Marker, device, system, and measurement method for measuring the position and orientation of an object

Abstract

In the present disclosure, a marker (16) is provided which is disposed on the surface of an object and capable of measuring the position and posture of the object. The marker includes: a first surface (15a) having a first feature point (Ht1); and a second surface (16b) formed to have a predetermined height difference (D) starting from the first feature point and having a predetermined relative posture with respect to the first surface below the first surface. Based on the shadow of the first surface projected onto the second surface in an image obtained by photographing the marker by a photographing unit (19), a second feature point (Kb1) corresponding to the first feature point is obtained, and based on the first feature point and the second feature point, the position and posture of the object can be measured.

Description

Technical Field

[0001] The present invention relates to a technique for accurately measuring the position and posture of an object using a marker and a photographing device. Background Art

[0002] In a manufacturing site, a workpiece to be processed is combined with various machine tools and industrial robots for processing. There is known a technique in which, in order to make a machine tool and a robot cooperate with each other, a calibration marker is formed on the machine tool, and a camera of the robot photographs the calibration marker, thereby performing coordinate transformation between the coordinate system of the robot and the coordinate system of the machine tool (for example, refer to Patent Document 1).

[0003] In the method using the calibration marker formed on the robot, when the workpiece to be processed is moved and the workpiece is transferred between a machine tool and a robot that are separately arranged, the movable range becomes narrow.

[0004] There is known a technique for determining the three-dimensional position of a workpiece by forming a posture marker on a holding member of the workpiece (for example, refer to Patent Document 2).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2016-101640

[0008] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2017-144534 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] An object of the present invention is to provide a marker, a device, and a system capable of accurately measuring the position and posture of an object.

[0011] Means for Solving the Problems

[0012] According to one aspect of the present invention, there is provided a marker provided on a surface of an object and capable of measuring the position and posture of the object, the marker including: a first surface having a first feature point; and a second surface formed to have a predetermined height difference from the first feature point and having a predetermined relative posture with respect to the first surface below the first surface. Based on a shadow of the first surface projected onto the second surface in an image obtained by photographing the marker by a photographing unit, a second feature point corresponding to the first feature point is obtained, and based on the first feature point and the second feature point, the position and posture of the object can be measured.

[0013] According to the above method, a marker can be provided, which has a first surface and a second surface formed below the first surface with a predetermined height difference, and can accurately measure the position and posture of an object provided with the marker based on a first feature point of the first surface in an image captured by a photographing unit and a second feature point of a shadow of the first surface projected onto the second surface.

[0014] According to another aspect of the present invention, there is provided an apparatus including: a light irradiation unit disposed on the surface of an object, which can irradiate light to the marker of the above aspect to form a shadow of the first surface on the second surface; a photographing unit that photographs the marker; and a measurement unit that obtains a second feature point corresponding to the first feature point based on the shadow of the first surface projected onto the second surface in an image of the marker photographed by the photographing unit, and obtains the position and posture of the object based on the first feature point and the second feature point.

[0015] According to the above another aspect, an apparatus can be provided: by photographing a marker having a first surface with a first feature point and a second surface formed below the first surface with a predetermined height difference by a photographing unit, and by measuring and calculating the first feature point of the first surface in the image and a second feature point of a shadow of the first surface projected onto the second surface by a light irradiation unit, the position and posture of an object provided with the marker can be accurately measured.

[0016] According to other aspects of the present invention, there is provided a method for measuring the position and posture of an object, including the following steps: a first measurement step of photographing the marker of the above aspect by a photographing unit, and measuring coordinate components of the first feature point and a third feature point in the second surface having the predetermined height difference from the first feature point based on first image data obtained by a measurement unit; a second measurement step of irradiating light by a light irradiation unit and photographing the marker by the photographing unit, and measuring coordinate components of the second feature point corresponding to the first feature point based on the shadow of the first surface projected onto the second surface according to second image data obtained by the measurement unit; and a step of determining information on the position and posture of the marker by calculation based on the coordinate components of the first to third feature points obtained by the measurement unit in the first and second measurement steps.

[0017] According to the above-described other method, a mark having a first surface with a first feature point and a second surface formed below the first surface with a predetermined height difference is photographed, and coordinate components of the first feature point and a third feature point in the second surface having the predetermined height difference from the first feature point are measured based on the acquired first image data. Coordinate components of a second feature point of a shadow of the first surface projected onto the second surface by light irradiated by a light irradiation unit are measured, and information on the position and orientation of the mark is determined by calculation based on the coordinate components of the first to third feature points. Thus, the position and orientation of an object provided with the mark can be measured with high precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FIG. 1 is a schematic configuration diagram of a machine tool including a position and orientation measurement system according to an embodiment of the present invention.

