Data processing: generic control systems or specific application – Specific application – apparatus or process – Robot control
Reexamination Certificate
1998-05-28
2001-02-20
Gordon, Paul P. (Department: 2786)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Robot control
C700S254000, C901S042000, C318S568160
Reexamination Certificate
active
06192298
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a correcting method, and in particular to a method of correcting a shift of a working position of a working tool for use in a robot manipulation system.
2. Description of the Prior Art
In a conventional method of correcting a shift in positioning of a working tool in a robot manipulation system, there has been suggested a method of correcting a shift of bead in alignment in the disclosure of e.g. Japanese Paten Laid Open Unexamined Publication 1-257593.
In this robot mechanical arrangement, the following briefly describes an example of a conventional correcting method for correcting a shift of a position of a working tool for a robot manipulator system. In the conventional method, as shown in
FIGS. 5 and 6
, in order to adjust a working point of a working tool of a robot, a contact piece member provided on the working tool is brought into contact with a specified jig. Then, an error between the working point of the working tool and a reference working point determined in control programming of the robot is calculated for use as an offset amount according to data of the contact positions, thereby eliminating troublesome problems in calculating the offset amount.
In the method as shown in
FIGS. 5 and 6
, it is noted that, in the case where a subject work for a robot is a welding operation, a welding torch
58
is used as a working tool which is fitted to the robot main body. A welding wire
58
b
serving as a kind of contact piece is provided on the welding torch
58
and a tip portion
58
a
of the welding wire is brought into contact with a specified jig
59
. The jig
59
has three conductive plates (
59
a
,
59
b
,
59
c
) installed generally in a three-dimensional relationship to each other within the operating range of the robot, so that the tip
58
a
of the welding wire is moved in three dimensional directions P
0
-P
1
, P
0
-P
2
, and P
0
-P
3
to be brought into contact with each of the three conductive plates
59
a
through
59
c.
The position data at a timing of detecting the contact between the tip
58
a
of the welding wire
58
b
and each of the three conductive plates of the jig
59
is stored in a storage portion of a robot controller
60
. The detection of the contact is electrically performed by applying a voltage between the welding torch
58
and the jig
59
by a voltage applying unit (not shown). Then, a difference between the position data of the preceding contact position and the position data of the present contact position is calculated by an arithmetic method to thereby compute an error between the position of the tip
58
a
of the welding wire and the reference point determined in control programming of the robot. The obtained error is stored as an offset amount, and the position of the welding torch
58
is shifted in a direction of absorbing the offset amount. Thus, the tip position of the welding wire is aligned with the reference point determined in control programming of the robot to thereby correct a shift of bead caused in a welding work and the like.
In this conventional method, there has been employed a step of detecting an electrical contact between the contact piece of the welding torch and the three jig plates in three dimensional directions different from each other. However, in the conventional methods, there has been a problematic case such that a working tool per se can not be directly used as a contact piece member, for example, in the case where a non-conductive or electrically insulating member is used as a working tool in the robot manipulation for such as laser sealing, bonding material and the like.
In such a problematic case, it is necessary to further provided an additional detecting unit for detecting an electrical contact such as e.g. a limit switch which detects an electrical contact when a working tool is moved to a predetermined position. Since the detection of the electrical contact with the three conductive plates must be carried out in the three different directions in the conventional method, therefore three contact detecting units are further required for detecting the contacts with the three conductive plates, respectively, which increases the cost of the robot system, undesirably making the construction thereof more complex.
SUMMARY OF THE INVENTION
The present invention has been developed with a view to substantially solving the above described disadvantages. Accordingly, an essential objective of the present invention is therefore to provide a noble correcting method for correcting a shift of bead to adjust a working point of a working tool in a robot control system with a low cost and simple construction.
In order to achieve the above objective, according to as aspect of the present invention, a shift correcting method of correcting a shift of a tool working position in a robot manipulation system, comprises the steps of:
rotating a working tool around a tool longitudinal axis as a rotating center axis on a tool coordinate system to change a posture of the tool;
moving the working tool in one direction toward a specified part of a contact detecting member to be brought into contact therewith to detect a contact between the working tool and the contact detecting member;
storing data of the detected contact positions;
calculating an actual tool working position from the stored position data to obtain a difference as a shift amount between the actual tool working position and a theoretical tool working position previously obtained by a robot control program; and
storing the calculated shift amount for use as a correcting amount for correcting a shift in the following robot manipulating operation.
The method further comprises the steps of repeating the entire steps as recited above in common before and after a shift of the tool working position is caused to thereby obtain the difference between the calculated shift amounts before and after the shift is caused, wherein the obtained difference is used as a practical correcting amount in the following robot manipulating operation.
By the method of the present invention, by repeating the rotating operations around the tool longitudinal axis on the tool coordinate system together with executing the contact sensing operations in one direction toward the contact face of the contact detecting unit, the practical correcting amount can be obtained for correcting the relative shift amount between the tool working positions before and after subject to a shift. Thus, the mechanical construction of the robot manipulator system can be remarkably simplified with a lower cost.
REFERENCES:
patent: 4014495 (1977-03-01), Oda et al.
patent: 4229641 (1980-10-01), Ihara
patent: 4448342 (1984-05-01), Abe et al.
patent: 4629860 (1986-12-01), Lindbom
patent: 4700118 (1987-10-01), Kishi et al.
patent: 4706000 (1987-11-01), Kishi et al.
patent: 4794547 (1988-12-01), Nishida
patent: 4816733 (1989-03-01), Sakakibara et al.
patent: 4899095 (1990-02-01), Kishi et al.
patent: 5911892 (1999-06-01), Kosaka et al.
patent: 5929584 (1999-07-01), Bunnarsson et al.
patent: 5932122 (1999-08-01), Hong
patent: 1257593 (1989-10-01), None
An English Language abstract of JP 1-257593.
Gain, Jr. Edward F.
Gordon Paul P.
Greenblum & Bernstein P.L.C.
Matsushita Electric - Industrial Co., Ltd.
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