JP3170987B2 - Screw hole position recognition method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position recognition method for a visual recognition device for a screw tightening robot, and more particularly to a method for detecting the positions of an upper hole and a lower hole including an arc shape from an image picked up by an image pickup means. The present invention relates to a screw hole position recognizing method for determining whether or not a screw can be tightened.

[0002]

2. Description of the Related Art In recent years, a position recognition method for detecting a position of an object from an image picked up by an image pickup device has been widely used for a visual recognition device of a robot in various production facilities.

A conventional example in which the position of a circular object is recognized from among the position recognition methods used above will be described.

FIG. 6 shows the principle of a conventional position recognition method, and shows a basic configuration for detecting the center position of a circular object. In FIG. 6, reference numeral 20 denotes an image pickup means for picking up an image of an object to output a video signal, reference numeral 21 denotes a gray-scale image storage means for storing the video signal in image data, and reference numeral 22 scans the gray-scale image data by a contour scanning window described later. The scanning means 23 is a position calculating means for calculating the position of the object using the scanning data.

FIG. 7 shows a contour scanning window A. In FIG. 7, reference numeral 24 denotes a scanning contour equal to the contour of the circular object, 25 denotes a density correlation line orthogonal to the scanning contour and measuring the image density inside and outside the scanning contour, and contour scanning window A denotes this density correlation line. Is provided in a plurality of windows.

The position calculating means 23 calculates the absolute value of the difference between the measured density total value at a measurement point inside the contour of the object and the measured density sum value at a measurement point outside the contour of the object on the density correlation line 25. It is.

[0007] The image data of the circular object imaged by the image pickup means 20 and stored by the grayscale image storage means 21 are scanned by the contour scanning window A, and each density correlation line 25 is calculated by the position calculation means 23. The position of the contour scanning window A where the number of the density correlation lines 25 whose value is larger than the predetermined threshold value becomes maximum can be detected as the position of the circular object.

[0008]

However, in the above-mentioned conventional method, if the hole of the upper hole object 6 is not circular as shown in FIG. 2, the position of the upper hole cannot be detected. Although only the position of No. 7 was detected and the screw was tightened, when the upper and lower holes overlap, screw tightening may be poor or the object may be damaged.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and makes it possible to detect the position of an object even if the upper plate of the object is not circular. An object of the present invention is to provide a screw hole position recognizing method for preventing screw tightening failure.

[0010]

According to the present invention, there is provided a method for recognizing a screw hole position, wherein image data of an object obtained by an image pickup means is orthogonal to a circular contour of the object. The image is scanned by a contour scanning window provided with a plurality of density correlation lines, and the absolute value of the difference between the measured density total value at the measurement point inside the circular contour and the measured density value outside the circular contour is measured. The position of the contour scanning window in which the number of density correlation lines whose value is larger than the predetermined threshold value is maximized is detected as the position of the object, and whether or not the pilot hole center position exists in the preset screw tightenable range. Is used to determine whether or not the upper hole and the lower hole overlap. .

[0011]

According to the screw hole position recognition method of the present invention, the positions of the upper and lower holes can be detected and the overlap of the upper and lower holes can be determined by the above-described method, and defective screw tightening can be prevented.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for recognizing a screw hole position according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a main part of a position recognition device using the screw hole position recognition method of the present invention.

In FIG. 1, an image pickup means 1 picks up an image of an object and outputs a video signal, a gray-scale image storage means 2 stores the video signal as gray-scale image data, and a scanning means 3 controls the gray scale by a contour scanning window. The image data is scanned, and the position calculation means 4 calculates the position of the target object using the above-mentioned scan data. Further, the shift amount judging means 5 uses the imaging means 1 and
An overlap between the position of the upper hole and the position of the prepared hole obtained by the gray image storage means 2, the scanning means 3, and the position calculating means 4 is determined.

FIG. 2 shows grayscale image data according to the present embodiment. Reference numeral 6 denotes an upper hole object having an open hole 6a. Reference numeral 7 denotes a hole of a prepared object to be screwed.

FIG. 3 shows a contour scanning window A used in the present embodiment. Reference numeral 8 denotes a scanning contour having a diameter equal to the diameter of the arc portion of the image of the open hole 6a of the upper hole object 6.
Reference numerals 9a to 9h denote a plurality of density correlation lines orthogonal to the scanning contour 8 and measuring image densities inside and outside the scanning contour 8.