[0019] Figure 2 FIGS. 2A and 2B are a plan view and a sectional view of a mark according to an embodiment of the present invention.

[0020] Figure 3 FIG. 3 is a schematic configuration diagram of a position and orientation measurement system according to an embodiment of the present invention.

[0021] Figure 4 FIG. 4 is an explanation of the principle of a position and orientation measurement system according to an embodiment of the present invention. Figure 1 .

[0022] Figure 5 FIG. 5 is an explanation of the principle of a position and orientation measurement system according to an embodiment of the present invention. Figure 2 .

[0023] Figure 6 FIG. 6 is a flowchart showing a position and orientation measurement method according to an embodiment of the present invention.

[0024] Figure 7 FIG. 7 is a modified example of a mark according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same reference numerals are assigned to elements common to a plurality of drawings, and redundant detailed descriptions thereof are omitted.

[0026] Figure 1 FIG. 1 is a schematic configuration diagram of a machine tool including a position and orientation measurement system according to an embodiment of the present invention. Refer to Figure 1, the machine tool 10 including the position and orientation measurement system according to an embodiment of the present invention has: a machine tool frame 11, a spindle 12, a tool 13, a moving worktable 14, a workpiece 15, a mark 16 formed on the surface of the workpiece 15, a light irradiation unit 18 that irradiates light onto the mark 16, a camera 19 that photographs the mark 16, and a measurement unit 20 that receives the image data from the camera 19 and measures the position and orientation of the workpiece 15. In the machine tool 10, the camera 19 photographs the mark 16 formed on the workpiece 15, the measurement unit 20 measures the position and orientation of the mark 16 based on the image data, determines the position and orientation of the workpiece 15 based on the information on the position and orientation of the mark 16 and the relative position information between the mark 16 and the workpiece 15, and processes the workpiece 15 with the tool 13 by controlling the spindle 12 and the moving worktable 14.

[0027] Figure 2 is a schematic view of a mark according to an embodiment of the present invention. (a) is a top view obtained by approaching the mark, and (b) is a cross-sectional view taken along line AA shown in (a). Refer to Figure 2 in (a) and (b), the mark 16 has a cavity (recess) provided on the surface 15a of the workpiece 15. The mark 16 has an opening 16a on the surface 15a of the workpiece 15, and the shape of the opening 16a in a top view is a polygon, and as an example, it is a quadrilateral. The length of one side of the opening 16a is appropriately selected according to the size of the workpiece 15, for example, it is 10 mm, and from the viewpoint of photographing the entire opening 16a and its interior with the camera 19, it is preferably set to 0.01 mm to 1000 mm.

[0028] The opening 16a has four vertices Ht1 to Ht4. Feature points (hereinafter also referred to as "surface feature points") are selected from the four vertices Ht1 to Ht4, for example, Ht1.

[0029] The bottom surface 16b is formed in a predetermined relative orientation with respect to the surface 15a of the workpiece 15. As an example, it is formed parallel to the surface 15a. The side wall surface 16c extends from each side of the quadrilateral of the opening 16a vertically by a predetermined length (height difference) D to the bottom surface 16b. The height difference D is, for example, 8 mm, and from the viewpoint of photographing the shadow projected onto the bottom surface 16b with the camera 19, it is preferably set to 0.01 mm to 1000 mm. The vertices Hb1 to Hb4 of the bottom surface 16b respectively correspond to the vertices Ht1 to Ht4 of the quadrilateral of the opening 16a. Among the vertices of the bottom surface 16b, a feature point (hereinafter also referred to as "bottom surface feature point") Hb1 corresponding to the surface feature point Ht1 is selected.

[0030] Figure 3 is a schematic structural diagram of a position and orientation measurement system according to an embodiment of the present invention. Refer to Figure 1 , Figure 2 andFigure 3 , the position and orientation measurement system 17 has a marker 16 and a position and orientation measurement device 21. The position and orientation measurement device 21 has: a light irradiation unit 18 that irradiates light onto the marker 16; a camera 19 that captures an image of the marker 16; and a measurement unit 20 that processes the image data of the marker 16 captured by the camera 19. The measurement unit 20 has a determination unit 22, an arithmetic unit 23, and a control unit 24.

