JP2000094370A - Inclination measuring method of work surface of robot and measuring device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily obtain relative inclination by obtaining inclination of a surface of a work bench for reference coordinates by computation based on coordinates of three detected positions. SOLUTION: A controller computes outer product of vectors J, K. The size of this outer product is equal to an area of parallelogram using vectors J, K as adjacent two sides, its direction is vertical to both of two vectors J, K, and when vector J is turned within 180 deg. and is superposed on vector K, it becomes vector M having the direction of advance of a right hand thread. That is, two vectors J, K are calculated, and an outer product of two vectors J, K is calculated. The controller functions as a computing means. Vector M coincides with a normal of a plane including two vectors J, K, namely, a plane parallel with a surface of a work bench, and the inclination of vector M becomes the inclination of the surface of the work bench.

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 measuring the inclination of a work surface of a robot for measuring the inclination of the surface of a work table with respect to reference coordinates of a robot body.

[0002]

The posture of the robot, that is, the posture of the hand portion at the tip of the robot arm is, for example, the same as the approach vector extending vertically from the center of the end face of the flange provided at the tip of the wrist. An orient vector extending from the center of the end face of the flange in the direction perpendicular to the approach vector is set, and when these two vectors are translated so that the intersection point coincides with the origin of the reference coordinates of the robot, the approach vector and the orient vector are set. The vector is indicated by the direction of the robot on the reference coordinates.

When teaching work to a robot,
Depending on the content of the work, it may be necessary to teach the end surface of the flange so as to be parallel to the surface of the worktable. FIG. 7 shows an example of this, in which the hand H is held at the front end face f of the flange F while the front end face f of the flange F which is the front end of the robot body is held parallel to the worktable D.
Is lowered straight down along the normal line (vertical line), and the work W1 gripped by the hand H is moved to the work W
2 shows the work of assembling.

However, the surface of the worktable D and the XY coordinate plane (horizontal plane) of the reference coordinate system of the robot are not always parallel to each other from the state of installation of the worktable D or the robot body. Absent. Therefore, when the surface of the worktable D is inclined with respect to the XY coordinate plane of the reference coordinate system, during the teaching of the robot operation as described above, each joint of the robot main body is delicately moved, and the flange F is moved. Is parallel to the surface of the worktable D.
However, if there are many joints, such as a six-axis articulated robot, how to operate each joint is the flange F
It is difficult to estimate whether or not the front end face f is parallel to the surface of the worktable D, and there is a problem that much time is required for teaching work.

To solve this problem, Japanese Unexamined Patent Publication No.
There is a technique disclosed in Japanese Patent Application Laid-Open No. 9-182076. This is because the spatial relative error between the reference coordinates of the robot and the coordinates of the surface of the worktable can be expressed using the displacement between the origins of both coordinates and the rotational displacement between the coordinate axes. The distance from the worktable surface is measured at six or more points, and from the measured distances, vectors in three coordinate axis directions representing the displacement between the origins of the two coordinates are calculated, and Euler angles such as the Euler angles representing the rotational displacement between the coordinate axes are calculated. It is to calculate the components.

In the technique disclosed in Japanese Patent Application Laid-Open No. Sho 59-182076, it is necessary to express the positional relationship between the reference coordinates of the robot and the coordinates of the surface of the worktable in terms of the displacement between the origins of the two coordinates and the rotational displacement between the coordinate axes. Therefore, a separate distance measuring device for accurately measuring the distance from the tip of the robot to the coordinate system on the surface of the worktable is required separately, and there is a problem that the system becomes complicated. Therefore, if it is sufficient to detect only the relative inclination between the reference coordinates of the robot and the surface of the worktable,
It becomes an over-system.

The present invention has been made in view of the above circumstances, and an object of the present invention is to determine the relative inclination between the reference coordinates of the robot and the surface of the worktable without using a special distance measuring device.
It is an object of the present invention to provide a method and an apparatus for measuring the inclination of a work surface of a robot which can be easily obtained.

