Full-digital control system for precise surfacing repair of inner wall of small-diameter pipe fitting

Abstract

The invention provides a full-digital control system for precise surfacing repair of the inner wall of a small-diameter pipe fitting. The full-digital control system comprises a TIG welding gun, a processor main control module, a man-machine interaction module, a welding power source module, a motor driving module and a distance measuring module. The TIG welding gun comprises a welding gun head, a rotary driving device, an axial driving device and a radial driving device; the distance measuring module is arranged on a welding gun head and used for detecting the distance between the distance measuring module and the inner wall of a pipe fitting in real time. The actual value of the eccentric distance is calculated according to the distance, detected by the distance measuring module in real time, between the distance measuring module and the inner wall of the pipe fitting, then the difference value between the theoretical value and the actual value of the eccentric distance is obtained, and the eccentric distance is dynamically corrected by combining a PID control algorithm so that local deformation of the inner wall of the pipe fitting can be compensated in a self-adaptive mode. According to the system, the distance between a welding point and the pipe wall is fed back in real time, the system dynamically corrects the radial motor track, the short circuit and arc breaking risks caused by pipe wall deformation are restrained, and the thickness uniformity of a surfacing layer is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of pipe fitting repair, and more particularly to a fully digital control system for precise surfacing welding repair of the inner wall of a small-diameter pipe fitting. Background Art

[0002] With the continuous growth of global energy demand, nuclear power, as an important component of clean energy, faces the challenge of efficient and precise repair of a large number of small-diameter pipes (<φ20mm) in power plant heat exchangers and condensers, especially heat transfer tubes. As a key component of nuclear power plant operation, heat transfer tubes, if their corrosion and wear problems reach a certain level, may lead to unplanned shutdowns of nuclear power plants and even cause major nuclear power safety incidents. Therefore, their maintenance and repair work is of vital importance. Traditional heat transfer tube repair technologies include plugging, tube replacement, and lining. Compared with plugging and tube replacement processes, lining repair technology can maintain the working efficiency of the evaporator to a certain extent. However, since the liner aperture is much smaller than the heat transfer tube, this solution not only sacrifices some heat exchange efficiency, but also significantly increases the technical difficulty of actuator development.

[0003] Hardfacing repair technology not only meets the needs of pipe inner wall repair but also, due to its large dimensional margin, effectively reduces the difficulty of developing repair actuators. It has become the primary method for repairing the inner walls of small-diameter pipes. However, for pipes as small as 20mm in diameter, the extremely confined environment places even more stringent requirements on the hardfacing repair process. Because pipes are prone to deformation such as localized dents and protrusions during long-term service or when subjected to external forces, the irregularly shaped surfaces formed at the bends prevent the welding nozzle from maintaining a constant distance from the surface to be welded. During the hardfacing repair process, the concave areas cause the distance between the end of the welding wire and the pipe wall to decrease sharply, making it easy for the molten droplet to contact the unmelted base material during transfer, causing frequent short circuits and pulsed release of arc energy. Meanwhile, the limited lifting of the welding nozzle in the protruding areas causes the arc length to be passively extended, resulting in an increased arc failure rate. These dynamic changes can cause drastic fluctuations in the welding current, affecting weld quality and leading to uneven weld layer thickness.

[0004] In addition, to ensure the stability of the repair process and the quality of the weld, key parameters such as welding current, wire feeding speed, axial movement speed and rotation speed must be precisely controlled; otherwise, problems such as weld porosity, insufficient penetration depth and excessive heat accumulation will occur. Summary of the Invention

[0005] In order to overcome the shortcomings and deficiencies in the prior art, the purpose of the present invention is to provide a fully digital control system for precision surfacing repair of the inner wall of small-diameter pipes; the system dynamically corrects the radial motor trajectory by providing real-time feedback on the distance between the welding point and the pipe wall, thereby suppressing the risks of short circuits and arc failures caused by pipe wall deformation and ensuring the uniformity of the thickness of the surfacing layer.

[0006] In order to achieve the above-mentioned object, the present invention is implemented by the following technical solutions: a fully digital control system for precision surfacing welding repair of the inner wall of a small-diameter pipe fitting, comprising a TIG welding gun, a processor main control module, a human-computer interaction module, a welding power supply module for outputting welding power to the TIG welding gun, a motor drive module for driving a motor of the TIG welding gun, and a distance measurement module; the TIG welding gun comprises a welding gun head, a rotary drive device for rotating the welding gun head around a rotating axis of the TIG welding gun, an axial drive device for moving the welding gun head along the axial direction of the rotating axis of the TIG welding gun, and a radial drive device for driving the welding gun head to move in a vertical direction along the rotating axis of the TIG welding gun to adjust the eccentricity between the central axis of the welding gun head and the rotating axis of the TIG welding gun; the motor drive module is used to drive the rotary drive device, the axial drive device and the radial drive device respectively; the distance measurement module is provided on the welding gun head for real-time detection of the distance m to the inner wall of the pipe fitting;

[0007] Based on the distance m between the ranging module and the inner wall of the pipe obtained by real-time detection by the ranging module, the actual value e of the eccentricity is calculated, and then the difference Δe between the theoretical value e′ and the actual value e of the eccentricity is obtained. Combined with the PID control algorithm, the eccentricity is dynamically corrected to adaptively compensate for the local deformation of the inner wall of the pipe.