[0031] The light irradiation unit 18 has at least one light source, such as an LED light source, and is arranged around the lens of the camera 19. For example, the light irradiation unit 18 arranges 2 light sources on both sides of the lens, and in addition, arranges 4 light sources at the four corners around the lens. The light irradiation unit 18 is arranged such that the shadow of the feature points on the surface 15a of the marker 16 can be formed on the bottom surface 16b. The light irradiation unit 18 is controlled by the control unit 24 to be turned on and off, and can be turned on and off for each light source. From the viewpoint of making the contour (the boundary between light and dark) of the shadow clearer, the light irradiation unit 18 is preferably a point light source. The light source is arranged obliquely above the marker 16. From the viewpoint of easily forming a shadow on the bottom surface 16b, the light source is preferably arranged at an angle of 1 degree to 89 degrees, more preferably 10 degrees to 80 degrees, and particularly preferably 30 degrees to 45 degrees with respect to the virtual plane formed by the opening 16a. In addition, when the height difference D is small (shallow), from the viewpoint of easily forming a shadow on the bottom surface 16b and from the viewpoint of improving the measurement resolution in the depth direction, it is preferable to reduce this angle.

[0032] The camera 19 is composed of a lens, an imaging element, a camera control unit, etc., and for example, a digital video camera, a digital still camera, etc. can be used. The lens 19a can be a single-focus lens or a zoom lens. In the case of a zoom lens, the zoom lens can also be set on the short-focus side for wide-angle shooting to determine the position of the marker 16 formed on the workpiece 15, and then the zoom lens can be set on the long-focus side to obtain a magnified image of the marker 16. Thereby, the position of the marker 16 can be easily determined on the short-focus side, and the position of the contour of the shadow formed on the marker 16 can be obtained more accurately on the long-focus side.

[0033] From the viewpoint of being able to capture an image in which the opening 16a and the bottom surface 16b of the marker 16 are in focus, the camera 19 is preferably a pinhole camera. The pinhole camera can be formed by installing a pinhole lens on the camera body or installing a pinhole filter in front of the lens. The camera 19 can also install a monochromatic transmission filter that only transmits green, blue, red, etc. on the lens 19a. Thereby, by emphasizing the contrast between light and dark, the contour of the shadow can be measured with high precision.

[0034] The measurement unit 22 is provided in the measuring unit 20, and based on the image data of the marker 16 captured by the camera 19, measures the coordinate components of the surface feature point Ht1 selected from the surface 15a, the projection feature point of the shadow of the surface feature point Ht1 formed on the bottom surface 16b, and the bottom surface feature point Hb1 on the bottom surface 16b that is vertically lowered by a predetermined height difference D from the surface feature point. The coordinate components measured here are the coordinate components of a plane parallel to the imaging element of the camera 19, and as will be described later, for example, the x coordinate and the y coordinate.

[0035] Based on the respective coordinate components (for example, the x coordinate component and the y coordinate component) of the surface feature point Ht1, the projection feature point, and the bottom surface feature point Hb1 measured by the measurement unit 22, the arithmetic unit 23 calculates by arithmetic the other coordinate components (for example, the z coordinate) of the surface feature point Ht1, the projection feature point, and the bottom surface feature point Hb1, and the slope of the marker 16, and obtains the position and / or slope of the workpiece 15.

[0036] The control unit 24 can control the light irradiation unit 18, the camera 19, the measurement unit 22, the arithmetic unit 23, and the moving table 14. Specifically, the control unit 24 controls the lighting and extinguishing of the light irradiation unit 18, the timing of shooting by the camera 19, the timing of receiving the image data of the measurement unit 22, and the like.

[0037] The measuring unit 20 can be composed of a personal computer and software that cooperates with the personal computer. As an alternative, the measuring unit 20 can be composed of a dedicated circuit for the measurement unit 22, the arithmetic unit 23, and the control unit 24, or can be composed of a combination of a personal computer and software. The measuring unit 20 may also include a display, a keyboard, and other user interfaces (not shown).

[0038] Figure 4 This is an explanation of the principle of the position and orientation measurement system according to an embodiment of the present invention. Figure 1 , (a) is a diagram showing the positional relationship between the camera, the light irradiation unit, and the marker, and (b) is a top view of the marker on which the projected shadow is formed.

