JP2678005B2 - Robot interference check method - Google Patents

Description

The present invention relates to a robot interference checking method used for motion simulation, and in particular, a tool (effector) gripped by the robot when moving according to a robot motion program is a work or the like. The present invention relates to a robot interference check method for checking whether a robot interferes with a robot.

<Prior Art> A robot operation program may be created by an off-line programming operation instead of a teaching operation. This offline programming is performed by defining the motion of the robot in a simple robot language and converting a source program created in the robot language into a robot operation program executable by the robot controller by the translation function of the offline programming device. .

By the way, in off-line programming, it is not necessary to create a program while actually moving the robot, so it is necessary to check whether or not movable parts such as nozzles, torches and other tools (end effectors) interfere with the work after the robot operation program is created. There is.

For this reason, recently, an interference check method using a shape approximation method has been considered.

<Problems to be Solved by the Invention> However, in the conventional interference check method, all the surfaces of the target solids (for example, the effector and the work),
This is to check the interference between the ridges and the surfaces to judge the interference between the solids, and there is a problem that the processing takes too much time and is not practical.

In view of the above, an object of the present invention is to provide a robot interference check method that can significantly reduce the time required for interference check by reducing the number of surfaces that form a shape approximation solid.

<Means for Solving the Problem> A robot interference checking method according to the present invention includes a step of creating two or more types of shape approximation solids of a rectangular parallelepiped, a sphere, and a cylinder for the first and second solids, respectively. The step of individually selecting the shape approximating solid having the smallest volume among the two or more shape approximating solids created at that time for the first and second solids, and the two shape approximating solids having the selected minimum volumes. Is used to determine the presence or absence of interference.

<Operation> In the present invention, two of a rectangular parallelepiped, a sphere, and a cylinder are respectively provided for the first and second solid bodies, for example, the effector and the work.
Create more than three types of shape approximation solids, and create 2
Among the shape approximation solids of more than types, the shape approximation solid having the smallest volume is individually selected for the effector and the work,
The presence or absence of interference between the effectors and the work is determined using two shape approximation solids of the minimum volume selected for each of these effectors.

<Embodiment> FIG. 1 is a block diagram of a robot offline programming apparatus to which the present invention can be applied.

1 is the main part of the offline programming device,
Processor 1a, ROM1b, RAM1c for storing control programs
have. Reference numeral 2 is a printer, 3 is a keyboard, 4 is a graphic display device, 5 is a disk controller, 6 is a tablet device, and 6a is a tablet cursor. The RAM 1c is a storage area 1c-1 for storing the created source program SPR, a storage area 1c-2 for storing the robot operation program RAP obtained by the conversion, and a work shape data FD.
It has a storage area 1c-3 for storing w, effector shape data FDe, processing results and the like.

FIG. 2 is a flow chart of the processing of the present invention, and FIGS. 3 to 5 are diagrams for explaining the robot interference checking method of the present invention. Hereinafter, a robot interference checking method according to the present invention will be described. It is assumed that the robot operation program RAP has already been created, and that the effector shape data FDe (each vertex coordinate value) and the work shape data FDw (each vertex coordinate value) have been input and stored in the RAM 1c. .

First, a shape-approximated rectangular parallelepiped for a solid (effector or work) to be subjected to interference check is created (step 101). The shape approximate rectangular parallelepiped is defined as follows with reference to FIG. That is, each vertex P (X, X,
Y, Z), find the maximum and minimum values of each component X, Y, Z, and calculate the maximum value (Xmax, Ymax, Zmax) of each axis and the minimum value (Xmin, Ymin, Zmin) of each axis. Obtain the points Pmax (Xmax, Ymax, Zmax) Pmin (Xmin, Ymin, Zmin) that are coordinate values.

Next, a line segment is set as a diagonal line, and each ridge line parallel to the X, Y, and Z axes is defined as a shape approximating rectangular parallelepiped 11 according to the present invention.