[0008] Preferably, the calculation method of the difference Δe between the theoretical value e′ and the actual value e of the eccentricity is as follows: according to the structure of the TIG welding gun, the distance h between the distance measuring module and the central axis of the welding gun head and the distance r between the welding point and the central axis of the welding gun head are obtained; and the distance s between the preset welding point and the inner wall of the pipe is obtained;

[0009] The TIG welding gun's rotating axis is set coaxially with the pipe. During the precision surfacing repair process on the inner wall of the pipe, the distance m between the distance measuring module and the inner wall of the pipe is obtained in real time, and the difference Δe between the theoretical value e′ and the actual value e of the eccentricity is obtained:

[0010] Δe=h+mrs.

[0011] Preferably, the ranging module refers to a laser ranging module; the laser ranging module is installed at a position near the welding point of the welding gun head, and the laser beam emitted by the laser ranging module is projected vertically to the inner wall of the pipe and is equipped with a high-temperature resistant protective cover.

[0012] Preferably, the rotary drive device, the axial drive device and the radial drive device are respectively equipped with a brushless DC motor; each brushless DC motor corresponds to each motor drive module; each motor drive module includes: a Hall sensor, a drive control module MCU3, a PWM2 drive module, a Hall signal input module, an optocoupler isolation 3 input module, a three-phase inverter module, a motor control signal interface, a limit switch, a Hall signal interface, and a motor main power interface;

[0013] The Hall sensor detects the Hall signals of the three phases of the DC brushless motor and inputs them into the drive control module MCU3 through the Hall signal input module. The drive control module MCU3 determines the current rotor position of the DC brushless motor based on the three Hall signal waveforms, and then controls the conduction of the upper and lower bridge arms of the three-phase inverter module according to the current rotor position to realize the drive of the DC brushless motor.

[0014] When the brushless DC motor is running, the processor main control module sends PWM and direction signals according to the values ​​set by the human-computer interaction module. The duty cycle of the PWM signal is the ratio of the set motor speed to the maximum speed. The drive control module MCU3 receives the signal sent by the processor main control module through the motor control signal interface. After the drive control module MCU3 processes the signal, it controls the three-phase inverter module through the PWM2 drive module, and then connects to the brushless DC motor through the motor main power interface to drive the brushless DC motor to rotate.

[0015] When the brushless DC motor is turned off, the processor main control module sends PWM and brake signals; the duty cycle of the PWM signal is 0; the brushless DC motor stops rotating;

[0016] When the limit switch is encountered, the drive control module MCU3 receives the limit signal of the limit switch and turns off the brushless DC motor.

[0017] Preferably, the drive control module MCU3 is provided with a PID2 controller; the drive control module MCU3 inputs a speed target value for the PID2 controller according to the received PWM and direction signals; and the actual speed obtained by dividing the number of high and low level pulses collected by the Hall sensor by the time is used as the speed feedback value; the difference between the speed target value and the speed feedback value is used to adjust the speed output value through the PID2 controller, and then the conduction time ratio of the upper and lower bridge arms of the three-phase inverter module is changed through the PWM2 drive module, and finally the speed of the DC brushless motor is controlled to realize closed-loop control of the speed of the DC brushless motor.

[0018] Preferably, the processor main control module is based on a PID control algorithm: current sampling is performed on the output of the welding power module to obtain a real-time current feedback value; the processor main control module dynamically adjusts the output signal of the welding power module according to preset current parameters and the real-time current feedback value obtained by sampling, controls the opening duty cycle of the full-bridge inverter circuit of the welding power module, and realizes closed-loop control of the output current of the welding power module; the preset current parameters include peak value, base value, duty cycle, and frequency.

[0019] Preferably, it also includes a water cooling protection module, a gas protection module, a start-stop button module, a working status indicator light module, and a start signal output module which are respectively connected to the processor main control module.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] 1. The fully digital control system of the present invention dynamically corrects the radial motor trajectory by providing real-time feedback on the distance between the welding point and the pipe wall, suppressing the risks of short circuit and arc failure caused by pipe wall deformation (concavity / protrusion), and ensuring the uniformity of the thickness of the weld layer;

[0022] 2. The fully digital control system of the present invention adopts a four-axis linkage control algorithm (rotation, radial, axial, and wire feeding). Based on a high-precision Hall sensor, a laser ranging sensor, and an ADC sampling module, combined with a PID control algorithm, it achieves precise output of speed, position, and current. It can meet the requirements of precision cladding repair of pipe inner walls in all positions and significantly improve the process adaptability of precision cladding repair equipment for pipe inner walls. In addition, the eccentric distance of the rotating axis of the TIG welding gun head can be adjusted through radial movement. On the one hand, the TIG welding gun can be adapted to pipes of different specifications and sizes, and on the other hand, it can realize multi-layer and multi-pass cladding repair operations.

