C) and satisfies Tout > Tin. The system confirms that the pipeline is in a state of severe overheating of the outer wall. At this time, the outer wall material is weakened, and under strong bending tensile stress, it is very easy to cause the outer wall to thin drastically beyond the standard or even crack.

[0043] Linkage adjustment steps: The PLC's built-in external wall cooling algorithm is immediately activated, performing asymmetric targeted parameter decoupling adjustments: 1) Enhanced induction coil water cooling: The PLC sends a valve opening increase command to the electric sleeve regulating valve through the Modbus-RTU bus, which increases the volume flow rate of cooling water in the induction coil, increasing the water flow velocity from 1.5m / s to 1.8m / s (the valve opening increases by about 8%), forcibly reducing the temperature of the induction coil itself, and significantly reducing the share of radiation and conduction heat from the induction coil to the outer wall surface of the pipe.

[0044] 2) Increase propulsion speed: Output incremental current signal to the hydraulic proportional servo valve to appropriately increase the propulsion speed of the cylinder by 3% from the current reference speed, shorten the residence time of the outer wall of the pipeline in the high heat radiation zone of the induction coil, and achieve physical "evasion".

[0045] 3) Fine-tuning of heating power and air cooling: The medium-frequency heating power remains unchanged for the time being, and the frequency of the air-cooled inverter remains unchanged to avoid large-scale changes that may cause thermal field oscillations.

[0046] Stabilization Delay: A physical transition delay of 4 seconds was also performed on the actuator. After the delay, the temperature was re-sampled. The data showed that the outer wall temperature was successfully suppressed to 510°C, and the inner wall temperature was slightly adjusted to 498°C due to the increased pushing speed. At this time, the latest absolute value of the temperature difference was reduced to 12°C, successfully returning to the process safety threshold range, effectively avoiding defects such as outer wall cracking and excessive thinning rate.

[0047] The intelligent system of this invention is also designed with a comprehensive intrinsic safety protection loop. During the actual processing, if a sudden hardware failure occurs, the system can achieve millisecond-level safety protection. For example, when the pipe is bent to a large angle of 85°, the signal from the wireless antenna at the pipe opening may experience multipath fading or be completely blocked due to the severe bending of the pipe. The PLC may fail to receive the temperature data packets sent by the inner wall temperature measuring cart for five consecutive cycles (5 seconds), triggering the wireless communication link timeout protection.

[0048] At this moment, the PLC's internal abnormal safety protection module instantly cuts off the output, and the red-spot buzzer on the main control cabinet emits a high-frequency audible and visual alarm. Simultaneously, within 10 milliseconds, the PLC's digital output module sends a power-off signal to the high-frequency solenoid valve of the hydraulic system's main oil inlet circuit, causing the main propulsion cylinder to instantly depressurize and stop propulsion; synchronously, it sends a trip signal to the main circuit breaker of the intermediate frequency power supply, completely shutting off the intermediate frequency heating power, putting the entire pipe bending unit into a safe emergency shutdown and locking state. A prompt appears on the screen: "Internal wall wireless node communication interrupted, please check." This fundamentally eliminates the possibility of blindly processing under temperature-measuring "blind" conditions, which could lead to the scrapping of the entire expensive pipe or major equipment accidents, ensuring safe production on the industrial site.

[0049] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other implementations obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A real-time monitoring and control system for the temperature difference between the inner and outer walls of a bent pipe, characterized in that: It includes a real-time external wall temperature monitoring module, a real-time internal wall temperature monitoring module, a real-time data transmission module, a data processing module, and an execution module; The real-time external wall temperature monitoring module is located downstream of the heating zone of the outer wall of the pipe being processed, and is used to collect the outer wall temperature data of the pipe in real time. The real-time internal wall temperature monitoring module includes a temperature measuring trolley that can move bidirectionally along the inner wall of the pipe. The temperature measuring trolley is equipped with a non-contact miniature infrared temperature measuring probe. The movement step of the temperature measuring trolley is controlled by the real-time displacement feedback of the hydraulic cylinder propulsion mechanism of the pipe bending machine, so that the axial position of the temperature measuring trolley inside the pipe and the external bending processing point maintain a dynamic spatial tracking mapping, which is used to collect the internal wall temperature data of the corresponding position in real time. The real-time data transmission module connects the real-time outer wall temperature monitoring module and the real-time inner wall temperature monitoring module, and is used to synchronously send the outer wall temperature data and the inner wall temperature data to the data processing module at a preset frequency through a wireless communication protocol. The data processing module receives the outer wall temperature data and the inner wall temperature data and calculates the absolute value of the current temperature difference between the inner and outer walls in real time. ΔT The absolute value of the temperature difference is determined through a built-in linkage control algorithm. ΔT With respect to the preset allowable temperature difference upper limit threshold ΔTmax The comparison is performed, and process parameter adjustment instructions are output in real time based on the comparison results and the temperature relationship between the inner and outer walls. The execution module includes a real-time control module for the cylinder propulsion speed, a real-time control module for the medium-frequency heating power, a real-time control module for the water flow velocity within the induction coil, and a real-time control module for the air volume. The execution module receives process parameter adjustment commands output by the data processing module, based on the absolute value of the temperature difference between the inner and outer walls. ΔT As a closed-loop feedback quantity, the cylinder feed speed, medium-frequency heating power supply, induction coil cooling water flow rate, and air-cooled air volume of the pipe bending machine are coordinated and adjusted to control the temperature difference between the inner and outer walls within the preset allowable upper limit threshold. ΔTmax Within.