Then, a shape approximate sphere for the solid (effector or work) to be subjected to the interference check is created (step 102). The shape approximation sphere is defined as follows with reference to FIGS. 4 (a) and 4 (b). That is, for each vertex P (X, Y, Z) of a solid, the maximum and minimum values of its components X, Y, Z are calculated, and the maximum values of each axis (Xmax, Ymax, Zma
x), and the point Pmax (Xmax, Ymax, Zmax) Pmin (Xmin, Ymin, Zmin) where the coordinate values are the minimum values (Xmin, Ymin, Zmin) of each axis.

Next, a shape approximation sphere S ₁ having a diameter of a line segment is created. Where c ₁ is the center of the shape approximation sphere S ₁ , r ₁
Represents the radius of the shape approximation sphere S ₁ . Next, the longest _one of the line segment = (x, y, z) components of the shape approximation sphere S ₁ is selected (here, the y component), and the radius of the shape approximation sphere S ₂ to be newly created. Let r ₂ . Then, it is checked whether or not all the vertices of the solid are included in the inside.
If there is a point P that is not included, a shape approximate sphere S ₂ is newly created. Radius r ₂ and the center c ₂ of this shape approximating sphere S ₂ is However, d is the distance between c ₂ (= c ₁ ) and P. It is checked again whether or not all the points of the solid are included in this shape approximation sphere S ₂ . If there is a point that is not included, a shape approximate sphere S ₂ is newly created in the same manner, and the process is repeated until all points are included. Then, a shape approximation sphere that includes all the vertices of a solid inside is defined as a shape approximation sphere S ₂ according to the present invention.

Next, a shape approximate cylinder for a solid (effector or work) to be subjected to interference check is created (step 103). The shape approximation cylinder is defined as follows with reference to FIG. That is, the regression line obtained by the method of least squares is set as the central axis of the cylinder by referring to the distribution of each vertex of the solid. The farthest vertex from this central axis is detected, and the distance from the central axis to the detected vertex is defined as radius R. Further, the coordinates of the intersection of the perpendicular line hanging from each vertex to the central axis and the central axis are obtained, and the distance between the maximum value and the minimum value of these coordinates is defined as the height H of the cylinder. The cylinder thus created is defined as a shape approximation cylinder 21 according to the present invention.

Then, after selecting the shape approximate solid having the smallest volume from the three types of shape approximate solids (step 104), it is judged whether or not the shape approximate solids have been determined for the two solids (step 105). 2 with the minimum volume
An algorithm for interference check is selected by a combination of three shape approximation solids (step 106).

Next, the two shape approximation solids having the minimum volume are the combination of sphere and sphere (step 107), the combination of sphere and cuboid (step 108), the combination of sphere and cylinder (step 109), and the combination of cuboid and cuboid ( In step 110), the interference check is performed according to the algorithm selected by the combination of the rectangular parallelepiped and the cylinder (step 111) and the combination of the cylinder and the cylinder (step 112), and the process ends.

On the other hand, if NO in the determination in step 105, the process returns to step 101.

FIG. 6 is a diagram for explaining an interference check algorithm between shape approximate spheres.

In the figure, the radius of the shape approximation sphere S ₁ of the first solid is r ₁ ,
The center is c ₁ , and the radius of the second solid approximation sphere S ₁₁ is r
₁₁ and the center is c ₁₁ . At this time, if the following conditions are satisfied, it is determined that the two interfere.

Where is the distance between c ₁ and c ₁₁ .

FIGS. 7 (a) to 7 (c) are diagrams for explaining the interference check algorithm between the shape approximate cylinders.

In the figure, AB is the center axis of the shape approximation cylinder defined for the first solid, CD is the center axis of the shape approximation cylinder defined for the second solid, li (where i is 1 to 3). Is the shortest distance between the central axes AB and CD, α and β are straight lines including the central axes AB and CD, and Pi and Qi are points on the straight lines α and β.

The necessary condition for the interference to occur is that, assuming that the radii of the cylinder are R ₁ and R ₂ , respectively, the shortest distance li between the center axes AB and CD of the cylinder is smaller than the sum of the radii R ₁ and R ₂ of the cylinder. . That is, li ≦ R ₁ + R ₂ (1) Then, a method for obtaining the shortest distance li between the center axes AB and CD of the cylinder will be described below according to the arrangement pattern of the center axes AB and CD.