FIG. 4 shows details of 9c among the density correlation lines 9a to 9h of the contour scanning window A used in this embodiment, and 10c shows a scanning contour position of the density correlation line 9c,
Reference numerals 11c, 12c and 13c denote a predetermined number of inner image density measurement points constituting the inner density correlation line B, and 14c, 15c and 1
Reference numeral 6c denotes a predetermined number of outer image density measurement points forming the outer density correlation line C.

FIG. 5 shows an open hole 6a used in this embodiment.
The configuration of the upper hole object 6 and the prepared hole 7 of the prepared hole object having the following is shown. Reference numeral 17 denotes a reference position of the upper hole object 6, and reference numeral 18 denotes a center position of the lower hole 7. Reference numeral 19 denotes a screwable range of the prepared hole determined by the diameter of the screw. Reference numeral 19 can be freely set from the reference position 17.

Next, the position recognition operation in this embodiment will be described with reference to FIGS. First, the imaging means 1 shown in FIG. 1 images the upper hole object 6 including the open hole 6a to obtain a grayscale image, and stores the grayscale image in the grayscale image storage means 2.

As shown in FIG. 2, the grayscale image includes an upper hole object 6 having an open hole 6a and a lower hole object 7 having a prepared hole object.

The operation of this embodiment for detecting the position of the opening 6a in this case will be described below. First, the scanning means 3 shown in FIG. 1 starts scanning rightward from the upper left of the grayscale image stored by the grayscale image storage means 2 using the contour scanning window A shown in FIG. Is calculated by the position calculation means.

For each density correlation line, the measured density total value 11c + 12c + 13c of the inner density correlation line B composed of a predetermined number of inner image density measurement points and the measured density of the outer density correlation line C composed of a predetermined number of outer image density measurement points. The absolute value of the difference from the total value 14c + 15c + 16c is calculated, and the position of the contour scanning window A where the absolute value is larger than the predetermined density threshold and the number of density correlation lines is the largest is defined as the position of the arc portion of the open hole 6a. To detect.

Based on the position detected by the above-described method, it is calculated whether or not a preset screw-fastening range includes the pilot hole detected by the conventional method.

As described above, it is possible to determine whether or not the upper hole object 6 having the open hole 6a and the prepared hole 7 overlap each other based on the amount of displacement.

[0025]

As described above, in the present invention,
Even if the object to be screwed is not circular, the positions of the upper and lower holes can be detected, and the overlap of the upper and lower holes can be determined based on the allowable screw tightening range and the position of the prepared hole, thereby preventing screw tightening failure.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a position recognition device using a screw hole position recognition method of the present invention.

FIG. 2 is a diagram showing an example of a grayscale image used in the screw hole position recognition method of the present invention.

FIG. 3 is a diagram showing a configuration of a contour scanning window used in the embodiment of the present invention.

FIG. 4 is a partial detailed view of the contour scanning window shown in FIG. 3;

FIG. 5 is a diagram showing a screw tightenable range in the position recognition device according to the embodiment of the present invention;

FIG. 6 is a block diagram showing a configuration of a position recognition device using a conventional screw hole position recognition method.

FIG. 7 is a diagram showing a configuration of a contour scanning window used in a conventional screw hole position recognition method.

[Explanation of symbols]

A Contour Scan Window B Inner Density Correlation Line C Outer Density Correlation Line 1 Imaging Means 2 Contrast Image Storage Means 3 Scanning Means by Contour Scan Window 4 Position Calculation Means 5 Deviation Amount Determination Means 9a, 9b, 9c, 9d, 9e, 9f 9g, 9h Density correlation line 10c Scanning contour position 11c, 12c, 13c Inner image density measurement point 14c, 15c, 16c Outer image density measurement point 19 Screw tightenable range

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shinya Nakao 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-63-124181 (JP, A) JP-A-63- 234103 (JP, A) JP-A 1-244077 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 102 G06T 1/00 G06T 7/00 G06T 7/60

Claims (1)

(57) [Claims] An image of a screw-tightened object formed by an upper hole of a screw-fastened portion including an arc shape is obtained by an imaging means to obtain a grayscale image, which is equal to a circular contour including an arc portion on the grayscale image. The grayscale image is scanned by a scanning contour and a contour scanning window provided with a plurality of density correlation lines orthogonal to the scanning contour and measuring image densities inside and outside the scanning contour. The absolute value of the difference between the measured density total value of the inner density correlation line composed of image density measurement points and the measured density total value of the outer density correlation line composed of a predetermined number of outer image density measurement points is calculated. The position of the contour scanning window at which the number of density correlation lines larger than the density threshold is maximized is detected as the reference position of the screw-tightening object having the upper hole, and the screw-fastening range is set from the position. And determining whether the center position of the pilot hole detected by the above method is within the screw tightenable range.