EP1412696A1

EP1412696A1 - Method and device for the detection of information on a tool

Info

Publication number: EP1412696A1
Application number: EP03702523A
Authority: EP
Inventors: Wolfgang Eckstein
Original assignee: E Zoller GmbH and Co KG; E Zoller GmbH and Co KG Einstell und Messgeraete
Current assignee: E Zoller GmbH and Co KG; E Zoller GmbH and Co KG Einstell und Messgeraete
Priority date: 2002-01-26
Filing date: 2003-01-24
Publication date: 2004-04-28
Also published as: DE10203018A1; WO2003062745A1

Abstract

The invention relates to a method for detecting information on a tool (10), particularly for measuring a mechanical tool in a setting device (11), according to which at least one camera (12) takes pictures (13 to 17) of the tool (10) from various viewing positions. The pictures (13 to 17) are then sorted into a data structure (18) for a three-dimensional space according to the viewing position.

Description

Method and device for acquiring information about a tool

State of the art

The invention relates to a method and a device for recording information of a tool.

From DE 44 31 059 C2 a generic method and a generic device is known. The device has a tool holder that can be rotated about an axis, a video camera, via which tool contours of a tool section in different rotational positions during a rotation of the tool about the axis of the tool holder below

Generation of images for the tool positions are detectable, a computer for determining and outputting dimension values with a memory for storing the geometry data determined from the images and a device for comparing detected in different rotational positions

Contour sections with the result of an extreme value determination under the compared geometry data when comparing the geometry data of images over the entire contour section. The device is designed in such a way that an envelope is determined as a result of the extreme value determination which represents the real working contour of the tool in the workpiece.

The proposed invention evaluates three-dimensional data with regard to the measurement of a tool. An overview of methods of evaluating three-dimensional data can be found in Carsten Steger: Unbiased Extraction of Curvilinear Structures from 2D and 3D Images; Dissertation, Faculty of Computer Science, Technical University of Munich, 1998; Herbert Utz Verlag, Munich, ISBN 3-89675-346-0

The invention is based in particular on the object of providing a generic method and a generic device with increased measuring accuracy and the possibility of visualizing a tool. It is solved according to the invention by the features of the independent claims. Further refinements result from the subclaims.

Advantages of the invention

The invention is based on a method for acquiring information from a tool, in particular for visualizing and measuring a machine tool in a setting device, in which images of the tool are recorded in at least one camera in different recording positions.

It is proposed that the images be divided into a data structure for a three-dimensional len space can be sorted. In particular, interpolations in three-dimensional space can be used to obtain further usable information, so that high measuring and imaging accuracy can be achieved with short measuring times or with few images. Furthermore, the tool can be visualized, in particular by calculating a three-dimensional surface model from the data structure that represents at least part of the tool. Instead of a three-dimensional surface model, individual lines spanning the tool could also be calculated.

The camera and / or advantageously the tool can be moved to record the images. Furthermore, a camera can be used to record one or more visible edges, or several cameras can be used, which in turn saves measurement time, for example by taking two visible edges of the tool offset by 180 ° and after rotating the tool by 180 ° is completely covered.

The three-dimensional surface model can be created with little computational effort by evaluating cross-sectional areas through the three-dimensional space represented by the data structure. The selected cross-sectional areas can include various angles to the longitudinal and / or axis of rotation of the tool that appear useful to the person skilled in the art, but advantageously the longitudinal and / or axis of rotation is perpendicular to the selected cross-sectional areas. If voxel information, including three-dimensional neighborhoods or neighboring voxel information, is used at least in partial areas to determine the surface model, more usable information can be obtained compared to the determination of the surface model with cross-sectional areas and thereby more precise values can be determined or calculated, namely by enabling interpolation in several spatial directions.

Furthermore, the measurement accuracy can be increased in particular by using information about the relative movement of the tool to the camera, for example by describing, in particular approximating, the movement of the tool to the camera by a function, and determining a maximum deflection by calculating an extreme value of the function , wherein the function is approximated, for example, by a polynomial in a rotatingly driven tool. The information can be used after the determination of the three-dimensional surface model or during the determination of the surface model, in particular for determining the surface model, in the latter case again more accurate measurement values can be obtained, in particular by providing information about the image sharpness for the weight adjustment can be used easily.

If information about the surface shape of the tool is known and can be used, the computational effort required can be reduced, the measuring accuracy increased and / or the measuring time shortened. The information about the surface shape of the tool can be entered manually or advantageously recorded in a partially or fully automated manner, for example via a code attached to the tool and a readout unit.

