A laser cladding distance real-time control system and method

Abstract

The application discloses a kind of laser cladding distance real-time control system and method, mainly related to laser additive manufacturing technical field.It includes: composite nozzle structure, capacitance sensing unit, CCD vision unit and comprehensive control module;The composite nozzle structure includes powder feeder device, transition ceramic ring, outer nozzle and inner nozzle;The capacitance sensing unit is with ceramic ring as core, ceramic ring and transition ceramic ring coaxial package to isolate laser head matrix and workpiece, together constitute capacitance detection area;The CCD vision unit includes vision device and support frame, and vision device is installed on the clamp of laser head by support frame and is used to capture molten pool morphology and temperature field;The comprehensive control module is electrically connected with capacitance sensing unit, CCD vision unit and laser head drive system respectively, for receiving the detection data of double sensing unit and generating distance compensation and process parameter adjustment instruction.The beneficial effects of the application are that it breaks through the technical bottleneck of response delay and precision mutual exclusion.

Description

Technical Field

[0001] This invention relates to the field of laser additive manufacturing technology, specifically a real-time control system and method for laser cladding distance based on capacitive-visual fusion sensing. Background Technology

[0002] In existing laser cladding technology, the stability of the relative distance between the nozzle and the workpiece is the core factor determining the cladding quality. However, existing control systems suffer from technical bottlenecks that make it difficult to balance response speed and detection dimensions.

[0003] On the one hand, although a system using a single capacitance sensor can achieve a fast response of 0.5ms (sensing distance through changes in capacitance between electrodes), it can only acquire distance parameters and cannot sense key quality indicators such as the width and temperature of the molten pool. This results in the inability to control the molten pool in time when defects such as spheroidization and edge collapse occur, and the thickness of the cladding layer often fluctuates by more than ±0.15mm, which easily leads to cracks.

[0004] On the other hand, while systems using a single CCD vision can acquire multi-dimensional information such as molten pool morphology and temperature field through image analysis, they are affected by image acquisition and processing delays (typically greater than or equal to 20ms). This is particularly problematic when the laser head is moving at high speeds (greater than 1m / min) or when the workpiece surface has a large curvature (greater than 1m / min). When the distance changes suddenly, the CCD cannot respond in real time, resulting in a decrease in geometric accuracy. Furthermore, the CCD is susceptible to interference from strong light and dust in the molten pool, with a downtime rate of over 30% under high dust conditions, which seriously affects production stability.

[0005] Furthermore, existing technologies lack a fusion architecture that can coordinate the advantages of both sensing methods, making it impossible to dynamically balance response speed and detection dimensions according to working conditions. This results in poor quality control of laser cladding under complex working conditions (such as curved parts and high-speed additive manufacturing).

[0006] Therefore, there is an urgent need for a real-time control system for laser cladding distance that combines high-speed response, multi-dimensional sensing, and adaptive adjustment capabilities. Summary of the Invention

[0007] The purpose of this invention is to provide a real-time control system and method for laser cladding distance based on capacitive-visual fusion sensing, which breaks through the technical bottleneck of mutual exclusion between response delay and accuracy.

[0008] To achieve the above objectives, the present invention employs the following technical solution:

[0009] On one hand, a real-time control system for laser cladding distance is provided, including a composite nozzle structure, a capacitive sensing unit, a CCD vision unit, and an integrated control module. The composite nozzle structure includes a powder feeder device, a transition ceramic ring, an outer nozzle, and an inner nozzle. The powder feeder device and the transition ceramic ring are nested to form an interference fit, and the inner nozzle and the outer nozzle are coaxially arranged to form an annular powder-gas channel. The capacitive sensing unit has a ceramic ring as its core, and the ceramic ring and the transition ceramic ring are coaxially packaged to isolate the laser head substrate from the workpiece, together forming a capacitance detection area. The CCD vision unit includes a vision device and a support frame. The vision device is obliquely mounted on the clamp of the laser head through the support frame and is used to capture the molten pool morphology and temperature field. The integrated control module is electrically connected to the capacitive sensing unit, the CCD vision unit, and the laser head drive system, respectively, and is used to receive the detection data of the dual sensing units and generate distance compensation and process parameter adjustment commands.

[0010] Preferably, the interference fit parameters between the powder feeder device and the transition ceramic ring are as follows: the interference is 0.02mm~0.03mm at room temperature, and when the working temperature is maintained at 86℃±5℃ by water circulation cooling, the interference is maintained at 0.008mm~0.01mm to achieve mechanical sealing; the gap between the inner nozzle and the outer nozzle is the powder outflow channel, and the laser is focused by the inner nozzle and acts on the surface of the workpiece, forming a molten pool together with the outflowing powder.

