JP2712885B2 - Work direction identification method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for identifying the direction of a work, and more particularly, to a method and an apparatus particularly suitable for identifying the direction of a work sequentially fed by a component feeder such as a bowl feeder. The present invention relates to a direction identification method and an apparatus thereof.

[0002]

2. Description of the Related Art Conventionally, in a system for gripping a work such as a part using an industrial robot, a visual system including an image detection device and an image processing device is incorporated by paying attention to an advantage that positioning of the work can be made unnecessary. A system has been proposed that controls an industrial robot based on the position, posture, and the like of a workpiece obtained by a vision system ("Part supply system using vision").
Hitachi, Ltd. Production Technology Laboratory Michio Takahashi 1988
29th, Japan Society of Precision Engineering, Automatic Assembly Special Committee, 62nd Research Presentation).

In this system, the outline of a binary image area is approximated by a polygon, and data of a series of vertices is used to calculate the approximate value.
The graphic features of ten or more items such as the center of gravity, the area, the perimeter, and the like are calculated, and these many graphical features are combined by a user program to determine the type, orientation, position, and the like of the work. Therefore, if a user program is created to indicate how to combine the graphical features, then it is possible to determine the type of work, determine the orientation, and determine the gripping position without any special work. Can be.

[0004]

However, as described above, it is necessary to create a user program, and it is necessary to create a user program according to the type of work. In the current situation where small-lot production is becoming common, not only does the amount of work required to create a user program significantly increase, but also the user program changes in response to changes in the shape of the work accompanying model changes, etc. Is required and the user
There is a disadvantage that the amount of work for changing the program is increased.

[0005] In the above, the determination of the type of work, the orientation,
The case where the determination of the gripping position and the like are all performed has been described, but among these, there is a similar inconvenience even if attention is paid only to the identification of the direction of the work.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is unnecessary to create a user program for each work, and a new work direction can be accurately identified. An object is to provide an identification method and an apparatus thereof.

[0007]

According to a first aspect of the present invention, there is provided a method for identifying a direction of a workpiece, the method comprising the steps of:
Obtaining a vector, identifying the direction of the workpiece based on the first vector when the length of the first vector is equal to or longer than a predetermined length, and when the length of the first vector is shorter than the predetermined length,
In this method, a second vector having both ends of the center of gravity of the work and other feature points of the work is obtained, and the direction of the work is identified based on the second vector.

According to a second aspect of the present invention, there is provided a method for identifying a direction of a workpiece.
This is a method of identifying the direction of the workpiece based on the sign of the inner product of the vector or the second vector and the inertial principal axis direction vector. According to a third aspect of the present invention, there is provided a method of identifying a direction of a work, comprising: a work center of gravity calculating means for calculating a center of gravity of the work; a circumscribed rectangle center of gravity calculating means for calculating a center of gravity of the circumscribed rectangle; First vector calculating means for calculating a first vector having the barycentric position as both end points; first vector determining means for determining whether a length of the calculated first vector is greater than or equal to a predetermined length; First direction identifying means for identifying the direction of the work based on the first vector in response to the determination that the length of the first vector is greater than or equal to the predetermined length; Characteristic point calculating means for calculating a position of a characteristic point different from the barycentric position of the circumscribed rectangle in response to the determination that the center of gravity of the circumscribed rectangle is short, and determining the calculated barycentric position of the work and the positions of other characteristic points of the work at both ends. Toss Second calculating a second vector
A vector calculation unit includes a second direction identification unit that identifies a direction of the workpiece based on the second vector in response to the calculation of the second vector.

According to a fourth aspect of the present invention, there is provided a work direction identifying apparatus comprising:
The direction discriminating means and the second direction discriminating means discriminate the direction of the workpiece based on the sign of the inner product of the corresponding vector and the inertial principal axis direction vector.