[0039] Refer to Figure 4 In (a) of, for the sake of easy explanation, the vertical direction is set as the z axis, the horizontal direction is set as the x-axis direction, a light source 181 of the light irradiation unit 18, the vertex (surface feature point) Ht1 of the surface 15a of the marker, and the center of the lens of the camera 19, which is set as the center 25a of the pinhole lens 25 in this example, are arranged on the xz plane, and the surface 15a of the marker is inclined at an angle θ with respect to the x axis. xAn image of the marker 16 that has passed through the pinhole lens 25 is formed on the camera element 26, converted into image data, and sent to the measurement unit 20. One light source 181 of the light irradiation unit 18 at the upper left of the marker 16 is lit according to a control signal from the control unit 24. As a result, a shadow of the surface 15a of the marker is formed on the bottom surface 16b.

[0040] Refer to Figure 4 (b) of, and set the feature point (surface feature point) of the surface 15a of the marker 16 as Ht1. The surface feature point Ht1 is the intersection of the side Ht1 - Ht2 and the side Ht4 - Ht1. A shadow is formed on the bottom surface 16b and the side wall surface 16c of the cavity of the marker 16. The shaded part is called the dark part DS (shaded part), and the part directly irradiated with light is called the bright part BS. Among the boundaries between the dark part DS and the bright part BS on the bottom surface 16b, the side Kb1 - Kb2 is the side projected by the side Ht1 - Ht2, and the side Kb4 - Kb1 is the side projected by the side Ht4 - Ht1. The intersection of the side Kb1 - Kb2 and the side Kb4 - Kb1 is taken as the feature point (projection feature point) Kb1. The projection feature point Kb1 is the point projected by the surface feature point Ht1. That is, the light source 181 and the surface feature point Ht1 are connected by a straight line (indicated by a one-dot chain line in Figure 4 (a) of), and the intersection with the bottom surface 16b that extends beyond the surface feature point Ht1 is the projection feature point Kb1. The vertex Hb1 on the bottom surface 16b in the direction perpendicular to the surface 15a from the surface feature point Ht1 is set as the bottom surface feature point.

[0041] Figure 5 This is an explanation of the principle of the position and orientation measurement system according to an embodiment of the present invention Figure 2 . Figure 5 Indicates the same configuration as Figure 4 . Since the components and each feature point are located on the xz plane, in the components of these coordinates, the y coordinate is omitted and shown as (x coordinate, z coordinate).

[0042] Refer to Figure 5 , and the measurement unit 22 obtains the x coordinates of the surface feature point Ht1, the bottom surface feature point Hb1, and the projection feature point Kb1 based on the image data. The coordinates of the surface feature point Ht1 of the marker 16 are expressed as (Ht 1x , Ht 1z ), the coordinates of the bottom surface feature point Hb1 are expressed as (Hb 1x , Hb 1z ), and the coordinates of the projection feature point Kb1 are expressed as (Kb 1x , Kb 1z ). In the plane z = Ht parallel to the x-axis passing through the surface feature point Ht1 1zIn the case of observing from the lens center 25a of the pinhole lens 25, the bottom surface feature point Hb1 becomes the intersection point P 1z with the plane z = Ht Hb , so the coordinates can be represented as (Hb 1x , Ht 1z ) in the image data. Similarly, since the projected feature point Kb1 becomes the intersection point P 1z with the plane z = Ht Kb , the coordinates can be represented as (Kb 1x , Ht 1z ) in the image data. In this way, the measurement unit 22 obtains the x coordinate Ht 1x of the surface feature point Ht1, the x coordinate Hb 1x of the bottom surface feature point Hb1, and the x coordinate Kb 1x of the projected feature point Kb1 from the image data.

[0043] The arithmetic unit 23 uses the x coordinates Ht 1x , Hb 1x , and Kb 1x of the surface feature point Ht1, the bottom surface feature point Hb1, and the projected feature point Kb1 obtained by the measurement unit 22, the coordinates (S 1x , S 1z ) of the preset light source 181, and the height difference D of the mark. According to the image data, by the simultaneous equations (the following equations (1) to (3)) obtained from the geometric relationship, the z coordinate Ht 1z of the surface feature point Ht1, the slope θ x of the mark, and the length <Kb 1x > of the shadow on the xz plane are obtained, and the position and slope of the mark 16 are acquired.