[0023] 3. The fully digital control system of the present invention can realize the automated collaborative control of the entire process of precision surfacing welding repair operations on the inner wall of pipe fittings in all positions, significantly improving the stability of the operation process; it can control the welding power supply module to achieve stable output of fast-frequency DC pulse current with a pulse frequency of up to 20kHz; through the multi-tasking real-time operating system, the welding power supply, motion control, water cooling and gas protection modules are coordinated to achieve synchronous collaboration of the entire process including rotation, radial, axial and wire feeding motor drive, water cooling and gas protection switch, current control, etc.; in addition, when an abnormal working condition (such as short circuit, arc break, etc.) is detected, the system automatically triggers the emergency retraction mechanism (TIG welding gun disengagement speed ≥ 50mm / s) to avoid burning through the pipe fitting; the full process automated control covers arc initiation, surfacing, interlayer cooling and other links. Compared with traditional manual operation, the repair efficiency is significantly improved, and the deviation of layer thickness uniformity is smaller;

[0024] 4. The fully digital control system of the present invention adopts a fully digital human-machine interaction module (HMI), which integrates multi-level parameter settings and real-time data display (such as current, speed, etc.) interfaces, significantly improving the portability of operation (parameter configuration time is shortened by 50%) and the timeliness of fault monitoring; the system supports automatic and manual modes, which can be switched as needed to ensure that the TIG welding gun has excellent flexibility and controllability; in automatic mode, after one-click start, the TIG welding gun performs precision surfacing repair on the inner wall of the pipe according to preset parameters (rotation speed, wire feed amount, pulse current waveform), and uploads parameters to the touch screen in real time through the RS485 bus. The dynamic monitoring interface is synchronously displayed and abnormal threshold warnings (such as current exceeding the limit by ±5%) are issued; in manual mode, manual control of the motor is supported for preliminary preparation, and the working position of the TIG welding gun and welding wire can be adjusted in real time through the touch screen, and initial parameter calibration is performed. The system uses redundant control algorithms to ensure smooth transition of welding parameters when switching modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the overall structural block diagram of the fully digital control system of the present invention;

[0026] Figure 2 This is a simplified diagram of the output current closed-loop control of the fully digital control system of the present invention;

[0027] Figure 3 It is the manual operation interface, parameter setting interface and parameter monitoring interface of the human-machine interactive touch screen module of the fully digital control system of the present invention;

[0028] Figure 4 This is a block diagram of the motor drive module structure of the fully digital control system of the present invention;

[0029] Figure 5 This is a schematic diagram of the motor speed closed-loop control of the fully digital control system of the present invention;

[0030] Figure 6 This is a schematic diagram of the relative positions of the TIG welding gun and the pipe to be repaired in the fully digital control system of the present invention;

[0031] Figure 7 It is a flowchart of the precision surfacing welding repair task of the pipe inner wall of the fully digital control system of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

[0033] Example

[0034] This embodiment is a fully digital control system for precision surfacing welding repair of the inner wall of small diameter pipes. Figure 1As shown, the system includes a TIG welding gun, a processor main control module, a human-machine interaction module, a welding power supply module for outputting welding power to the TIG welding gun, a motor drive module for driving the motor attached to the TIG welding gun, a distance measurement module, a water cooling protection module, a gas protection module, a start / stop button module, a working status indicator module, and a start signal output module. The processor main control module includes MCU1, a DAC output module, an ADC1 sampling module, an optocoupler isolation input module 1, a relay isolation output module 1, a motor drive signal output module, and an RS485 communication module 1.

[0035] MCU1 is the minimum core system of the control system, using an ARM microprocessor with a 32-bit RISC core. This processor has a high degree of peripheral integration, rich peripheral functions, and supports RS485 communication, ensuring communication between the control system and external devices, meeting the diverse functional requirements of welding. The PWM speed control signals output to the rotary motor drive module, radial motor drive module, axial motor drive module, and wire feed motor drive module are generated by the four channels TIM1-CH1, TIM1-CH2, TIM1-CH3, and TIM1-CH4 of the advanced timer TIM1, respectively. The RS485 communication module 1 is connected to the RS485 communication interfaces of the human-machine interactive touch screen, rotary motor drive module, radial motor drive module, axial motor drive module, and wire feed motor drive module, using a one-master-multiple-slave communication mode to enable real-time parameter transmission between the processor main control module, the human-machine interactive touch screen, and the motor drive module.

[0036] The welding power module includes a main circuit module, MCU2, ADC2 sampling module, optocoupler isolation 2 input module, relay isolation 2 output module, PWM1 drive module, high-frequency arc ignition module, and current output module. The main circuit module includes three-phase rectification, filtering, full-bridge inverter, high-frequency transformer, ultra-fast recovery rectification, and inductor filtering modules. The main circuit module is connected to the 3X380VAC main power supply. The negative terminal of the current output module is connected to the TIG welding gun, and the positive terminal is connected to the pipe workpiece to be repaired. The welding power module can achieve stable output of fast-frequency DC pulse current during the precision surfacing repair process of the pipe inner wall.