[0010]

According to the first aspect of the present invention, the first method uses the center of gravity of the work and the center of gravity of the circumscribed rectangle as both end points based on the position of the center of gravity of the work and the position of the center of gravity of the circumscribed rectangle regardless of the type of the work. Get a vector. And the first
When the length of the vector is equal to or longer than a predetermined length, the direction of the work is identified based on the first vector. Conversely, if the length of the first vector is shorter than the predetermined length, the discrimination accuracy in the direction based on the first vector will be significantly reduced. A second vector having both ends as points is obtained, and the direction of the workpiece is identified based on the second vector.

Therefore, for each type of work,
There is no need to create a program, the amount of work for creating and changing the program can be greatly reduced, and highly accurate direction identification can be achieved for all the works. Further, since the direction of the work can be identified based on the first vector unless the outline of the work and the circumscribed rectangle are not so different, the load for identifying the direction of the work can be greatly reduced.

According to the method for identifying the direction of a workpiece according to the second aspect, it is possible to determine whether or not the principal axis of inertia can be directly used as the direction of the workpiece by calculating the inner product and determining whether the sign is positive or negative. The processing load and the control load of an industrial robot can be greatly reduced. Further, by determining whether or not the value of the inner product is close to 0, it is possible to identify whether or not the product is horizontally long.

According to a third aspect of the present invention, the work center-of-gravity calculating means calculates the center of gravity of the work, and the circumscribed rectangle center-of-gravity calculating means calculates the center of gravity of the circumscribed rectangle. The first vector calculating means calculates a first vector having both ends of the center of gravity of the workpiece and the center of gravity of the circumscribed rectangle based on the position of the center of gravity of the circumscribed rectangle. Then, the first vector determining means determines whether the calculated length of the first vector is equal to or longer than a predetermined length.

If the first vector discriminating means determines that the length of the first vector is equal to or greater than the predetermined length, sufficient direction discrimination accuracy can be obtained. , The direction of the workpiece is identified based on the first vector. Conversely, if the first vector discriminating means determines that the length of the first vector is shorter than the predetermined length, it is not possible to obtain sufficient direction identification accuracy as it is. The position of a feature point different from the position of the center of gravity of the circumscribed rectangle is calculated. Based on the calculated position of the center of gravity of the work and the position of the other feature points of the work, the second vector calculation means calculates the center of gravity of the work and the corresponding feature point at both ends. A second vector as a point is calculated. Then, the direction of the work is identified by the second direction identification means based on the second vector.

As is apparent from the above description, since the direction of the work can be identified based on the first vector except when the outline of the work and the circumscribed rectangle are not so different, it is necessary to identify the direction of the work. Can be greatly reduced. According to the work direction identification device of the present invention, it is possible to determine whether or not the inertia principal axis angle can be directly used as the work direction only by calculating the inner product and determining whether the sign is positive or negative. In addition, the control load of the industrial robot can be further reduced. Further, by determining whether or not the value of the inner product is close to 0, it is possible to identify whether or not the product is horizontally long.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 7 is a diagram schematically showing a configuration of a component supply apparatus to which the work direction identification method of the present invention is applied.
A part of the component transport truck 1a of the circulation type bowl feeder 1 is constituted by a translucent plate 1b, and the lighting devices 2 and 3 are arranged above and below the translucent plate 1b. . Then, a half mirror 3a is arranged between the translucent plate 1b and the lower illumination device 3, and a CCD is provided at a predetermined position where the light reflected by the half mirror 3a can be received.
An image detection unit 4 including a camera and the like is arranged. Further, the industrial robot 5 is provided with a suction head 5a for sucking a work. Further, an image processing unit 4a that performs a binarization process or the like by using an image signal captured from the image detection unit 4 as an input, and a robot that receives a processing result signal from the image processing unit 4a and gives an operation command to the industrial robot 5 And a controller 4b.