[0008]

According to a first aspect of the present invention, there is provided a method for measuring the inclination of a work surface of a robot, comprising the steps of: To detect the tip position of the robot main body at each of these measurement points by coordinates on the reference coordinates of the robot main body, and based on the detected coordinates of at least the three positions, the position of the robot relative to the reference coordinates is detected. It is characterized in that the inclination of the worktable surface is obtained by calculation.

According to a second aspect of the present invention, there is provided an apparatus for measuring the inclination of a work surface of a robot, wherein the robot body and a predetermined portion of a tip portion of the robot body are brought into contact with at least three measurement points on the worktable surface. Coordinate position detecting means for detecting the position of the tip of the robot body at each measurement point by coordinates on the reference coordinates of the robot body, and based on the coordinates of at least the three positions detected by the coordinate position detecting means. Calculating means for calculating the inclination of the surface of the worktable with respect to the reference coordinates by calculation.

According to the first and second aspects of the present invention,
When a predetermined portion of the tip portion of the robot body is brought into contact with at least three measurement points on the surface of the worktable, the coordinates of the tip of the robot body at each of those measurement points are coordinates originally provided in the robot controller. It can be easily detected using an arithmetic function for conversion. Also, the calculation for obtaining the inclination of the surface of the worktable based on the detected coordinates of at least three positions can be easily performed similarly by using the calculation function of the robot controller. For this reason, the relative inclination between the reference coordinates of the robot and the surface of the worktable can be easily obtained without using a special distance measuring device.

According to a third aspect of the present invention, there is provided an apparatus for measuring the inclination of a work surface of a robot. Is characterized by being present around. According to this configuration, the inclination of the worktable surface can be obtained as the inclination at a part where the robot actually performs the work.

According to a fourth aspect of the present invention, there is provided an apparatus for measuring the inclination of a work surface of a robot, wherein, when the robot body has a plurality of work areas on the work table surface, a predetermined part of a tip portion of the robot body is brought into contact with the work body. At least three measurement points on the table surface are for each of the working parts. According to this configuration, the inclination of the worktable surface can be obtained for each of a plurality of parts where the robot actually performs the work.

According to a fifth aspect of the present invention, in the apparatus for measuring the inclination of a work surface of a robot, the calculating means obtains at least two sets of vectors based on the coordinates of the at least three positions detected by the coordinate position detecting means. By calculating the cross product of the two vectors, the inclination of the work table surface is obtained as the inclination of the normal line of the work table surface. According to this configuration, the inclination of the worktable surface can be easily obtained without performing complicated calculations.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described with reference to FIGS.
A description will be given based on FIG. As shown in FIG. 6, the robot includes a robot body 1, a control device 2 as control means for controlling the robot body 1, and a teach pendant 3 as teaching means connected to the control device 2.
It is composed of

The robot body 1 is, for example, configured as a 6-axis vertical articulated type, and has a base 4 and a shoulder 5 supported on the base 4 so as to be able to turn horizontally.
And a lower arm 6 supported by the shoulder portion 5 so as to be pivotable in the vertical direction, and an upper arm 7 supported by the lower arm 6 so as to be pivotable in the vertical direction and rotatable (twisting).
And a wrist 8 supported on the upper arm 7 so as to be pivotable in the vertical direction. The wrist 8 has a flange 9 at its tip end that can rotate (twist). As will be described later, the hand 10 for gripping the work is attached to the flange 9 which is the tip of the robot.

On the other hand, as shown in FIG. 5, the control device 2 includes a CPU 11, a drive circuit 12, and a position detection circuit 13 as position detection means. Then, the CPU 1
A ROM 14 for storing a system program of the entire robot and a program for detecting a tilt of the surface of a work table, which will be described later, and a RAM 15 for storing an operation program of the robot body 1 are connected to the storage device 1. The teaching pendant 3 used when performing a teaching operation is connected. As shown in FIG. 6, the teaching pendant 3 includes various operation sections 3a as operation means and a display 3b as display means.

