JPH08255011A - Control method for robot - Google Patents

Abstract

PURPOSE: To provide a method for obtaining a correction quantity to be added to original teaching data through easy operation even in a case when the operation point (control point) of the robot is not at the tip part of a jig or even if the jig of the robot changes owing to replacement, deformation, etc. CONSTITUTION: Position and attitude data on the jig (hand) 2 fitted to the wrist of the robot 1 are previously stored by positioning three points (ORG, XX, and XY), determining a coordinate system on the jig 2, at a pin 4 whose position is already known. If the jig deforms owing to its replacement, collision, etc., the three points on the jig after deformation which is fitted to the tip of the arm of the robot are positioned at the pin 4 to store the position and attitude data. The correction quantity for robot operation after the deformation of the jig is obtained from the relative position relation between coordinate systems before and after deformation which are determined by the respective three points.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a robot control method, and more particularly to a robot control method in which teaching data up to now can be used as it is even when a jig is deformed due to collision or replacement.

[0002]

2. Description of the Related Art When a jig attached to the tip of a robot arm is deformed or the jig is replaced with another shape, the original teaching data can be used as it is to perform a reproducing operation. To correct the operation of the robot, Japanese Patent Publication No. 62-55475 and Japanese Patent Publication No. 7-471
It is publicly known as disclosed in the publication.

[0003]

However, in any case, the working point (also referred to as a control point) P of the robot is at the tip of the jig (the tip of the wire sent from the torch) like a welding torch. It corresponds only to the case where they match (see FIG. 8A). Therefore, unlike the case where the jig is a hand mechanism, the case where the working point P of the robot is not at the tip of the jig (see FIG. 8B) cannot be handled. Therefore, it is an object of the present invention to restore the original teaching data with a simple operation even if the robot working point is not located at the tip of the jig or if the robot jig changes due to replacement or deformation. It is to provide a method of obtaining the correction amount to be added.

[0004]

SUMMARY OF THE INVENTION The present invention is a robot control method for reproducing the operation of a robot based on previously stored teaching data of the robot. In this method, a jig of known size and shape is attached to the wrist of the robot. Then, position the jig at the tip position of the pin installed near the robot, teach the tip position of the pin in the robot coordinate system, and determine the coordinate system on the jig attached to the wrist of the robot. By positioning the three points on the jig at the positions of the tips of the pins,
The posture data is stored in advance in the storage device of the robot, and when the jig is deformed due to the conversion or collision of the jig, the three points on the jig after the deformation are positioned at the positions of the tips of the pins. Thus, the position / orientation data is stored in the storage device of the robot in advance, and the correction amount of the robot operation after the deformation of the jig is calculated from the relative positional relationship of the coordinate system before and after the deformation determined by the above three points. It is characterized by obtaining.

[0005]

According to the present invention, even when the jig is changed by conversion or deformation of the jig, three points on the jig (the origin for defining a plane on the jig and the point for defining the X axis). , And X
The focus is on the fact that the relative positional relationship between the points (defining the Y plane) hardly changes in many cases, and the coordinate shift amount is obtained from the positional relationship of these three points before and after deformation. is there.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings in which the jig is a hand. FIG. 1 is a diagram showing an example of an apparatus for carrying out the present invention. In the figure, 1 is a robot, 2 is a hand, 3 is a robot controller, and 4 is a pin placed in the vicinity of the robot. Now, in the present invention, first, in order to obtain the tip position of the pin 4, a jig having a known size and shape is made to wait for the robot, and the working point P at the tip thereof is positioned at the tip of the pin 4. From the joint angle data of the robot at this time, the known tip position of the jig (that is, the tip position of the pin 4) can be obtained. Up to this point, it is known. It should be noted that the jig for teaching the tip position of the pin 4 is not a hand that is deformed as will be described later, but the work point (control point) P of the robot is the tip portion of the jig for the sake of simplifying the coordinate conversion process. It is desirable to use a jig 2'that matches (see Fig. 2).

Next, as shown in FIG. 3, the three points on the hand 2 before being deformed are manually positioned so as to come into contact with the tip points of the pins 4, and the respective position / posture data (at the time of the contact) The rotation angle data of each joint of the robot 1) is stored. As shown in the figure, the three points on the hand are, for example, an origin (ORG) for defining a plane on the jig, a point (XX) for defining the X axis, and a point for defining the XY plane. These are (XY). With these three points, the coordinate system of the XY plane, that is, the hand coordinate system H is defined on the jig. The hand coordinate system H just defined has a different positional relationship from the conventional tool coordinate system T, and the tool coordinate system T has its origin at the work point P. The conventional robot controller is controlled based on the tool coordinate system T and the robot coordinate system R. Therefore, in order to inherit that technical resource, the present invention determines the relationship between the hand coordinate system H just defined and these conventional coordinate systems, as will be described later.