FIGS. 1 and 2 are flowcharts showing one embodiment of the method for identifying the direction of a work according to the present invention.
2 shows a teaching process based on a sample work, and FIG. 2 shows a direction identification process based on a work to be identified. First, the flowchart of FIG. 1 will be described. In step SP1, wait until the sample work is set in the field of view of the image detection unit 4. In step SP2, an image of the sample work is fetched, and the image processing unit 4a performs binarization processing to obtain a sample work image. In step SP3, the image processing unit 4a calculates the position of the feature value of the sample work based on the binarized image.
Then, in step SP4, it is determined whether or not the processing has been performed on a predetermined number of sample works. If the processing has not reached the predetermined number, the processing in step SP1 is performed again. Conversely, if it is determined that the number has reached the predetermined number, in step SP5, among the feature values of the sample work,
The center of gravity of the sample work and the center of the circumscribed rectangle are selected, the average value and the variance of the distance between the center of gravity of the sample work and the center of the circumscribed rectangle are calculated in step SP6. Is also determined to be short. If it is determined that the average value of the distances is shorter than the predetermined distance, step SP
In step 8, a feature value that provides a longer distance than the predetermined distance is selected instead of the center of gravity of the circumscribed rectangle. The feature points selected here include, for example, the center of gravity of the largest hole, the center of gravity of the smallest hole, the passing point of the largest radius circle, the passing point of the smallest radius circle, the point of the maximum angle, the point of the minimum angle, and the like.

If it is determined in step SP7 that the average value of the distances is not shorter than the predetermined distance, or if the processing in step SP8 is performed, step SP9
In step SP10, a direction vector of the principal axis of inertia and a direction identification vector starting from the center of gravity of the sample work and ending at the selected feature point are obtained. In step SP10, the inner product of both vectors is calculated. In step SP11, the absolute value of the value of the inner product is obtained. And a predetermined value are determined. Then, only when it is determined that the absolute value of the value of the inner product is smaller than a predetermined value, that is, when it is determined that the value of the inner product is close to 0, the corresponding sample work is identified as being horizontally long in step SP12. Then, a series of processing ends.

Next, the flowchart of FIG. 2 will be described. In step SP1, the image of the work to be identified is fetched. In step SP2, the position of the center of gravity of the work and the position of the feature point (the center of gravity of the circumscribed rectangle or another feature point) selected in the flowchart of FIG. 1 are obtained. It is determined whether or not the work is horizontally long. If it is determined that the object is horizontally long, the main inertia axis angle is increased by 90 ° in step SP4. However, the inertia principal axis angle may be reduced by 90 °.

Thereafter, in step SP5, a direction identification vector starting from the center of gravity of the work to be identified and starting from the selected feature point is calculated. In step SP6, an inner product of the direction identification vector and the inertial principal axis direction vector is calculated. In step SP7, the sign of the inner product is determined. If it is determined in step SP7 that the inner product is negative, in step SP8, the inertia principal axis angle is set to 180.
Decrease by °. That is, the direction of the principal axis of inertia is reversed.

If it is determined in step SP7 that the inner product is positive, or if the processing in step SP8 has been performed, in step SP9, the inertia principal axis angle is output as the direction angle of the workpiece to be identified, and a series of processing is performed. finish. This will be described in more detail with reference to FIGS. FIG. 3A shows a case where the shape of the sample work is an isosceles triangle, and FIG. 3B shows a case where the shape of the sample work is a trapezoid. C indicates the position of the center of gravity of the rectangle. As is clear from these figures, in the case of an isosceles triangle, the distance between the center of gravity G and the center of gravity C is large, and in the case of a trapezoid, the distance between the center of gravity G and the center of gravity C is small. Therefore,
Comparing the two, in the case of an isosceles triangle, sufficient direction identification can be achieved by employing a direction identification vector having the center of gravity G as a starting point and the center of gravity C as an end point. Is small and the lengths of the sides are close to each other), the length of the direction identification vector starting from the center of gravity G and ending at the center of gravity C becomes extremely short, and the influence of calculation errors and the like increases. Therefore, the direction identification accuracy is reduced.

FIG. 4 is a diagram for explaining a direction identification vector based on a feature point that can be adopted in place of the center of gravity C of the circumscribed rectangle when the length of the direction identification vector is short. Is the starting point. In FIG. 4, V1 is a direction identification vector ending at the maximum hole centroid, V2 is a direction identification vector ending at the minimum hole centroid, V3 is a direction identification vector ending at the maximum radius circle passing point, V4 is a direction identification vector ending at the point passing through the minimum radius circle, V5 is a direction identification vector ending at the point of the maximum angle, and V6 is a direction identification vector ending at the point of the minimum angle.