[0044] (Ht 1z - S 1z )(<Kb 1x >cosθ x - V 1x - Dcosθ x ) = Dcosθ x (S 1x - Ht 1x )…(1)

[0045] Ht 1z (<Kb 1x >cosθ x + V’ 1x ) = (Hb 1x - K b1x )(Ht 1z + Dcosθ x )…(2)

[0046] (Ht 1x -Kb 1x )<Kb 1x >sinθ x =(V 1x +V’ 1x )(<Kb 1x >sinθ x +D cosθ x )…(3)

[0047] Equation (1) is an equation obtained from the positions of the light source 181, the surface feature point Ht1, and the bottom surface feature point Hb1 based on the relationship of similar triangles. Equation (2) is an equation obtained from the positions of the lens center 25a of the pinhole lens 25 and the bottom surface feature point Hb1 based on the relationship of similar triangles. Equation (3) is an equation obtained from the positions of the projection feature point Kb1 and the surface feature point Ht1 based on the relationship of similar triangles.

[0048] V 1x and V’ 1x contained in Equations (1) to (3) are as follows. The surface feature point Ht1 is projected by the light source 181 onto the point P 1z on the x-axis parallel plane z = Hb A that passes through the bottom surface feature point Hb1. The x coordinate K b1x of the projection feature point Kb1 is offset by V 1x . In addition, when observed from the lens center 25a of the pinhole lens 25, the projection feature point Kb1 is located at the position of the point P 1z in the plane z = Hb B . The x coordinate K b1x of the projection feature point Kb1 is offset by V’ 1x . These offsets V 1x , V’ 1x can be expressed by the following Equation (4) according to geometric relationships.

[0049] [Mathematical formula 1]

[0050]

[0051]

[0052] The above Equations (1) to (3) can be solved analytically. The arithmetic unit 23 obtains the z coordinate Ht 1z of the surface feature point Ht1, the slope θ x of the mark, and the length <Kb 1x > of the shadow on the xz plane by numerical calculation, for example, the Newton method.

[0053] In addition, when the marker 16 is also inclined with respect to the y-axis, the measurement unit 22 measures the x-coordinates and y-coordinates of the surface feature point Ht1, the bottom surface feature point Hb1, and the projection feature point Kb1 based on the image data, and the arithmetic unit 23 uses the formulas (1) to (3) that take the y-coordinate into consideration, thereby obtaining the position and slope of the marker 16.

[0054] Based on the above, the position and orientation of the marker 16 can be measured. Moreover, by previously obtaining the information on the positional relationship between the marker 16 and the workpiece 15 using a three-dimensional measuring machine or the like and setting it in the measuring unit 20, the position and orientation of the workpiece 15 can be determined with high precision.

[0055] According to the marker 16 of the present embodiment, the marker 16 has: an opening 16a formed on the surface 15a of the workpiece 15; and a bottom surface 16b having a predetermined height difference D from the surface 15a. Based on the image obtained by photographing the surface feature point Ht1 on the surface 15a and the projection feature point Kb1 corresponding to the surface feature point Ht1 of the shadow of the surface 15a projected onto the bottom surface 16b, the position and orientation of the marker 16 can be measured with high precision through measurement and calculation, and thereby the position and orientation of the workpiece 15 can be determined with high precision.

[0056] According to the position and orientation measuring device 21 of the present embodiment, the surface feature point Ht1 of the marker 16 formed on the surface 15a of the workpiece 15 and the projection feature point Kb1 corresponding to the surface feature point Ht1 of the shadow of the surface 15a projected onto the bottom surface 16b are photographed by the camera 19, and the coordinate components of the surface feature point Ht1 and the projection feature point Kb1 based on the shadow of the surface 15a projected onto the bottom surface 16b by the light irradiated by the light irradiation unit in the image obtained by the measuring unit 20 are measured and calculated, thereby enabling the position and orientation of the workpiece 15 provided with the marker 16 to be measured with high precision.

[0057] Figure 6 is a flowchart showing a position and orientation measuring method according to an embodiment of the present invention. Refer to together Figure 6 、 Figure 1 、 Figure 2 、 Figure 4 and Figure 5 to describe a position and orientation measuring method according to an embodiment of the present invention.

[0058] First, in S100, the coordinate data of the camera 19 and the light source of the light irradiation unit 18 are set.

