Intelligent laser head with molten pool monitoring

Abstract

The application discloses a kind of intelligent laser head with molten pool monitoring, belong to laser welding technical field.The application of a kind of intelligent laser head with molten pool monitoring, including device shell, fiber laser and molten pool detection head, the lower end of positioning support is provided with clamping plate, magnetorheological fluid damper is installed between clamping plate and positioning support, two micro piezoelectric ceramic drive structures are provided in molten pool detection head, lens assembly is provided in molten pool detection head.The application solves the problem that existing laser welding head cannot ensure the long-term stability of processing focal point and monitoring line in hot machine state, the angle and position of lens assembly and built-in lens can be changed in the application, the lens position is adjusted reversely according to real-time temperature, actively compensates the optical path deviation caused by thermal expansion, lens assembly changes from passive heat to active real-time correction, ensures the long-term stability of processing focal point and monitoring line of lens assembly in hot machine state, improves work effect.

Description

Technical Field

[0001] This invention relates to the field of laser welding technology, specifically to an intelligent laser head with molten pool monitoring. Background Technology

[0002] Laser-directed energy deposition (LDED) is an additive manufacturing technology that uses a laser as a heat source to form a molten pool on a substrate. Powder is then fed into the molten pool via a powder feeding device, and deposition occurs according to a pre-defined model. While LDED offers numerous advantages, the simultaneous interaction between the laser, powder, and metal substrate during deposition makes the chemical metallurgical and thermophysical processes highly complex. The rapid heating and cooling solidification process easily leads to defects such as microcracks, porosity, spheroidization, spatter, and collapse in the workpiece. These metallurgical defects and poor forming quality severely impact the microstructure and mechanical properties of the parts, hindering the development of this technology. Therefore, real-time monitoring of the parts during LDED is of paramount importance.

[0003] The molten pool is a tiny region of liquid metal formed on the surface of a material by laser action. Its state directly determines the quality of the final weld or printed layer. Traditional laser processing is "open-loop," meaning it is executed after preset parameters, which cannot cope with tiny fluctuations during the processing and requires monitoring of the molten pool.

[0004] Existing laser welding heads cannot ensure the long-term stability of the processing focus and monitoring line of sight under thermal conditions during actual use; therefore, they do not meet current requirements. To address this, we propose an intelligent laser head with molten pool monitoring. Summary of the Invention

[0005] The purpose of this invention is to provide an intelligent laser head with molten pool monitoring, which solves the problem mentioned in the background art that the laser welding head cannot ensure the long-term stability of the processing focus and monitoring line of sight in the hot-motor state during actual use.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an intelligent laser head with molten pool monitoring, comprising a device housing, a fiber laser, and a molten pool detection head. The fiber laser is disposed on both sides below the device housing, and the molten pool detection head is mounted on one side of the fiber laser. The fiber laser and the molten pool detection head are set at the same angle. Welding work is performed on the welding point and weld by using the fiber laser in conjunction with the laser emitting head, and the molten pool detection head detects the molten pool of the material above the processing table and the positioning worktable.

[0007] Positioning brackets are provided on both sides of the lower part of the device housing. A clamping plate is provided at the lower end of the positioning bracket. The fiber laser passes through the clamping plate and is embedded in the positioning bracket, engaging with the positioning bracket. A magnetorheological fluid damper is installed between the clamping plate and the positioning bracket. The magnetorheological fluid damper can effectively filter the high-frequency micro-amplitude vibrations during the high-speed movement of the robot, as well as the vibrations from the external workshop, thereby providing a stable environment for the precision optics and monitoring system inside the fiber laser, ensuring the clarity of the monitoring image and the stability of the processing beam during high-speed movement.

[0008] The molten pool detection head is equipped with two micro-piezoelectric ceramic drive structures and a lens assembly. The front end of the micro-piezoelectric ceramic drive structure is movably connected to both sides of the lens assembly via connecting ears. During use, the temperature around the molten pool is detected by a temperature sensor on the positioning worktable. After the detected temperature is received by the PLC module, the micro-piezoelectric ceramic drive structures are adjusted by extending and retracting to different lengths, thereby changing the angle and position of the lens assembly and the built-in lens. In long-term operation, laser welding is performed using a fiber laser. During welding, a clamping plate and a retainer are used to fix the fiber laser. After the fiber laser is kept in a stable position, high-precision laser welding can be performed.

[0009] Preferably, the device housing is equipped with a QBH interface, which is connected to the fiber laser and electrically connected to the optical calibrator. A laser positioning sensor is installed at the lower end of the device housing. During long-term operation, laser welding is performed using the fiber laser. During welding, the fiber laser is fixed by a clamping plate and a retainer. Once the fiber laser is in a stable position, high-precision laser welding can be performed.

[0010] Preferably, radiators are fixedly connected to both sides of the device housing, and the radiators are attached to the inside of the device housing through heat exchange pipes. A cooling fan is installed at the lower end of the radiator, and the cooling fan is connected to the radiator by fixing screws.

[0011] Preferably, a positioning bracket is installed on the lower side of the device housing. The positioning bracket is connected to the device housing by fixing bolts, and an adjustment head is provided at the lower end of the positioning bracket. The adjustment head is fixedly connected to the lower end of the positioning bracket by a locking member. Before and after operation, the position and angle of the molten pool detection head are adjusted by the adjustment head to ensure detection accuracy.

[0012] Preferably, a laser emitting head is installed at the lower end of the fiber laser, and a bypass protection nozzle is provided on one side of the laser emitting head. The bypass protection nozzle is fixedly connected to the device housing through a connecting rod. The bypass protection nozzle is used to introduce cold air to quickly cool the molten pool. A cleaning tube is provided inside the device housing. The position of the air blowing port of the cleaning tube corresponds to the welding position of the laser emitting head, and an air guide port is provided at the upper end of the cleaning tube.