Pattern 1: Both the central axis AB, a case where linear P ₁ Q ₁ orthogonal to the CD is present, the length of the straight line P ₁ Q ₁ becomes the shortest distance l _1.
(See FIG. 7 (a)) Pattern 2: In a case other than the above, it is possible to draw a perpendicular line from the end point of one central axis to the other central axis.
The shortest length of the perpendiculars P ₂ Q ₂ and P ₂ ′ Q ₂ ′ is the shortest distance l
It becomes ₂ . (See FIG. 7 (b)) Pattern 3: In cases other than the above Patterns 1 and 2, the shortest distance among the end points between the central axes AB and CD is the shortest distance l ₃ . (See FIG. 7 (c)) Next, a procedure for determining which of the above-described patterns the two central axes AB, CD having an arbitrary positional relationship belong to will be described below. The line segment perpendicular to the straight lines α and β is PQ.

[Position calculation of points P and Q] Since points P and Q are points on straight lines α and β, respectively, they can be expressed as follows using parameters s and t.

pi = ai + (bi-ai) s (2) qi = ci + (di-ci) t (3) However, i = 1 to 3, and p ₁ , q ₁ , a ₁ , b ₁ , c ₁ and d ₁ represent the X coordinate values of the points P, Q, A, B, C and D, respectively, and p ₂ , q ₂ , a ₂ , b ₂ , c
₂ and d ₂ respectively represent the Y-axis coordinate values of the points P, Q, A, B, C and D, and p ₃ and
_{q 3, a 3, b 3} , c 3, d 3 respectively represent points P, Q, A, B, C, a Z-axis coordinate value of D.

If the points P and Q are in the central axes AB and CD, respectively, 0 ≦ s ≦ 1,
0 ≦ t ≦ 1 holds.

By the way, since the line segment PQ is perpendicular to the straight lines α and β, the following equation holds: ・ 0 …… (4) ・ = 0 …… (5), and from the formulas (2) to (5), pi, qi When is deleted, the values of the parameters s and t are obtained.

[Judgment of Pattern 1] Whether or not the points P and Q are inside the central axes AB and CD is judged from the parameters s and t.

When 0 ≦ s ≦ 1, 0 ≦ t ≦ 1, the points P and Q are located within the center axes AB and CD, so the arrangement relationship between the cylinder center axes AB and CD is pattern 1, and the shortest distance l ₁ (= PQ).

[Determination of Patterns 2 and 3] Of the end points of both central axes AB and CD, a perpendicular line is drawn from the end points near points P and Q to the other central axes. If at least one of the intersections of the perpendiculars is in the other central axis, it can be determined as pattern 2. Therefore, the shortest distance is the length l ₂ of this line segment.

Also, if both intersections of the perpendiculars are off the other central axis,
It can be determined to be pattern 3. In this case, the shortest distance between the end points of both line segments is the shortest distance l ₃ .

FIGS. 8 (a) and 8 (b) are diagrams for explaining the interference check algorithm between the shape approximate sphere and the shape approximate cylinder.

First, as shown in FIG. 8A, if the center c ₂ of the approximate shape sphere S ₂ is located within the central axis AB of the approximate shape cylinder 21,
That is, if A ≦ c ₂ ≦ B, it is understood that the shape approximate sphere S ₂ and the shape approximate cylinder 21 interfere with each other when the condition of 1 <r ₂ + R is satisfied. However, l is the length of a perpendicular line hung from the center c ₂ of the shape approximation sphere S ₂ to the center axis AB of the shape approximation cylinder 21, r ₂ is the radius of the shape approximation sphere S ₂ , and R is the radius of the shape approximation cylinder 21. Represent

Subsequently, as shown in FIG. 8 (b), if the center c ₂ of the approximate shape sphere S ₂ is outside the central axis AB of the approximate shape cylinder 21, that is, c ₂ <A or B <c ₂ If so, l <r ₂ + R, L
It can be seen that when the condition of <r ₂ is satisfied, the shape approximate sphere S ₂ and the shape approximate cylinder 21 interfere with each other. However, l is the length of a perpendicular line hung from the center c ₂ of the shape approximation sphere S ₂ on the extension line of the central axis AB of the shape approximation cylinder 21, and d is the center c ₂ of the shape approximation sphere S ₂ of the shape approximation cylinder 21. The distance to the end point of the central axis AB, L represents the length of a perpendicular line L = d cos θ hung from the center c ₂ of the approximate shape sphere S ₂ .

