CN112119359B

CN112119359B - Method for determining the fidelity of the contour of a moving component

Info

Publication number: CN112119359B
Application number: CN201980032226.0A
Authority: CN
Inventors: C·沙尔芬贝格
Original assignee: Trumpf Laser und Systemtechnik GmbH
Current assignee: Trumpf Laser und Systemtechnik GmbH
Priority date: 2018-05-14
Filing date: 2019-05-13
Publication date: 2024-03-12
Anticipated expiration: 2039-05-13
Also published as: WO2019219628A1; DE102018111473B4; CN112119359A; EP3794417A1; DE102018111473A1

Abstract

A method for determining the fidelity of the contour of a moving component (10), comprising the following steps: a. moving an end effector (20) of a movement assembly (10) along a predetermined desired contour (71), said end effector being assigned a Tool Center Point (TCP); b. recording an image stream of individual images at more than 100 individual images/s by means of an image recording device (51) moving with the moving assembly (10); c. positioning a marker (75), in particular a reticle, at predetermined positions of at least some of the individual images to mark the position of the TCP; d. stitching at least some of the individual images into an overall image (70); e. the global image (70) is stored.

Description

Method for determining the fidelity of the contour of a moving component

Technical Field

The invention relates to a method for determining the fidelity of the contour (Konturtreee) of a moving component. The invention further relates to a detection device which can be arranged, in particular can be mounted on a moving component.

Background

It is often difficult to assess whether the contour fidelity of a moving component is adequate for a particular task. The values given by the component manufacturer are typically general data that are only applicable to a particular test scenario. The manufacturer typically gives only positioning accuracy. However, since the positioning accuracy is measured in a stationary state, these values cannot be extrapolated into a three-dimensional dynamic process.

Disclosure of Invention

The object of the invention is to specify a method and a device by means of which the contour fidelity of a moving component can be detected and determined even during the operation of the moving component.

According to the invention, this object is achieved by a method for determining the fidelity of the contour of a moving component, comprising the following steps:

a. moving an end effector of the movement assembly along a predetermined desired profile, the end effector being assigned a tool center point (Tool Center Point, TCP);

b. recording an image stream of single images (einzelb) at more than 100 single images per second with an image recording device moving with the moving assembly;

c. positioning a marker, in particular a reticle, at a predetermined position of at least some of the individual images to mark the position of the TCP;

d. stitching at least some of the individual images into an overall image (Gesamtbild);

e. the overall image is stored.

A motion component can be understood, for example, as a machine tool and/or an industrial robot. It is usually composed of a plurality of shafts arranged one behind the other, each of which can have its own drive and its own control, regulation and measurement systems. The movement assembly may in particular have a link movement chain with a rotary and/or translational hinge, which cooperates with the drive and the mechanical transmission element to carry out a predefined movement for the respective shaft.

The kinematic chain may include the following components: the assembly is responsible for driving in only one axis of motion and places a second assembly with the other axis of motion in motion. Other components may be connected until the desired overall motion is achieved.

Thus, in the sense of the present invention, a moving component may be the following: the assembly has at least two shafts with associated drives that move the end effector in a plane or in space by a subsequent or superimposed movement.

However, the movement assembly may also represent a parallel movement device in which parallel-connected movement axes are present. This avoids the drive having to cause a subsequent movement. The (parallel) rod movement device works by: the spatial distance from the point of the moving object (tool) to the predefined fixed point is changed. Here, the spatial position and posture of the moving object are described not in terms of a vector-based coordinate system but in terms of the distance between object-space-point-pairs. Accurate positioning is achieved by varying the length of a plurality of telescopic arms, each fixed at one end in a position that is not relatively movable, and at the other end to which the object to be positioned, in particular the end effector, is fixed.

The end effector may represent the final element of a kinematic chain or kinematic assembly. Here, it may be, for example, a unit or a holder for welding. The end effector may in particular be a tool for workpiece processing.

The tool center point is understood to be the tool working point.

A profile may be applied to the workpiece as a desired profile. The desired profile may be scored, imprinted, cut or welded on the workpiece, for example. Here, the desired contour should be adapted to be clearly visible in the camera image. Particularly preferred is a laser inscription of the desired contour in the workpiece. A desired contour may be added to the sports component (term of art "Teaching"). This may be done online or offline.

In order to detect the contour fidelity of the moving component, the following parameters can be determined, for example: average path distance, average path dispersion range, average path orientation deviation, average path orientation dispersion range, average path radius difference when traversing a circular path, average corner error (Eckenfehler), and/or average over-swing error (uberschwenkfehler). In particular, data which can be evaluated, for example, by means of VDI 2861 can be determined by the method according to the invention.