[0013] Preferably, the two ends of the magnetorheological fluid damper are fixedly connected to the fastening frame and the retainer, respectively. The damper contains an excitation coil, magnetic poles, and a magnetorheological fluid filling cavity. The clamping plate engages with the fiber laser via damping washers. When current passes through the excitation coil, a controllable magnetic field is generated, with the magnetic field strength proportional to the current magnitude. Under the influence of the magnetic field, the yield stress of the magnetorheological fluid increases sharply, and the flow resistance significantly increases. By adjusting the current, the damping force can be continuously and rapidly changed, achieving the dissipation of vibration energy. A corresponding number of magnetorheological fluid dampers are installed between the fiber laser and the retainer. These dampers effectively filter high-frequency micro-amplitude vibrations during high-speed robot movement, as well as external workshop vibrations, thus providing a stable environment for the precision optics and monitoring system inside the fiber laser, ensuring the clarity of the monitored images and the stability of the processing beam during high-speed movement.

[0014] Preferably, the molten pool detection head is externally provided with a fixing plate, which is fixedly connected to the molten pool detection head and the adjustment head respectively by fixing screws. The front end of the lens assembly is provided with an internal lens, which extends out of the molten pool detection head and is movably connected to the molten pool detection head. The position of the lens is finely adjusted in reverse according to the real-time temperature to actively compensate for the optical path offset caused by thermal expansion. The lens assembly changes from passively bearing heat to actively correcting in real time, ensuring the long-term stability of the processing focus and monitoring line of the lens assembly under hot conditions, and improving the working efficiency.

[0015] Preferably, movable grooves are provided on both sides of the molten pool detection head, and a connector is provided at the upper end of the micro piezoelectric ceramic driving structure. The upper end of the micro piezoelectric ceramic driving structure is movably connected to the molten pool detection head in the movable groove through the connector.

[0016] Preferably, a vision camera is installed inside the molten pool detection head. The vision camera includes a CCD camera, a spectrometer, and an infrared thermal imager. A monitoring camera is installed in the middle of the device housing. Both the monitoring camera and the vision camera are connected to the terminal through a transmission module. The size, shape, and tail drag of the molten pool are acquired through the monitoring camera and the vision camera to perform thermal imaging monitoring, measure the temperature field distribution of the molten pool and the heat-affected zone in real time, and perform spectral monitoring. By analyzing the spectral characteristics of the plasma above the molten pool, element burn-off and defect generation can be inferred.

[0017] Preferably, a processing table is provided at the bottom of the device housing, a positioning worktable is installed at the upper end of the processing table, a temperature sensor is provided at the upper end of the positioning worktable, and the temperature sensor is electrically connected to the micro piezoelectric ceramic drive structure through a PLC module.

[0018] Preferably, the PLC module has a preset nonlinear compensation strategy based on thermomechanical coupling effect. The PLC module is configured to read the real-time temperature data of the temperature sensor at a preset sampling frequency and calculate the real-time driving voltage applied to the micro piezoelectric ceramic driving structure using the following thermal drift compensation formula. :

[0019]

[0020] In the formula, The real-time driving voltage applied to the micro piezoelectric ceramic drive structure is calculated and is expressed in volts (V). The zero-bias voltage of the lens assembly at its standard focal length is expressed in volts (V). The effective optical path physical length of the lens assembly at the reference temperature is expressed in meters (m). The equivalent linear thermal expansion coefficient of the materials of the device housing and the lens assembly is expressed in degrees Celsius (1 / ℃). The current real-time temperature collected by the temperature sensor is expressed in degrees Celsius (°C). The reference temperature for system calibration, in degrees Celsius (°C); The number of layers of piezoelectric ceramic stacks inside the micro-piezoelectric ceramic driving structure is a dimensionless constant. The longitudinal inverse piezoelectric constant of the micro-piezoelectric ceramic driving structure is used to characterize the voltage-displacement conversion efficiency, and its unit is meters per volt (m / V). is the thermal inertia gain coefficient, used to compensate for the time lag caused by heat conduction, and is a dimensionless constant; It is a natural logarithmic function used to simulate the nonlinear saturation characteristics of thermal stress accumulation; This represents the absolute value of the rate of temperature change within the current sampling period, expressed in degrees Celsius per second (°C / s). This is the thermal response sensitivity threshold, used to normalize the rate of temperature change, with units of degrees Celsius per second (°C / s).

[0021] The PLC module uses the thermal drift compensation formula to actively feedforward compensate the position of the lens assembly when the continuous operation of the fiber laser causes a cumulative increase in temperature or a sudden power change causes a drastic temperature fluctuation.

[0022] Preferably, the terminal is further configured to execute a visually sharp magnetorheological damping adaptive vibration suppression method, the method specifically including the following steps:

[0023] Step S1: The terminal receives the real-time video stream of the molten pool captured by the vision camera through the transmission module, and extracts the region of interest (ROI) containing the edge of the molten pool from each frame image.

[0024] Step S2: The terminal performs convolution operation on the region of interest using the Laplacian operator, calculates the average edge gradient magnitude of the current frame image, and defines it as the image sharpness index. ;

[0025] Step S3: The terminal monitors the image sharpness index in real time. When detected When the value is lower than the preset clarity threshold, it is determined that the device housing is being interfered with by a slight high-frequency vibration.

[0026] Step S4: The terminal immediately starts the active vibration suppression optimization mode and sends an adjustment command to the controller connected to the magnetorheological fluid damper to change the current input to the excitation coil of the magnetorheological fluid damper in a stepped manner with a preset step size.

[0027] Step S5: After each change in current magnitude, the terminal recalculates the new image sharpness index. And compare the current before and after the change. Value changes, retain The direction of increasing current value, until... The value reaches a local maximum, thus locking in the optimal damping stiffness that can suppress micro-amplitude vibrations to the greatest extent under the current working conditions.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] This invention utilizes a fiber laser with a laser emitter head to perform welding work on welding points and welds. A molten pool detection head monitors the molten pool above the processing table and positioning table. During operation, a temperature sensor on the positioning table detects the temperature around the molten pool. The detected temperature data is received by a PLC module and adjusted via a micro-piezoelectric ceramic drive structure. Two micro-piezoelectric ceramic drive structures extend and retract to different lengths, thereby changing the angle and position of the lens assembly and built-in lenses. The lens position is finely adjusted in reverse according to the real-time temperature, actively compensating for optical path offset caused by thermal expansion. The lens assembly changes from passively enduring heat to actively correcting it in real time, ensuring the long-term stability of the lens assembly's processing focus and monitoring line of sight under thermal conditions, thus improving work efficiency.