Next, when the hand 2 is deformed, the above three points are taught in the same manner as before the deformation. As a result, the hand coordinate system H'after the hand deformation is defined. At this time, it is assumed that the relative positional relationship between the above three points does not change much (is sufficiently rigid) due to the jig deformation. 3 points before transformation,
The amount of displacement of the hand is calculated from the three points after deformation, and the stored motion path is parallel shifted by the amount of displacement and reproduced. The above is the operation procedure on the surface of the present invention.

With the above operation procedure, the following arithmetic processing is performed in the robot controller in order to obtain the desired effect. Since the known technique can be performed until the tip position of the pin 4 is taught, the calculation processing procedure after the tip position of the pin 4 is taught will be described in detail here. (1) Three points (ORG, XX, XY) on the hand The data of the three points on the hand are converted into the data on the tool coordinate from the teaching posture and the robot coordinates of the pin tip. The tool coordinates during ORG teaching are shown in FIG. 4A, and the tool coordinates during XX teaching are shown in FIG.
(B) The tool coordinates at the time of XY teaching are shown in FIG. 4 (c).
The transformation matrix (matrix showing the tool coordinate system viewed from the robot coordinate system) at the time of each teaching is T _R1 ,
_Let T _R2 and T _R3 . FIG. 5A generally shows the old coordinate system and the new coordinate system, and the specific conversion formulas are as follows.

[0010]

[Equation 1]

Therefore, T ₁ in the above equation is replaced with T _R1 ,
If T _R2 and T _R3 are satisfied, then P _ORG-R = T _R1 P _ORG-T P _XX-R = T _R2 P _XX-T P _XY-R = T _R3 P _XY-T . Here, P _ORG-R ... ORG point viewed from robot coordinates P _ORG-T ... ORG point viewed from tool coordinates P _XX-R ... XX point viewed from robot coordinates P _XX-T ... XX point viewed from tool coordinates P _{XY- R} ... XY point seen from robot coordinates P _XY-T ... XY point seen from tool coordinates T _R1 ... Conversion matrix from robot coordinates to tool coordinates seen from ORG point T _R2 ... Tool seen from robot coordinates at XX point teaching Transformation matrix to coordinates T _R3 ... Transformation matrix to tool coordinates as seen from robot coordinates when teaching XY points

From the tool coordinates, P _ORG-T = T _R1 ^-1 P _ORG-R P _XX-T = T _R2 ^-1 P _XX-R P _XY-T = T _R3 ^-1 P _XY-R . Here, T _R1 ^-1 , T _R2 ^-1 , and T _R3 ^-1 are inverse matrices of T _R1 , T _R2 , and T _R3 , respectively.

(2) A coordinate system H _{T of the} hand is created on the tool coordinates from three points on the hand defined on the tool coordinates (see FIG. 6). U _X = X ₁ -X ₀ U _Y = Y ₁ -Y ₀ U _Z = Z ₁ -Z ₀ R _X = Y ₂ -X ₀ R _Y = X ₂ -Y ₀ R _Z = Z ₂ -Z ₀ where As shown in FIG. 5B, since the vector W is an outer product of the vector U and the vector R, W _X = U _Y * R _Z −U _Z * R _Y W _Y = U _Z * R _X −U _X * R _Z W _Z = U _X * R _Y −U _Y * R _X. Further, since the vector V is the outer product of the vector W and the vector U, V _X = W _Y * U _Z −W _Z * U _Y V _Y = W _Z * U _X −W _X * U _Z V _Z = W _X * It is U _Y −W _Y * U _X. Find the magnitudes of the vectors U, V, W. | U | = √ (U _X * U _X + U _Y * U _Y + U _Z * U _Z ) | V | = √ (V _X * V _X + V _Y * V _Y + V _Z * V _Z ) | W | = √ ( W _X * W _X + W _Y * W _Y + W _Z * W _Z ) N, O, A which are unit vectors in each axis direction (Fig. 5 (c))
(See) is as follows. _{N 3X = U X / | U} | N 3Y = U Y / | U | N 3Z = U Z / | U | O 3X = V X / | V | O 3Y = V Y / | V | O 3Z = V Z / | V | A _3X = W _X / | W | A _3Y = W _Y / | W | A _3Z = W _Z / | W | P _X , P _Y , and P _Z representing the translations are as follows. P _3X = X ₀ P _3Y = Y ₀ P _3Z = Z _{0 The} above is represented by a matrix as follows.

[0014]

[Equation 2]

Thus, the coordinate system H _T of the hand is obtained.