According to one method variant, the entire image and/or the image (Film) can be represented by at least some individual images. The desired contours and markings may be displayed in the overall image. By comparing the desired profile with the located markers, the accuracy with which the end effector, especially TCP, follows the desired profile can be ascertained. From this, the profile fidelity can be derived. The overall image may be generated by adjusting and connecting each individual image to its neighboring images.

If a single image is displayed as a movie, it may be slowed down, i.e. played in slow shots. This allows a "Slow Motion" analysis of the path taken by the moving component compared to the desired profile. Whereby the movement is visually displayed.

The actual profile may be created by a marker of TCP or the marker may display the actual profile and the actual profile may be compared to the desired profile. The deviation of the actual contour from the desired contour can be determined in particular by: a number of pixels between the desired contour and the actual contour is determined at one or more locations and a pixel pitch is determined. The contour fidelity can thus be determined at every arbitrary point. The fidelity of the contour at each arbitrary point may be, for example, the number of pixels between the desired contour and the actual contour. The pixel pitch is understood here as the distance between each pixel. For example, the pixel pitch may be 7 microns per pixel. The analysis of the contour errors can be performed automatically, for example, by image processing or by the naked eye. Thus, conclusions can be drawn about contour fidelity, accuracy, repeatability accuracy, mechanical play, softness or stiffness, natural frequency, amplitude and decay time on the contour, and achievable feed rates by simple pixel counting or automated image analysis.

The method according to the invention is much more intuitive than the prior art methods. The method is suitable for obtaining the fidelity of the contour at full speed (voller Fahrt). Furthermore, the method is suitable for determining the contour fidelity in an optional contour, i.e. not only in a standard contour but also in particular in a free geometry. Furthermore, the method is suitable for determining the fidelity of the contour in very small and very large contours (compared to methods using measuring heads). The method according to the invention provides images and pictures of the desired contour and of the actual contour. Information about the fidelity of the contour may be supplemented by tool information, such as the milling cutter radius or beam diameter of the tool, in order to obtain a true assessment of the actually formed contour.

The information content of the overall image with the marks may be reduced at least on a segment-by-segment basis. For example, the contrast of all colors except a specific color may be reduced. Automated image processing can thereby more easily identify the markers.

Further, binarization may be performed. In binarization, only the desired contour and the actual contour remain for analysis. In the analysis processing, the original image (whole image) and all gray tones thereof are ignored. The original image may then be superimposed again for visualization. By binarization, analysis and in particular determination of the fidelity of the contours in the automated image processing method is simplified.

The speed at which the end effector moves along the desired profile may be determined. The speed can be determined in particular by: the distance between the marks is detected and analyzed by means of knowledge of the recorded images per second. In this way, it is also possible to determine the maximum speed of the moving component which still leads to acceptable profile fidelity.

In particular, the relationship between the processing time and the fidelity of the contour can be determined.

At least steps a-e may be performed with respect to a number of different dynamic parameters, such as the speed of the end effector, the acceleration of the end effector, the weight of the moving assembly. Here, any combination of dynamic parameters can be set and checked without sacrificing the workpiece. Thereby reducing the cost of deriving the parameter combinations. In this case, the correct combination of parameters is in particular a trade-off between speed, service life and contour fidelity corresponding to the part tolerances. A particular advantage of the method according to the invention is also that only a single desired contour and thus only a single workpiece is required in order to perform the different analyses. The workpiece is not destroyed every time it passes (abfahren) the desired contour with the moving assembly. In addition, no laser beam or other measurement means other than a camera is required to find the contour fidelity.

As already mentioned above, the natural frequency, transient response, amplitude, decay time, softness, stiffness, play and/or accuracy of the moving component can be found by analyzing the actual profile. It has furthermore been found that by repeating the same desired profile over the lifetime of the moving assembly, the wear of the transmission can be ascertained. It can thus be predicted when worn transmissions may lead to predefined tolerances or predefined contour fidelity not being able to be maintained.

As already mentioned above, the desired profile may be "added", i.e. programmed into the motion component, online or offline. It is also conceivable to detect the desired contour during the movement of the end effector along the desired contour. For example, during the movement assembly driving over the desired contour, the desired contour may be identified by an additional camera.