[0030] In long-term operation, this invention utilizes a fiber laser for laser welding. During welding, a clamping plate and a cage secure the fiber laser, ensuring its stable position for high-precision laser welding. A corresponding number of magnetorheological fluid dampers are installed between the fiber laser and the cage. These dampers effectively filter high-frequency, low-amplitude vibrations during high-speed robot movement, as well as external workshop vibrations. This provides a stable environment for the precision optics and monitoring system within the fiber laser, ensuring the clarity of the monitored images and the stability of the processing beam during high-speed movement. Furthermore, the symmetrical layout and counterweight design of the fiber laser and cage minimize angular momentum and vibration during high-speed deflection, effectively reducing the recoil disturbance of the laser head caused by internal movement, improving scanning positioning accuracy and dynamic response speed, and further enhancing operational precision. Attached Figure Description

[0031] Figure 1 This is an isometric view of the front view of the present invention;

[0032] Figure 2 This is an axonometric view of the invention from below;

[0033] Figure 3 For the present invention Figure 2 Enlarged view of a portion of area A in the middle;

[0034] Figure 4 This is an isometric view of the side view of the present invention;

[0035] Figure 5 For the present invention Figure 4 Enlarged view of a section in area B;

[0036] Figure 6 This is an isometric view of the molten pool detection head of the present invention from the rear.

[0037] Figure 7 This is an isometric view of the front view of the molten pool detection head of the present invention;

[0038] Figure 8 This is an internal isometric view of the front view of the molten pool detection head of the present invention;

[0039] Figure 9 This is an isometric view of the front view of the cage of the present invention.

[0040] In the diagram: 1. Device housing; 101. QBH interface; 102. Heat sink; 103. Cooling fan; 104. Positioning bracket; 2. Cage; 201. Fiber laser; 202. Laser emitter head; 203. Fastening bracket; 204. Magnetorheological fluid damper; 205. Clamping plate; 3. Molten pool detection head; 301. Adjustment head; 302. Fixing plate; 303. Lens assembly; 304. Built-in lens; 305. Micro-piezoelectric ceramic drive structure; 306. Vision camera; 307. Connector; 4. Extremity protection nozzle; 5. Machining table; 501. Positioning worktable; 6. Cleaning tube; 601. Air vent; 7. Monitoring camera. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0042] To address the issue that existing laser welding heads cannot guarantee the long-term stability of the processing focus and monitoring line of sight under thermal conditions during practical use, please refer to... Figure 1 , Figure 4 - Figure 8 This embodiment provides the following technical solution:

[0043] This embodiment of an intelligent laser head with molten pool monitoring includes a device housing 1, a fiber laser 201, and a molten pool detection head 3. The fiber laser 201 is disposed on both sides below the device housing 1, and the molten pool detection head 3 is installed on one side of the fiber laser 201. The fiber laser 201 and the molten pool detection head 3 are set at the same angle. Welding work is performed on the welding point and weld by using the fiber laser 201 in conjunction with the laser emitting head 202. The molten pool detection head 3 detects the molten pool of the material above the processing table 5 and the positioning worktable 501.

[0044] Positioning brackets 104 are provided on both sides of the lower part of the device housing 1. A clamping plate 205 is provided at the lower end of the positioning bracket 104. The fiber laser 201 passes through the clamping plate 205 and is embedded in the positioning bracket 104 and engaged with the positioning bracket 104. A magnetorheological fluid damper 204 is installed between the clamping plate 205 and the positioning bracket 104. The magnetorheological fluid damper 204 can effectively filter the high-frequency micro-amplitude vibration during the high-speed movement of the robot, as well as the vibration from the external workshop, thereby providing a stable environment for the precision optics and monitoring system inside the fiber laser 201, ensuring the clarity of the monitoring image and the stability of the processing beam during high-speed movement.

[0045] The molten pool detection head 3 is equipped with two micro-piezoelectric ceramic drive structures 305 and a lens assembly 303. The front end of the micro-piezoelectric ceramic drive structure 305 is movably connected to both sides of the lens assembly 303 through connecting ears. During use, the temperature around the molten pool is detected by the temperature sensor on the positioning worktable 501. After the detected temperature is received by the PLC module, it is adjusted by the micro-piezoelectric ceramic drive structure 305. The two micro-piezoelectric ceramic drive structures 305 can be extended and retracted to different lengths, thereby changing the angle and position of the lens assembly 303 and the built-in lens 304. During long-term operation, laser welding is performed by the fiber laser 201. During welding, the fiber laser 201 is fixed by the clamping plate 205 and the retainer 2. After the fiber laser 201 is kept in a stable position, high-precision laser welding can be performed.

[0046] In fact, the outside of the molten pool detection head 3 is provided with a fixing plate 302. The fixing plate 302 is fixedly connected to the molten pool detection head 3 and the adjusting head 301 respectively by fixing screws. The front end of the lens assembly 303 is provided with an internal lens 304. The internal lens 304 extends out of the molten pool detection head 3 and is movably connected to the molten pool detection head 3.

[0047] In addition, movable slots are provided on both sides of the molten pool detection head 3, and a connector 307 is provided at the upper end of the micro piezoelectric ceramic drive structure 305. The upper end of the micro piezoelectric ceramic drive structure 305 is movably connected to the molten pool detection head 3 in the movable slot through the connector 307. The lens position is adjusted in reverse according to the real-time temperature to actively compensate for the optical path offset caused by thermal expansion. The lens assembly 303 changes from passively bearing heat to actively correcting in real time, ensuring the long-term stability of the processing focus and monitoring line of the lens assembly 303 under hot conditions, and improving the working effect.

[0048] The molten pool detection head 3 is equipped with a vision camera 306, which includes a CCD camera, a spectrometer, and an infrared thermal imager. The monitoring camera 7 is installed in the middle of the device housing 1. Both the monitoring camera 7 and the vision camera 306 are connected to the terminal through a transmission module. The size, shape, and tail drag of the molten pool are acquired through the monitoring camera 7 and the vision camera 306 to perform thermal imaging monitoring, measure the temperature field distribution of the molten pool and the heat-affected zone in real time, and perform spectral monitoring. By analyzing the spectral characteristics of the plasma above the molten pool, element burn-off and defect generation can be inferred.