[0037] like Figure 2 As shown, the processor main control module is based on the PID control algorithm: the output current of the welding power module is sampled to obtain a real-time current feedback value; the processor main control module dynamically adjusts the output signal of the welding power module according to the preset current parameters and the real-time current feedback value obtained by sampling, controls the opening duty cycle of the full-bridge inverter circuit of the welding power module, and realizes closed-loop control of the output current of the welding power module; the preset current parameters include peak value, base value, duty cycle, and frequency.

[0038] During the peak current output period, the processor main control module inputs a current target value to the PID1 controller, and the actual current value sampled by ADC1 is used as the current feedback value. The difference between the current target value and the feedback value is used to adjust the current output value through the PID1 controller, and then output to the welding power module through the DAC module; the MCU2 of the welding power module determines the duty cycle of the PWM1 drive module according to the current output value, changes the on-off time of the switch tube of the driving full-bridge inverter module to control the output current, and realizes closed-loop control of the output current; the same process is used during the base current output period.

[0039] like Figure 3 As shown, the human-machine interaction module refers to the human-machine interaction touch screen; the human-machine interaction touch screen includes a manual operation interface, a parameter setting interface, and a parameter monitoring interface; it can realize real-time communication during the precision surfacing repair process of the inner wall of the pipe fitting, real-time transmission and dynamic monitoring of working parameters, and real-time control of the manual operation motor; the human-machine interaction touch screen is connected to the RS485 communication 1 module of the processor main control module;

[0040] The manual operation interface of the human-machine interactive touch screen can accurately adjust the initial position of the TIG welding gun and welding wire in real time, and manually calibrate the eccentricity zero point between the welding gun tip and the rotating axis;

[0041] The "Manual Motor Enable" button is set to prevent misoperation when manually operating the motor. Confirmation is required to turn it on. When the "Manual Motor Enable" button is in the off state, the "Manual Motor Start" button can only be in the off state, all motors are stopped, and manual operation is impossible.

[0042] Turning on the "Manual Motor Enable" button will trigger the human-computer interaction touch screen to send the speed and direction of the rotation, axial, and wire feeding motors and the "movement to eccentricity" parameters to the processor main control module. The parameters are stored in a separate spare register; at the same time, the processor main control module sends the current eccentricity parameters to the touch screen in real time for dynamic update; when the state of the "Manual Motor Start" button of each motor changes, it will trigger the human-computer interaction touch screen to send an 8-bit motor state variable State to the processor main control module; the switch state of the "Manual Motor Enable" button and the "Manual Motor Start" button of each motor is mapped in the variable State, as shown in Table 1; the lower 5 bits of the variable State represent the switch state of the "Manual Motor Enable" button and the "Manual Motor Start" button of the rotation, axial, wire feeding, and radial motors, 1 for on, 0 for off; Figure 3 In the manual operation interface, the value of the variable State is: 00011111; each time the processor main control module receives the State variable, it will update the on / off status of each motor;

[0043] Table 1 Meaning of variable State

[0044]

[0045] The system adopts a redundant control algorithm, integrating multiple command checks (button status cross-validation) in the manual operation of the motor, real-time data double buffer storage and heterogeneous software fault-tolerant design. Based on hardware redundancy, data redundancy and software redundancy, it ensures smooth transition of welding parameters when switching between manual and automatic modes.

[0046] Manually adjust the working position of the TIG welding gun and welding wire. The specific operations are as follows: open the manual operation interface of the human-computer interactive touch screen, set the speed and direction of the rotation, axial, radial and wire feeding movements; turn on the "Manual Motor Enable" button and confirm; turn on the "Manual Motor Start" button of the specified motor as needed to adjust the TIG welding gun and welding wire to the working position; turn off the "Manual Motor Enable" button; after the "Manual Motor Start" button is turned on, the rotation, axial and wire feeding motors will continue to move at the set speed and direction until the button is in the off state, and the radial motor will stop after moving to the specified eccentricity; the "Zero Point Calibration Button" will update the eccentricity zero point stored in the processor main control module. Frequent zero point calibration will help improve welding quality; the above logic is implemented as a program design independent of the automatic mode;

[0047] The parameter setting interface of the human-machine interactive touch screen can be used to set the working parameters of the precision surfacing repair of the inner wall of the pipe fitting, such as rotation, axial direction, wire feed speed, peak and base current, duty cycle, pulse frequency, repair depth, etc. Click the "Send Data" button to send the data to the processor main control module. After the repair operation begins, the digital control system will coordinate the welding power supply, motion control, water cooling and gas shielding modules according to the set working parameters through the multi-tasking real-time operating system to achieve synchronous collaboration of the entire process, including rotation, radial and axial directions, wire feed motor drive, water cooling and gas shielding switches, and current control, to ensure the stability of the repair operation process.

