JP5001521B2 - Tool shape measuring device - Google Patents

Description

  The present invention relates to a tool shape measuring apparatus, and more particularly to a technique for obtaining a cross-sectional shape of a processing tool and a holding mechanism that holds the processing tool from captured images of the processing tool and a holding mechanism that holds the processing tool.

  Automatic measurement of the shape of the processing tool mounted on the spindle of a machine tool (for example, a machining center) and the tool holding mechanism (for example, a shank or a shank holder) for holding it is necessary for proper operation of the machine tool. Useful. For example, by automatically measuring the shape of a machining tool or tool holding mechanism, the data of the dimensions of the machining tool or tool holding mechanism (for example, the length of the machining tool, the width or height of the tool holding mechanism) is automatically transmitted to the machine tool. It becomes possible to give. The dimensions of the processing tool and the tool holding mechanism are important data for the numerical control of the machine tool, and automatically giving them to the machine tool is effective for reducing the labor of the operator of the machine tool. In addition, by automatically measuring the shape of the processing tool and holding mechanism, it automatically checks whether the correct combination of the processing tool, shank, and shank holder is mounted on the machine tool, and the incorrect combination is mounted. If it is, the start of operation of the machine tool can be prohibited. In addition, by automatically measuring the shape of the processing tool or the tool holding mechanism, it is possible to check the presence or absence of interference between the processing tool or the tool holding mechanism and the processing target.

  Japanese Utility Model Laid-Open No. 62-192847 discloses a technique for measuring a tool length and a tool radius using a pair of image sensors and a laser measuring head. In the technique disclosed in this publication, the measurement of the tool length and the tool radius is roughly performed by the following procedure. First, the tool cutting edge height position is recognized by the image sensor, and the reference point of the laser measuring head is moved to the tool cutting edge height position. Further, the laser measuring head is scanned in the length direction of the machining tool, and the maximum tool diameter portion where the tool diameter is maximum is detected. The position of the maximum tool diameter portion is determined as the tool length, and the radius of the machining tool at the maximum tool diameter portion is determined as the tool radius.

  On the other hand, Japanese Patent Laid-Open No. 8-52638 discloses a tool in which a tool holder and a processing tool are two-dimensionally imaged by a CCD camera to generate actual tool shape data, and the actual tool shape data, the tool holder and the processing tool are defined. A technique for determining a mounting error of a processing tool and a tool holder by comparing with shape data is disclosed. In the publication, an interference check is further performed using machine shape data defining a machine-side three-dimensional shape including a machining tool and a spindle head on which a tool holder is mounted, and machining material shape data to be machined. Technology is disclosed.

In such a tool shape measuring apparatus, it is desired that the dimensions of the processing tool and the tool holding mechanism can be measured with an inexpensive and simple apparatus configuration, but the conventional technique does not sufficiently meet such a requirement. For example, a method of capturing a captured image of an object using a telecentric lens and obtaining the size of the object from the captured image is the most typical method for optically measuring the size of the object. However, a telecentric lens is expensive and requires a measurement object smaller than the diameter of the lens, so that it is not suitable for measuring the dimensions of a processing tool or a tool holding mechanism. In addition, the tool shape measuring device disclosed in Japanese Utility Model Publication No. 62-192847 requires three optical devices, that is, a pair of image sensors and a laser measuring head, and is inferior in terms of simplicity of the device configuration. . Further, although the apparatus disclosed in Japanese Patent Laid-Open No. 8-52638 can detect whether the processing tool and the tool holder are correctly mounted, the dimensions of the processing tool and the tool holder actually mounted on the machine tool. Cannot be measured.
Japanese Utility Model Publication No. 62-192847 JP-A-8-52638

  Accordingly, an object of the present invention is to provide a tool shape measuring apparatus capable of measuring the dimensions of a processing tool and a tool holding mechanism with an inexpensive and simple apparatus configuration.