[0049] Furthermore, a processing table 5 is provided at the bottom of the device housing 1, and a positioning worktable 501 is installed at the upper end of the processing table 5. A temperature sensor is provided at the upper end of the positioning worktable 501, and the temperature sensor is electrically connected to the micro piezoelectric ceramic drive structure 305 through a PLC module.

[0050] Specifically, welding is performed on the welding points and weld seams by using a fiber laser 201 with a laser emitting head 202. The molten pool detection head 3 detects the molten pool of the material above the processing table 5 and the positioning worktable 501. During use, the temperature sensor on the positioning worktable 501 detects the temperature around the molten pool. After the detected temperature is received by the PLC module, it is adjusted by the micro piezoelectric ceramic drive structure 305. The two micro piezoelectric ceramic drive structures 305 extend and retract to different lengths, thereby changing the angle and position of the lens assembly 303 and the built-in lens 304. The lens position is finely adjusted in reverse according to the real-time temperature to actively compensate for the optical path offset caused by thermal expansion. The lens assembly 303 changes from passively bearing heat to actively correcting in real time, ensuring the long-term stability of the processing focus and monitoring line of the lens assembly 303 under thermal conditions, thus improving the working efficiency.

[0051] To address the issue that existing laser welding heads cannot guarantee the long-term stability of the processing focus and monitoring line of sight under thermal conditions during practical use, please refer to... Figure 1 - Figure 3 , Figure 9 This embodiment provides the following technical solution:

[0052] In this embodiment, a QBH interface 101 is installed on the device housing 1. The QBH interface 101 is connected to the fiber laser 201 and electrically connected to the optical calibrator. A laser positioning sensor is installed at the lower end of the device housing 1. During long-term operation, laser welding is performed through the fiber laser 201. During welding, the fiber laser 201 is fixed by the clamping plate 205 and the retainer 2. After the fiber laser 201 is kept in a stable position, high-precision laser welding can be performed.

[0053] Heat sinks 102 are fixedly connected to both sides of the device housing 1, and the heat sinks 102 are in contact with the inside of the device housing 1 through heat exchange tubes. A cooling fan 103 is installed at the lower end of the heat sink 102, and the cooling fan 103 is connected to the heat sink 102 by fixing screws.

[0054] A positioning bracket 104 is installed on the lower side of the device housing 1. The positioning bracket 104 is connected to the device housing 1 by fixing bolts, and an adjustment head 301 is provided at the lower end of the positioning bracket 104. The adjustment head 301 is fixedly connected to the lower end of the positioning bracket 104 by a locking member. Before and after operation, the position and angle of the molten pool detection head 3 are adjusted by the adjustment head 301 to ensure detection accuracy.

[0055] A laser emitter 202 is installed at the lower end of the fiber laser 201. A bypass protection air nozzle 4 is provided on one side of the laser emitter 202. The bypass protection air nozzle 4 is fixedly connected to the device housing 1 through a connecting rod. The bypass protection air nozzle 4 is used to introduce cold air to quickly cool the molten pool. A cleaning tube 6 is provided inside the device housing 1. The position of the air outlet of the cleaning tube 6 corresponds to the welding position of the laser emitter 202. An air guide port 601 is provided at the upper end of the cleaning tube 6. During use, the bypass protection air nozzle 4 provides a certain protection for the laser emitter 202. Before and after work, air can be introduced through the cleaning tube 6 to treat the welding position and the molten pool to improve the working effect.

[0056] The magnetorheological fluid damper 204 is fixedly connected at both ends to the fastening frame 203 and the retainer 2, respectively. The damper 204 contains an excitation coil, magnetic poles, and a magnetorheological fluid filling cavity. The clamping plate 205 engages with the fiber laser 201 via damping washers. When current passes through the excitation coil, a controllable magnetic field is generated, with the magnetic field strength proportional to the current magnitude. Under the influence of the magnetic field, the yield stress of the magnetorheological fluid increases sharply, and the flow resistance significantly increases. By adjusting the current, the damping force can be continuously and rapidly changed, achieving the dissipation of vibration energy. A corresponding number of magnetorheological fluid dampers 204 are installed between the fiber laser 201 and the retainer 2. These dampers effectively filter high-frequency micro-amplitude vibrations during the robot's high-speed movement, as well as external workshop vibrations, thus providing a stable environment for the precision optics and monitoring system inside the fiber laser 201, ensuring the clarity of the monitored images and the stability of the processing beam during high-speed movement.

[0057] Specifically, during long-term operation, laser welding is performed using a fiber laser 201. During welding, a clamping plate 205 and a cage 2 are used to fix the fiber laser 201 in place. Once the fiber laser 201 is in a stable position, high-precision laser welding can be performed. Between the fiber laser 201 and the cage 2, a corresponding number of magnetorheological fluid dampers 204 are installed. These dampers effectively filter high-frequency micro-amplitude vibrations during the robot's high-speed movement, as well as external workshop vibrations. This provides a stable environment for the precision optics and monitoring system inside the fiber laser 201, ensuring the clarity of the monitoring images and the stability of the processing beam during high-speed movement. Furthermore, the symmetrical layout and counterweight design of the fiber laser 201 and the cage 2 minimize angular momentum and vibration during high-speed deflection, effectively reducing the recoil disturbance of the laser head caused by internal movement, improving scanning positioning accuracy and dynamic response speed, and further enhancing working precision.

