CN112004634A

CN112004634A - Method and apparatus for controlling position of laser tool

Info

Publication number: CN112004634A
Application number: CN201880088366.5A
Authority: CN
Inventors: M·斯特杰恩伯格
Original assignee: Huanbei Automation Co ltd
Current assignee: Huanbei Automation Co ltd
Priority date: 2018-02-01
Filing date: 2018-02-01
Publication date: 2020-11-27
Also published as: WO2019151911A1

Abstract

The invention relates to a method and system (10) comprising: a laser beam source (11) configured to generate a laser beam; and an illuminator (13) configured to produce a protrusion (20) on the surface (19); an image recorder (12) and a controller (17) are configured to receive the projected (20) image. The system (10) further comprises an image processing unit configured to process an image of the projection (20), and the controller is configured to control the position of the laser beam on the surface (19) with respect to the image processing result.

Description

Method and apparatus for controlling position of laser tool

Technical Field

The present invention is generally a method and apparatus for directing a laser tool and specifically controlling the position of a laser beam in the tool.

Background

Generally, the surface of the article may be welded, coated and alloyed by a laser beam and deposited powder material operating in concert. Currently, there is a system employing a laser light source and a focusing device, including a powder delivery device provided. The area of the article surface where the laser beam melts is relatively small and a controlled amount of alloy particles is delivered into the molten pool by the powder flow.

In additive manufacturing, i.e. solid free form manufacturing or 3D printing, a three-dimensional graphical object is composed of a starting material (e.g. a powder in a series of two-dimensional layers or cross-sections).

According to some methods, layers are produced by melting or softening materials, for example Selective Laser Melting (SLM) or Direct Metal Laser Sintering (DMLS), Selective Laser Sintering (SLS), Fused Deposition Modeling (FDM), while other methods use different techniques for solidifying liquid materials, for example Stereolithography (SLA).

In addition, there is sintering, which is the process of fusing small particles (e.g., powders) together to make an object. Sintering typically involves heating the powder, using a laser beam. When the powder material is heated to a sufficient temperature during sintering, atoms in the powder particles diffuse across the boundaries of the particles, fusing the particles together to form a solid mass. In contrast to melting, the powder used for sintering does not have to reach a liquid state. Since the sintering temperature does not have to reach the melting point of the material, sintering is commonly used for materials with high melting points, such as tungsten and molybdenum.

Both sintering and melting may be used for additive manufacturing. Selective Laser Melting (SLM) is used for additive manufacturing of metals or metal alloys that have discrete melting temperatures and melt in the SLM process.

In all of the above processes, the position of the nozzle and laser beam relative to the receiving substrate is critical to achieving satisfactory results.

Summary of The Invention

Therefore, there is a need for a fast and accurate system for determining the position of two objects relative to each other, in particular for determining the position of a laser beam and a material feed, in particular for accurately positioning a laser beam nozzle combination relative to a receiving surface.

To address these needs, the system includes: a laser beam source that generates a laser beam; and an illuminator operable to generate a projection on the surface; an image recorder that can receive the projected image; and a controller. The system further comprises an image processing unit which can process said projected image. The controller may control the position of the laser beam on the surface in dependence on the result relative to the image processing. The system also includes a nozzle. In one embodiment, the nozzle is a tubular body having an open end, and the laser beam passes through the tubular body. An image recorder may record an image of a projection through the tubular body. The system also includes an optical element for focusing the laser beam. In one embodiment, the system further comprises an optical element for focusing the reflection from the projection. In one embodiment, the laser beam passes through an illuminator. In one embodiment, the illuminator is disposed about the nozzle. The illuminator may produce concentric geometries comprising a plurality of light-emitting elements controlled by a controller. The illuminator may emit light in the visible and/or invisible spectrum. The nozzle may comprise an inner surface portion and an opposing outer surface portion which are slightly spaced from one another and which cooperate to form an annular conical passage through which the powder material is delivered to the outlet. The system is displaced vertically and/or horizontally relative to the substrate. The laser beam source may be an illuminator.