The position detecting circuit 13 is for detecting the position of each joint, that is, the shoulder 5, the arms 6, 7, the wrist 8, and the flange 9. The position detecting circuit 13 includes the shoulder 5 A rotary encoder 17 as a position sensor provided on a drive motor 16 for each of the arms 6 and 7, the wrist 8 and the flange 9 is connected. The position detection circuit 13 detects the rotation angle of the shoulder 5 with respect to the base 4, the rotation angle 7 of the lower arm 6 with respect to the shoulder 5, the rotation angle of the upper arm 7 with respect to the lower arm 6, and the upper arm 7 based on the detection signal of the rotary encoder 17. The rotation angle of the wrist 8 with respect to the wrist 8 and the rotation angle of the flange 9 with respect to the wrist 8 are detected.
Given to one. Then, when operating the shoulder portion 5, the arms 6, 7, the wrist 8, and the flange 9 based on the operation program, the CPU 11 controls the operation using the input signal from the position detection circuit 13 as a feedback signal. Has become. Although only one drive motor 16 and one rotary encoder 17 are shown in FIG. 6, a plurality of drive motors 16 and rotary encoders 17 are provided in a one-to-one relationship with the operation of each unit.

Here, three-dimensional coordinates are fixed to each joint. Of these, the coordinate system of the base 4 installed on the floor is stationary, and is used as the reference coordinates (coordinates indicated by S in FIG. 3) of the robot main body 1, and the other coordinate systems are based on the rotation of each joint. The position and orientation on the coordinates change. Then, the control device 2 (CPU 11) receives the position detection information of each joint such as the shoulder portion 5, the arms 6 and 7, the wrist 8 and the flange 9 input from the position detection circuit 13 and the joint information of each joint stored in advance. Based on the length information, the position and orientation of the coordinates of each joint can be converted into the position and orientation on the reference coordinates by a coordinate conversion operation function and recognized.

As shown in FIG. 4, the coordinate system of the flange 9 in the coordinate system of each joint has the origin at the center P0 of the distal end surface of the flange 9 and two coordinate axes on the distal end surface of the flange 9 as shown in FIG. If one coordinate axis is determined on the rotation axis of the flange 9, the directions of the three coordinate axes Xf, Yf, Zf can be freely set by the user. In this embodiment, as shown in FIG. 4, the two axes Xf and Yf are present on the front end face of the flange 9, and the remaining Zf axis is
It is assumed that it is determined to exist on the rotation axis of.

The posture of the robot, that is, the posture of the flange 9 at the tip of the robot arm, as shown in FIG. 4, is a unit length projecting in the negative direction from the origin Po of the coordinate system of the flange 9 along the Zf axis. Then, an approach vector A of "1" and an orientation vector O of unit length "1" protruding from the origin P0 along the Xf axis in the positive direction are set, and the coordinate system of the flange 9 is defined by the origin P0 as the reference coordinates. When translated so as to coincide with the origin of the system, it is represented by an approach vector A and an orientation vector O on the reference coordinate system.

At the time of teaching of the robot operation, the front end face of the flange 9 is defined by the X and Y of the reference coordinate system.
To make it parallel to the plane formed by the two coordinate axes, the coordinates (0, 0, -1) of the tip of the approach vector A are input by the teaching pendant 3 so that the approach vector A is directed vertically downward. I do. Then, the control device 2 takes the position of the coordinates (0, 0, -1) at which the approach vector A is input, that is, the approach vector A is directed vertically downward, and the tip end surface of the flange 9 is in the reference coordinate system. Drive motor 1 for each joint so as to be parallel to the horizontal plane formed by the two coordinate axes X and Y
6 is controlled.

However, the reference coordinates of the robot main body 1 and the surface of the work table 18 (on which an object to be subjected to robot work is placed) shown in FIG. 3 are not necessarily horizontal due to installation accuracy and the like. The surfaces are not necessarily parallel to each other. Therefore, in the robot configured as above, along with teaching of the robot work,
The operation of detecting the inclination of the surface of the worktable 18 with respect to the reference coordinates and correcting the attitude of the flange 9 of the robot main body 1 will be described with reference to the flowchart shown in FIG.