[0011] Preferably, in the capacitive sensing unit, the inner wall of the ceramic ring is provided with a metallized coating, and the metallized coating is connected to the gold-plated copper needle through conductive silver paste to achieve lossless transmission of the capacitive signal; both the ceramic ring and the transition ceramic ring are coaxially arranged with the laser optical path to ensure symmetrical distribution of the capacitive electric field; the powder feeder device has a built-in water-cooling circulation structure to cool the inner nozzle, outer nozzle and ceramic ring, and maintain the working temperature of each component at less than or equal to 80°C.

[0012] Preferably, in the CCD vision unit, the vision device is installed at a 45° angle to the horizontal plane and is calibrated to coincide with the laser focus through the elongated hole of the support frame; the vision device adopts 850nm / 950nm dual-band filtering technology to suppress strong light interference from the molten pool and can collect the molten pool width, trailing angle parameters and temperature field distribution data in real time.

[0013] Preferably, the integrated control module incorporates a dynamic weighting algorithm and a PID control algorithm, which can adaptively allocate decision weights between the capacitive sensing unit and the CCD vision unit according to the operating conditions, generate Z-axis distance compensation commands and laser power and scanning speed adjustment signals, and realize closed-loop control.

[0014] On the other hand, a control method for a laser cladding distance real-time control system as described above is provided, comprising the following steps:

[0015] Step S1: System initialization: Calibrate the capacitance sensing unit, determine the capacitance value corresponding to the target distance, set the target melt width and ideal alloy temperature parameters of the CCD vision unit, and initialize the PID control parameters and initial values ​​of dynamic weights.

[0016] Step S2: Dual-sensor real-time detection: The capacitive sensing unit detects the real-time capacitance value through the capacitor plate formed by the ceramic ring and the workpiece, and converts it into real-time distance data; the CCD vision unit simultaneously collects the actual melt width and temperature field data of the molten pool.

[0017] Step S3: Data Fusion Processing: The integrated control module receives dual-sensor data and calculates the fusion weight using a dynamic weighting algorithm. ,

[0018] When the laser head moves at a speed greater than 1 m / min At this point, the capacitor dominates the control.

[0019] When the curvature of the workpiece surface is greater than 0.1 hour, At this point, the CCD takes the lead in control;

[0020] Under other stable operating conditions According to the formula Calculate the final distance compensation amount, where This is the height compensation amount for the capacitor output. The height is calculated by the CCD based on the molten pool area;

[0021] Step S4: Closed-loop adjustment and control: Based on the final distance compensation amount, the Z-axis drive command is generated through the PID algorithm, and the laser power and scanning speed are adjusted based on the weld width deviation and temperature deviation.

[0022] Step S5: Anomaly Handling: If the CCD vision unit detects a broken cladding layer or light interference causing data failure, it triggers Modbus communication to transmit the anomaly signal to the integrated control module, switches to capacitive single-sensor control mode until the fault is cleared.

[0023] Preferably, the detection logic of the capacitive sensing unit in step S2 is as follows:

[0024] Through formula Calculate the height compensation amount, where To determine the capacitance value corresponding to the calibration distance, To detect capacitance values ​​in real time, , These are the proportional and derivative coefficients of the PID controller.

[0025] Preferably, the calculation logic for the weld width control of the CCD vision unit in step S2 is as follows:

[0026] Laser power adjustment ,in For the target melt width, For actual testing of melt width, A power-width gain coefficient specific to the material;

[0027] The temperature closed-loop control logic is as follows:

[0028] Scan speed adjustment ,in For the ideal temperature of the alloy, For the actual measured temperature, This is the ideal temperature for the alloy.

[0029] Preferably, the dynamic weight algorithm in step S3 achieves adaptive adjustment through the following logic:

[0030] When the laser head's movement speed is greater than 1.0 m / min, the dynamic weighting... When the value is 0.9, the capacitive sensing unit plays a dominant role in the distance compensation decision.

[0031] If the laser head's movement speed is no greater than 1.0 m / min, further determine the workpiece surface curvature. If the workpiece surface curvature is greater than 0.1... At that time, dynamic weight When the value is 0.3, the CCD vision unit dominates the distance compensation decision.

[0032] If neither of the above two conditions is met, the dynamic weighting... The value is set to 0.6, at which point the capacitive sensing unit and the CCD vision unit have balanced weights in the distance compensation decision.