[0058] Working Principle: During use, the material to be welded is placed and fixed on the positioning worktable 501. The temperature around the molten pool is monitored in real time by a temperature sensor on the surface of the positioning worktable 501. Welding is performed on the welding points and weld seams using a fiber laser 201 and a laser emitter 202. The molten pool is detected by a molten pool detection head 3 on the processing table 5 and the positioning worktable 501. During use, the temperature around the molten pool is detected by a temperature sensor on the positioning worktable 501. After the detected temperature is received by the PLC module, it is adjusted by the micro-piezoelectric ceramic drive structure 305. The two micro-piezoelectric ceramic drive structures 305 extend and retract to different lengths, thereby changing the angle and position of the lens assembly 303 and the built-in lens 304. The lens position is finely adjusted in reverse according to the real-time temperature, actively compensating for the optical path offset caused by thermal expansion. The lens assembly 303 changes from passively bearing heat to actively correcting in real time, ensuring that the processing focus and monitoring line of the lens assembly 303 are aligned with the heat source. The long-term stability under machine conditions improves work efficiency. During long-term operation, laser welding is performed using the fiber laser 201. During welding, the fiber laser 201 is fixed by the clamping plate 205 and the cage 2. After the fiber laser 201 is kept in a stable position, high-precision laser welding can be performed. Between the fiber laser 201 and the cage 2, a corresponding number of magnetorheological fluid dampers 204 are installed. The magnetorheological fluid dampers 204 can effectively filter the high-frequency micro-amplitude vibrations during the high-speed movement of the robot, as well as the vibrations from the external workshop. This provides a stable environment for the precision optics and monitoring system inside the fiber laser 201, ensuring the clarity of the monitoring images and the stability of the processing beam during high-speed movement. Furthermore, the symmetrical layout and counterweight design of the fiber laser 201 and the cage 2 minimize the angular momentum and vibration during high-speed deflection, effectively reducing the recoil disturbance of the laser head caused by internal movement, improving scanning positioning accuracy and dynamic response speed, and further improving working accuracy.

[0059] In this embodiment, in actual laser-directed energy deposition or high-power deep penetration welding scenarios, as the emission time of the fiber laser 201 continues, the device housing 1, lens assembly 303, and internal optical lenses will inevitably absorb some laser energy and high-temperature radiation from the molten pool. This heat accumulation manifests as increased vibration of the material lattice at the microscopic level and as slight thermal expansion of the precision optical structure at the macroscopic level. For precision laser processing with extremely short depth of focus, even a micrometer-level axial elongation of the optical path is sufficient to cause the focal point to deviate from the preset processing plane, resulting in decreased energy density, insufficient weld penetration, or blurred monitoring images. Traditional passive heat dissipation methods are limited by the heat conduction rate and cannot eliminate this dynamic thermal drift in real time.

[0060] Therefore, in this specific implementation, the PLC module establishes high-frequency data communication with temperature sensors distributed at key hot spots on the positioning workbench 501 and the device housing 1 via an industrial fieldbus, and is connected to the high-voltage linear amplifier controlling the micro-piezoelectric ceramic drive structure 305 via a high-precision digital-to-analog converter interface. To ensure the accuracy of compensation, the system performs a combined thermal, mechanical, and electrical calibration procedure before leaving the factory or during each power-on initialization phase. During the calibration phase, the system is in a constant temperature and dust-free environment, and the PLC module reads the temperature at this time as the reference temperature. (Typically set to a standard industrial ambient temperature, such as 25 degrees Celsius). Simultaneously, the optical focal length of the lens assembly 303 without thermal deformation is precisely measured using a laser interferometer, and the voltage applied to the micro-piezoelectric ceramic drive structure 305 is adjusted to be at the center of the linear displacement range; this voltage is recorded as the zero-point bias voltage. Usually Setting the voltage to the midpoint of the maximum drive voltage (e.g., 75V, corresponding to a drive range of 0-150V) not only provides preload to the piezoelectric ceramic, improving the dynamic stiffness of the system, but also provides ample voltage travel margin for subsequent bidirectional adjustment (compensating for both elongation due to thermal expansion and contraction due to rapid cooling). Furthermore, the system needs to store several key physical constants: The effective optical path physical length of lens assembly 303 at a reference temperature is precisely given by the optical design drawings; The comprehensive equivalent linear thermal expansion coefficient of the device housing 1 and lens assembly 303 reflects the dimensional response characteristics of a specific metallic material (such as aerospace aluminum or stainless steel) as temperature changes. This coefficient is a comprehensive coefficient calculated by weighted finite element thermal analysis (FEA). The number of layers of piezoelectric ceramic stacks inside the micro piezoelectric ceramic drive structure 305 determines the total stroke capability of the actuator. is the longitudinal inverse piezoelectric constant of the piezoelectric material, characterizing the efficiency of converting electric field energy into mechanical displacement.

[0061] Once the intelligent laser head enters its operational state, the PLC module initiates a real-time monitoring and compensation cycle. The execution period of this cycle is set to milliseconds (e.g., 10ms to 20ms) to ensure the capture of transient thermal shocks. The PLC module first reads the current real-time analog signal from the temperature sensor, processes it through analog-to-digital conversion and a moving average filtering algorithm to remove noise caused by high-frequency electromagnetic interference, and obtains the accurate current real-time temperature. Next, the PLC module uses its internal differential processing unit, combined with the temperature data from the previous sampling period, to calculate the rate of temperature change at the current moment in real time. At the moment of sudden change in laser power or start-up and shutdown of processing, the rate of temperature change often reflects the internal thermal stress state of the system before the absolute temperature value. Introducing the rate of temperature change is the key to solving the thermal hysteresis problem.

[0062] Subsequently, the PLC module calls its internally preset thermal drift compensation formula based on thermomechanical coupling effect to perform high-precision floating-point calculations. linear terms in It is responsible for handling thermal expansion compensation under steady-state conditions. Its physical logic is as follows: based on the current temperature difference... With expansion coefficient Calculate the theoretical elongation of the optical path and then divide it by the driving sensitivity of the piezoelectric ceramic. This allows us to determine the voltage adjustment required to offset the elongation. This part ensures that the micro piezoelectric ceramic drive structure 305 can smoothly correct the position of the lens assembly 303 when the temperature changes slowly, maintaining a constant physical length of the optical path.