Now, the hand 1 is located at the center of the flange 9.
0 is attached. To detect the inclination of the surface of the worktable 18, first, the teaching pendant 3
To set the workbench surface inclination detection mode. Then, while keeping the attitude of the flange 9 constant, for example, the approach vector A is parallel to the Z axis of the reference coordinates (the tip end surface of the flange 9 is parallel to the XY plane of the reference coordinates), and the orientation vector O is the reference coordinates. While maintaining a state parallel to the Y-axis of the work table 18 at any of three measurement points P1 to P
3 is brought into contact with the tip of the hand 10 which is a predetermined portion of the tip of the robot body 1. At this time, the above hand 10
Are set around the position where the robot operation is actually performed (the portion indicated by Pw in FIG. 3).

Then, the hand 10 is moved to three measurement points P1 to P3.
The teaching pendant 3 is operated each time it is brought into contact with the center P0 of the front end surface of the flange 9 at each position.
It is read as a coordinate position on the reference coordinates (step S1). The operation of detecting the position of the center P0 of the distal end surface of the flange 9 (hereinafter referred to as the robot distal end position) by coordinates in the reference coordinate system when the hand 10 abuts on the three positions P1 to P3 is performed by the controller 2 (CPU 11). ) Is performed by performing coordinate conversion based on the position information of the shoulder 5, the arms 6, 7, the wrist 8, and the flange 9 input from the position detection circuit 13 as described above. Therefore, the control device 2 functions as a coordinate position detecting unit. The detected coordinate position of the center P0 of the front end surface of the flange 9 is stored in the RAM 15 as storage means. Here, three measurement points P1
The reference coordinates of the robot tip position at P3 to P3 are (X
1, Y1, Z1), (X2, Y2, Z2) (X3, Y3
, Z3).

As described above, the surface 3 of the work table 18
After detecting the coordinates of the robot tip position corresponding to the specified point, the control device 2 then, as shown in FIG. 2, sets one of the three measurement points P1 to P3, for example, the first detected measurement point. Vectors J and K extending from the robot tip position P1 'of P1 to the robot tip positions P2' and P3 'of the other two measurement points are calculated (step S2). The reference coordinates of the robot tip position at the three measurement points P1 to P3 are (X1, Y1, Z1), respectively.
Since (X2, Y2, Z2) (X3, Y3, Z3), the vector J (Xj, Yj, Zj) is (X1-X2
, Y1 -Y2, Z1 -Z2), and the vector K
(Xk, Yk, Zk) are (X1-X3, Y1-Y3, Z
1 -Z3). The vectors J and K represented in this manner exist in a plane parallel to the surface of the worktable 18.

Thereafter, the control device 2 calculates an outer product of the vectors J and K (step S3). This vector J, K
The magnitude of the outer product of the vector J,
When K is equal to the area of a parallelogram having two adjacent sides, and its direction is perpendicular to both of the two vectors J and K, and the vector J is rotated within 180 ° to overlap the vector K, The vector M has the direction of the direction in which the right-hand screw advances. As described above, the control device 2 that calculates the two vectors J and K and calculates the cross product of the two vectors J and K functions as an arithmetic unit.

Here, as understood from the above description, the vector M is a plane including two vectors J and K,
That is, the normal of the plane parallel to the surface of the work table 18 is matched, and therefore, the inclination of the vector M is
Surface inclination.

Next, the control device 2 determines whether or not the component in the Z-axis direction of the vector M is positive (step S).
4). If the component in the Z-axis direction of the vector M is positive, the control device 2 makes the components in the X, Y, and Z directions of the vector M negative, and rotates the direction of the vector M by 180 °. (Step S5). Thereafter, the control device 2 determines the components (Xm, Ym, Zm) of the vector M in the X, Y, Z directions.
) Is displayed on the display 3b of the teaching pendant 3 (step S6). If the component Zm of the vector M in the Z-axis direction is negative, the control device 2 determines “NO” in step S4 and shifts to step S6, where the X, Y, Z The components in each axial direction are displayed on the display 3b of the teaching pendant 3.