[0048] The parameter monitoring interface of the human-computer interactive touch screen can conduct real-time dynamic monitoring of key parameters in the precision surfacing repair process of the inner wall of the pipe fitting; the processor main control module communicates with the motor drive module and laser ranging module through RS485 to obtain speed and distance parameters, and transmits the parameters to the human-computer interactive touch screen in real time for real-time dynamic monitoring, which helps to control abnormal situations that occur during the repair process in real time.

[0049] The TIG welding gun includes a gun head, a rotary drive device for rotating the gun head about the TIG gun's rotation axis, an axial drive device for moving the gun head axially along the TIG gun's rotation axis, and a radial drive device for moving the gun head perpendicular to the TIG gun's rotation axis to adjust the eccentricity between the gun head's center axis and the TIG gun's rotation axis. The motor drive module is used to drive the rotary drive device, the axial drive device, and the radial drive device, respectively. The structure of the TIG welding gun can adopt the structure described in the Chinese invention patent "TIG welding gun for all-position additive repair of the inner wall of a small-diameter threaded hole" (Publication No.: CN119457318A).

[0050] The rotary drive device, the axial drive device and the radial drive device are respectively provided with a DC brushless motor; each DC brushless motor corresponds to each motor drive module one by one.

[0051] like Figure 4 As shown, each motor drive module includes: Hall sensor, drive control module MCU3, PWM2 drive module, Hall signal input module, optocoupler isolation 3 input module, three-phase inverter module, motor control signal interface, limit switch, Hall signal interface, motor main power interface;

[0052] The Hall sensor detects the Hall signals of the three phases of the DC brushless motor and inputs them into the drive control module MCU3 through the Hall signal input module. The drive control module MCU3 determines the current rotor position of the DC brushless motor based on the three Hall signal waveforms, and then controls the conduction of the upper and lower bridge arms of the three-phase inverter module according to the current rotor position to realize the drive of the DC brushless motor.

[0053] When the brushless DC motor is running, the processor main control module sends PWM and direction signals according to the values ​​set by the human-computer interaction module. The duty cycle of the PWM signal is the ratio of the set motor speed to the maximum speed. The drive control module MCU3 receives the signal sent by the processor main control module through the motor control signal interface. After the drive control module MCU3 processes the signal, it controls the three-phase inverter module through the PWM2 drive module, and then connects to the brushless DC motor through the motor main power interface to drive the brushless DC motor to rotate.

[0054] When the brushless DC motor is turned off, the processor main control module sends PWM and brake signals; the duty cycle of the PWM signal is 0; the brushless DC motor stops rotating;

[0055] When the limit switch is encountered, the drive control module MCU3 receives the limit signal of the limit switch and turns off the brushless DC motor.

[0056] The system adopts a four-axis coordinated motion control algorithm (rotation, radial, axial, and wire feeding) based on a high-precision Hall sensor encoder and a closed-loop PID controller to achieve precise coordinated control of the TIG welding gun movement, effectively improving the quality of welding.

[0057] like Figure 5 As shown, the drive control module MCU3 is provided with a PID2 controller; the drive control module MCU3 inputs a speed target value to the PID2 controller according to the received PWM and direction signals; and the actual speed obtained by dividing the number of high and low level pulses collected by the Hall sensor by the time is used as the speed feedback value; the difference between the speed target value and the speed feedback value is used to adjust the speed output value through the PID2 controller, and then the conduction time ratio of the upper and lower bridge arms of the three-phase inverter module is changed through the PWM2 drive module, and finally the speed of the DC brushless motor is controlled to realize closed-loop control of the DC brushless motor speed.

[0058] like Figure 6 As shown, a distance measuring module 4 is mounted on the welding torch head 2 and is used to detect the distance m to the inner wall 1 of the pipe in real time. The distance measuring module is preferably a laser distance measuring module; the laser distance measuring module is mounted on the welding torch head near the weld point, which is the point of contact between the tungsten needle 6 and the welding wire 7. The laser distance measuring module emits a laser beam perpendicular to the inner wall 1 of the pipe and is equipped with a high-temperature protective shield 3 (with a temperature tolerance of ≥300°C) to prevent damage to the sensor from welding spatter and thermal radiation.

[0059] The laser ranging module includes a laser ranging sensor (resolution 0.01mm, range 0.5-50mm), a controller MCU4, and an RS485 communication module 3; it can detect the distance between the welding gun tip and the inner wall of the pipe to be repaired in real time, and feed back the data to the processor main control module through RS485 communication for dynamic adjustment of the welding gun eccentricity; the RS485 communication module 3 is connected to the RS485 communication module 1 of the processor main control module.