[0059] Specifically, the measurement unit 20 sets the coordinates of the lens center 25a of the pinhole lens 25 of the camera 19 and the respective coordinates of the light sources 181 to 184 of the light irradiation unit 18, and stores them in, for example, a memory (not shown). In this example, the x and z coordinate components of the light source 181 are set with the lens center 25a as the origin. The set data is stored, for example, in the memory of the measurement unit 20.

[0060] Next, in S110, the height difference between the top surface and the bottom surface of the marker is set. Specifically, the measurement unit 20 sets the height difference D from the top surface 15a to the bottom surface 16b of the marker 16, and stores it in, for example, a memory (not shown).

[0061] In S120, the marker is photographed with the camera, and the coordinate components of the surface feature points and the bottom surface feature points are measured based on the image data. Specifically, the control unit 24 uses the camera 19 to photograph the marker 16. The control unit 24 can also turn on a part or all of the light sources S1 to S4. The measurement unit 22 obtains the x coordinate Ht of the surface feature point Ht1 of the marker 16 from the photographed image data 1x and the x coordinate Hb 1x of the bottom surface feature point Hb 1x as measurement data, where the bottom surface feature point Hb1 is the point at the position where the height difference D is reduced from the surface feature point to the bottom surface 16b.

[0062] In S130, the light source is turned on, the marker is photographed with the camera, and based on the shadow of the shape of the surface of the marker projected onto the bottom surface according to the image data, the coordinate components of the projected feature points are measured. Specifically, the control unit 24 turns on the light source S1, projects the shadow of the top surface 15a onto the bottom surface of the marker 16, and uses the camera 19 to photograph the marker 16. The x coordinate Kb of the projected feature point Kb1 is obtained from the photographed image data 1x as measurement data.

[0063] In S140, based on the set data and the measurement data, information on the position and orientation of the marker is obtained through calculation. Specifically, through the arithmetic unit 23, using the coordinates of the light source 181 set in S100 and S110 (S 1x , S 1z ), the height difference D of the marker, the x coordinates Ht 1x , Hb 1x and Kb 1x of the surface feature point Ht1, the bottom surface feature point Hb1, and the projected feature point Kb1 measured in S120 and S130, and based on the image data, numerical calculations are performed on the simultaneous equations (the above equations (1) to (3)) obtained according to geometric relationships. For example, by the Newton method, the z coordinate Ht of the surface feature point Ht1 1z , the slope θ of the marker xand the length of the shadow on the xz plane < Kb 1x >, determines the coordinates and posture θx of the surface feature point Ht1 of the marker 16.

[0064] In S150, the position and posture of the workpiece are determined based on the information of the position and posture of the marker. Specifically, through the operation unit 23, based on the coordinates and posture θx of the surface feature point Ht1 of the marker 16 determined in S140, the position and posture of the workpiece 15 are determined through the information on the positional relationship between the marker 16 and the workpiece 15. In addition, the information on the positional relationship between the marker and the workpiece is preset in the measurement unit 20.

[0065] Through S100 to S150, the position and posture of the workpiece are measured using the marker formed on the workpiece. In addition, S100 and S110 can be performed simultaneously, or S110 can be performed first. S120 and S130 can be performed simultaneously, or S130 can be performed first.

[0066] According to the position and posture measurement method of the present embodiment, the marker 16 is photographed, the coordinate components of the surface feature point Ht1 and the bottom surface feature point Hb1 of the bottom surface 16b having a predetermined height difference D from the surface feature point Ht1 are measured based on the acquired image data, the coordinate components of the projection feature point Kb1 of the shadow projected onto the surface 15a of the bottom surface 16b by the light irradiated by the light source S1 are measured, and based on the coordinate components of the surface feature point Ht1, the bottom surface feature point Hb1, and the projection feature point Kb1, the information on the position and posture of the marker 16 is determined through calculation, whereby the position and posture of the workpiece 15 provided with the marker 16 can be measured with high precision.

[0067] Figure 7 is a modified example of the marker of an embodiment of the present invention, (a) is a top view, and (b) is a view in which the light source is lit and a shadow is projected on the bottom surface. For ease of explanation, the points different from the Figure 2 marker 16 shown previously are described. Refer to Figure 7 In (a) of, when viewed from above, the shape of the marker 116 on the surface 15a of the workpiece 15 is substantially polygonal, for example, a quadrilateral, and has an opening 116a formed by arc-shaped corners Rt1 to Rt4 and sides St1 to St4. The bottom surface 116b of the marker 116 has the same shape as the opening 116a, and has a shape formed by arc-shaped corners Rb1 to Rb4 and sides Sbt1 to Sb4.

