JPH0816605B2 - Automatic measurement method of position deviation and posture angle of an object with straight line 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. In addition, the present invention relates to a method for automatically measuring the position and orientation of a substantially rectangular object having straight portions on two orthogonal sides.

[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 two orthogonal sides. 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, by utilizing a substantially rectangular portion, more specifically, a portion that serves as a reference such as two orthogonal sides forming a part thereof, the positional deviation and posture of the object, that is, the reference position of the rectangular portion with respect to the reference position. It is desirable to be able to accurately recognize the positional deviation and the inclination of the attitude angle with respect to the reference attitude, which makes it possible to significantly simplify the apparatus itself and provide it at low cost.

[Problems to be Solved by the Invention] The present inventors utilize a two-dimensional image of an object by an ITV camera or other image sensor when recognizing a rectangular object having at least two orthogonal sides. 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 focus on the fact that the object to be recognized has two orthogonal sides serving as a reference for posture recognition, and the shape is usually known, and in the above-mentioned assembly work in the factory, etc. The purpose of the present invention is to make it possible to accurately measure the positional deviation and the attitude angle by simply processing the images of the two image sensors without using general pattern recognition technology.

[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, when the object is at the reference position of the measurement area, the substantially central portion in the longitudinal direction of each side of the two orthogonal sides of the object is approximately at the center in the visual field. Two image sensors that cover the entire width of the field of view are arranged, and the image of the object obtained by each image sensor is binarized by the difference in brightness, and the center of the two orthogonal sides of the object in the measurement range is approximately the center. Extract the point sequence on the straight line of the part, from the coordinates of each point that constitutes the point sequence, calculate the equation of the straight line of the two orthogonal sides on the object, and know the equation and the object By the calculation based on the width and length of The technical means of measuring the positional deviation and the posture angle of the object is 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 two orthogonal sides serving as a reference for posture recognition in the periphery, for example, a plan view of a car 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 two orthogonal sides, a rectangular portion attached on it or a rectangular table on which the object is placed may be used as the measurement target A. It doesn't matter.

In FIG. 1, the rectangular object A _{0 at the} reference position
The corner P _1, P _2, P ₃ and P _4, the corners of the object A take any posture and P _1, P _2, P ₃ and P _4, also, each side of the measurement object A Is indicated by the straight lines 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.

When the object is at the reference position of the measurement area, the measurement area for measuring the displacement and the posture angle of the object A has two sides (straight lines l, m) of the rectangular object A _{0 that} are orthogonal to each other. An ITV camera and other appropriate image sensors V ₁ and V ₂ are arranged so that the substantially central portions of the respective sides in the longitudinal direction are substantially centered within the visual field, respectively, over the entire width of the visual field.

In this way, both image sensors V ₁ and V ₂ are made to correspond to the substantially central portion in the length direction of the two sides of the object A ₀ that intersect at right angles, and each side is approximately in the center of the visual field over the entire width of the visual field. By arranging so as to hold it, even if the target object is displaced or the posture angle is changed, the straight line portions on each side of the object can be maximally placed within the visual field, and accurate measurement can be performed.

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 attitude angle, the image sensors V ₁ and V ₂ detect the positions of two sides of the object A, that is, the straight lines l and m as an image, and obtain their equations. The equation of this straight line is obtained by binarizing the image obtained by the image sensors V ₁ and V ₂ by the difference in brightness between the inside of the rectangular object A and other portions, and subjecting it to appropriate processing such as differentiation. It can be obtained by making it possible to extract a point sequence on a straight line, finding the coordinates of each point that makes up the point sequence, and substituting those coordinate values into the equations of the straight lines l and m to find the slope 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, and the average slope A ₂ and intercept When we ask for B ₂ , they are Given by.

Further, the coordinates of the corner P ₂ of the object A (the width W and the length H of which are known) whose position is deviated from the angle P ₂ of the object A ₀ are: Represented by

Therefore, since the straight line l has the inclination of the angle θ and passes through the point P ₂ , when the equation of the straight line l is obtained, Therefore, the slope A ₁ and the intercept B ₁ are A ₁ = tan θ (2) Is represented.

Similarly, the equation of the straight line m is And the slope A ₂ and intercept B ₂ are A ₂ = −tan θ Is represented.

Therefore, from the above formula (2), θ can be obtained by θ = tan ⁻¹ (A ₁ ) ... (5), and based on the intercept of the equation expressing the straight lines l and m, that is, the above (3 ) And (4), As a result, Δx and Δy can be obtained.

In the above, Δx and Δy are calculated based on the intercept of the equation expressing the straight line l, m.
The calculation can also be performed from the intersection coordinates of. That is, if the coordinates of the corner P ₂ of the object, which is the intersection of the straight lines l and m, is (x ₁ , y ₁ ), they are It is also possible to calculate Δx and Δy based on this relationship and the above equation (1).

As described above, according to the above-described measurement method, by performing the above-described calculation by the calculation device connected to the image sensors V ₁ and V ₂ , 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 easily obtained.

[Effect of the Invention] According to the measuring method of the present invention as described above, the positional deviation and the posture angle of the object can be accurately determined by a simple means of performing the calculation of the above-described formula based on the outputs of the two image sensors. In particular, since it is only necessary to obtain an equation of a straight line of two orthogonal sides on an object by using two image sensors, it is possible to observe the entire object with the image sensor and perform pattern recognition or With the technique based on it, not only the calculation processing becomes extremely simple, but also extremely accurate measurement can be performed, as compared with the case where the position shift and the posture angle of the object are measured.

Moreover, since both image sensors are arranged so as to correspond to substantially central portions in the lengthwise direction of the two orthogonal sides of the object, and each side is arranged so as to hold the entire width of the visual field at approximately the center in the visual field, Even if there is a deviation or a change in posture angle, the straight line parts on each side are maximized within the field of view, and the edges of each side are less likely to be in the field of view. It becomes possible to measure.

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 , V ₂ …… Image sensor, A …… Object.

 ─────────────────────────────────────────────────── --Continued from the front page Judgment panel for referees Judge Satoru Matsumoto Judge Judge Yoshikatsu Imakatsu Toshiko Nakata (56) References JP-A-53-39156 (JP, A) JP-A-53-145526 (JP, A) JP 54-92274 (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 target object, when the target object is at the reference position of the measurement area, the substantially central portion in the length direction of each side of the two orthogonal sides of the target object in the center of the field of view Two image sensors are installed to cover the entire width, the image of the object obtained by each image sensor is binarized by the difference in brightness, and the image of the center of the two orthogonal sides of the object on the object in the measurement area is binarized. Extract the point sequence on the straight line, calculate the equation of the straight line of the above-mentioned two orthogonal sides on the object from the coordinates of each point constituting the point sequence, and calculate the equation and the known width of the object. And an automatic measuring method of a positional deviation and an attitude angle of an object having a straight line portion, which is characterized by measuring the positional deviation and the attitude angle of the object by calculation based on the length.