The invention also relates to a method of guiding a fuselage. The method comprises the following steps: generating an illumination projection; and re-recording the projected image; processing the recorded image; and guiding the body according to the image processing result. The method may further comprise performing one or more of the following: thresholding, speckle analysis and image detection; and target and particle detection algorithms; non-adaptive methods include nearest neighbor, bilinear, and smooth hue transitions; an adaptive method of performing an interpolation function using a fringe sense or variable gradient algorithm; a secure image signature; delaying image transmission; or resolution ratio digital zoom (RPDZ). The projection may be a plurality of concentric circles. The deviation may be determined using a number of fixed parameters including one or more of: diameter of circular projection (d1), radius from center to inner circle (a), radius from center (a + b) to middle circle (a + b + c), radius from center to outer circle (a + b + c), thickness roundness projection of line, brightness or intensity, line continuity, bayer interpolation, flat field correction, defective pixel correction, image rotation, scaling and cropping. The body may be a nozzle. The method may further include successive image processing that calculates the edge-to-edge distances (r1, r2) from the center point to the visible portion and possible angel, and calculates the position of the center point relative to the edges and corners.

The present invention also relates to a computer-readable storage medium storing instructions that, when executed by a computer, cause the computer to perform a method for guiding a subject using a computer system, the method comprising generating an illumination projection; recording the projected image; processing the recorded image; and guiding information from the image processing results.

Drawings

Reference is made to the drawings wherein elements having the same reference number designation may represent like elements throughout.

FIG. 1 is a diagram of an exemplary embodiment of a system in which methods described herein may be implemented;

FIG. 2 is a flow diagram of an exemplary process of the system of FIG. 1;

3A-3D are schematic diagrams of image projections generated for measurement according to an embodiment of the present invention;

FIG. 4 is an embodiment of an edge detection principle according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a projection with fixed parameters according to the present invention;

FIG. 6 is another schematic of a projection with calculated parameters;

FIG. 7 is an embodiment of a groove detection principle according to an embodiment of the present invention; and (c).

Fig. 8 shows an embodiment of the controller of the present invention.

Detailed Description

The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements.

The system 10 of the present invention according to one embodiment is schematically illustrated in fig. 1. According to this embodiment, the system 10 includes a laser source 11, an image recorder 12, a nozzle 13, optical elements (141, 142, 143, 144), an illuminator 16, and a controller 17.

The laser source 11 may be any suitable high power laser capable of melting the feed material. The laser light source radiates a laser beam 111.

The image recorder 12 may be a camera for still or moving images operating in visible light, UV light, IR light, or the like. The image captured by the camera 12 or a signal representing the image may be processed in a camera control unit (not shown). The captured images may be provided to the controller 17 for further processing.

The nozzle 13 is generally circular in cross-section, followed by a tube and a conical tip 131 at the front. The nozzle is hollow and forms a longitudinally extending beam channel for the laser beam 111 emitted by the source 11.

In one embodiment, the conical tip 131 may be made of copper and removably secured to the front of the nozzle 13. In one embodiment, the conical tip is radially adjustable, i.e., the size of the passage 132 can be adjusted.

The inner surface portion of the nozzle 13 and the opposite outer surface portion at the nozzle are slightly spaced from each other and cooperate to form an annular conical channel 133 through which conical channel 133 (metal) powder 181 is delivered to the outlet opening 132. This powder enters the channel powder 133 through the receptacle 18. The powder may be carried by the inert gas flowing down in the tapered channel. In one embodiment, the outlet of the channel 133 or the entire channel is adjustable to control the amount of powder material fed.

During the operating mode, the nozzle is injected with a high power laser beam passing through the nozzle 13, and one or more powdered materials, for example powdered materials. In order to obtain a surface coating 191 on the workpiece 19 after melting the material, the gas is entrained in the gas 19. Thus, the nozzle has a structure that allows the laser beam to freely pass through and supply the material in powder form to the surroundings.

The optical elements include a first focusing lens 141, second and third focusing

lenses

142 and 143, and a bidirectional mirror 144. The number and function of the optical elements may vary depending on the function of the system.

The laser beam 111 emitted from the laser light source 11 passes through the third focusing lens 143, and the third focusing lens 143 focuses the beam onto the reflecting mirror 144. The light beam reflected from the mirror 144 passes through the second focusing lens 142 and through the narrow end of the mirror. A tapered tip 131 and exits through the outlet 132 to impinge on the upper surface of the workpiece 19, the workpiece 19 being disposed in front of the outlet 132 and immediately adjacent the outlet 132. In a manner known in the art, for example, during a welding or cladding process, the laser beam heats a localized surface of the workpiece 19 to form a shallow puddle of molten material.

The camera sees the surface of the workpiece 19 through the mirror and the nozzle internal tubular passage, i.e. the reflection 121 from the surface of the workpiece 19 is focused by the second lens 142, through the two-way mirror 144 and through the first lens. 141 to the image sensor of the camera 12 (not shown).