In the scope of the present invention also a computer-implemented method comprising at least some of the steps of the method according to the invention, in particular steps c.e. and the method steps specified in the dependent claims. The invention also comprises a computer program product comprising instructions which, when the computer program product is implemented by a computer, cause the computer to implement at least some of the steps of the method according to the invention, in particular steps c-e.

In the scope of the invention, it also relates to a detection device which can be arranged, in particular can be fitted, on a moving assembly, comprising: an image recording device configured to record 100 or more individual images per second; a memory means for storing the recorded single images; a first lighting device. The image recording device can be designed in particular as a gigabit ethernet grayscale camera. In this case, when the end effector is a laser head, the camera can be oriented, for example, onto the workpiece via the aperture of the laser head. It is particularly preferred that the image recording device is arranged to record more than 200 individual images per second, preferably more than 300 individual images. Here, the image may be recorded at a resolution of at least 640×480 pixels. Further, the camera may be arranged to record images at different optical resolutions. The camera may for example be arranged to record images at a resolution in the range of 1-20 micrometers per pixel, preferably at a resolution in the range of 2-15 micrometers per pixel. Additional lenses may be provided to achieve the resolution.

The first illumination device may be configured as a coaxial illumination. Thus, the first illumination device may be coaxially oriented to the tool used, e.g. a laser beam or an end mill. The workpiece is thus illuminated particularly well in the TCP region.

Additionally, spot lighting may be provided. The spot illumination may be configured as red continuous light. The spot illumination can be used to illuminate the workpiece so that the exposure time of the individual camera images is kept as short as possible and so that the individual images are not blurred.

The detection means may be assigned image processing means. The image processing device may here be a component of the detection device or be arranged externally, for example in an external PC.

Gigabit-ethernet-cameras may be configured to transmit 1000 megabits per second.

Furthermore, the detection device can also have a fastening point, so that one or more lasers, in particular a linear laser (Linienlaser), can be fastened. A linear laser may be used to learn the desired profile. Furthermore, the detection device may have a fixed point or a fixture, so that additional weight may be mounted on the detection device in order to simulate the weight of the components of the moving assembly, for example in order to simulate the weight of the beam forming device.

Drawings

Additional features and advantages of the invention are shown in the following description of embodiments.

The drawings show:

FIG. 1 illustrates one embodiment of a motion assembly;

fig. 2 shows a schematic illustration of a detection device;

FIG. 3 shows a schematic illustration of an overall image;

FIG. 4 shows a partial view of FIG. 3;

FIG. 5 shows the plot of FIG. 4 after binarization;

FIG. 6 illustrates an image for representing contour fidelity over a circle;

fig. 7 shows a diagram for explaining the speed of the moving assembly on a circle.

Detailed Description

Fig. 1 shows a schematic view of a laser processing machine 1 comprising a motion assembly 10. In this case, the movement assembly comprises a gantry 11 which is movable in the direction of the double arrow 12 relative to a machine base 13 over a workpiece 14. A carriage 16 which can be moved in the direction of the double arrow 17 is arranged on the gantry 11. A laser processing head 18, which can be moved in the direction of the double arrow 19, is arranged on the carriage 16. In the illustrated embodiment, the end effector 20 represents a laser nozzle. By superimposing the movements of the gantry 11, the slide 16 and the laser processing head 18, the end effector 20 can be moved and positioned relative to the workpiece 14.

A tool axis with a direction of movement in the direction of the double arrow 12 is realized by means of the gantry 11. A tool axis having a direction of movement in the direction of the double arrow 17 is realized by the slide 16. The laser processing head 18 achieves a tool axis in the direction of movement of the double arrow 19.

The following components of the machine tool 1 are also known from fig. 1; a control device 3, a workpiece support 5 and a focusing lens 7.

Fig. 2 shows a detection device 50 that can be arranged on the movement assembly 10. The detection device 10 comprises an image recording apparatus 51, a first and a second illumination device 52, 53. Here, the first illumination device 52 is configured as coaxial illumination, and the second illumination device 53 is configured as spot illumination. A securing device 54 is provided so that additional weight can be installed. Further, a fixing point 55 for fixing the linear laser 56 is provided.

The image processing means 57 comprising the memory means 58 are assigned to the detection means 50, but are arranged externally.