[0060] Insert the welding torch tip 2 into the pipe, with the TIG welding torch's rotating axis 5 coaxial with the pipe. When performing precision overlay welding repairs on the pipe's inner wall 1, the dimension s (the distance between the preset weld point and the pipe's inner wall 1) must be precisely controlled to ensure weld quality. The processor's main control module calculates the actual eccentricity e based on the distance m between the distance measurement module 4 and the pipe's inner wall 1, as measured in real time by the distance measurement module 4. This calculation then determines the difference Δe between the theoretical eccentricity e′ and the actual value e. Combined with the PID control algorithm, the eccentricity is dynamically corrected to adaptively compensate for local deformation of the pipe's inner wall 1 and suppress arc drift caused by abnormal weld point spacing.

[0061] Specifically, the difference Δe between the theoretical value e′ and the actual value e of the eccentricity is calculated as follows: based on the structure of the TIG welding gun, the distance h between the distance measurement module and the center axis of the welding gun head and the distance r between the welding point and the center axis of the welding gun head are obtained; in addition, Figure 6 Where d is the inner diameter of the pipe; d, h and r are all fixed values;

[0062] Obtain the distance s between the preset welding point and the inner wall of the pipe fitting. The theoretical value of the eccentricity e′ is:

[0063] e′=d / 2-rs

[0064] During the precision surfacing welding repair process on the inner wall of the pipe fitting, the distance m between the distance measuring module and the inner wall of the pipe fitting is obtained in real time. The actual value of the eccentricity is:

[0065] e=d / 2-hm

[0066] The difference Δe between the theoretical value e′ and the actual value e of the eccentricity is:

[0067] Δe=h+mrs.

[0068] If the real-time measured m value is too large (i.e., s is too large), and the eccentricity difference is greater than 0, the PID controller output force increases, increasing the value of e to reduce the value of s. Conversely, when the m value is too small, the PID controller output force decreases, decreasing the value of e to increase the value of s. Combining a laser ranging module with a PID closed-loop control algorithm, the distance between the weld point and the pipe inner wall is dynamically adjusted, improving the thickness uniformity of the repaired weld. Furthermore, based on the eccentricity difference formula (Δe = h + mrs), the system dynamically corrects the welding gun eccentricity by measuring the laser ranging value (m) in real time. This adjustment process is independent of the pipe inner wall dimension (d). This design adaptively compensates for local deformation of the pipe inner wall (such as fluctuations in the s value caused by depressions or protrusions), suppresses arc drift caused by abnormal weld point spacing, and significantly improves weld formation consistency.

[0069] like Figure 7 As shown, the working steps of the fully digital control system for precision surfacing welding repair of the inner wall of small-diameter pipe fittings in this embodiment are as follows:

[0070] Step S1: Preliminary preparation for pipe cladding repair task

[0071] The main power lines, Hall signal lines and limit switch signal lines of the TIG welding gun's rotation, axial, radial and wire feeding motors are respectively connected to the corresponding interfaces of each motor drive module of the digital control system; the gas pipe and water pipe of the TIG welding gun are respectively connected to the gas protection module and water cooling protection module of the digital control system; the TIG welding gun and the pipe workpiece to be repaired are fixed in the working position with a clamp to ensure that the rotation axis coincides with the axis of the pipe to be repaired; the 3X380VAC main power supply is connected to the welding power module of the digital control system; the negative pole of the current output module of the welding power module is connected to the TIG welding gun, and the positive pole is connected to the pipe workpiece to be repaired.

[0072] Step S2: Manually fine-tune the working position of the TIG welding gun and welding wire

[0073] Manually turn on the control switch of the digital control system, and the control indicator light will turn on; open the manual operation interface of the human-computer interaction touch screen module; set the speed and direction of each motor; turn on the manual operation enabling button; manually start the motor as needed to adjust the working position of the TIG welding gun and welding wire.

[0074] Step S3: Setting and sending parameters for pipe cladding repair work

[0075] Open the parameter setting interface of the human-computer interaction touch screen module; set the working parameters such as welding gun speed, axial speed, wire feeding speed, peak value, base value, duty cycle, pulse frequency, distance between welding point and pipe wall, repair thickness, axial direction, repair depth, etc.; click the send button, and the working parameter data will be sent to the processor main control module through the RS485 communication 1 module. The processor main control module assigns the working parameters to the variables in the program.

[0076] Step S4: Start the pipe cladding repair operation

[0077] Manually turn on the main power switch of the digital control system, and the main power indicator light will light up; wait for the start button to be pressed; after pressing the start button, the start signal is transmitted to the processor main control module, the pipe fitting cladding repair operation main program starts to run, and the pipe fitting cladding repair operation indicator light will light up; the processor main control module outputs a start signal to the water cooling protection module and the gas protection module to turn on the water cooling protection and gas protection devices in advance; the internal timer TIM2 of the processor main control module starts timing, and the timing time is the set advance water cooling and gas protection time, and the timing is completed and enters step S5.