  In order to achieve the above object, the present invention employs the means described below. In the description of technical matters constituting the means, in order to clarify the correspondence between the description of [Claims] and the description of [Best Mode for Carrying Out the Invention] Number / symbol used in the best mode for doing this is added. However, the added number / symbol should not be used to limit the technical scope of the invention described in [Claims].

  In one aspect of the present invention, a tool shape measuring apparatus of the present invention includes a machining tool (1) that can rotate around a central axis (4a) and a tool holding mechanism (2, 3) that holds the machining tool (1). ) And dimensional data generation for generating dimensional data indicating the dimensions of the processing tool (1) and / or the tool holding mechanism (2, 3) from the captured image Part (13). The imaging device (5) is positioned such that its optical axis (5a) intersects the central axis (4a) perpendicularly. The dimension data generation unit (13) includes a distance from the reference plane (S) defined to be perpendicular to the optical axis (5a) and including the central axis (4a) to the imaging device (5). And the corresponding data (α) representing the correspondence between the unit length on the captured image and the length on the reference plane (S) are set, and the dimension data generating unit (13 ) Generates the dimension data by correcting the perspective error of the captured image using the captured image, the reference distance (L), and the corresponding data (α).

  The dimension data generation unit (13) expresses the shape of the processing tool (1) and the tool holding mechanism (2, 3) using a cylinder, and converts the captured image into an orthogonal projection image on the reference plane. A semi-circular portion of the outline of the bottom surface of the cylinder is projected onto a straight line on the orthographic image, and the perspective error of the captured image is calculated using the calculated map. It is preferable to generate the dimension data by correcting.

  In another aspect of the present invention, the tool shape measuring apparatus of the present invention includes a machining tool (1) rotatable around a central axis (4a) and a tool holding mechanism (2, 3) that holds the machining tool (1). ) And dimensional data generation for generating dimensional data indicating the dimensions of the processing tool (1) and / or the tool holding mechanism (2, 3) from the captured image Part (13). The dimension data generation unit (13) includes a database (13a to 13c) in which models and dimensions of the machining tool (1) and the tool holding mechanism (2, 3) are stored in association with each other. The generation unit (13) selects, as a candidate model, an optimal model from the models stored in the database (13a to 13c) for each of the machining tool (1) and the tool holding mechanism (2, 3), Further, the position of the candidate model is determined by pattern matching between the combination image of the candidate model and the captured image, and the combination of the machining tool (1) and the tool holding mechanism (2, 3) corresponding to the candidate model, The dimension data is generated from the determined position.

  According to the present invention, it is possible to provide a tool shape measuring apparatus capable of measuring the dimensions of a processing tool and a tool holding mechanism with an inexpensive and simple apparatus configuration.

First embodiment:
FIG. 1 is a block diagram showing a configuration of a tool shape measuring apparatus 10 according to the first embodiment of the present invention. The tool shape measuring apparatus 10 according to this embodiment measures the dimensions of a machining tool 1 of a machining center, a shank 2 that holds the machining tool 1, and a holder 3 that mounts the shank 2 on a spindle 4, and sends it to a machining center controller 7. This is for use in controlling the machining center. Hereinafter, the configuration of the processing tool shape measuring apparatus 10 will be described in detail.

  The tool shape measuring device 10 includes a camera 5 and a shape measuring device 6. The camera 5 is positioned such that its optical axis 5a is perpendicular to the reference plane S; the reference plane S is a central axis 4a on which the processing tool 1, the shank 2, the holder 3 and the main shaft 4 rotate. The optical axis 5a of the camera 5 intersects the central axis 4a perpendicularly. A coordinate system in real space (hereinafter referred to as an XYZ coordinate system) is a direction in which the Z axis is parallel to the optical axis 5a and the Y axis is parallel to the central axis 4a with the position defined inside the camera 5 as the origin. The X axis is defined to be in a direction perpendicular to both the central axis 4a and the optical axis 5a. The distance between the reference plane S and the camera 5 is called a reference distance L. The camera 5 captures the captured image by capturing the processing tool 1, the shank 2, and the holder 3 under such an arrangement.