2. The real-time monitoring and control system for the temperature difference between the inner and outer walls of a bent pipe according to claim 1, characterized in that: The hydraulic cylinder propulsion mechanism is equipped with a rotary encoder or displacement sensor for real-time detection of the hydraulic cylinder propulsion distance, and is electrically connected to the data processing module. The data processing module accumulates the number of pulses from the rotary encoder in real time to calculate the actual thrust displacement of the hydraulic cylinder. ΔLcylinder ; When the actual propulsion displacement ΔLcylinder Each increment of the set step value δL At the same time, the data processing module generates a corresponding follow-up axial displacement command and sends it to the drive motor of the temperature measuring trolley via a wireless module, controlling the temperature measuring trolley to move synchronously into the pipeline a corresponding mapped distance. δx ,in δx=δL .

3. The real-time monitoring and control system for the temperature difference between the inner and outer walls of a bent pipe according to claim 2, characterized in that: After the temperature measuring trolley moves to the corresponding position, the data processing module triggers a dwell timer to control the temperature measuring trolley to remain stationary at the current position for 2 to 5 seconds. During this dwell period, the miniature infrared temperature probe continuously collects multiple sets of inner wall temperature data and takes the average value as the inner wall temperature data of the current position and sends it back. After the data collection is completed, the temperature measuring trolley remains stationary at the current position until the cylinder advances a distance that triggers the next movement command.

4. The real-time monitoring and control system for the temperature difference between the inner and outer walls of a bent pipe according to claim 1, characterized in that: The data processing module has a built-in asymmetric decoupling control algorithm. When the data processing module determines that the current temperature difference between the inner and outer walls meets the requirements... Tin> Tout+ΔTmax When the internal wall is determined to be in an overheated state, the data processing module executes the following internal wall cooling decoupling linkage strategy: 1) The real-time control module for controlling the cylinder's thrust speed reduces the cylinder's thrust speed; 2) Control the real-time control module of the medium-frequency heating power to reduce the heating power of the medium-frequency power supply; 3) The real-time air volume control module is controlled to increase the air cooling volume, thereby increasing the external air cooling intensity of the pipeline by increasing the output frequency of the fan inverter.

5. The real-time monitoring and control system for the temperature difference between the inner and outer walls of a bent pipe according to claim 1, characterized in that: When the data processing module determines that the current temperature difference between the inner and outer walls meets the requirements Tout>Tin+ΔTmax When the outer wall is determined to be in an overheated state, the data processing module executes the following outer wall cooling decoupling linkage strategy: 1) The real-time control module for controlling the water flow rate inside the induction coil increases the flow rate of cooling water inside the induction coil and increases the cooling water flow rate by adjusting the opening of the electric regulating valve, so as to accelerate the cooling of the induction coil adjacent to the outer wall. 2) The real-time control module for controlling the cylinder's propulsion speed increases the cylinder's propulsion speed to shorten the local radiative heating time of the high-temperature induction coil on the outer wall of the pipe.

6. The real-time monitoring and control system for the temperature difference between the inner and outer walls of a bent pipe according to claim 1, characterized in that: The data processing module uses an industrial-grade programmable logic controller (PLC) with a built-in proportional-integral-derivative (PID) closed-loop control algorithm. The output of the process parameter adjustment command has a preset stable delay period of 3 to 5 seconds, which is used to wait for the execution module to complete its action and for the heat conduction state of the pipeline to stabilize before the data processing module enters the next round of temperature difference comparison and adjustment cycle.

7. The real-time monitoring and control system for the temperature difference between the inner and outer walls of a bent pipe according to claim 1, characterized in that: The real-time data transmission module adopts a 2.4GHz industrial-grade wireless communication protocol, and its data transmission frame rate is not less than 1Hz; the real-time external wall temperature monitoring module adopts a fixed infrared temperature sensor, and its temperature probe is fixed on the outside of the induction coil of the pipe bending machine and aligned with the heating area of ​​the external wall.

8. The real-time monitoring and control system for the temperature difference between the inner and outer walls of a bent pipe according to claim 1, characterized in that, It also includes an anomaly protection module electrically connected to the data processing module, used to execute the following security protection logic: When the data processing module detects that the wireless communication interruption link of the temperature measuring trolley has timed out for more than 5 seconds, or the signal of the real-time monitoring module for the outer wall temperature is lost, or any of the execution modules reports an overload fault, the data processing module immediately outputs a trigger audible and visual alarm signal and issues an emergency cut-off command to the main control system of the pipe bending machine to stop the cylinder advance and shut down the medium frequency heating power supply.

9. The real-time monitoring and control system for the temperature difference between the inner and outer walls of a bent pipe according to claim 4 or 5, characterized in that: The real-time control module for the cylinder propulsion speed infinitely adjusts the oil supply flow of the cylinder by controlling the opening of the proportional servo valve; the real-time control module for the medium-frequency heating power adjusts the output power by tuning the rectified voltage or current of the inverter of the medium-frequency power supply; and the real-time control module for the air volume changes the blade speed of the cooling fan by adjusting the output operating frequency of the frequency converter.

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