[0078] Step S5: Wait for high-frequency arc ignition to succeed

[0079] The processor main control module enters the TIM2 timer interrupt and outputs a start signal to the welding power supply module; the welding power supply module starts the high-frequency arc ignition device to ignite the arc; the ADC1 sampling module of the processor main control module samples the current at a specific frequency; the processor main control module repeatedly determines whether the current value sampled by ADC1 meets the arc ignition condition until the arc ignition condition is met and the arc is successfully ignited;

[0080] Step S6: Refined output of current waveform

[0081] The DAC module of the processor main control module outputs the current value to the welding power module at the corresponding frequency according to the set current base value, current peak value, duty cycle, and pulse frequency; the welding power module controls the PWM1 drive module to control the switching tube of the full-bridge inverter module at the set frequency according to the size of the received current value, thereby realizing the refined output of the current waveform.

[0082] Step S7: Coordinated control and drive of the four-axis motors

[0083] The processor main control module sends PWM signals to the rotation, axial and wire feeding motor drive modules according to the rotation, axial and wire feeding speeds set in the parameter setting interface of the human-computer interaction touch screen module, and the rotation, axial and wire feeding motor drive modules drive the rotation, axial and wire feeding motors to operate; the duty cycle of the PWM is the ratio of the set rotation, axial and wire feeding speeds to their maximum speeds respectively; the processor main control module drives the radial motor to start and stop according to the set s value (the distance between the welding point and the pipe wall) and the m value measured in real time, and adjusts the eccentricity between the welding gun head and the rotating axis in real time to achieve dynamic fine-tuning of the s value to ensure the quality of welding; at the same time, the internal timer TIM3 of the processor main control module starts timing, and the timing time is the ratio of the set repair depth to the axial movement speed. After the timing is completed, it enters step S8;

[0084] Steps S6 to S7 are performed simultaneously.

[0085] Step S8: Stop the pipe cladding repair operation

[0086] The processor main control module enters the TIM3 timer timing interrupt, first sending PWM and brake signals to the wire feeding motor drive module, with the PWM duty cycle being 0, turning off the wire feeding motor; then the DAC module outputs a current value of 0 to the welding power module to stop the current output; the processor main control module sends PWM and brake signals to the rotary and axial motor drive modules, with the PWM duty cycle being 0, turning off the rotary and axial motors; finally, the internal timer TIM2 of the processor main control module starts timing, and the timing time is the set hysteresis water cooling and gas protection time. After the timing is completed, the process enters step S9;

[0087] Turn off the wire feeding motor first, then stop the current output and turn off the rotary and axial motors to effectively prevent the welding wire from sticking.

[0088] Step S9: Ending a pipe surfacing repair operation

[0089] The processor main control module enters the TIM2 timer interrupt and outputs a shutdown signal to the water cooling protection module and the gas protection module to turn off and on the water cooling protection and gas protection devices; the additive operation indicator light goes out;

[0090] Manually turn off the main power switch of the digital control system, and the main power indicator light goes out; if the pipe to be repaired has not been repaired by surfacing welding to the required thickness, repeat steps S2 to S9 until the pipe to be repaired has been repaired by surfacing welding to the required thickness.

[0091] Step S10: Waiting for the next pipe surfacing repair task

[0092] Manually turn off the control switch of the digital control system, and the control indicator light goes out; disconnect the 3X380VAC main power supply from the welding power module of the digital control system; disconnect the positive pole of the current output module of the welding power module from the pipe to be repaired; and wait for the next pipe surfacing repair task.

[0093] In particular, during steps S4 to S7, when encountering an emergency (such as a problem with the actual output current), the emergency stop button is manually pressed to stop the signal from being transmitted to the processor main control module; or when an abnormal working condition (such as short circuit, arc break, etc.) is detected, the system automatically triggers the emergency retraction mechanism (TIG welding gun disengagement speed ≥ 50mm / s); the pipe fitting cladding repair operation stops running, and the pipe fitting cladding repair operation emergency indicator light is on; the pipe fitting cladding repair operation enters steps S8 to S9, ending the current pipe fitting cladding repair operation; after handling the emergency, reset the emergency stop button, the emergency indicator light goes out, and the pipe fitting cladding repair operation can be resumed.

[0094] In particular, after the start button is pressed in step S4, the human-computer interaction touch screen module enters the parameter monitoring interface, which can dynamically monitor the actual current, motor speed and other working parameters during the pipe fitting surfacing repair operation in real time; the actual current value sampled by the processor main control module ADC1, the actual motor speed and position converted from the signal detected by the Hall sensor by the motor drive module, and the distance value between the welding point and the pipe wall obtained by the value measured by the laser ranging module are sent to the human-computer interaction touch screen module through the RS485 communication 1 module for dynamic monitoring in the parameter monitoring interface.