[0033] Preferably, the method is applicable to scenarios such as outer circle cladding, 3D printing, coaxial wire feeding welding and bypass wire feeding welding. By real-time compensation for sudden changes in distance, the cladding layer thickness fluctuation can be controlled within ±0.06mm.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. Significantly improved response speed: Through the dual-sensor fusion architecture of "capacitive + CCD" and dynamic weight control algorithm, the response speed of laser head movement is significantly improved compared with the traditional pure CCD system. It can compensate for sudden changes in distance in real time and effectively solve the geometric distortion problem caused by delay in the traditional system.

[0036] 2. Significantly improved consistency of cladding layer thickness: Compared with the traditional pure CCD system where the cladding layer thickness fluctuates by ±0.15mm, this technology controls the fluctuation within ±0.06mm, which can accurately control the additive layer thickness, internal structure and geometric dimensions, and reduce defects such as cracks;

[0037] 3. Enhanced anti-interference capability and reduced downtime: Addressing the issue of weak anti-dust interference capability in traditional pure CCD systems, this technology leverages the strong dust penetration capability of capacitive sensing and combines it with a dynamic weight allocation mechanism to increase the capacitor weight under strong dust interference conditions, thereby significantly reducing the downtime rate and improving system operational stability. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the system structure of the present invention;

[0039] Figure 2 This is a schematic diagram of a partial system structure of the present invention;

[0040] Figure 3 This is a flowchart of the method of the present invention.

[0041] The labels shown in the attached diagram:

[0042] 1. Powder feeder device; 2. Transition ceramic ring; 3. Ceramic ring; 4. Outer nozzle; 5. Inner nozzle; 6. CCD vision device; 7. CCD support frame; 8. Clamp. Detailed Implementation

[0043] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined in this application.

[0044] In this invention, terms such as "upper," "lower," "left," "right," "front," "back," "vertical," "horizontal," "side," and "bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only to facilitate the description of the structural relationships of the various components or elements of this invention and do not specifically refer to any component or element in this invention. They should not be construed as limiting the invention.

[0045] Example:

[0046] like Figure 1-2 As shown, this embodiment provides a real-time control system for laser cladding distance, including a composite nozzle structure, a capacitive sensing unit, a CCD vision unit, and an integrated control module;

[0047] The composite nozzle structure includes a powder feeder device, a transition ceramic ring, an outer nozzle, and an inner nozzle. The powder feeder device and the transition ceramic ring are nested to form an interference fit. The inner nozzle and the outer nozzle are coaxially arranged to form an annular powder-gas channel.

[0048] The capacitance sensing unit is centered on a ceramic ring. The ceramic ring and the transition ceramic ring are coaxially packaged to isolate the laser head substrate from the workpiece, together forming the capacitance detection area.

[0049] The CCD vision unit includes a vision device and a support frame. The vision device is mounted at an angle on the clamp of the laser head via the support frame and is used to capture the morphology and temperature field of the molten pool.

[0050] The integrated control module is electrically connected to the capacitive sensing unit, the CCD vision unit, and the laser head drive system, respectively, and is used to receive the detection data from the dual sensing units and generate distance compensation and process parameter adjustment commands.

[0051] The interference fit parameters between the powder feeder device and the transition ceramic ring are as follows:

[0052] At room temperature, the interference fit is 0.02mm~0.03mm. When the working temperature is maintained at 86℃±5℃ by water circulation cooling, the interference fit is maintained at 0.008mm~0.01mm to achieve mechanical seal.

[0053] The gap between the inner and outer nozzles serves as a powder outflow channel. After the laser is focused by the inner nozzle, it acts on the surface of the workpiece, forming a molten pool together with the outflowing powder.

[0054] In the capacitive sensing unit, the inner wall of the ceramic ring is provided with a metallized coating. The metallized coating is connected to the gold-plated copper needle through conductive silver paste to achieve lossless transmission of capacitive signals.

[0055] Both the ceramic ring and the transition ceramic ring are coaxially aligned with the laser optical path to ensure a symmetrical distribution of the capacitive electric field.

[0056] The powder feeder has a built-in water-cooled circulation structure to cool the inner nozzle, outer nozzle and ceramic ring, and maintain the working temperature of each component at less than or equal to 80°C.

[0057] In the CCD vision unit, the vision device is installed at a 45° angle to the horizontal plane and is calibrated to coincide with the laser focus through the elongated hole of the support frame;

[0058] The vision device uses 850nm / 950nm dual-band filtering technology to suppress strong light interference from the molten pool, and can collect data on the molten pool width, trailing angle, and temperature field distribution in real time.