FIG. 5 is a diagram for explaining the relationship between the work direction identification vector and the inertia main axis vector. When the inner product of the work direction identification vector and the inertia main axis direction vector is close to 0, the sample work is horizontally long. Therefore, it is sufficient to increase or decrease the principal axis of inertia by 90 °, and the value of the inner product of the two vectors after the principal axis of inertia has been increased or decreased by 90 ° can be made sufficiently large. When the sign of the inner product of both vectors is positive as shown in FIG. 5 (A), the principal axis of inertia coincides with the direction angle of the work, and as shown in FIG. 5 (B), When the sign of the inner product is negative, the supplementary angle of the inertia principal axis angle matches the direction angle of the workpiece.

Therefore, after the teaching based on the flowchart of FIG. 1 is performed and the processing based on the flowchart of FIG. 2 is performed, the direction angle of the work can be easily obtained.

[0025]

[Embodiment 2] FIG. 6 is a block diagram showing an embodiment of a work direction discriminating apparatus according to the present invention, wherein a feature value of a work is obtained and output based on an image of the work taken in from an image detector 4. A value output unit 11, a first selection unit 12 for selecting the position of the center of gravity of the work and the position of the center of gravity of the circumscribed rectangle among the characteristic values output from the characteristic value output unit 11, A first distance calculation unit 13 for calculating a distance from the center of gravity, and a feature value output unit 11, a first selection unit 12, and a first distance for n sample workpieces in response to the instruction of the teaching mode. An iterative controller 14 for repeatedly operating the calculator 13, an average distance / variance calculator 15 for calculating an average value and a variance of the distances calculated by the first distance calculator 13 for n sample works, It operates based on a discrimination signal from the distance discriminating unit 16 for discriminating the magnitude of the separation from the preset reference distance, and the discriminating signal from the distance discriminating unit 16 indicating that the average distance is shorter. A second selection unit 17 that selects a feature value whose distance from the center of gravity of the work is longer than a reference distance among other feature values output from the feature value output unit 11, and a determination signal from the determination unit 16. The center of gravity of the work selected by the first selector 12 and the center of gravity of the circumscribed rectangle or the feature value selected by the second selector 17 are selected based on the center of gravity of the work. A first vector calculation unit for calculating a work direction identification vector having the feature value as an end point; and an inner product of the work direction identification vector calculated by the first vector calculation unit and the inertia main axis direction vector. First inner product calculation unit 1
9, an inner product value determining unit 20 for determining the magnitude of the absolute value of the inner product calculated by the first inner product calculating unit 19 and a predetermined value, and a determination indicating that the absolute value of the inner product is smaller. A landscape instruction data output unit 21 that outputs instruction data indicating that the corresponding sample work is landscape based on the result, and a feature value output unit 11 in response to the instruction of the work direction identification mode. A third selection unit 22 that selects the same feature value as the feature value selected by the second selection unit 17 from the position of the center of gravity of the work among the output feature values.
A first inertia principal axis angle correction unit 23 that increases or decreases the inertia principal axis angle by 90 ° only when instruction data indicating that the work is horizontally long is output from the horizontally long instruction data output unit 21; A second vector calculation unit 2 which calculates and outputs a work direction identification vector having the center of gravity of the work as a start point and an end point of the feature value selected by the third selection unit 22
4, a second inner product calculating unit 25 that calculates an inner product of the work direction identification vector calculated by the second vector calculating unit 24 and the inertia main axis direction vector, and an inner product calculated by the second inner product calculating unit 25. A code determining unit 26 for determining a code;
A work direction angle output unit 27 that obtains an inertia principal axis angle or an angle obtained by reducing the inertia principal axis angle by 180 ° based on the sign judgment result by the sign judgment unit 26 and outputs the obtained angle as a work direction angle.
And