  The shape measuring device 6 measures the dimensions of the processing tool 1, the shank 2, and the holder 3 using the captured image acquired by the camera 5. The shape measuring device 6 sends the measured dimensions to a machining center controller 7 that controls the machining center.

  In the present embodiment, a telecentric system is not adopted as the optical system of the camera 5. While this is useful for reducing the cost of the tool shape measuring apparatus 10, the size of the image on the captured image includes a perspective error, that is, the size of the image corresponds to the actual size. It also causes the problem of not.

  In order to overcome the occurrence of perspective errors due to the non-adoption of the telecentric system and obtain the correct dimensions of the processing tool 1, the shank 2, and the holder 3, the shape measuring device 6 includes the processing tool 1, the shank 2, and the holder 3 From the dimensions on the captured image, the actual dimensions are calculated by a special process. Below, the structure and operation | movement of the shape measuring apparatus 6 are demonstrated in detail.

  FIG. 2 is a block diagram showing the configuration of the shape measuring apparatus 6. The shape measuring device 6 includes a target image photographing processing unit 11, a contour image extraction processing unit 12, and a dimension data generation unit 13. The target image capturing processing unit 11 controls the camera 5 with the control signal 15 and acquires a desired captured image from the camera 5. More specifically, when receiving the shape measurement request 16 from the machining center controller 7, the target image capturing processing unit 11 causes the camera 5 to capture the captured images of the processing tool 1, the shank 2, and the holder 3, and captures the captured images. Receive from camera 5. The contour image extraction processing unit 12 performs image processing on the captured image taken by the camera 5 and extracts a contour image (edge image). The dimension data generation unit 13 calculates the dimensions of the machining tool 1, the shank 2, and the holder 3 from the contour image by calculation, and sends the dimension data indicating the calculated dimensions to the machining center controller 7. The dimension on the contour image includes a perspective error similarly to the dimension on the captured image, and does not reflect the correct dimensions of the processing tool 1, the shank 2, and the holder 3. For this reason, the dimension data generation unit 13 corrects the perspective error of the captured image using the reference distance L and the parameter α indicating the length on the reference plane S corresponding to one pixel of the captured image. Identify the correct dimensions of tool 1, shank 2 and holder 3.

  For correcting the perspective error, the shape of the machining tool 1, the shank 2 and the holder 3 shown in the contour image is roughly a cylinder arranged so as to be rotationally symmetric about the central axis 4a, and The assumption that it is represented by a combination of hemispheres is used. Specifically, many machining tools 1, the shank 2, and the holder 3 are represented by a combination of cylinders. A machining tool having a hemispherical tip, such as a ball end mill, is a cylinder with a hemispherical tip. expressed. Those skilled in the art will understand that the assumption that the shapes of the processing tool 1, the shank 2, and the holder 3 are represented by a combination of a cylinder and a hemisphere is appropriate.

  When such a premise is adopted, in order to measure the dimensions of the processing tool 1, the shank 2, and the holder 3, the width (that is, the diameter) of the cylinder representing the processing tool 1, the shank 2, and the holder 3 is measured. The height position of the upper and lower bottom surfaces of the cylinder, and the height position of the tip of the hemispherical surface for a cylinder with a hemispherical surface may be determined; where the width is a direction perpendicular to the central axis 4a. Note that the height position is defined in the direction along the central axis 4a. Hereinafter, a determination method for correcting the perspective error and determining the width of the cylinder, the height position of the upper and lower bottom surfaces, and the height position of the tip of the hemisphere will be described in detail.

ここで、Ｗ’は、ピクセル数で表された、輪郭線画像上における（即ち、撮像画像上における）対象部分の幅であり、αは、撮像画像の１ピクセルに対応する基準平面Ｓ上での長さであり、Ｌは、基準距離（即ち、基準平面Ｓとカメラ５との距離）である。 1. Width of target object Referring to FIG. 3, the width W of a desired portion (target portion) of the processing tool 1, the shank 2, and the holder 3 is calculated by the following formula under the assumption that the cross section is circular. Is:

Here, W ′ is the width of the target portion on the contour image (that is, on the captured image) expressed in the number of pixels, and α is on the reference plane S corresponding to one pixel of the captured image. L is a reference distance (that is, a distance between the reference plane S and the camera 5).

