Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Reexamination Certificate
2001-07-13
2003-01-21
Pyo, Kevin (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
C901S003000, C901S047000, C700S259000
Reexamination Certificate
active
06509576
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority of Korea patent Application No. 2000-57276, filed on Sep. 29, 2000.
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a method for compensating the position of a robot using a laser measuring instrument. More particularly, the present invention relates to a method for compensating the position of a robot in which a laser measuring instrument is used to simultaneously compensate for the positioning of a welding gun, a welding robot, various jigs, etc. such that a robot teaching process time is reduced and a precision of welding point teaching for a vehicle body panel robot is enhanced.
(b) Description of the Related Art
Computer simulations are commonly used in the design of assembly processes for automobiles. That is, using computer simulations, all the processes involved in manufacture-design, manufacture and installation of manufacturing processes and lines, and the operation of the processes can be modeled before actual application. Then by running the simulation, problems can be detected and rectified before actual implementation. Accordingly, the time to prepare for production is reduced, quality is enhanced and costs are minimized. In addition to these advantages, benefits are realized through the off-line programming capabilities of simulations.
However, since in the robot programs the modeling of the situations in which the robots are placed is based on CAD data with the use of simulations, exact replication of the true conditions is not possible. That is, there results a difference between the model and the actual situation such that direct application of the robots designed using the simulations is not possible. Accordingly, it is necessary to undergo a calibration process in which these differences in the programs written off-line (i.e., differences between the designed data and actual circumstances) is compensated for, after which the calibrated programs are downloaded to a robot controller.
Such calibration of the positions of a welding gun, welding robot, various jigs and other manufacturing machinery placed in a vehicle body assembly line is referred to as a robot position compensation method. The conventional robot position compensation method is divided into two sub-methods: a welding gun calibration method, in which the difference between CAD modeling data of a welding gun and information of an actual welding gun is compensated, and a layout calibration method, in which CAD modeling data of the positioning of robots and jigs and actual positioning of the robots and jigs is calibrated.
As an example of the welding gun calibration method, with reference to
FIGS. 3 and 4
, with a welding gun
53
mounted to an arm of a vehicle body panel welding robot
51
, six axis joints of which are driven by a servo motor (not shown), production errors of the welding gun
53
and attachment errors of the robot
51
are compensated. In more detail, a needle pin
55
, which has a sharp end and is made of steel, is first produced and is installed within a working radius of the robot
51
in step S
100
. Next, the user/operator teaches the robot
51
through a robot controller
61
such that that a lower tip
57
of the welding gun
53
is positioned at the end of the needle pin
55
in step S
110
.
Subsequently, in a state where the lower tip
57
of the welding gun
53
is positioned at the end of the needle pin
55
, a reference point is designated and teaching of the robot
51
of at least four postures is performed in step S
120
. Next, teaching program data corresponding to the four or more positions is transmitted to a main computer
59
in step S
130
. At this time, the four or more positions of the robot
51
do not merge at a single point (i.e., the reference point) in the robot teaching program as a result of robot position errors (backlash). Accordingly, possibly four or more reference points result.
Following the above, the main computer
59
runs the uploaded robot teaching program, then compensates the four or more reference points to a single point in step S
140
. Next, an error between CAD data of a distance from a first axis at an end of the lower tip
57
of the welding gun
53
to a second axis, which is a connecting portion of the welding gun
53
, and data modeled through a simulation is compared with a predetermined value. That is, in step S
150
, it is determined if the error between the CAD data and the simulation data is less than the predetermined value.
If the condition of step S
150
is satisfied, position compensation of the welding gun
53
is completed, then the robot teaching program is downloaded to the robot controller
61
in step S
160
. However, if the condition of step S
150
is not satisfied, welding gun data modeled through the simulation is revised in step S
170
, after which step S
160
is performed, thereby completing the welding gun calibration method.
An example of the layout calibration method will now be described with reference to
FIGS. 5 and 6
. In a state where a welding gun
53
is mounted to an arm of a vehicle body panel welding robot
51
, six axis joints which are driven by a servo motor (not shown), and jigs
65
, which include a clamp, locator and a tooling pin for controlling a vehicle body panel
63
, are installed according to car assembly line coordinates, errors in the positioning of the robot
51
and the jigs
65
are compensated. This will be described in more detail below.
First, a distance T
1
is measured using a tape measure to determine a position of the robot
51
and a distance T
2
is determined from a robot product drawing, after which a robot position is calculated in step S
200
. Next, a dowel pin
67
, which is made of steel and has a sharp end is inserted in a NC hole to connect one jig
65
to another, is manufactured and installed in one of the jigs in step S
210
. The user/operator then teaches the robot
51
through a robot controller
61
such that that a lower tip
57
of the welding gun
53
is positioned at the end of the dowel pin
67
. In this state, a reference point is designated and teaching of the robot
51
to at least four postures is performed in step S
220
.
Following the above, teaching program data corresponding to the four or more positions is transmitted to a main computer
59
in step S
230
. The main computer
59
then runs the uploaded robot teaching program, and considering the four or more reference points that do not merge at a single point, makes a comparison of data modeled through simulation such that robot position data are compensated to correspond to actual positions in step S
240
. Next, after position compensation of the welding gun
53
is completed, the robot teaching program is downloaded to the robot controller
61
in step S
250
, thereby concluding the layout calibration method.
However, in the conventional robot position compensation method as described above, manufacturing time is increased as a result of the method being divided into two sub-methods that are separately performed, that is the welding gun calibration method, in which the difference between CAD modeling data of the welding gun and information of the actual welding gun is compensated, and the layout calibration method, in which CAD modeling data of the positioning of robots and jigs and actual positioning of the robots and jigs is calibrated. Also, errors are common in the actual measuring of the robot position such that a second compensation procedure performed through operator teaching is required.
SUMMARY OF THE INVENTION
The present invention has been made in an effort to solve the above problems.
It is an object of the present invention to provide a method for compensating the position of a robot in which a laser measuring instrument is used to simultaneously compensate for the positioning of a welding gun, a welding robot, various jigs, etc. such that a robot teaching process time is reduced and a precision of welding point teaching for a vehicle body panel robot is enhanced.
T
Christie Parker & Hale LLP
Hyundai Motor Company
Meyer David C.
Pyo Kevin
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