[0063] However, linear compensation alone cannot address the transient thermal shock problem commonly encountered in laser welding. When the laser power jumps instantaneously from preheating power (e.g., 10%) to welding power (e.g., 100%), or when the welding path passes through areas with drastically different heat dissipation conditions, the lens assembly 303 experiences severe thermal shock. In this situation, because heat conduction takes time, the temperature sensor reading often lags behind the actual thermal stress experienced by the optical lens, and the accumulation of thermal stress within the material exhibits nonlinear saturation characteristics. Therefore, a nonlinear correction factor in the formula is needed. This is the core of the invention. Among them, The thermal inertia gain coefficient is a dimensionless physical quantity whose value depends on the thermal conductivity and specific heat capacity of the device housing 1. For structures with slow thermal conductivity and large heat capacity, heat transfer from the surface to the internal mirrors takes a long time, exhibiting a significant time lag. In such cases, a larger gain coefficient needs to be set. Values ​​(such as 0.3 to 0.5) are used to enhance the strength of the feedforward compensation. Natural logarithm function The introduction of this method is to simulate the saturation characteristics during the establishment of thermal stress in materials. As the rate of temperature change increases, the internal thermal stress of the material does not increase linearly indefinitely, but rather tends towards saturation due to limitations imposed by heat capacity and phonon scattering. The growth curve of the logarithmic function (fast at first, then slow) effectively matches this physical law. When the laser power suddenly increases, the rate of temperature change... When the voltage rises sharply, several parameters increase rapidly, causing the calculated driving voltage to rise even more. A significant overshoot component is superimposed on the linear value. This overshoot component drives the micro piezoelectric ceramic drive structure 305 to move rapidly and push the lens assembly 303 to the predicted thermal equilibrium position in advance. Thus, the pre-compensation of the optical focus is completed before the heat is fully conducted and causes physical deformation of the optical path. As a thermal response sensitivity threshold, it is a normalization factor with physical dimensions (°C / s), which sets the threshold for the system to initiate nonlinear compensation. When the rate of temperature change is much smaller than... When the temperature change rate increases dramatically (in the steady state), the ratio approaches zero and the natural logarithm term approaches zero, and the system mainly performs linear compensation. When the temperature change rate increases dramatically (in the transient state), the nonlinear compensation mechanism is strongly activated.

[0064] Ultimately, the calculated The voltage is converted to analog voltage by a DAC module, amplified by a high-voltage amplifier, and then applied to the micro-piezoelectric ceramic drive structure 305. Utilizing the inverse piezoelectric effect, the stacked piezoelectric ceramics generate precise displacements at the nanometer to micrometer level. This displacement, via connector 307 and connecting ears, drives the lens assembly 303 to move slightly along the optical axis, thus counteracting the effects of thermal expansion in real time. This feedforward control based on a physical model effectively solves the hysteresis problem of traditional feedback control, ensuring the focus stability of the laser head across the entire power and temperature range. Furthermore, the PLC module incorporates safety protection logic; once a calculated... If the voltage exceeds the hardware safety threshold (e.g., beyond the range of -20V to 150V), the system will automatically limit the voltage and issue an alarm to prevent piezoelectric stack breakdown or mechanical overload.

[0065] Furthermore, in this embodiment, in modern high-end manufacturing, the intelligent laser head is typically mounted on a six-axis industrial robot or a high-speed gantry milling machine. When the actuator performs sudden stops, sudden rotations, or high-speed scanning actions, or when the workshop environment is affected by low-frequency ground vibrations caused by large stamping equipment, the device housing 1 and its internal precision optical components will be subjected to complex multidimensional vibration interference. Although such micro-amplitude high-frequency vibrations (typically with amplitudes between 10μm and 100μm and frequencies between 10Hz and 200Hz) are difficult to detect with the naked eye, they are the cause of image motion blur and edge ghosting for high-magnification molten pool monitoring systems, severely interfering with subsequent molten pool feature extraction algorithms. Traditional passive damping solutions (such as rubber pads or springs) cannot simultaneously meet the requirements for suppressing both low-frequency large-amplitude shaking and high-frequency micro-amplitude flutter due to their fixed damping characteristics. To solve this problem, this invention utilizes the existing vision system inside the molten pool detection head 3 as a vibration sensor, combined with a magnetorheological fluid damper 204 as an intelligent actuator, to construct an adaptive vibration suppression system.

[0066] The system's execution entity is a terminal (such as a high-performance industrial computer or embedded edge computing unit) electrically connected to the molten pool detection head 3 and the magnetorheological fluid damper 204. The entire control logic is designed as a gradient optimization closed loop based on visual feedback. This method directly correlates the optical path imaging quality with the mechanical damping control, forming a closed loop.

[0067] First, step S1 is executed: Molten pool video stream acquisition and dynamic locking of the region of interest (ROI). To meet the real-time requirements of vibration suppression control (the control period must be much shorter than the vibration period), the terminal first receives the real-time video stream of the molten pool acquired by the vision camera 306 at a high frame rate (e.g., above 120fps) via a high-speed digital interface (such as GigEVision or Camera Link). Since the original image resolution is high (e.g., 5 megapixels), the data throughput for full-image processing is extremely large, leading to significant computational latency. Therefore, the terminal first executes the ROI locking algorithm. This algorithm utilizes the high brightness characteristics of the molten pool itself to quickly locate the centroid coordinates of the molten pool in the first frame image using grayscale thresholding or a Gaussian mixture model (GMM). Subsequently, a rectangular region of a fixed size (e.g., 256x256 pixels) is cropped around this centroid as the region of interest (ROI). In subsequent frame processing, the terminal uses a Kalman filter or particle filter algorithm to predict the position of the molten pool centroid in the next frame, dynamically updating the cropped coordinates of the ROI. In this way, no matter how the laser head moves, the ROI always tracks the molten pool area, which contains high-frequency texture information such as the edge of the molten pool, keyhole, and heat-affected zone. It is the most sensitive area to blurring caused by vibration and is also the best sample for calculating image sharpness.