Fig. 3 shows an overall image 70 formed by stitching a certain number of individual images recorded by the image recording apparatus 51. Thus, the whole image 70 is displayed in a mosaic type. The image shows a desired contour 71 that has been added to the motion assembly 10 and driven through by the motion assembly 10 in a counter-clockwise direction indicated by arrow 72. The tool center point location of the motion assembly 10 has been embedded into the overall image 70. This can be seen from the enlarged illustration of fig. 4, which shows a partial view IV of fig. 3. The marks 75 represented by cross hairs can be seen in the enlarged illustration of fig. 4. Here it can be seen that the mark 75 representing the actual profile along which the end effector 20 moves is spaced from the desired profile 71. This distance may be found, for example, by determining the number of pixels between the desired contour 71 and the mark 75. Preferably, the distance is determined in a direction perpendicular to the desired contour 71. To simplify the determination of this distance, the graph of fig. 4 may be binarized, which is shown in fig. 5. Only the desired contour 71 and the marks 75 can be seen here, which simplifies the digital analysis process by the image processing means.

The distance of the desired contour 71 from the actual contour can be detected along the entire desired contour 71. This is shown in fig. 6. In this case, the length of the desired contour, in particular the circumference of the circular desired contour 71, is plotted on the horizontal axis. The distance of the desired profile from the actual profile is plotted in microns on the vertical axis. From the plotted distances, the contour fidelity can be found. The distance is represented by curve 80.

In fig. 7 it is shown how the speed of the moving assembly 10 can be represented. The perimeter of the desired contour 71 is plotted on the horizontal axis. The speed is illustrated in millimeters per second on the vertical axis. The speed of the moving assembly 10 is represented by curve 85. The velocity may be found, for example, by determining the distance between the individual markers 75. The speed at which the end effector 20 moves along the desired contour 71 can be determined from knowledge of the image recording speed, i.e., the number of images recorded per second, and the distance taken between the marks 75.

Claims

1. A method for determining the fidelity of the contour of a moving component (10), comprising the following steps:

a. moving an end effector (20) of the movement assembly (10) along a predetermined desired contour (71), said end effector being assigned a tool center point TCP;

b. recording an image stream of individual images at more than 100 individual images/s by means of an image recording device (51) moving with the moving assembly (10);

c. positioning markers (75) at predetermined locations of at least some of the individual images to mark the location of the TCP;

d. stitching at least some of the individual images into an overall image (70);

e. the global image (70) is stored,

wherein an actual contour is created by a marker (75) of the TCP or the marker displays an actual contour and the actual contour is compared with the desired contour (71).

2. The method according to claim 1, characterized in that the whole image (70) and/or the presentation is represented by at least some single images.

3. The method of claim 2, wherein the image is displayed or played in a slow shot.

4. Method according to claim 1 or 2, characterized in that the deviation of the actual profile from the desired profile (71) is determined by: a number of pixels and/or a pixel pitch between the desired contour (71) and the actual contour is determined at one or more locations.

5. Method according to claim 1 or 2, characterized in that the overall image (70) with the marking (75) is reduced at least section by section in terms of the information content of the overall image (70).

6. A method according to claim 1 or 2, characterized in that binarization is performed.

7. The method according to claim 1 or 2, characterized in that a speed of movement of the end effector (20) along the desired profile (71) is determined.

8. The method of claim 7, wherein a relationship between the speed and the fidelity of the profile is found.

9. Method according to claim 1 or 2, characterized in that at least the method steps a-e are performed in relation to a plurality of different dynamic parameters.

10. Method according to claim 1, characterized in that the natural frequency, transient response, amplitude, decay time, softness, stiffness, play and/or accuracy of the moving component (10) is found by analyzing the actual profile.

11. The method according to claim 1 or 2, characterized in that the desired contour (71) is detected during the movement of the end effector (20) along the desired contour (71).

12. The method of claim 1, wherein the marker (75) is a reticle.

13. The method of claim 7, wherein the speed is determined by: the distance of the marks (75) is detected and analyzed by means of knowledge of the recorded images per second.

14. The method of claim 9, wherein the dynamic parameter is a speed of the end effector, an acceleration of the end effector, a weight of the motion assembly (10).

15. A machine-readable storage medium having stored thereon a computer program comprising instructions which, when the computer program is implemented by a computer, cause the computer to implement the method according to any of claims 1 to 14.

16. A detection device (50) capable of being arranged on a moving assembly (10), comprising: an image recording device (51) configured to record 100 or more individual images per second; a memory means (58) for storing the recorded single images; -a first lighting device (52), wherein the detection device (50) is arranged for implementing the method according to any one of claims 1 to 14.

17. The detection device according to claim 16, wherein the first illumination device (52) is configured as an on-axis illumination.

18. The detection device according to claim 16 or 17, characterized in that there is additionally provided spot lighting.

19. The detection device according to claim 16 or 17, characterized in that the detection device comprises an image processing device (57).