[0059] The integrated control module incorporates a dynamic weighting algorithm and a PID control algorithm, which can adaptively allocate decision weights between the capacitive sensing unit and the CCD vision unit according to the operating conditions, generate Z-axis distance compensation commands and laser power and scanning speed adjustment signals, and realize closed-loop control.

[0060] like Figure 3 As shown, this embodiment also provides a control method applied to the above-mentioned laser cladding distance real-time control system, including the following steps:

[0061] Step S1: System initialization: Calibrate the capacitance sensing unit, determine the capacitance value corresponding to the target distance, set the target melt width and ideal alloy temperature parameters of the CCD vision unit, and initialize the PID control parameters and initial values ​​of dynamic weights.

[0062] Step S2: Dual-sensor real-time detection: The capacitive sensing unit detects the real-time capacitance value through the capacitor plate formed by the ceramic ring and the workpiece, and converts it into real-time distance data; the CCD vision unit simultaneously collects the actual melt width and temperature field data of the molten pool.

[0063] Step S3: Data Fusion Processing: The integrated control module receives dual-sensor data and calculates the fusion weight using a dynamic weighting algorithm. ,

[0064] When the laser head moves at a speed greater than 1 m / min At this point, the capacitor dominates the control.

[0065] When the curvature of the workpiece surface is greater than 0.1 hour, At this point, the CCD takes the lead in control;

[0066] Under other stable operating conditions According to the formula Calculate the final distance compensation amount, where This is the height compensation amount for the capacitor output. The height is calculated by the CCD based on the molten pool area. The weights are dynamic, as shown in Table 1;

[0067] Table 1

[0068]

[0069] Step S4: Closed-loop adjustment and control: Based on the final distance compensation amount, the Z-axis drive command is generated through the PID algorithm, and the laser power and scanning speed are adjusted based on the weld width deviation and temperature deviation.

[0070] Step S5: Anomaly Handling: If the CCD vision unit detects a broken cladding layer or light interference causing data failure, it triggers Modbus communication to transmit the anomaly signal to the integrated control module, switches to capacitive single-sensor control mode until the fault is cleared.

[0071] The detection logic of the capacitive sensing unit in step S2 is as follows:

[0072] Through formula Calculate the height compensation amount, where To determine the capacitance value corresponding to the calibration distance, To detect capacitance values ​​in real time, , These are the proportional and derivative coefficients of the PID controller.

[0073] The calculation logic for the melting width control of the CCD vision unit in step S2 is as follows:

[0074] Laser power adjustment ,in For the target melt width, For actual testing of melt width, A power-width gain coefficient specific to the material;

[0075] The temperature closed-loop control logic is as follows:

[0076] Scan speed adjustment ,in For the ideal temperature of the alloy, For the actual measured temperature, This is the ideal temperature for the alloy.

[0077] In step S3, weights are assigned programmatically using Python:

[0078] defweight_adjust(speed,curvature):

[0079] ifspeed>1.0m / min:#High-speed operating condition

[0080] ;

[0081] elifcurvature>0.1 :# High curvature surface

[0082] #CCD weight 70% (requires normal compensation)

[0083] else:#Stable operating conditions

[0084] ;

[0085] returnγ.

[0086] The method in this embodiment is applicable to scenarios such as outer circle cladding, 3D printing, coaxial wire feeding welding, and bypass wire feeding welding. By real-time compensation for sudden changes in distance, the cladding layer thickness fluctuation can be controlled within ±0.06mm.

[0087] The above is a detailed description of the preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.