[0068] Next, step S2 is executed: image sharpness quantification evaluation based on the Laplacian operator. After acquiring the ROI image, the system needs an objective mathematical indicator to quantify the current level of vibration. Physical optics principles show that mechanical vibration causes image point displacement within the imaging system during exposure time, resulting in motion blur in the image, manifested as the diffusion of edge gradients and the loss of high-frequency details. This embodiment selects the Laplacian operator as the core tool for edge detection and sharpness evaluation. The Laplacian operator is an isotropic second-order differential operator with a strong response to abrupt changes in image grayscale (i.e., edges), while its response is zero for regions with gradual grayscale changes. In specific computation, the terminal utilizes a preset convolution kernel (e.g., ... standard core Or enhance the core A sliding convolution operation is performed on the pixel matrix within the ROI region. If the device housing 1 vibrates, the imaging points will shift on the sensor target surface during the exposure time, causing the originally sharp edges of the molten pool to blur, the grayscale gradient to become gentler, and the output value (gradient magnitude) after convolution to decrease significantly. Conversely, if the system is stable and the edges are steep, the gradient magnitude will be high. The terminal calculates the average gradient magnitude (or energy spectral density) of all pixels in the convolved image and defines it as the image sharpness index Q. This Q value is monotonically negatively correlated with the amplitude of mechanical vibration, that is, the smaller the vibration, the larger the Q value.

[0069] Subsequently, step S3 is executed: real-time monitoring and threshold determination of vibration status. A monitoring thread runs in the background on the terminal, recording the time-series changes of the Q value in real time. To prevent Q value fluctuations caused by welding spatter or arc flash from falsely triggering vibration suppression, a statistical filtering mechanism is introduced. The system has a preset sharpness threshold. This threshold is 90% of the average Q value measured under a baseline condition where the laser head is absolutely stationary and the welding process is stable. When the monitoring thread detects a continuous real-time Q value... Frames (e.g.) to (lower than) If the sliding variance of the Q value exceeds the set limit, and optical interference such as smoke and dust obstruction has been eliminated (which can be eliminated with the assistance of infrared thermal imager data), the terminal immediately determines that the device housing 1 and its internal precision optical system are being interfered with by micro-amplitude high-frequency vibration. At this time, it indicates that the original passive damping state is insufficient to dissipate the current vibration energy, or that the movement frequency of the robotic arm has coupled and resonated with the natural frequency of the laser head, and the active vibration suppression mode is immediately activated.

[0070] Next, steps S4 and S5 are executed: active vibration suppression optimization control. Once the vibration suppression mode is triggered, the terminal immediately switches to the active optimization control state. At this time, the terminal sends an adjustment command to the precision programmable current source connected to the magnetorheological fluid damper 204. The magnetorheological fluid damper 204 is filled with a suspension of magnetic particles (such as micron-sized carbonyl iron powder), which behaves as a low-viscosity Newtonian fluid when there is no magnetic field; when the excitation coil is energized to generate a magnetic field, the magnetic particles arrange themselves into chains along the magnetic field lines within milliseconds, and the fluid instantly transforms into a high-viscosity, high-yield-stress Bingham plastic body. This embodiment adopts an online optimization strategy based on the perturbation observation method or the hill climbing algorithm. Since the source and mode of vibration are unknown and constantly changing, there is no fixed optimal current. Therefore, the terminal changes the current input to the excitation coil in a stepwise manner with a preset step size (e.g., 10mA). For example, if the initial current is 0.5A, the system instructs it to increase to 0.51A. This current change directly enhances the magnetic field inside the damper, increases the shear yield stress of the magnetorheological fluid, and thus changes the damping ratio and dynamic stiffness of the entire suspension system, attempting to disrupt the resonance condition or absorb vibration energy.

[0071] After each current adjustment command is issued and a very short physical response time has elapsed (e.g., waiting 10ms to 20ms for the magnetorheological fluid to complete the phase change and the mechanical system to respond), the terminal acquires a new frame of image and repeats steps S1 and S2 to calculate a new image sharpness index. The terminal will Compared with the previous The comparison is made, and the direction of the next adjustment is determined based on the comparison results. Specific situations include:

[0072] Scenario 1: If This indicates that increasing the current (i.e., increasing the damping / stiffness) effectively suppressed the current vibration mode, and the image became clearer. The terminal will determine that the adjustment direction is correct and maintain this current direction, continuing to increase the current in stepwise increments in an attempt to obtain a higher Q value until the Q value stops increasing or begins to decrease.

[0073] Scenario 2: If This indicates that increasing the current actually worsened the vibration. This usually signifies overdamping or a hard connection, meaning the damper has become too stiff, causing high-frequency flutter from the robot's end effector to be transmitted to the laser head without attenuation, or triggering new higher-order modal vibrations. In this case, the end effector will immediately reverse its adjustment direction (i.e., reduce the current) in an attempt to isolate the vibration by reducing its stiffness.

[0074] Through this high-frequency iterative cycle of "adjustment, detection, comparison, and readjustment," the terminal can find a current operating point that brings the image sharpness index Q to a local maximum within a very short time (typically within 0.1 to 0.3 seconds). This operating point corresponds to the optimal damping matching state under the current specific operating condition. Once this optimal value is locked, the system will maintain a constant current until a significant decrease in the Q value is detected again, thereby achieving dynamic adaptation to the vibration environment.

[0075] Furthermore, the magnetorheological fluid damper 204 is structurally tightly coupled to the fiber laser 201 and the device housing 1 via a clamping plate 205. When the damper is in optimal control, it efficiently converts the mechanical vibration energy transmitted from the outside into fluid shear heat energy inside the magnetorheological fluid and dissipates it, thereby creating a relatively static inertial stabilization platform for the internal vision camera 306 and precision lens assembly.