The operation of the apparatus for identifying the direction of a workpiece having the above-mentioned structure is as follows. When the teaching mode is instructed, a feature value is output from the feature value output unit 11 for each of the n number of sample works, and the first selection unit 12 outputs the center of gravity position of the work and the center of gravity of the circumscribed rectangle. And the first distance calculator 13 calculates the distance between the center of gravity of the work and the center of gravity of the circumscribed rectangle. Then, the average value and variance of the distance are calculated by the average distance / variance calculation unit 15, and the distance determination unit 16 determines the magnitude of the average distance and a preset reference distance. That is, it is determined whether or not the distance is sufficient to obtain sufficient direction identification accuracy. As a result of this determination, if it is determined that the average distance is shorter, the second selector 17 replaces the center of gravity of the circumscribed rectangle with the feature value output from the feature value output unit 11 among the other feature values. A feature value whose distance to the center of gravity is longer than the reference distance is selected. After that, in the first vector calculation unit 18, the position of the center of gravity of the work selected by the first selection unit 12 and the position of the center of gravity of the circumscribed rectangle based on the determination signal from the determination unit 16 or selected by the second selection unit 17. A feature value is selected, and a work direction identification vector is calculated with the center of gravity of the work as a start point and any selected feature value as an end point. Then, the first inner product calculating unit 19 calculates the inner product of the work direction identification vector and the inertia main axis direction vector, and the inner product value determining unit 20 determines the magnitude of the absolute value of the inner product and a predetermined value. Then, only when it is determined that the absolute value of the inner product is smaller, the horizontally long instruction data output unit 21 outputs instruction data indicating that the corresponding sample work is horizontally long.

After the teaching of the sample work has been performed as described above, the work direction discrimination mode may be designated.
From among the characteristic values output from 1, the same characteristic value as the position of the center of gravity of the work and the characteristic value selected by the second selection unit 17 is selected, and the landscape instruction data output unit 21 indicates that the work is horizontally long. Only when the instruction data is output, the first inertial principal axis angle correction unit 23 sets the inertial principal axis angle to 9
Increase or decrease by 0 °. Next, the second vector calculation unit 24 calculates and outputs a work direction identification vector starting from the center of gravity of the work and starting at the feature value selected by the third selection unit 22, and outputs the work direction identification vector using the second inner product calculation unit 25. An inner product of the work direction identification vector and the inertia main axis direction vector is calculated, and the sign of the inner product is judged by the sign judging section 26. Then, only when the inner product is negative, the inertia principal axis angle is reduced by 180 ° by the work direction angle output unit 27, and when the inner product is positive, the inertia principal axis angle is adopted as it is and output as the work direction angle.

As is apparent from the above description, for most works, inner product calculation, sign discrimination, etc. are performed based on the work direction identification vector and the inertia main axis direction vector obtained based on the center of gravity of the work and the center of gravity of the circumscribed rectangle. , The direction of the workpiece can be easily and accurately identified. Also, only when the distance between the center of gravity of the work and the center of gravity of the circumscribed rectangle is short, another characteristic value whose distance to the center of gravity of the work is sufficiently large is selected instead of the center of gravity of the circumscribed rectangle to obtain the work direction identification vector. The direction of the workpiece can be identified with high accuracy.

It should be noted that the present invention is not limited to the above embodiment. For example, it is possible to omit the processing involved in calculating the inner product and to identify the direction of the work based only on the work direction identification vector. In addition, various design changes can be made without departing from the scope of the present invention.

[0030]

As described above, according to the first aspect of the present invention, there is no need to create a user program for each type of work, and the amount of work for creating and changing the program can be greatly reduced. Since it is possible to achieve high-precision direction identification of the work and to identify the direction of the work based on the first vector except when the outline of the work and the circumscribed rectangle are not so different, it is necessary to identify the direction of the work. This has a specific effect that the load on the device can be greatly reduced.