ここでＲ’は、ピクセル数で表された、輪郭線画像上における（即ち、撮像画像上における）底面の半径であり、αは、撮像画像の１ピクセルに対応する基準平面Ｓ上での長さであり、Ｌは、基準距離である。 2. Height position of the top and bottom of the cylinder (position in the direction of the central axis 4a)
Referring to FIG. 4, first, the radius R (in real space) of the bottom surfaces 21 and 22 of the target cylinder is estimated by the following formula:

Here, R ′ is the radius of the bottom surface on the contour image (that is, on the captured image) expressed by the number of pixels, and α is the length on the reference plane S corresponding to one pixel of the captured image. And L is a reference distance.

Furthermore, the height position h (in real space) of the end point of the contour line 23 on the side surface of the cylinder is estimated by the following formula:
_{h = α · (J 0 -J} P), ··· (3)
Here, J ₀ is in a coordinate system (hereinafter, this coordinate system is referred to as an xy coordinate system or an image coordinate system) defined on the contour image (and the captured image) as shown in FIG. a y-coordinate of the optical axis 5a, _{J P} is the y coordinate of the end point of the contour line 23 in the xy image coordinate system.

  Returning to FIG. 4, for each of the target bottom surfaces 21, 22, the front or back semicircle of the contour line is selected. As for the bottom surface 21 which is the upper bottom surface, when it is located above the optical axis 5a, the front semicircle is selected, and when it is not, the back semicircle is selected. On the other hand, for the bottom surface 22 which is the lower bottom surface, when it is located above the optical axis 5a, the semicircle on the back side is selected, and when it is not, the front semicircle is selected. In the present embodiment, for the bottom surface 21 that is the upper bottom surface, a semicircle on the back side is selected, and for the bottom surface 22 that is the lower bottom surface, the front semicircle is selected.

奥側の半円については下記式：

によって算出される。ここで、Ｒは、式（２）によって算出された半径であり、ｈは、式（３）によって算出された高さ位置であり、ΔＨは、領域２４、２５の高さの半分であり、θ_ｉは、下記式を満足する任意の値である：

Subsequently, the projection onto the image coordinate system (xy coordinate system) of the regions 24 and 25 having a height of 2ΔH centered on the selected semicircle is calculated. Specifically, first, coordinates (X ₁ , Y ₁ , Z ₁ ), (X ₂ , Y ₂ ) of a plurality of points P ₁ , P ₂ ,. , Z ₂ )... Are calculated. Specifically, the coordinates of the point P _i in real space are given by the following formula for the front semicircle:

For the back half circle:

Is calculated by Here, R is the radius calculated by the equation (2), h is the height position calculated by the equation (3), ΔH is half the height of the regions 24 and 25, θ _i is an arbitrary value satisfying the following formula:

ここで、ｆは、カメラ５のレンズの焦点距離であり、ξは、カメラ５に内蔵された撮像素子の画素のＸ軸方向のサイズであり、ηは、画素のＹ軸方向のサイズである。 Further, the coordinates (x ₁ , y ₁ ), (x ₂ , y ₂ ),... Projected onto the image coordinate system of the points P ₁ , P ₂ ,.

Here, f is the focal length of the lens of the camera 5, ξ is the size in the X-axis direction of the pixel of the image sensor incorporated in the camera 5, and η is the size in the Y-axis direction of the pixel. .

Subsequently, using the coordinates of the projections of the points P ₁ , P ₂ ,... Onto the image coordinate system, the captured images of the processing tool 1, the shank 2, and the holder 3 are orthogonal to the reference plane S. An expression representing a map to be converted into an image is obtained. The reason why the orthographic image is obtained is that the perspective error is excluded from the orthographic image, and therefore the correct dimension can be calculated from the orthographic image. If the coordinate system defined for the orthographic image is called an x′y ′ coordinate system, the mapping for converting the captured image to the orthographic image is a mapping from the xy coordinate system to the x′y ′ coordinate system. In other words. However, in the present embodiment, since only the height position is interested, only the expression for obtaining y ′ in the mapping is calculated.