[0068] At the corner of the opening 116a, for example, Rt1, the virtual vertex H't1 can be set as the intersection point of extending the sides St1 and St4 sandwiching the corner Rt1. Similarly, on the bottom surface 116b, the virtual vertex H’b1 can be set as the intersection point of extending the sides Sb1 and Sb4 sandwiching the corner Rb1. By obtaining the virtual vertices H't1 and H’b1 in this way, they can be set as the surface feature point H't1 and the bottom surface feature point H’b1 respectively.

[0069] Refer to Figure 7 In (b) and (a) of, when the light source 181 is lit and light is irradiated onto the marker 116, the shadow (dark part DS (shadow area)) of the side on the surface is projected onto the bottom surface 116b. The boundary between the dark part DS and the bright part BS, that is, the contour of the shadow, has sides Ks1 and Ks4 and an arc part. The arc part is the part where the corner Rt1 is projected. Let the intersection point of extending the side Ks1 and the side Ks4 be K’b1. The intersection point K'b1 is the point after the virtual light source 181 projects the surface feature point H't1, and can be set as the virtual projection feature point K'b1.

[0070] Therefore, the marker 116 has the same function as the marker 16 and can function as a marker for the position and orientation measurement system of an embodiment of the present invention. In addition, it can be used as a marker for the position and orientation measurement method of an embodiment of the present invention.

[0071] In the above description, the shapes of the bottom surfaces 16b and 116b of the markers 16 and 116 are quadrilaterals and are the same as the shapes of the openings 16a and 116a on the surface 15a. The shapes of the bottom surfaces 16b and 116b can also be different from the shapes of the openings 16a and 116a. In this case, since the height difference D from the surface 15a to the bottom surfaces 16b and 116b is the same, the position of the projection feature point Kb1 is the same as the case where the bottom surfaces 16b and 116b are quadrilateral shapes, and the above formulas (1) to (5) can be applied.

[0072] In the above description, the relative postures of the bottom surfaces 16b and 116b of the markers 16 and 116 with respect to the surface 15a are parallel. The bottom surfaces 16b and 116b can also be relative postures other than parallel with respect to the surface 15a. The position of the projection feature point Kb1 is only different in the offset amount of the relative posture of the bottom surface compared to the parallel case, but as long as the <Kb 1x > compensates for the offset amount. Regarding the offset amount, it can be measured in advance with a three-dimensional measuring instrument and set in the measuring unit 20.

[0073] In the above description, the marks 16 and 116 are described as cavities (recesses) provided on the surface 15a of the workpiece 15. The marks may also be protrusions (convex portions) provided on the surface 15a of the workpiece 15. The shape of the top surface of the protrusion is the same as the shape of the openings 16a and 116a of the marks 16 and 116. In this case, the surface feature point Ht1 is selected from the vertex or virtual vertex of the top surface of the protrusion. The shadow of the surface feature point is projected onto the surface 15a of the workpiece 15, and the projected feature point Kb1 is formed on the surface 15a. The surface 15a of the workpiece 15 only needs to extend to the extent of forming the projected feature point Kb1. Thus, by applying the above formulas (1) to (5), the marks of the protrusions have the same functions as the marks 16 and 116 and can function as marks for the position and posture measurement system according to an embodiment of the present invention.

[0074] The marks 16 and 116 may also display identification information, attribute information, etc. of the workpiece 15 on which the marks 16 and 116 are formed, such as the specification number, manufacturing batch number, etc., on its surface 15a, bottom surface 16b, and top surface. The image is captured by the camera 19 and recognized by the measuring unit 20 to manage the workpiece 15. Thus, information on the position and posture of the workpiece 15, as well as identification information, attribute information, etc. are obtained simultaneously, making production management easier.

[0075] As described above, the preferred embodiments of the present invention have been described in detail. However, the present invention is not limited to the specific embodiments involved, and various deformations and changes can be made within the scope of the present invention described in the claims. For example, the marks 16 and 116 may also be formed on the fixture that fixes the workpiece 15. Thus, by presetting the information on the relative position and relative posture between the workpiece 15 and the fixture, the position and posture of the workpiece can be determined based on the information on the position and posture of the mark 16 through the position and posture measuring device 21 and the position and posture measuring method of this embodiment.