Claims

1. A laser cladding distance real-time control system, characterized in that, The composite nozzle structure, the capacitive sensing unit, the CCD vision unit and the comprehensive control module are comprised; The composite nozzle structure comprises a powder feeder device, a transition ceramic ring, an outer nozzle and an inner nozzle, the powder feeder device is nested with the transition ceramic ring to form an interference fit, the inner nozzle is coaxially arranged with the outer nozzle to form an annular powder gas passage, and laser is focused through the inner nozzle to act on the workpiece surface together with the powder to form a molten pool; The capacitive sensing unit takes the ceramic ring as the core, the ceramic ring is coaxially packaged with the transition ceramic ring to isolate the laser head base body from the workpiece, the ceramic ring and the transition ceramic ring jointly constitute a capacitive detection area, the relative distance data between the nozzle and the workpiece is output in real time by detecting the capacitive change of the area within 0.5ms; The CCD vision unit includes a vision device and a support frame, the vision device is obliquely installed on the clamp of the laser head through the support frame, strong light interference is suppressed by adopting a double-band filter technology, the fusion width, the trailing angle and the temperature field distribution of the molten pool are captured in real time to realize multi-dimensional perception of the cladding state; the comprehensive control module is electrically connected with the capacitive sensing unit, the CCD vision unit and the laser head driving system, can adaptively distribute the decision weight of the double sensing unit based on the laser head movement speed and the workpiece surface curvature, fuse to generate Z-axis distance compensation instructions and laser power and scanning speed adjustment signals, and realize real-time closed-loop control of the relative distance between the nozzle and the workpiece; The control system performs the following control steps: Step S1: system initialization: calibrate the capacitive sensing unit, determine the capacitive value corresponding to the target distance, set the target fusion width and ideal alloy temperature parameters of the CCD vision unit, initialize the PID control parameters and dynamic weight initial value; Step S2: real-time detection of double sensors: the capacitive sensing unit detects the real-time capacitive value through the capacitive plate formed by the ceramic ring and the workpiece, and converts it into real-time distance data; The CCD vision unit synchronously collects the actual fusion width and temperature field data of the molten pool; Step S3: data fusion processing: the integrated control module receives the double sensing data, and calculates the fusion weight through a dynamic weight algorithm , When the moving speed of the laser head is greater than 1.0 m / min, the dynamic weight is 0.9, at this time, the capacitive sensing unit is dominant in the distance compensation decision. If the movement speed of the laser head is not greater than 1.0 m / min, the curvature of the workpiece curved surface is further judged, and when the curvature of the workpiece curved surface is greater than 0.1 , the dynamic weight is 0.3, at this time, the CCD vision unit is dominant in distance compensation decision. If the above two working conditions are not met, the dynamic weight is 0.6; according to the formula Calculate the final distance compensation amount, wherein is the height compensation amount of the capacitor output, is the height calculated by the CCD based on the molten pool area; Step S4: closed-loop adjustment control: generate Z-axis driving instructions through the PID algorithm according to the final distance compensation amount, and adjust the laser power and scanning speed based on the fusion width deviation and temperature deviation; Step S5: abnormal processing: if the CCD vision unit detects that the cladding layer is broken or the light interference causes data failure, trigger Modbus communication to transmit the abnormal signal to the comprehensive control module, and switch to the capacitive single sensing control mode until the fault is eliminated.

2. The laser cladding distance real-time control system according to claim 1, wherein, The interference fit parameters of the powder feeder device and the transition ceramic ring are: the interference amount is 0.02mm~0.03mm at room temperature, and the interference amount is kept at 0.008mm~0.01mm when the water circulation cooling maintains the working temperature at 86℃±5℃ to realize mechanical sealing; the gap between the inner nozzle and the outer nozzle is a powder outflow channel, and laser is focused through the inner nozzle to act on the workpiece surface, together with the outflowing powder to form a molten pool.

3. The system according to claim 1, wherein, The metalized plating layer is connected to the gold-plated copper needle through conductive silver glue to realize lossless transmission of the capacitance signal; the ceramic ring and the transition ceramic ring are coaxially arranged with the laser light path to ensure symmetrical distribution of the capacitance electric field; the powder feeder device is internally provided with a water cooling circulation structure for cooling the inner nozzle, the outer nozzle and the ceramic ring, so that the working temperature of each component is maintained to be less than or equal to 80 DEG C.

4. The system of claim 1, wherein the system further comprises a laser power control unit. In the CCD vision unit, the vision device is installed at an inclination of 45 DEG with respect to the horizontal plane and is calibrated to coincide with the laser focal point through the long hole of the support frame; the vision device adopts 850 nm / 950 nm dual-band filtering technology to suppress the strong light interference of the molten pool and can collect the molten pool width, trailing angle parameters and temperature field distribution data in real time.

5. The system of claim 1, wherein the system further comprises a laser power control unit. The integrated control module is internally provided with a dynamic weight algorithm and a PID control algorithm, which can adaptively distribute the decision weight of the capacitance sensing unit and the CCD vision unit according to the working conditions, generate Z-axis distance compensation instructions and laser power and scanning speed adjustment signals, and realize closed-loop control.

6. The system of claim 1, wherein the system further comprises a laser power control unit. The detection logic of the capacitance sensing unit in step S2 is as follows: The height compensation amount is calculated by the formula , wherein is a capacitance value corresponding to the calibration distance, is a real-time detection capacitance value, , is a PID proportional coefficient and a differential coefficient.

7. The system of claim 1, wherein the system further comprises a laser power control unit. The control system is suitable for outer circle cladding, 3D printing, coaxial wire feeding welding and bypass wire feeding welding scenes, and can control the cladding layer thickness fluctuation within plus or minus 0.06 mm through real-time compensation of distance mutation.

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