[0076] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0077] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A smart laser head with molten pool monitoring, comprising a device housing (1), a fiber laser (201), and a molten pool detection head (3), characterized in that, The fiber laser (201) is located on both sides below the device housing (1), and the molten pool detection head (3) is installed on one side of the fiber laser (201). The fiber laser (201) and the molten pool detection head (3) are set at the same angle. Positioning brackets (104) are provided on both sides of the lower part of the device housing (1). A clamping plate (205) is provided at the lower end of the positioning bracket (104). The fiber laser (201) passes through the clamping plate (205) and is embedded in the positioning bracket (104) and engaged with the positioning bracket (104). A magnetorheological fluid damper (204) is installed between the clamping plate (205) and the positioning bracket (104). The molten pool detection head (3) is provided with two micro piezoelectric ceramic driving structures (305), and the molten pool detection head (3) is provided with a lens assembly (303). The front end of the micro piezoelectric ceramic driving structure (305) is movably connected to both sides of the lens assembly (303) through connecting ears. The bottom of the device housing (1) is provided with a processing table (5), and the upper end of the processing table (5) is provided with a positioning worktable (501). The upper end of the positioning worktable (501) is provided with a temperature sensor, and the temperature sensor is electrically connected to the micro piezoelectric ceramic drive structure (305) through a plic module. The PLC module has a preset nonlinear compensation strategy based on thermomechanical coupling effect. The PLC module is configured to read the real-time temperature data of the temperature sensor at a preset sampling frequency and calculate the real-time driving voltage applied to the micro piezoelectric ceramic driving structure (305) using the following thermal drift compensation formula. : In the formula, The calculated real-time driving voltage applied to the micro piezoelectric ceramic drive structure (305); The zero-bias voltage of the lens assembly (303) when it is at its standard focal length; The effective optical path physical length of the lens assembly (303) at the reference temperature; The equivalent linear thermal expansion coefficient of the materials of the device housing (1) and the lens assembly (303); The current real-time temperature collected by the temperature sensor; The reference temperature used for system calibration; The number of layers of piezoelectric ceramic stacks inside the micro piezoelectric ceramic driving structure (305); The longitudinal inverse piezoelectric constant of the micro-piezoelectric ceramic drive structure (305) is used to characterize the voltage-displacement conversion efficiency; This is the thermal inertia gain coefficient, used to compensate for the time lag caused by heat conduction; It is a natural logarithmic function used to simulate the nonlinear saturation characteristics of thermal stress accumulation; This represents the absolute value of the rate of temperature change within the current sampling period. This is the thermal response sensitivity threshold, used to normalize the rate of temperature change. The PLC module performs active feedforward compensation on the position of the lens assembly (303) by means of the thermal drift compensation formula, when the continuous operation of the fiber laser (201) causes the temperature to rise cumulatively or the power change causes the temperature to fluctuate drastically.

2. The intelligent laser head with molten pool monitoring according to claim 1, characterized in that, A QBH interface (101) is installed on the device housing (1). The QBH interface (101) is connected to the fiber laser (201) and electrically connected to the optical calibrator. A laser positioning sensor is installed at the lower end of the device housing (1).

3. The intelligent laser head with molten pool monitoring according to claim 1, characterized in that, Heat sinks (102) are fixedly connected to both sides of the device housing (1), and the heat sinks (102) are attached to the inside of the device housing (1) through heat exchange tubes. A cooling fan (103) is installed at the lower end of the heat sink (102), and the cooling fan (103) is connected to the heat sink (102) by fixing screws.

4. The intelligent laser head with molten pool monitoring according to claim 3, characterized in that, A positioning bracket (104) is installed on the lower side of the device housing (1). The positioning bracket (104) is connected to the device housing (1) by fixing bolts, and an adjustment head (301) is provided at the lower end of the positioning bracket (104). The adjustment head (301) is fixedly connected to the lower end of the positioning bracket (104) by a locking member.

5. The intelligent laser head with molten pool monitoring according to claim 1, characterized in that, The lower end of the fiber laser (201) is equipped with a laser emitter head (202). A bypass protection nozzle (4) is provided on one side of the laser emitter head (202). The bypass protection nozzle (4) is fixedly connected to the device housing (1) through a connecting rod. The bypass protection nozzle (4) is used to introduce cold air to quickly cool the molten pool. A cleaning tube (6) is provided inside the device housing (1). The position of the air outlet of the cleaning tube (6) corresponds to the welding position of the laser emitter head (202). An air guide port (601) is provided at the upper end of the cleaning tube (6).

6. The intelligent laser head with molten pool monitoring according to claim 1, characterized in that, The two ends of the magnetorheological damper (204) are fixedly connected to the fastening frame (203) and the retainer (2) respectively. The magnetorheological damper (204) is provided with an excitation coil, magnetic poles and a magnetorheological fluid filling cavity. The clamping plate (205) is engaged with the fiber laser (201) through a damping washer. ‌ 7. The intelligent laser head with molten pool monitoring according to claim 1, characterized in that, The outside of the molten pool detection head (3) is provided with a fixing plate (302), which is fixedly connected to the molten pool detection head (3) and the adjusting head (301) respectively by fixing screws. The front end of the lens assembly (303) is provided with an internal lens (304), which extends out of the molten pool detection head (3) and is movably connected to the molten pool detection head (3). Both sides of the molten pool detection head (3) are provided with movable grooves, and the upper end of the micro piezoelectric ceramic driving structure (305) is provided with a connector (307). The upper end of the micro piezoelectric ceramic driving structure (305) is movably connected to the molten pool detection head (3) in the movable groove through the connector (307). The inside of the molten pool detection head (3) is equipped with a vision camera (306), which includes a CCD camera, a spectrometer and an infrared thermal imager. The inside of the device housing (1) is equipped with a monitoring camera (7). Both the monitoring camera (7) and the vision camera (306) are connected to the terminal through a transmission module.

8. The intelligent laser head with molten pool monitoring according to claim 7, characterized in that, The terminal is also configured to execute a visual acuity-based magnetorheological damping adaptive vibration suppression method, which specifically includes the following steps: Step S1: The terminal receives the real-time video stream of the molten pool collected by the vision camera (306) through the transmission module, and extracts the region of interest (ROI) containing the edge of the molten pool from each frame image. Step S2: The terminal performs convolution operation on the region of interest using the Laplacian operator, calculates the average edge gradient magnitude of the current frame image, and defines it as the image sharpness index. ; Step S3: The terminal monitors the image sharpness index in real time. When detected When the value is lower than the preset clarity threshold, it is determined that the device housing (1) is being disturbed by a slight high-frequency vibration; Step S4: The terminal immediately starts the active vibration suppression optimization mode and sends an adjustment command to the controller connected to the magnetorheological fluid damper (204) to change the current input to the excitation coil of the magnetorheological fluid damper (204) in a stepped manner with a preset step size. Step S5: After each change in current magnitude, the terminal recalculates the new image sharpness index. And compare the current before and after the change. Value changes, retain The direction of increasing current value, until... The value reaches a local maximum, thus locking in the optimal damping stiffness that can suppress micro-amplitude vibrations to the greatest extent under the current working conditions.

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