JPH0816606B2 - Automatic measurement method of position deviation and posture angle of an object with right angle part - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has a known width and length of an object, especially its outer shape, for assembly of parts in a production line of automobiles and home appliances. A method for automatically measuring the position and orientation of a substantially rectangular object having at least one right angle portion.

[Prior Art] Various types of pattern recognition technology have been conventionally developed in order to automate work on a production line. Such pattern recognition technology attempts to determine the shape, posture, etc. of the object itself by some means, and the device used for pattern recognition is usually relatively complicated and expensive. Is.

However, the pattern recognition technique as described above is not always necessary in the assembly work in various factories, for example, in the case of automating the assembly of various parts to the body of the automobile or the body of the home electric appliance. That is, the body of the automobile, the body of the home electric appliance, the IC substrate, etc., which is the object of recognition or the like, usually has a substantially rectangular shape, or at least a part of its outer shape can be used as a reference for recognition. It has a right-angled part. Furthermore, even if the recognition target object itself is not rectangular, it is often the case that it is moved on a rectangular cart, or a rectangular portion exists on the target object, and the target object to be recognized is It is customary that the shape itself is known.

Therefore, the substantially rectangular portion, more specifically, the right-angled portion forming a part thereof is used as a reference, and the positional deviation and posture of the object, that is, the positional deviation and the reference with respect to the reference position of the rectangular portion or the like. It is desirable to be able to accurately recognize the inclination of the posture angle with respect to the posture, whereby the device itself can be significantly simplified and provided at a low cost.

[Problems to be Solved by the Invention] The present inventors utilize a two-dimensional image of an object obtained by an ITV camera or other image sensor when recognizing a rectangular object having at least a right angle portion. The present invention has been made by studying a method of accurately measuring the position shift and the posture by the simplest possible arithmetic processing and using the smallest possible number of image sensors.

That is, the object of the present invention is to recognize that the recognition object has a right-angled portion that serves as a reference for posture recognition, and that the shape is generally known, and in the above-described assembly work in the factory, An object of the present invention is to make it possible to accurately measure a position shift and an attitude angle by a simple process of an image of an image sensor without using a general pattern recognition technique.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method for measuring a positional deviation and an attitude angle of a substantially rectangular object whose width and length are known. Then, in the measurement area of the object, an image sensor that holds one right-angled part of the object in the approximate center of the field of view when the object is at the reference position of the measurement area is obtained by the image sensor. The image of the obtained object is binarized by the difference in brightness, a point sequence on two straight lines orthogonal to each other in the above-mentioned right angle portion on the object in the measurement area is extracted, and those points are extracted for each straight line. A technical means of calculating straight line equations from the coordinates of each point forming a column and measuring the positional deviation and posture angle of the object by calculation based on these equations and the known width and length of the object. Has been adopted.

[Examples] The method of the present invention will be described in more detail below with reference to the drawings.

As shown in FIG. 1, the object at the reference position is now in the space where the object A for measuring the positional deviation and the attitude angle exists.
Establish an xy coordinate system with origin 0 at the center of A ₀ . The measurement object A has a substantially rectangular shape, but may be any object having at least a right-angled portion that serves as a reference for posture recognition. For example, the measurement object A is a plan view of a vehicle body. Alternatively, it may be the body of an electric home appliance, an IC substrate, or the like. Furthermore, when the target object does not have a right-angled part, the rectangular part attached on it or a part of the rectangular table on which the object is placed is used as the measurement target. Does not matter.

In FIG. 1, the rectangular object A _{0 at the} reference position
Corners of P ₁ , P ₂ , P ₃ and P ₄ , and corners of the object A having an arbitrary posture are ▲ P ^' ₁ ▼, ▲ P ^' ₂ ▼, ▲ P ^' ₃ ▼ and ▲ P ^' ₄
▼, and each side of the measurement object A is a straight line l, m, s
And t.

Note that it is assumed here that the shape of the target object A itself is known, and particularly the width W and the length H of the target object A are known.

In the measurement area for measuring the displacement and the posture angle of the object A, when the object is at the reference position of the measurement area, two rectangular sides (straight lines l, m) of the rectangular object A ₀ are orthogonal to each other. An ITV camera or other suitable image sensor V ₁ is placed so that the intersection is located almost in the center of the field of view.

When the object A is transported by a belt conveyor or the like and reaches the measurement range, it usually has an arbitrary amount of positional deviation with respect to a reference position and an arbitrary amount of posture angle inclination, as shown in FIG. . That is, the center of the object A is Δx and Δy in the x-axis and y-axis directions with respect to the origin 0 of the coordinate system.
It has a positional deviation of 10 mm, and is inclined by an angle θ with respect to the reference posture of the object.