Once the surface model has been determined, an effective contour of the tool can be determined from this by at least one extreme value determination, which contour represents a relevant parameter of the tool.

In addition, meaningful information about the tool can be obtained by combining local extreme values of the surface model into an image of a tool cutting edge and / or determining the clearance angle of a tool cutting edge of the tool by means of the orientation of a surface against the cutting direction behind the tool cutting edge. If the local extreme values of the surface model have been combined into an image of a tool cutting edge, the pitch of the tool cutting edge can also advantageously be easily determined by the geometric relationship of the local extreme values.

The surface model can be calculated after the images have been taken or advantageously while the images are being taken, as a result of which overall measurement time can be saved.

In addition, measurement time can be saved and / or more precise values can be determined in relevant areas of the tool by creating the surface model only in the extreme value areas to be expected. The range of extreme values to be expected can be determined by the calculation values determined during the recordings. te result and / or can be based on known information about the tool.

In a further embodiment of the invention, it is proposed that more images are taken in the expected extreme value areas than in other areas, in particular through a lower relative movement between the camera and the tool and / or through an increased recording frequency, which in turn means that the measuring accuracy and imaging accuracy in relevant areas can be increased and / or measuring time can be saved.

Furthermore, radial and / or axial maxima of the tool can be determined by the proposed method and the maxima for measuring the tool can be arithmetically related to one another. Information about deviations from cutting edges among one another, about possible damage to individual cutting edges, about a concentric or axial runout and / or about a number of cutting edges can be determined in a partially and / or fully automated manner.

drawing

Further advantages result from the following description of the drawing. In the drawing, an embodiment of the invention is shown. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into useful further combinations. Show it :

Fig. 1 shows an inventive device with a

Camera and an image processing device, Fig. 2 is a schematic representation of a first camera image of a tool section, Fig. 3 is a schematic representation of a second

4 a schematic representation of a 3D space with sorted camera images and individual ones

Section planes, FIG. 5 the individual section planes from FIG. 4, FIG. 6 an extreme value determination in a section plane and FIG. 7 a three-dimensional surface model generated from the camera images.

Description of the embodiment

1 shows a setting device 11 with a movable optics carrier 33. The optics carrier 33 can be displaced along at least two axes and carries a CCD camera 12 and a lighting unit 33. The CCD camera 12 takes from the tool 10, which is clamped in a tool holder 31 and can be rotated about its longitudinal axis 32, images 13, 14, 15, 16, 17 in different recording positions, specifically in different rotary positions of the tool 10. It is also conceivable that another CCD camera 12 'is offset for taking images first CCD camera 12 is arranged to take additional pictures to be able to take up another angle, as indicated in FIG. 1.

The measurement and visualization of the tool 10 begins when the setting device 11 is switched on. A user positions the CCD camera 12 mounted on the optics carrier 30 manually or this is automatically positioned such that the tool 10 appears in the field of view of the CCD camera 12. The tool 10 is rotated about its longitudinal axis 32 via the tool holder 31, the tool holder 31 via a

Motor can be rotated automatically or manually, step by step or advantageously continuously. During the rotation, images 13, 14, 15, 16, 17 of the contour 40 of the tool 10 are recorded in various rotary positions with the CCD camera 12 and the angular position associated with each image 13, 14, 15, 16, 17 is stored ( Fig. 2 and Fig. 3).

Depending on the rotational position of the tool 10, a different contour profile is visible in the field of view of the CCD camera 12. In order to completely grasp the tool 10 advantageously, it is rotated through 360 ° at least once during the measurement process. However, it is also possible for the tool 10 to be grasped or measured accordingly only in a partial area or in individual partial areas, for example that in the case of tools with a plurality of tool cutting edges, the tool cutting edges are measured individually, and the tool here only by a fraction of 360 ° must be rotated.

The starting point for the generation of a 3D surface or a three-dimensional surface model 19 is the approach that every point on the surface 34 of the tool 10 when the tool holder 31 rotates on a circular path (FIGS. 4 to 7). The radius of the circular path is determined by the distance to the longitudinal axis 32 or to the axis of rotation, in particular points on a tool cutting edge 28 run around with a larger radius than points away from the tool cutting edge 28 10 images 13, 14, 15, 16, 17 not evaluated directly with regard to their gray values, but sorted into a data structure 18 for a three-dimensional space with a common Z axis in accordance with their acquisition position (FIG. 4). The images 13, 14, 15, 16, 17 here form a cylinder 35 which has the Z axis as the central axis. The central axis of the cylinder 35 corresponds to the longitudinal axis 32 or the axis of rotation of the tool holder 31

Angle of rotation is denoted by (Θ), while the axis perpendicular to the longitudinal axis 32 is denoted by (R).