[0095] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A fully digital control system for precision surfacing welding repair of the inner wall of small diameter pipes, characterized by: It includes a TIG welding gun, a processor main control module, a human-computer interaction module, a welding power supply module for outputting welding power to the TIG welding gun, a motor drive module for driving the motor of the TIG welding gun, and a distance measurement module; the TIG welding gun includes a welding gun head, a rotary drive device for rotating the welding gun head around the TIG welding gun rotation axis, an axial drive device for moving the welding gun head along the axial direction of the TIG welding gun rotation axis, and a radial drive device for driving the welding gun head to move in a vertical direction along the TIG welding gun rotation axis to adjust the eccentricity between the central axis of the welding gun head and the TIG welding gun rotation axis; the motor drive module is used to drive the rotary drive device, the axial drive device and the radial drive device respectively; the distance measurement module is arranged on the welding gun head and is used to detect the distance m to the inner wall of the pipe in real time; Based on the distance m between the ranging module and the inner wall of the pipe obtained by real-time detection by the ranging module, the actual value e of the eccentricity is calculated, and then the difference Δe between the theoretical value e′ and the actual value e of the eccentricity is obtained. Combined with the PID control algorithm, the eccentricity is dynamically corrected to adaptively compensate for the local deformation of the inner wall of the pipe.

2. The fully digital control system for precision surfacing welding repair of the inner wall of small-diameter pipes according to claim 1 is characterized by: The difference Δe between the theoretical value e′ and the actual value e of the eccentricity is calculated by: obtaining the distance h between the distance measuring module and the central axis of the welding gun head and the distance r between the welding point and the central axis of the welding gun head according to the structure of the TIG welding gun; obtaining the distance s between the preset welding point and the inner wall of the pipe; The TIG welding gun's rotating axis is set coaxially with the pipe. During the precision surfacing repair process on the inner wall of the pipe, the distance m between the distance measuring module and the inner wall of the pipe is obtained in real time, and the difference Δe between the theoretical value e′ and the actual value e of the eccentricity is obtained: Δe=h+mrs.

3. The fully digital control system for precision surfacing welding repair of the inner wall of small-diameter pipes according to claim 1 is characterized in that: The ranging module refers to a laser ranging module; the laser ranging module is installed at a position near the welding point on the welding gun head, and the laser beam emitted by the laser ranging module is projected vertically onto the inner wall of the pipe and is equipped with a high-temperature resistant protective cover.

4. The fully digital control system for precision surfacing welding repair of the inner wall of small-diameter pipes according to claim 1 is characterized in that: The rotary drive device, axial drive device and radial drive device are respectively equipped with a brushless DC motor; Each brushless DC motor corresponds to each motor drive module one by one; each motor drive module includes: Hall sensor, drive control module MCU3, PWM2 drive module, Hall signal input module, optocoupler isolation 3 input module, three-phase inverter module, motor control signal interface, limit switch, Hall signal interface, motor main power interface; The Hall sensor detects the Hall signals of the three phases of the DC brushless motor and inputs them into the drive control module MCU3 through the Hall signal input module. The drive control module MCU3 determines the current rotor position of the DC brushless motor based on the three Hall signal waveforms, and then controls the conduction of the upper and lower bridge arms of the three-phase inverter module according to the current rotor position to realize the drive of the DC brushless motor. When the brushless DC motor is running, the processor main control module sends PWM and direction signals according to the values ​​set by the human-computer interaction module. The duty cycle of the PWM signal is the ratio of the set motor speed to the maximum speed. The drive control module MCU3 receives the signal sent by the processor main control module through the motor control signal interface. After the drive control module MCU3 processes the signal, it controls the three-phase inverter module through the PWM2 drive module, and then connects to the brushless DC motor through the motor main power interface to drive the brushless DC motor to rotate. When the brushless DC motor is turned off, the processor main control module sends PWM and brake signals; the duty cycle of the PWM signal is 0; the brushless DC motor stops rotating; When the limit switch is encountered, the drive control module MCU3 receives the limit signal of the limit switch and turns off the brushless DC motor.

5. The fully digital control system for precision surfacing welding repair of the inner wall of small-diameter pipes according to claim 4 is characterized in that: The drive control module MCU3 is provided with a PID2 controller; the drive control module MCU3 inputs a speed target value for the PID2 controller according to the received PWM and direction signals; and the actual speed obtained by dividing the number of high and low level pulses collected by the Hall sensor by the time is used as the speed feedback value; the difference between the speed target value and the speed feedback value is used to adjust the speed output value through the PID2 controller, and then the conduction time ratio of the upper and lower bridge arms of the three-phase inverter module is changed through the PWM2 drive module, and finally the speed of the DC brushless motor is controlled to realize closed-loop control of the speed of the DC brushless motor.

6. The fully digital control system for precision surfacing welding repair of the inner wall of small-diameter pipes according to claim 1 is characterized in that: The processor main control module is based on the PID control algorithm: the output current of the welding power module is sampled to obtain a real-time current feedback value; the processor main control module dynamically adjusts the output signal of the welding power module according to the preset current parameters and the real-time current feedback value obtained by sampling, controls the opening duty cycle of the full-bridge inverter circuit of the welding power module, and realizes closed-loop control of the output current of the welding power module; The preset current parameters include peak value, base value, duty cycle, and frequency.

7. The fully digital control system for precision surfacing welding repair of the inner wall of small-diameter pipes according to claim 1 is characterized in that: It also includes a water cooling protection module, a gas protection module, a start-stop button module, a working status indicator light module, and a start signal output module that are respectively connected to the processor main control module.

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