In this way, when the vector M along the normal line of the surface of the worktable 18 is calculated and displayed on the display 3b, the operator can calculate the X, Y, and Z of the vector M displayed on the display 3b. Components in each axis direction (Xm, Ym,
Zm) is input to the teaching pendant 3 ("YES" in step S7). Then, no matter what position the center P0 of the front end face of the flange 9 takes, the control device 2 adjusts the posture of the flange 9 such that the front end face of the flange 9 is orthogonal to the input vector M. The joint drive motor 16 is operated (step S8). For this reason, teaching of the robot operation can be performed while the distal end surface of the flange 9 is kept parallel to the surface of the worktable 18.

By the way, in the above step S4,
The reason why the sign of the component Zm in the Z-axis direction of the vector M is determined, and if it is positive, the components of the vector M in the X-, Y-, and Z-directions are made negative is that the robot of this embodiment is Since the approach vector A is defined as a vector having a length of “1” in the negative direction on the Z axis, if the component of the vector M in the Z axis direction is positive, the direction of the vector M is determined by the approach vector In order to facilitate subsequent calculations.

As described above, in this embodiment, the inclination of the surface of the worktable 18 can be easily obtained. Moreover, the inclination of the surface of the worktable 18 can be determined by using the coordinate transformation calculation function inherent in the robot controller 2 itself without using a special distance measuring device. Is obtained automatically, the inclination of the surface of the worktable 18 can be easily obtained.

In this embodiment, the inclination of the surface of the worktable 18 is determined as the inclination of the normal line, and among the three measurement points P1 to P3, the measurement point P1 is determined. From the robot tip position P1 'corresponding to the measurement point P2 and the robot tip position P1 corresponding to the measurement points P3
Since the inclination of the surface of the workbench 18 and the inclination of the normal line (vector M) are directly obtained by calculating the cross product of the vectors J and K up to '2 and P2', the calculation can be easily performed.
The burden on (CPU 11) can be reduced.

In contrast to the method of obtaining the vectors J and K and calculating the inclination of the surface of the worktable 18 from the cross product thereof as the inclination of the normal line, first, the worktable is obtained from the coordinates of the robot tip position at three measurement points P1 to P3. Find the slope of the surface of 18, then
There is a method of determining the inclination of the normal line of the surface of the worktable 18. The method is as follows.

First, the plane is represented by the following equation (1).

(Equation 1)

Since the above three positions P1 to P3 exist in one plane parallel to the surface of the worktable 18, the following equations (2) to (4) hold for each position.

(Equation 2)

Then, in order to express the above constants b, c and d by a, first, the following equations (5) are obtained from the equations (2) and (3).
The following equation (6) is obtained from the equations (2) and (4).

(Equation 3)

(Equation 4)

Next, the following equation (7) is obtained from the equations (5) and (6), and c is obtained from the equation (7).
It looks like an expression.

(Equation 5)

The following equation (9) is obtained by substituting the equation (8) into the equation (5), and d is obtained from the equation (9) to obtain the following equation (10).

(Equation 6)

Also, from the above equations (2) and (3), the following equation (11), and from the equations (2) and (4), the following (1)
2) Formula is obtained.

(Equation 7)

(Equation 8)

Then, the following equation (13) is obtained from the equations (11) and (12), and b is obtained from the equation (13).

(Equation 9)

Accordingly, an expression representing one plane parallel to the surface of the worktable 18 is as follows:

(Equation 10)

A normal vector passing through one plane parallel to the surface of the worktable 18 is represented by the following coordinates.

[Equation 11]

In this way, the normal vector M can be obtained, but this requires a very complicated calculation as described above. On the other hand, it is simpler to calculate the normal vector M by calculating the cross product of the vectors J and K as in the present embodiment, and the control device 2 (C
It will be appreciated that the burden on PU 11) can be reduced.