[0076] In addition, the workpiece 15 or the fixture having the marks 16 and 116 in this embodiment can determine the position and posture of the workpiece 15 or the fixture through the marks 16 and 116, so the workpiece 15 can be transferred between the machine tool and the robot.

[0077] When placing the workpiece 15 on Figure 1 In the case of placing the workpiece 15 on a moving workbench 14 or an automatic guided vehicle (AGV) as shown and machining it through multiple machine tools in the factory, the marks 16 and 116, the position and posture measuring device 21, and the position and posture measuring method of this embodiment can also be applied.

[0078] Description of reference numerals

[0079] 10 Machine tool

[0080] 14 Moving worktable

[0081] 15 Workpiece

[0082] 16, 116 Mark

[0083] 17 Position and posture measurement system

[0084] 18 Light irradiation unit

[0085] 19 Camera

[0086] 20 Measurement unit

[0087] 21 Position and posture measuring device

[0088] 22 Measuring unit

[0089] 23 Operation unit

[0090] 24 Control unit.

Claims

1. A marker that is provided on the surface of an object and can measure the position and posture of the object, characterized in that, The marker has: A first surface having a first feature point; and A second surface formed to have a predetermined height difference from the first feature point and having a predetermined relative posture with respect to the first surface below the first surface, Based on the shadow of the first surface projected onto the second surface in the image obtained by photographing the marker by the photographing unit, a second feature point corresponding to the first feature point is obtained. Based on the first feature point and the second feature point, the position and posture of the object can be measured.

2. The marker according to claim 1, wherein The marker is a recess having an opening on the surface of the object, the first surface is the surface, and the second surface is the bottom surface of the recess.

3. The marker according to claim 2, wherein The opening is a polygon, and the first feature point is a vertex of the polygon.

4. The marker according to claim 2, wherein The opening is a polygon having an arc shape, and the first feature point is a virtual vertex of the polygon.

5. The marker according to claim 1, wherein The marker is a protrusion formed on the surface of the object, the first surface is the top surface of the protrusion, and the second surface is the surface.

6. The marker according to claim 5, wherein The outer shape of the top surface is a polygon, and the first feature point is a vertex of the polygon.

7. The marker according to claim 5, wherein The outer shape of the top surface is a polygon having an arc shape, and the first feature point is a virtual vertex of the polygon.

8. A position and posture measuring device, characterized in that, Comprising: A light irradiation unit disposed on the surface of the object, capable of irradiating light to the marker according to any one of claims 1 to 7 to form a shadow of the first surface on the second surface; A photographing unit that photographs the marker; And A measurement unit that obtains a second feature point corresponding to the first feature point based on the shadow of the first surface projected onto the second surface in the image of the marker photographed by the photographing unit, and obtains the position and posture of the object based on the first feature point and the second feature point.

9. The device according to claim 8, wherein The measurement unit has: A measurement unit that measures, based on the photographed image of the marker, the coordinate components of the first feature point, the second feature point corresponding to the first feature point based on the shadow of the first surface projected onto the second surface, and a third feature point in the second surface having the predetermined height difference from the first feature point on the image; And An arithmetic unit that obtains the other coordinate components of the first feature point to the third feature point by arithmetic according to the coordinate components of the first feature point to the third feature point measured by the measurement unit, and obtains the position and posture of the object.

10. The device according to claim 8, wherein The photographing unit can photograph the marker at a wide angle separately from the object to detect the position of the marker and photograph the marker after magnification.

11. A position and posture measurement system, characterized in that, Comprising: The mark according to any one of claims 1 to 7 formed on the surface of the object; and The device according to claim 8.

12. A method for measuring the position and posture of an object by the system according to claim 11, characterized in that, The method includes the following steps: A first measurement step of photographing the mark according to any one of claims 1 to 7 by a photographing unit, and measuring coordinate components of the first feature point and a third feature point in the second plane having the predetermined height difference from the first feature point based on first image data obtained by a measurement unit; A second measurement step of irradiating light by a light irradiation unit and photographing the mark by the photographing unit, and measuring coordinate components of the second feature point corresponding to the first feature point based on a shadow of the first plane projected onto the second plane according to second image data obtained by the measurement unit; And A step of determining information on the position and orientation of the mark by calculation based on the coordinate components of the first feature point to the third feature point obtained by the measurement unit in the first measurement step and the second measurement step.

13. The method according to claim 12, wherein In the step of determining by the calculation by the measurement unit, the calculation is performed using the predetermined height difference and the coordinate components of the light irradiation unit.

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