奥側の半円については下記式（６ｂ）：

と仮定される。ここでｋ_１〜ｋ_８は係数である。ｒは、下記式
ｒ^２＝ｘ^２＋ｙ^２， ・・・（６ｃ）
で表される。更に、ｘ_ｍａｘは、対象となる円筒の画像座標系への投影のｘ座標の最大値であり、下記式：

で表される。 The expression for obtaining y ′ in the mapping from the xy coordinate system to the x′y ′ coordinate system is the following expression (6a) for the front semicircle:

For the back semicircle, the following formula (6b):

Is assumed. Here, k ₁ to k ₈ are coefficients. r is the following formula: r ² = x ² + y ² , (6c)
It is represented by Furthermore, x _max is the maximum value of the x coordinate of the projection onto the image coordinate system of the target cylinder,

It is represented by

In addition, the following two conditions:
(1) The point P ₁ , P ₂ ,... Of the point located at the upper boundary of the region 24 is a straight line parallel to the x ′ axis (a straight line with a constant y ′). The map of the point located on the lower boundary is located on another straight line parallel to the straight line. (2) Of the points P ₁ , P ₂ ,. The mapping of the point to the x'y 'coordinate system is located on another straight line parallel to the x' axis, and the mapping of the point located at the lower boundary is located on another straight line parallel to the straight line. In order to satisfy, the coefficients k _{1 to} k ₈ are determined by the method of least squares.

  According to the mapping thus determined, the mapping of the selected semicircle to the x′y ′ coordinate system becomes a line segment parallel to the x ′ axis.

The height position H _U of the upper bottom surface of the cylinder and the height position H _D of the lower bottom surface are expressed by the following equation using the y ′ coordinate of the line segment that is a mapping of the selected semicircle to the x′y ′ coordinate system. Represented by:
H _U = α · y _U ', (7a)
H _D = α · y _D ', (7b)
Where y _U ′ is the y ′ coordinate of the line segment that is a mapping of the semicircle selected for the upper base to the x′y ′ coordinate system, and y _D ′ is the x of the semicircle selected for the lower base. The y coordinate of the line segment that is a mapping to the 'y' coordinate system. The length along the central axis 4a of the cylinder representing the processing tool 1, the shank 2, and the holder 3 is the difference in the height position of the upper and lower bottom surfaces of the cylinder.

3. As shown in FIG. 6, the cylinder with the hemispherical surface attached to the tip of the hemispherical surface is close to the height position on the captured image when the tip is above the optical axis 5a. An error ΔH is included. In order to eliminate this perspective error, the height position H ′ of the tip of the hemisphere is obtained by the following equation using the height position Y in the contour image (ie, the captured image):

  In this way, the width of the cylinder representing the processing tool 1, the shank 2, and the holder 3, the height position of the top and bottom surfaces, and the height position of the tip of the hemispherical surface are determined, and from these values, the processing tool 1, The dimensions of the shank 2 and the holder 3 are calculated.

  As described above, the tool shape measuring apparatus 10 according to the present embodiment processes a captured image without using a telecentric system as an optical system of the camera 5 (that is, without using an expensive telecentric lens). The dimensions of the tool 1, the shank 2 and the holder 3 can be measured. Therefore, the tool shape measuring apparatus 10 of the present embodiment is excellent in economic efficiency and the apparatus configuration is simple.

Second embodiment:
In the second embodiment, the dimensions of the processing tool 1, the shank 2, and the holder 3 are measured by a process different from that of the first embodiment. FIG. 7 shows a flow of processing performed by the dimension data generation unit 13 in the second embodiment. In the second embodiment, a machining tool model database 13a that stores a model (that is, a template image) of the machining tool 1, a shank model database 13b that stores a model of the shank 2, and a holder model that stores a model of the holder 3. The database 13c is prepared in the dimension data generation unit 13, and these databases are used for dimension measurement. In the machining tool model database 13a, the shank model database 13b, and the holder model database 13c, in addition to the models of the machining tool 1, the shank 2, and the holder 3, data indicating respective dimensions (for example, length and width) are stored. ing.