The algorithm for the collision check between the rectangular parallelepiped and the rectangular parallelepiped is the space disclosed in Japanese Patent Application No. 62-332130 filed on Dec. 28, 1987 “Method for checking interference in robot” to find a space that may interfere with the interference. Interference check shall be strictly performed only in the space where there is a risk of

<Effects of the Invention> According to the present invention, two or more kinds of shape approximation solids of a rectangular parallelepiped, a sphere, and a cylinder are created for each of the first and second solids, and two or more kinds of shape approximations created at this time are created. A shape approximation body having a minimum volume in the solid bodies is individually selected for the first and second solid bodies, and the presence or absence of interference is determined using the two shape approximation solid bodies having the selected minimum volumes. Therefore, the shape of the three-dimensional object to be checked can be approximated with the minimum required surface, and the interference check can be executed at high speed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a robot off-line programming device to which the present invention can be applied, FIG. 2 is a flow chart of processing of the present invention, FIG. 3 is a diagram for explaining a method of creating a shape approximating rectangular parallelepiped, and FIG. ) And (b) are diagrams for explaining a method for creating a shape approximate sphere, FIG. 5 is a diagram for explaining a method for creating a shape approximate cylinder, and FIG. 6 is a diagram for explaining an interference check algorithm between shape approximate spheres. 7 (a) to 7 (c) are diagrams for explaining the interference check algorithm between the shape approximation cylinders, and FIGS. 8 (a) and 8 (b) are shape approximation spheres and shape approximation cylinders. 4 is a diagram for explaining the interference check algorithm of FIG. 1a ... Processor, 1b ... Program memory (ROM), 1c ... RAM, RAP ... Robot operation program, FDw ... Work shape data, FDe ... Effector shape data, 11 ... Shape box S ₁ , S ₂ …… Shape approximating sphere 21 …… Shape approximating cylinder

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-63-158620 (JP, A) JP-A-58-171615 (JP, A) JP-A-62-43706 (JP, A) JP-A-63- 300903 (JP, A) JP 62-70911 (JP, A) JP 64-48107 (JP, A) JP 1-173205 (JP, A) JP 1-180602 (JP, A)

Claims (4)

(57) [Claims] 1. A robot interference check method for determining the presence or absence of interference by defining shape approximate solids for the first and second solids subject to interference check, wherein the first and second solids are provided. For each of the above, two or more types of shape-approximating solids of a rectangular parallelepiped, a sphere, and a cylinder are created. The method for checking interference of a robot, in which each of the three solids is individually selected, and the presence or absence of interference is determined by using the two shape approximate solids having the selected minimum volumes. 2. A shape-approximating rectangular parallelepiped has a line segment having a maximum distance between vertices of a solid subject to interference check as its diagonal line, and each ridge line is parallel to the x, y, z axes. The interference check method for a robot according to claim 1, wherein 3. The shape approximating sphere is set with a line segment having the maximum value of the distance between the vertices of the solid body subject to the interference check as its diameter, and all coordinate points of the solid body subject to the interference check. The method for checking interference of a robot according to claim 1, wherein the set value of the diameter is updated and created until is included therein. 4. The shape approximation cylinder has a regression line obtained by the least squares method with reference to the distribution of the vertices of the solid subject to the interference check, with the center axis of the cylinder being the vertex farthest from this center axis. The radius is the distance to, and the maximum value of the coordinates of the intersection of the perpendicular line hung from each vertex to the central axis and the central axis.
The robot interference checking method according to claim 1, wherein the distance between the minimum values is created as the height of the cylinder.