A three-dimensional surface model 19 representing the tool 10 is calculated from the data structure 18 (FIG. 7). To determine the surface model 19, cross-sectional areas 20, 21, 22, 23, 24 are evaluated through the three-dimensional space represented by the data structure 18 (FIGS. 4, 5 and 7). Only a few images 13, 14, 15, 16, 17 and cross-sectional areas 20, 21, 22, 23, 24 are shown by way of example from a large number of images when the tool 10 is rotated through 360 ° and from a large number of cross-sectional areas.

A single cross-sectional area that represents a section along the R axis at a fixed Z value and also as (R, Θ) -sectional image can also be constructed without the construction of a three-dimensional surface model, for example by adding together the gray value information of a certain line from all the images in a series of images. A 3D data record of a tool can thus be generated from the combination of a plurality of (R, -S) cuts or a plurality of cross-sectional areas which, as described above, were generated from the gray value information of individual lines of the images.

In order to determine a surface course of the tool 10, in the simplest case it can be taken directly from the 3D volume without using information about a relative movement of the tool 10 to the CCD camera 12 or information about the surface shape of the tool 10. Refined methods adapt corresponding functions, which describe the movement of the tool 10 and / or known surface shapes of the tool 10, to the volume data, e.g. by a local approximation with planes, parabolas or hyperboloids.

To determine an effective dimension, the 3D data set is evaluated with regard to maximum deflections of the tool 10. This is shown as an example on a cross-sectional area 20 (FIG. 6). The method can be applied analogously to several cross-sectional areas 21, 22, 23, 24 and thus to the entire 3D data set. The relevant part of the 3D model of the tool is formed with the local extreme values 27 from the individual cross-sectional areas 21, 22, 23, 24. With the three-dimensional surface model 19, individual tool cutting edges 28 can be detected. Due to the geometrical Drawings of the local extreme values 27, a slope of the tool cutting edge 28 can be determined.

Furthermore, a clearance angle of the tool cutting edge 28 can be determined by orienting a surface against the cutting direction behind the tool cutting edge 28, it being possible for a normal vector 37 to be determined on the corresponding surface in an expanded 3D model in the vicinity of the tool cutting edge (FIG. 7).

The limitation initially to only one cross-sectional area 20 means nothing other than that the effective dimension is determined using a single Z value. The effective dimensions are determined by the movement of the tool cutting edge 28. This movement runs along a circular path when rotating around the Z axis and can thus be determined by a circular equation f (Θ) of the shape

/ (Θ) = Ä-cos (Θ)

are described, with (R) the radius of the tool 10 and with (Θ) the angle of rotation. A tool cutting edge 28 can be seen in the cross-sectional area 20 when it passes through a maximum, i.e. when the circular path reaches its maximum extent in (R). In the case of multi-bladed tools, several maxima are run through according to the number of cutting edges.

For the exact determination of the effective dimensions, the maxima of the tool cutting edge 28 in the cross-sectional areas 20 are used

Circle 36 adapted (Fig. 6). This is image processing technology nisch realized so that the course of the light / dark transition is first determined in the cross-sectional areas 20, 21, 22, 23, 24. This is done with image processing methods for edge extraction and can either be performed with pixel accuracy or, in order to achieve higher accuracy, with sub-pixel accuracy. The circular function is then adapted to an edge 38 determined in this way. As a result, the circular function supplies the maximum radius of the tool cutting edge 28, that is to say the points of the 3D model and the effective dimension.

For numerical reasons and without a noticeable loss of accuracy, the cos function can be developed as a polynomial and provides a modified function / 'for adaptation to the edge 38 in the form

The result of the adjustment is a function that describes the course of the tool cutting edge 28 during rotation. The maximum deflection or the effective dimension is the vertex of the parabola, ie the radius of the tool 10 (FIG. 6).

The determined active contour 26 consists of sub-pixel-precise values, specifically as a result of taking into account the angular ranges between individual images. In the simplest case, the results of different cross-sectional areas 20, 21, 22, 23, 24 are combined with one another for the active contour 26 of the entire tool 10.

