Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1993-05-24
1995-09-19
Ro, Bentsu
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318632, B25J 900
Patent
active
054518504
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of correcting a tool center point, which corrects a position of the tool center point of a robot, and in particular, to a method which corrects a change amount of the tool center point caused by consumption, wear or the like, thus accurately controlling the position of the tool center point.
BACKGROUND ART
Tools attached to a robot are consumed or worn by different using modes. For example, in the case of a spot welding robot, a welding gun is used as a tool, but the gun tip is consumed in accordance with the number of robot's works. In this case, a position of a TCP (Tool Center Point) is changed by the consumption of the tip, so that the robot is required to correct the changed position to perform the welding operation. For this reason, a spring mechanism for correcting the change is ordinarily located in a mechanical section of the welding gun.
Further, for example, in the case of a grinding robot, a grinder is used as a tool, but the grinder attached to the robot is worn in accordance with the working time when grinding the workpiece surface. In this case, there is also a need of correcting the changed position of the TCP, for this reason, a spring mechanism for pressing the grinder against the workpiece must be attached to the grinder likewise.
However, the spring mechanisms as mentioned above causes problems such as of making the welding gun or grinder heavy and the cost higher. In addition, in the case of the grinding robot, there is a limit of pressing force by the spring mechanism, so that the grinder must be exchanged when exceeding the limit. This increases the frequency of the grinder change.
Furthermore, in the case of the grinding robot, in order to allow the robot to perform suitable grinding operations in accordance with the consumption of the grinder, it is required to prepare a plurality of robot manipulation programs in addition to the spring mechanism. For this reason, it is troublesome and difficult to handle and control the robot manipulation programs.
DISCLOSURE OF THE INVENTION
The present invention has been made in view of the above problems. Therefore, an object of the present invention is to provide a method of correcting a position of a tool center point, which is capable of designing lightweight and inexpensive tools such as a welding gun, grinder or the like.
Another object of the present invention is to provide a method of correcting a position of a tool center point, which is capable of readily handling and controlling robot manipulation programs.
To achieve the above problems, in the present invention, there is provided a method of correcting a position of a tool center point, which corrects the position of the tool center point of the robot, comprising the steps of: previously storing in memory the relationship between the working time of the robot and a change amount of the tool center point of the robot, accumulating the working time, determining the change amount of the tool center point corresponding to the accumulated working time, when the tool center point is aligned with a moving target position, correcting the moving target position of the tool center point on the basis of the determined change amount of the tool center point, and moving the tool center point to the corrected moving target position.
Data indicating the relationship between the working time and the change amount of the tool center point of the robot are previously stored in memory. Further, the time when the robot is working is accumulated. Then, when the tool center point is moved to the moving target position, the change amount of the tool center point corresponding to the accumulated working time is determined on the basis of the data stored in the memory. The moving target position of the tool center point is corrected on the basis of the determined changed amount of the tool center point. Thus, the tool center point is moved to the corrected moving target position. Accordingly, even though the position of the tool center point is
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Fanuc Ltd.
Ro Bentsu
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