According to the second aspect of the present invention, it is possible to identify whether or not the inertia principal axis angle can be directly used as the direction of the work by calculating the inner product and determining whether the sign is positive or negative. It is possible to significantly reduce the control load such as the above. According to the third aspect of the present invention, since the direction of the work can be identified based on the first vector unless the outline of the work and the circumscribed rectangle are not so different, the load for identifying the direction of the work is large. This has a specific effect of being able to reduce the number of times.

According to the fourth aspect of the present invention, it is possible to determine whether or not the inertia principal axis angle can be directly used as the direction of the workpiece by simply calculating the inner product and determining whether the sign is positive or negative. This has a specific effect that the control load of the robot can be further reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a teaching process based on a sample work in one embodiment of the work direction identification method of the present invention.

FIG. 2 is a flowchart showing a direction identification process based on a workpiece to be processed, in one embodiment of the work direction identification method of the present invention.

FIG. 3 is a diagram illustrating the relationship between the center of gravity of the sample work and the center of the circumscribed rectangle when the shape of the sample work is an isosceles triangle and a trapezoid.

FIG. 4 is a diagram illustrating a direction identification vector based on a feature point that can be adopted instead of the center of gravity of a circumscribed rectangle when the length of the direction identification vector is short.

FIG. 5 is a diagram illustrating a relationship between a work direction identification vector and an inertia main axis vector.

FIG. 6 is a block diagram showing one embodiment of a work direction identification device of the present invention.

FIG. 7 is a diagram schematically showing a configuration of a component supply apparatus to which the work direction identification method of the present invention is applied.

[Explanation of symbols]

11 Feature value output unit 12 First selection unit 15 Average distance / variance calculation unit 16 Distance discrimination unit 17 Second selection unit 18 First
Vector calculation unit 22 Third selection unit 23 First inertia principal axis angle correction unit 24 Second vector calculation unit 25 Second inner product calculation unit 26 Sign determination unit 27 Work direction angle output unit

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location G01B 11/00 G01B 11/00 Z 11/26 11/26 H

Claims (4)

(57) [Claims] 1. A first vector having one of a center of gravity of a work and a center of gravity of a circumscribed rectangle as a start point and the other as an end point is obtained based on the position of the center of gravity of the work and the position of the center of gravity of the circumscribed rectangle.
When the length of the first vector is equal to or longer than a predetermined length, the direction of the work is identified based on the first vector. When the length of the first vector is shorter than the predetermined length, the position of the center of gravity of the work and the position of the work are determined. A method for identifying a direction of a work, comprising: obtaining a second vector having other feature points as both end points; and identifying a direction of the work based on the second vector. 2. The method according to claim 1, wherein the direction of the workpiece is identified based on a sign of an inner product of the first vector or the second vector and the inertial principal axis direction vector. 3. A work center of gravity calculating means (11, 12) for calculating a center of gravity position of a work, a circumscribed rectangular center of gravity calculating means (11, 12) for calculating a center of gravity of a circumscribed rectangle, and a calculated center of gravity position of the work. A first vector calculating means (18) for calculating a first vector having both ends of the center of gravity of the circumscribed rectangle, and determining whether or not the length of the calculated first vector is not less than a predetermined length. One vector discriminating means (15, 16), and first direction discriminating means for discriminating the direction of the workpiece based on the first vector in response to the discrimination that the length of the first vector is equal to or longer than a predetermined length. (22,
23, 24, 25, 26, 27) and a feature point calculation for calculating a position of a feature point different from the center of gravity of the circumscribed rectangle in response to the determination that the length of the first vector is shorter than the predetermined length. Means (11, 17) and second vector calculating means (18) for calculating a second vector having both ends of the calculated center of gravity position of the work and positions of other feature points of the work.
And second direction identification means (22, 23, 24, 25, 26, 27) for identifying the direction of the work based on the second vector in response to the calculation of the second vector. Direction identification device of the workpiece. 4. A first direction identifying means (22, 23, 24, 2)
, 26, 27) and second direction identifying means (22, 2).
4. The work direction identifying apparatus according to claim 3, wherein (3, 24, 25, 26, 27) identifies the direction of the work based on the sign of the inner product of the corresponding vector and the inertial principal axis direction vector.