Method of teaching an operation program to a line robot wherein a master robot positioned at a location remote from said line robot is first taught the program

An off-line teaching method for an industrial robot wherein a master robot, separate from a line robot, placed in an actual operation line, and a model work similar to the line work processed in the operation line are prepared. Four predetermined points which are not in the same plane are obtained on each of the works, and are taught to the line and master robots in the same order to obtain a reciprocal transformation matrix. The transformation matrix is used to automatically transform an operation program taught to the master robot into an operation program for the line robot.

BACKGROUND OF THE INVENTION 
This invention relates to a method of teaching an operation to an 
industrial robot, and more particularly to an off-line teaching method for 
an industrial robot in which teaching is conducted not to a robot in the 
actual operating line but to a master robot placed off the line and the 
operation program thereby prepared is utilized as such for the robot in 
the line. 
Conventionally, in the playback system industrial robots, instruction as to 
the desired operation, namely teaching, is conducted either by a remote 
teaching method using a teaching pendant or a joy stick, or by a direct 
teaching method in which the arms of a robot are actually held for the 
teaching thereof. These methods are the same in that the operations are 
taught to robots used in the actual operating line, so that the normal 
operation of the robots must be interrputed for teaching. This system may 
not cause a problem when the robots are first installed in the line, but 
when work is to be changed it imposes a heavy burden on the teaching 
operation especially under the pressure of time. For instance, when new 
work is to be processed during the next month in place of the present 
work, it is sometimes necessary to set aside at the end of the previous 
month an entire night for teaching the robot. 
SUMMARY OF THE INVENTION 
According to the invention there is provided an off-line teaching method 
for an industrial robot comprising the steps of: preparing a master robot 
separate from a line robot placed in an actual operating line and a model 
work similar to the line work processed in the operating line; previously 
determining, on each of the line and model works, four points which are 
not in the same plane; teaching the line and master robots the respective 
four points in the same order to obtain a reciprocal transformation 
matrix; teaching an operation program to the master robot by using the 
model work; and automatically transforming the operation program taught to 
the master robot into an operation program for the line robot by using the 
reciprocal transformation matrix. Thus, in teaching, a robot working in an 
actual operation line is not used but instead a master robot off the line 
is used, so that the above problems are solved. Besides, this enables 
operation programs for several tens of line robots to be produced by using 
one master robot.

DETAILED DESCRIPTION OF THE PREFERRRED EMBODIMENT 
This invention will be described with reference to the accompanying 
drawings. 
Referring to FIG. 1, a line robot (1) is placed in an actual operating line 
and a line work (2) is placed near the line robot (1) to be processed in 
the line. A coordinate system having coordinate axes (x, y, z) is assumed 
on the line robot. A tool (3) is attached to the end of an arm (4) of the 
robot (1). 
Referring to FIG. 2, a master robot (11) exclusively used for teaching is 
placed in another room. A master work (22) similar to the line work is 
disposed near the master robot (11) as in FIG. 1. Further, a coordinate 
system having coordinate axes (X, Y, Z) is assumed on the master robot 
(11) as is the case with the line robot (1). A model tool (33) is attached 
to the end of an arm (44) of the master robot (11). 
Now, the positions (P) of the ends of tools (3) and (33) are represented 
with vectors such as P (x, y, z) and P (X, Y, Z), respectively. Since the 
line work (2) and the master work (22) are completely similar, four points 
which are not in the same plane are previously determined on each of the 
works and they are considered as reference positions (A, B, C, D) and (A', 
B', C', D'), respectively. At this time, the point A is represented as 
vector P.sub.A (x.sub.A, y.sub.A, z.sub.A), and the other points also 
represented similarly. 
Next, by processing in accordance with the flowchart shown in FIG. 3, the 
operation programs of P.sub.1, P.sub.2, P.sub.3, . . . which have been 
taught to the master robot (11) can be automatically transformed into 
those for the line robot, simply with the four point teaching applied to 
the line robot (1). 
This will be explained in more detail in accordance with the flowchart. In 
the first step, the predetermined four points (A, B, C, D) are first 
taught to the line robot (1) in that order to obtain the following data: 
##EQU1## 
In the second step, the predetermined four points (A', B', C', D') are 
taught to the master robot (11) in that order to obtain the following 
data: 
##EQU2## 
Further, in the third step, a transformation matrix M is obtained from the 
two four-point programs. A transformation matrix in three dimension space 
is expressed as a three row and four column matrix, providing that 
rotation, parallel displacement, symmetry, extension and diminution are 
considered. Thus, is defined as follows: 
##EQU3## 
(d means being defined as, and m.sub.ij is a component of i row and j 
column.) 
In the above definition, m.sub.11 .about.m.sub.13, m.sub.21 .about.m.sub.23 
and m.sub.31 .about.m.sub.33 are related to rotation, symmetry, extension 
and diminution, respectively, and m.sub.14, m.sub.24 and m.sub.34 
represent parallel displacement. 
Each component of matrix is determined to obtain a transformation matrix. 
First, considering that .sub.A is transformed into .sub.A ', the 
following formula is obtained: 
##EQU4## 
(Here, 1 is a constant in consideration of parallel displacement.) 
Similarly, considering the relation between .sub.8 and .sub.B ', .sub.C 
and .sub.C ' and .sub.D and .sub.D ', the following formulae are 
obtained. 
##EQU5## 
Each of the formulae (1), (2), (3) and (4) consists of three linear 
equations with twelve (12) unknowns, and synthesis of the formulae (1), 
(2), (3) and (4) forms a system of twelve linear equations with twelve 
(12) unknowns. 
By solving this, matrix is determined. The necessary and sufficient 
condition for solving this linear equation system is that the four points 
are not on the same plane. 
Next, in the fourth step, an operation program is taught to the master 
robot (11) in the order of points 1, 2, 3, 4 . . . to produce .sub.i 
(x.sub.i, y.sub.i, z.sub.i) where i=1, 2, 3, 4 . . . . 
Finally, using the transformation matrix, this program is transformed into 
a program for the line robot (1) so that .sub.j (x.sub.j, y.sub.j, 
z.sub.j)= .multidot. .sub.i is obtained. 
This invention has many advantageous features as will be described in the 
following; Since, in teaching, a robot working in an actual operating line 
is not used but instead a master robot off the line is used, a mere copy 
of a program is sufficient for a change of program, and the period of 
suspension of a line robot which was heretofore 1 to 10 hours is shortened 
to less than a tenth, or several minutes, for example. Furthermore, since 
the master robot can be placed in a stable position, a safe teaching 
operation is ensured. In addition, using one master robot, an operation 
program for each of several tens of robots can be produced, and it is even 
possible to form a program for a robot of a different axis system and a 
different size.