Each lens can be adjusted in the vertical direction (lenses 141 and 142) or horizontal direction (lens 143), respectively, to focus the laser beam or to reflect. In this case, one or several motors (not shown) may cooperate with the lenses to move them vertically and/or horizontally. The mirror 144 may be rotatably adjusted to adjust the projection of the laser beam.

The illuminator 16 may include a plurality of light emitting elements 161, such as Light Emitting Diodes (LEDs), for emitting light 162 in the visible or invisible spectrum. In this example, the illuminator 16 is configured as a collar around the body of the nozzle 13, which includes three rows of LEDs. In this example, the emitted light forms three concentric light circles (e.g., as shown in fig. 3A) concentric with the focal point of the laser beam 111. The shape 20 of the light generated by means of the element 161 is in the visible. The line of sight of the camera 12 is concentric with the point of incidence of the laser light on the workpiece. This means that the illuminator can produce a shape having the largest dimension of opening 134 of nozzle 13, which is the largest line of sight of the camera with respect to opening 132.

Obviously, the circular shape of the protrusions 20 may vary according to the application and the needs. In one embodiment, the illuminator 16 may be connected to a controller 17 to control the illuminator to produce different forms or shapes having different intensities, colors, etc.

The light emitting element 161 may also include a laser diode. In one embodiment, a second laser source may be used as the illuminator. In yet another embodiment, the additional laser source may be located at the same location as the laser source 11 or the camera, or any other suitable location where a projection may be generated. In an embodiment, a laser source 11 may be used as the illumination source.

FIG. 8 is a diagram of an exemplary controller 17 in which methods and systems described herein may be implemented. Controller 17 may include a bus 171, a processor 172, a memory 173, a Read Only Memory (ROM)174, a storage device 175, an input device 176, an output device 177, and a communication interface 178. Bus 171 allows communication. Among the components of the controller, the controller 17 may also include one or more power supplies (not shown). Those skilled in the art will recognize that controller 17 may be configured in a variety of other ways and may include other or different elements.

Processor 172 may include any type of processor or microprocessor that interprets and executes instructions. Processor 172 may also include logic capable of decoding media files, such as audio files, video files, multimedia files, image files, video games, etc., and generating output, such as speakers, displays, etc. Memory 130 may include a Random Access Memory (RAM) or another type of dynamic storage device that stores information and instructions for execution by processor 172, and memory 130 may also be used to store temporary variables or other intermediate information during execution of instructions by the processor.

ROM 173 may include a conventional ROM device and/or another static storage device that stores static information and instructions for processor 172. Storage device 175 may include a magnetic or optical disk and its corresponding drive or some other type of magnetic or optical recording medium and its corresponding drive for storing information and instructions. Storage device 175 may also include a flash memory (e.g., an electrically erasable programmable read-only memory (EEPROM)) device for storing information and instructions.

Input device 176 may include one or more conventional mechanisms that allow a user to input information to controller 17, such as a keyboard, keypad, steering wheel, mouse, pen, voice recognition, touch screen, biometric recognition mechanisms, and the like.

Output device 177 may include one or more conventional mechanisms that output information to the user, including a display, a printer, one or more speakers, and the like. Communication interface 178 may include any transceiver-like mechanism that enables controller 17 to communicate with other devices and systems. For example, communication interface 178 may include a modem or an Ethernet interface to a LAN. Communication interface 178 may include other mechanisms for communicating via a network, such as a wireless network. For example, the communication interface may include a Radio Frequency (RF) transmitter and receiver and one or more antennas for transmitting and receiving RF data.

According to an exemplary embodiment, the translator 17 may perform various processes in response to the processor 172 executing sequences of instructions contained in the memory 173. Such instructions may be read into memory 173 from another computer-readable medium, such as storage device 175, or from memory 173. A stand-alone device via communications interface 180. A computer-readable medium may include one or more storage devices or carrier waves. Execution of the sequences of instructions contained in memory 173 causes processor 172 to perform acts that will be described hereinafter. In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions to implement aspects consistent with the invention. Thus, the present invention is not limited to any specific combination of hardware circuitry and software.

The entire system 10 may be arranged to be movable relative to the workpiece 19; however, the entire system 10 may be movable relative to the workpiece 19. It can move in the X, Y (perpendicular to the plane of the engineering drawing) and Z directions (i.e. vertical and horizontal).

The main object of the present invention is to help guide and position the nozzle 13 and the laser beam vertically and/or horizontally with respect to the workpiece: the camera 12 is configured to record an image from the shape (projection) of the illumination. The recorded image signals are processed in the camera or are supplied to the conversion means 17 via the interface 178 for processing the recorded image signals and analyzing the images to determine parameters related to the position and/or distance of the nozzle to the workpiece 19.