  The contour line of the contour image extracted by the contour line image extraction unit 12 is tracked, and the processing tool 1, the shank 2, and the holder 3 are separated at the bending point of the contour line (step S01).

  Subsequently, the concave portion is filled in the portion corresponding to the processing tool 1, and the contour image is simplified (step S02).

  Subsequently, the respective widths of the processing tool 1, the shank 2, and the holder 3 are calculated from the contour image by the above-described formula (2), and an optimum model (candidate model) is processed based on the calculated width. It is selected from the tool model database 13a, the shank model database 13b, and the holder model database 13c (step S03).

  Further, the position of each candidate model in the height direction (direction parallel to the central axis 4a) is determined (step S04). The position of each candidate model in the height direction is performed by pattern matching of the combined image of the three candidate models and the binarized image of the captured image. More specifically, the position in the height direction of each candidate model is determined so that the difference absolute value between the combined image of the three candidate models and the binarized image of the captured image is minimized.

  With the above procedure, the combination of the processing tool 1, the shank 2, and the holder 3 and their positions are identified. The dimensions of the machining tool 1, the shank 2, and the holder 3 are calculated from the identified combination of the machining tool 1, the shank 2, and the holder 3 and their positions (step S05).

  Even in the procedure of the present embodiment, the dimensions of the processing tool 1, the shank 2, and the holder 3 are measured from the captured image without using a telecentric system as the optical system of the camera 5 (that is, without using an expensive telecentric lens). Is possible.

FIG. 1 is a block diagram showing a configuration of a tool shape measuring apparatus according to the first embodiment of the present invention. FIG. 2 is a block diagram of the shape measuring apparatus according to the first embodiment. FIG. 3 is a conceptual diagram illustrating a method for calculating the width of an object. FIG. 4 is a conceptual diagram illustrating a method for calculating the height position of the upper and lower bottom surfaces of the cylinder. FIG. 5 is a conceptual diagram for explaining a method for estimating the height position of the end point of the contour line of the side surface. FIG. 6 is a conceptual diagram illustrating a method for calculating the height position of the tip of the hemispherical surface connected to the cylinder. FIG. 7 is a flowchart illustrating a calculation method for calculating the dimensions of the machining tool, the shank, and the holder in the second embodiment.

Explanation of symbols

1: Processing tool 2: Shank 3: Holder 4: Spindle 4a: Center axis 5: Camera 5a: Optical axis 6: Shape measuring device 7: Machining center controller 11: Target image photographing processing unit 12: Outline image extraction processing unit 13: Dimension data generation unit 21, 22: bottom 23: (side) contour 24, 25: region

Claims (1)

An imaging device that captures an image of a processing tool that can rotate around a central axis and a tool holding mechanism that holds the processing tool;
A dimension data generation unit that generates dimension data indicating the dimensions of the processing tool and / or the tool holding mechanism from the captured image;
The imaging device is positioned such that its optical axis intersects the central axis perpendicularly,
The dimension data generation unit includes a reference distance that is a distance from a reference plane that is perpendicular to the optical axis and includes the central axis to the imaging device, and a unit length on the captured image. Correspondence data representing the correspondence with the length on the reference plane is set,
The dimension data generation unit generates the dimension data by correcting a perspective error of the captured image using the captured image, the reference distance, and the corresponding data ,
The dimension data generation unit expresses the shape of the processing tool and the tool holding mechanism using a cylinder, and converts the captured image into an orthogonal projection image on the reference plane, and the contour line of the bottom surface of the cylinder A tool that calculates the semicircle portion of the image to be projected onto a straight line on the orthographic image, and corrects the perspective error of the captured image using the calculated map to generate the dimension data Shape measuring device.

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