(3) The hand coordinate H _R seen from the robot coordinate system is calculated from the tool coordinate (transform matrix) T _R3 seen from the robot coordinate at the time of XY teaching and the hand coordinate (transform matrix) H _T seen from the tool coordinate. Ask. That is, H _R = T _R3
H _T. (4) the tool coordinate (a transformation matrix) viewed from the robot coordinate during XY teaches that T _R3, from the hand coordinate (inverse transformation matrix) H _R ^-1 viewed from the robot coordinate, the tool coordinate T _H as viewed from the hand coordinate system Ask. That is, T _H = H _R ⁻¹ T
It is _R3 . (5) Save the tool coordinate system T _H viewed from the hand coordinate system before hand deformation. (6) Re-teaching the three points on the hand with the hand deformed. P _ORG-R = T _R1 'P _ORG-T P _XX-R = T _R2 ' P _XX-T P _XY-R = T _R3 'P _XY-T Where, T _R1 '… When teaching the ORG point after deformation Transformation matrix from the robot coordinates to the tool coordinates seen from T _R2 '... Transformation matrix from the robot coordinates seen from the robot coordinates when teaching the transformed XX points _TR3 ' ... Tools seen from the robot coordinates when teaching the transformed XY points Transformation matrix to coordinates

[0017] When viewed from the tool _{coordinate, P ORG-T = T R1} '-1 P ORG-R P XX-T = T R2' -1 P XX-R P XY-T = T R3 '-1 P XY- _{R ^{here, T R1 '-1, T R2}} ' -1, T R3 '-1 each _{T R1', T R2 ',} T R3' is an inverse matrix of.

Thereafter, as before the deformation, the coordinate system H _T 'of the hand is obtained on the tool coordinates from the three points on the hand defined on the tool coordinates.

(7) The hand coordinate H seen from the robot coordinate system from the tool coordinate (transform matrix) T _R3 'from the robot coordinate at the time of XY teaching and the hand coordinate (transform matrix) H _T ' from the tool coordinate. _{Ask for R} '. That is,
H _R '= T _R3 H _T '.

(8) From the stored reference data (tool coordinates T _H viewed from the hand coordinate system before hand deformation) and the hand coordinate data H _R 'viewed from the robot coordinate system created after the hand deformation occurs, the hand position on the imaginary robot coordinate to shift the control point after deformation occurred (conversion matrix) T _R3 "is obtained as follows (see FIG. 7). that is, T _R3" is a = _{H R} 'T H.

(9) The shift amount ΔT on the tool coordinate from the control point position after hand displacement (imaginary data obtained in the previous stage) to the actual control point position is calculated. That is, ΔT =
T _R3 " ^-1 T _R3 '.

[0022]

As described above, according to the present invention, even in the case where the working point (control point) of the robot is not at the tip of the jig like the hand mechanism, the jig of the robot is replaced. It is possible to obtain the correction amount to be added to the original teaching data by a simple work even if the amount of modification changes due to deformation or deformation. Therefore, since the same operation can be reproduced even after the jig is deformed, there is an effect that it is not necessary to teach again.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an apparatus for carrying out the present invention.

FIG. 2 is a diagram showing an example of teaching a pin position.

FIG. 3 is a diagram showing a teaching state of three points on a hand.

FIG. 4 is a diagram showing a positional relationship between tool coordinates and pins when three points on a hand are taught.

FIG. 5 is a diagram for explaining coordinate system conversion.

FIG. 6 is a diagram showing a coordinate system of a hand on tool coordinates.

FIG. 7 is a diagram showing a state in which the hand is deformed.

FIG. 8 is a diagram showing a relationship between a working point (control point) and a jig.

[Explanation of symbols]

 1 ... Robot 2 ... Hand 3 ... Robot control device 4 ... Pin ORG ... Origin for defining plane on jig XX ... Point for defining X-axis on jig XY ... To define XY plane on jig Point of

Claims (2)

[Claims] 1. In a robot control method for reproducing the operation of a robot on the basis of pre-stored robot teaching data, a pin having a jig of a known size and shape attached to the wrist of the robot and installed near the robot. The jig on the jig for positioning the jig at the tip position of the robot, teaching the tip position of the pin in the robot coordinate system, and determining the coordinate system on the jig attached to the wrist of the robot. By locating the points at the position of the tip of the pin,
The posture data is stored in advance in the storage device of the robot, and when the jig is deformed due to replacement of the jig or collision, the three points on the jig after the deformation are positioned at the positions of the tips of the pins. Thus, the position / orientation data is stored in advance in the storage device of the robot, and the jig is determined from the relative positional relationship between the coordinate system of the jig before deformation and the coordinate system of the jig after deformation, which are determined by the respective three points. A method for controlling a robot, characterized in that a correction amount of the robot motion after deformation of the robot is obtained. 2. The three points on the jig are an origin for defining a plane on the jig, a point for defining an X axis of the jig, and a point for defining an XY plane of the jig. The robot control method according to claim 1, wherein there are three points.