Fig. 2 illustrates exemplary steps of the method according to the invention:

1) starting;

2) the illuminator 16 illuminates the surface of the workpiece 19 in an appropriate shape;

3) the image recorder 12 captures an image of the illumination area;

4) the images are processed in an image processor in the camera and controller 17. The image processing function processes the image to detect the illuminated concentric circles (according to this example);

5) the controller 17 determines deviations in the image, such as one or more of the following: the size of the circles, the distance between the circles, the deviation of the form of one or more circles, the light intensity, the color, etc.;

6) the controller 17 adjusts the tool (i.e. the combination of laser beam and nozzle) relative to the determined deviation. The adjustment may include a vertical distance of the nozzle to the workpiece; as well as the X and Y position of the nozzle relative to the workpiece, laser power, tilt angle, etc.,

7) the process continues until the operation stops;

8) fig. 3A-3D show examples of protrusions 20 of a light source 161 on a surface of a workpiece, in this case the protrusions 20 comprising

concentric circles

21, 22 and 23.

In fig. 3A, the rings are spaced apart. The size of the rings and the distance between the rings can be interpreted as (in this case) the distance between the nozzle 13 and the workpiece 19 being too long.

In fig. 3B, the size of the rings and the distance between the rings can be interpreted as focus, i.e. the correct position.

In fig. 3C, the size of the rings and the distance between the rings may be interpreted as the distance between the nozzle 13 and the workpiece 19 being too short.

In fig. 3D, the circle is partially invisible, which means that there may be level differences or edges in the workpiece.

Thus, with multiple rings (or other suitable shapes) having different diameters, geometry, edges, etc. can be detected regardless of how the tool is oriented or moved.

Fig. 4 shows exemplary steps of edge detection using a system according to the present invention. It is assumed that the system (not shown) according to the described embodiment is used for example in one of cladding, welding, cutting, 3D printing or similar applications, that the laser beam 111 is centered in a concentric circle 5 projection above the workpiece 19. The projections are indicated at three different positions by three different dashed circles and the arrows indicate the movement of the directional nozzles.

Fig. 5 shows a number of parameters that can be fixed and used to determine the deviation: these parameters may include the projected diameter "d 1", the radius "a" from the center to the inner circle, and the radius "a" + "b" from the center. Center to middle circle; radius "a" + "b" + "c" from center to outer circle, line thickness (not shown), projected "roundness", brightness or intensity, line continuity, bayer interpolation, flat field correction, difference pixel correction, image rotation, scaling and cropping, and the like.

As shown in fig. 1, with reference to fig. 6, the successive image processing calculates the distance (r1, r2) from the center point to the visible part and possibly the edge, and calculates the position of the center point relative to the edge, in the example of fig. 4, also at the corners.

Examples of other algorithms and methods that may be used are:

threshold, blob analysis and image detection;

object and particle detection algorithms;

non-adaptive methods include nearest neighbor, bilinear and smooth hue transitions;

adaptive method: the interpolation function may be performed using edge-sensing or variable gradient algorithms;

secure Image Signature (Secure Image Signature) which places a digital timestamp, a frame counter and a trigger counter in real time into each Image that the camera outputs in real time. Monitoring the trigger frame counter may indicate a lost frame, which may be very useful in time-critical systems.

Delayed image transfer allows multiple cameras to acquire images simultaneously and upload the images to a PC in a controlled manner. This ensures that the camera to PC bus bandwidth is not exceeded.

Resolution-proportional digital zoom (RPDZ) is a post-processing algorithm that can maintain a constant data rate between the camera and the host while digitally modifying (zooming) the camera field of view (FOV). This is done by sub-sampling the pixels in the image in a manner proportional to the digital zoom level.

Based on the calculated edge detection, the movement of the tool relative to the edge is controlled and adjusted.

Fig. 7 shows another illustrative example, such as fig. 3. In welding applications. In this case, the groove 70 is welded. In the same way as in the previous example, three different concave circles are shown in three different positions and the arrows show the direction of movement of the nozzle. In this case, however, the groove 70, the extent and depth thereof, and the path of the nozzle are detected by detecting the deviation of the protrusion during the image processing.

The processed image may be compared to a predetermined threshold or shape to determine distances and edges.

Method steps may be stored on a computer-readable storage medium as instructions that, when executed by a computer, cause the computer to perform a method for directing a nozzle using a computer system.