The present invention is not limited to the embodiment described above and shown in the drawings, but can be extended or modified as follows. The surface of the worktable is not limited to a horizontal surface and may be a vertical surface, or may be any surface that is not limited to horizontal or vertical and has any inclination. The position at which the hand 10 abuts to determine the inclination of the surface of the worktable is 3
The number of positions is not limited to four, and may be four or more.
In this case, there can be a plurality of pairs of two vectors, but the cross product may be obtained for each pair, and the average may be set as the normal vector of the surface of the worktable. When a robot operation is performed at a plurality of locations on the surface of the worktable, the inclination of the surface of the worktable is determined for each work location. According to this configuration, the robot body may be in a state where the X, Y, and Z axes of the reference coordinates are bent due to the manufacturing accuracy, assembly accuracy, rigidity, and the like of each component. Even under circumstances, the error on the reference coordinate side can be absorbed, and the actual inclination of the worktable surface can be detected for each work position. Display 3b
After the components (Xm, Ym, Zm) in the X, Y, and Z directions of the vector M displayed on the control unit 2 are input from the teaching pendant 3, the control device 2 changes the attitude of the flange 9 and The drive motor 16 of each joint was operated so that the end face of the joint 9 is orthogonal to the input vector M. This is because step S6 is performed without waiting for the input of (Xm, Ym, Zm). After execution, the control device 2 may directly correct the attitude of the flange 9 so as to be (Xm, Ym, Zm).

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention, and is a flowchart for determining the inclination of the worktable surface.

FIG. 2 is a diagram showing a relationship between two vectors and a cross product.

FIG. 3 is a perspective view when detecting coordinates of three positions on a plane parallel to the work table surface;

FIG. 4 is a perspective view of a flange portion of the robot.

FIG. 5 is a block diagram showing an electrical configuration of the robot.

FIG. 6 is a perspective view of a robot.

FIG. 7 is a longitudinal sectional side view for explaining a conventional problem.

[Explanation of symbols]

1 is a robot main body, 2 is a control device (coordinate position detecting means,
Computing means), 3 is a teaching pendant, 10 is a hand, 11 is a CPU, and 18 is a work bench.

Claims (5)

[Claims] At least three measurement points on the surface of a worktable are brought into contact with predetermined portions of a tip portion of a robot body, and the tip position of the robot body at each of these measurement points is determined on a reference coordinate of the robot body. A method for measuring the inclination of a work surface of a robot, wherein the inclination of the work table surface with respect to the reference coordinates is calculated based on the detected coordinates of the at least three positions. 2. When a predetermined portion of a front end portion of the robot main body is brought into contact with at least three measurement points on a worktable surface, the position of the front end of the robot main body at each measurement point is determined by the robot. Coordinate position detecting means for detecting the coordinates on the reference coordinates of the main body; calculating means for calculating the inclination of the surface of the work table with respect to the reference coordinates based on the coordinates of at least the three positions detected by the coordinate position detecting means An inclination measuring device for a work surface of a robot, comprising: 3. The robot according to claim 1, wherein at least three measurement points on the surface of the worktable where the predetermined portion of the distal end portion of the robot body abuts are present around a region where the robot body performs work. An apparatus for measuring the inclination of a work surface of a robot according to claim 1. 4. When there are a plurality of parts on the surface of the worktable on which the robot body performs work, at least three measurement points on the surface of the worktable with which a predetermined part of a tip part of the robot body is brought into contact with each other. The inclination measuring device for a work surface of a robot according to claim 1, wherein the work surface is a work part. 5. The calculating means calculates a set of at least two vectors based on the coordinates of the at least three positions detected by the coordinate position detecting means, and calculates an outer product of the two vectors, The tilt measuring device for a work surface of a robot according to any one of claims 2 to 4, wherein the tilt of the work table surface is obtained as a tilt of a normal line of the work table surface.