Improved processes do not evaluate cross-sectional areas 20,

21, 22, 23, 24 individually, but use functions that describe the surface in the vicinity of the maximum deflection in space. An advantageously simple procedure could consist of adapting a plane locally to the surface data. Functions that describe the reality more precisely include the circular movement of the tool cutting edge 28 perpendicular to the axis of rotation and follow the surface parallel to the axis of rotation. Functions that describe a spindle or simple, curved surfaces, such as hyperboloids, can be used.

The improved methods are characterized in particular by the fact that 19 voxel information including three-dimensional neighborhoods are used in the evaluation to determine the surface model, voxels 25 being shown enlarged in FIGS. 5 and 7. It no longer works in two-dimensional pixel data, but in three-dimensional voxel information. Information about neighboring cross-sectional areas 20, 21, 22, 23, 24 can be taken into account via the three-dimensional voxel information.

In the implementation according to the invention for determining the active contour 26, it makes sense to already take the individual images, i.e. start online with the calculation of the surface model 19 and the evaluation of the volume data, including a calculation after recording all

Pictures offline is possible. In particular, during the rotation, extrapolation can be used to determine the angular ranges in which a maximum deflection of the tool cutting edge 28 can be expected. The surface model 19 can then only be created in the extreme value ranges to be expected and computing time can be saved or in the to be expected extreme value ranges, more images 13, 14, 15, 16, 17 can be recorded than in other regions by reducing the rotational speed of the tool 10 in the vicinity of the extremum and / or increasing the recording frequency.

reference numeral

10 Tool 33 lighting unit

11 Setting device 34 surface

12 camera 35 cylinder

13 Figure 36 Circle

14 Figure 37 Normal vector

15 Fig. 38 edge

16 Figure 39 Contour

17 picture

18 Data structure

19 surface model

20 cross-sectional area

21 cross-sectional area

22 cross-sectional area

23 cross-sectional area

24 cross-sectional area

25 voxels

26 active contour

27 Extreme value

28 tool cutting edge

29 Image processing device

30 optics carrier

31 tool holder

32 longitudinal axis

Claims

Expectations

1. A method for acquiring information of a tool (10), in particular for measuring a machine tool in an adjusting device (11), in which images (13 to 17) of the tool (10) in different recording positions with at least one camera (12). are recorded, characterized in that the images (13 to 17) are sorted into a data structure (18) for a three-dimensional space according to their recording position.

2. The method according to claim 1, which also means that a three-dimensional surface model (19) is calculated from the data structure (18), which represents at least part of the tool (10).

3. The method according to claim 2, since you rchgek characterized in that to determine the surface model (19) cross-sectional areas (20 to 24) are evaluated by the three-dimensional space mapped by the data structure (18).

4. The method according to claim 2 or 3, d a d u r c h g e k e n n z e i c h n e t that voxel information, including three-dimensional neighborhoods, is used at least in partial areas for determining the surface model (19).

5. The method according to any one of claims 2 to 4, so that information about the relative movement of the tool (10) to the camera (12) is used.

6. The method according to any one of claims 2 to 5, so that information of the surface shape of the tool (10) is used.

7. The method according to any one of claims 2 to 6, so that an effective contour (26) of the tool (10) is determined from the surface model (19) by at least one extreme value determination.

8. The method according to any one of claims 2 to 7, characterized in that local extreme values (27) of the surface model (19) are combined to form an image of a tool cutting edge (28).

9. The method as claimed in claim 8, so that the pitch of the tool cutting edge (28) is determined by the geometric relationship of the local extreme values (27).

10. The method according to any one of claims 2 to 8, so that the clearance angle of a cutting edge (28) of the tool (10) is determined by means of the orientation of a surface against the cutting direction behind the cutting edge (28).

11. The method according to any one of claims 2 to 10, so that the surface model (19) is still calculated while the images (13 to 17) are being taken.

12. The method according to any one of claims 2 to 11, so that the surface model (19) is created only in the extreme value ranges to be expected.

13. The method according to any one of claims 2 to 11, characterized in that more images are taken in expected extreme value ranges than in other areas.

14. Device for acquiring information of a tool, in particular for visualizing and measuring a machine tool (10) in a setting device (11), with at least one camera (12) for recording the tool (10) in different recording positions, and with an image processing device (29), characterized in that the images (13 to 17) can be sorted into a three-dimensional space with the image processing device (29) according to their recording positions.

15. The apparatus of claim 14, so that a three-dimensional surface model (19) can be calculated with the image processing device (29).