Various embodiments of the invention described herein are described in the general context of method steps or processes, which are implemented in one embodiment by a computer program product, embodied in a computer-readable medium, including computer-executable instructions, such as: program code executed by computers in networked environments. The computer readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), Compact Disks (CDs), Digital Versatile Disks (DVDs), and the like. Generally, program modules may include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Program modules represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps.

Software and web implementations of the various embodiments of the present invention could be accomplished with standard programming techniques with rule based logic and other logic to accomplish the various database searching steps or processes, comparison steps or processes and decision steps or processes. It should be noted that the words "component" and "module," as used herein and in the appended claims, is intended to encompass implementations using one or more lines of software code, and/or hardware implementations, and/or manual input devices for receiving.

The foregoing descriptions of embodiments of the present invention have been presented for purposes of illustration and description. The foregoing description is not intended to be exhaustive or to limit embodiments of the present invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of various embodiments of the present invention. The embodiments discussed herein were chosen and described in order to explain the principles and the nature of various embodiments of the present invention and its practical application to enable one skilled in the art to utilize the present invention in various embodiments and with various modifications as are suited to the particular use contemplated. The specific use contemplated. The features of the embodiments described herein may be combined in all possible combinations of methods, apparatus, modules, systems, and computer program products.

Claims

1. A system (10) comprising:

a laser beam source (11) capable of generating a laser beam (111);

an illuminator (13) operable to generate a projection (20) on a surface (19)

An image recorder (12) that can receive an image of the projection (20);

a controller (17);

is characterized in that the utility model is characterized in that,

the system (10) further comprises an image processing unit configured to process the image of the projection (20); and

the controller is configured to control the position of the laser beam on the surface (19) relative to the image processing result.

2. The system according to claim (1), wherein the system further comprises a nozzle (13).

3. The system according to claim 1 or 2, wherein the nozzle is a tubular body having an open end and the laser beam passes through the tubular body.

4. The system of any one of the preceding claims, wherein the image recorder records the image of the projection through the tubular body.

5. The system according to any of the preceding claims, further comprising an optical element for focusing (141, 143) the laser beam (111).

6. The system according to any one of the preceding claims, further comprising an optical element (141, 142) for focusing the reflection (121) from the projection (20).

7. The system of any one of the preceding claims, wherein the laser beam passes through the illuminator.

8. The system according to any one of claims 2-7, wherein the illuminator is arranged around the nozzle.

9. The system of any preceding claim, wherein the illuminator is arranged to produce concentric geometries.

10. The system of claim 8, wherein the luminaire comprises a plurality of light-emitting elements (161) controlled by the controller.

11. The system according to any one of the preceding claims, wherein the illuminator emits light in the visible and/or invisible spectrum.

12. System according to any one of claims 2 to 11, wherein the nozzle (13) comprises an inner surface portion and an opposite outer surface portion, slightly spaced from each other and cooperating to form an annular conical channel (133), the powder material (181) being delivered to the outlet (132).

13. The system according to any of the preceding claims, which is arranged to be displaced vertically and/or horizontally with respect to the substrate.

14. The system of any one of the preceding claims, wherein the laser beam source is the illuminator.

15. A method of guiding an object (13), the method comprising the steps of:

generating an illumination projection;

recording the projected image;

processing the recorded image;

directing the object according to the image processing result.

16. The method of claim 15, further performing one or more of:

threshold, blob analysis and image detection;

object and particle detection algorithms;

an adaptive method for performing an interpolation function using an edge-sensing or variable gradient algorithm;

secure image signatures;

delaying image transmission;

resolution ratio digital zoom (RPDZ).

17. The method of claim 15, wherein the projections are a plurality of concentric circles.

18. The method of claim 17, wherein the deviation is determined using a plurality of fixed parameters, the parameters including one or more of: a diameter of the circular projection (d1), a radius (a) from the center to the inner circle, and a radius (a + b) from the center to the middle circle; radius from center to outer circle (a + b + c), line thickness, projected circularity, brightness or intensity, line continuity, bayer interpolation, flat field correction, defective pixel correction, image rotation, scaling, and cropping.

19. The method of claim 17, further comprising continuous image processing that calculates distances (r1, r2) from a center point to edges of the visible portion and possible angel and calculates the position of the center point relative to the edges and corners.

20. The method of any one of claims 15 to 19, wherein the body is a nozzle.

21. A computer-readable storage medium storing instructions. When executed by a computer, cause the computer to perform a method for a computer system to guide a body, the method comprising:

generating an illumination projection;

re-recording the projected image;

processing the recorded image;

directing the object according to the image processing result.