Therefore, in order to measure the displacement and the posture angle, the image sensor V _{1 is used} to measure two sides of the object A, that is, the straight line l,
The intersection position of m is detected as an image, and their equations are calculated. The equation of the straight line on the image can be obtained by various commonly used means. For example, the image obtained by the image sensor V ₁ can be used to determine the brightness of the rectangular object A and the brightness of other parts. By binarizing by the difference and performing appropriate processing such as differentiation, the point sequence on the straight line can be extracted and the data on the straight lines 1 and m can be separated, and the point sequence can be calculated for each straight line. It is possible to use means such as obtaining the coordinates of each of the constituent points and substituting those coordinate values into the equation of the straight lines l and m to obtain the gradient and intercept.

That is, the equation of the straight line l is set as y = A ₁ x + B ₁ and each point (x _1i , y _1i ) forming the point sequence on the straight line 1 is substituted to obtain the average slope A ₁ and the intercept B ₁ , They are Given by.

Similarly, the equation of the straight line m is set as x = A ₂ y + B _2, and each point (x _2i , y _2i ) forming the point sequence on the straight line m is substituted into it, and the average gradient A ₂ and intercept If we ask for B ₂ ,
They are, Given by.

Further, assuming that the coordinates of the corner portion ▲ P ^′ ₂ ▼ of the object A whose position is deviated from the angle P ₂ of the object A ₀ are (x ₁ , y ₁ ),
Its ▲ ^P _'2 ▼ since the straight line l, m intersect at _{point, y 1 = A 1 x 1} + B 1 ··· (1) x 1 = A 2 y 1 + B 2 ··· (2) is satisfied Then, based on these equations (1) and (2), Get.

In addition, the object (width W and length H) at the intersection of the straight lines l and m
The coordinates of the corner P ₂ of Therefore, Δx and Δy are given by the following equations,
The values of Δx and Δy are obtained in relation to the expressions (3) and (4).

Further, since A ₁ = tan θ, θ can be obtained by θ = tan ⁻¹ (A ₁ ) (8).

In the above description, Δx and Δy are calculated based on the coordinates of the intersections of the equations representing the straight lines l and m, but the calculation can also be performed from the intercept of the straight lines l and m.
That is, since the coordinates of the corner portion ▲ P ^′ ₂ ▼ of the object, which is the intersection of the straight lines l and m, are given by the equation (5), the intercept B
₁ , B ₂ It is also possible to calculate Δx and Δy based on these.

As described above, according to the above-described measuring method, the image sensor V ₁ is connected. Thus, according to the above-described measuring method, the arithmetic device connected to the image sensor V ₁ performs the above-described simple calculation. Thus, the positional deviations Δx and Δy of the object A in the x-axis and y-axis directions and the posture angle θ with respect to the reference posture can be obtained.

[Effect of the Invention] According to the measuring method of the present invention as described above, a single image sensor is arranged at a corner portion of an object, and a simple means of calculating the above formula based on the output thereof is used. , It is possible to accurately measure the position deviation and posture angle of the object, and in particular, since the image sensor is used only to obtain the equation of the straight line of the right angle part, the image sensor is used to measure the whole object. In comparison with the case of measuring the position shift and the posture angle of the target object by observing the pattern recognition technology or the like, not only the calculation process becomes extremely simple but also very accurate measurement can be performed. It can be carried out.

In addition, since the measurement can be performed easily in this way, not only is it easy to implement a device for processing the output from the image sensor as hardware, but also real-time processing is possible, and therefore, in a production line of a factory or the like. Very suitable for use.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a measuring method according to the present invention. V ₁ …… Image sensor, A …… Object.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-53-39156 (JP, A) JP-A-53-27450 (JP, A) JP-A-54-92274 (JP, A) JP-A 52- 133050 (JP, A)

Claims (1)

[Claims] 1. A method for measuring a positional deviation and an attitude angle of a substantially rectangular object of which width and length are known,
In the measurement area of the object, an image sensor is arranged which holds one right-angled part of the object in the approximate center of the visual field when the object is at the reference position of the measurement area. The image of the object is binarized according to the difference in brightness, the point sequences on the straight lines of the two sides orthogonal to each other in the above-mentioned right-angled portion on the object in the measurement area are extracted, and the point sequences are calculated for each straight line. A right angle characterized by calculating the equation of a straight line from the coordinates of each of the constituent points and measuring the positional deviation and posture angle of the object by calculation based on these equations and the known width and length of the object. A method for automatically measuring the positional deviation and posture angle of an object having a portion.