Electricity: motive power systems – Motor-reversing – Armature or primary circuit control
Patent
1997-03-28
1999-02-16
Elmore, Reba I.
Electricity: motive power systems
Motor-reversing
Armature or primary circuit control
395 80, 395 88, 31856812, 31856813, 31856815, 318573, G05B 1904, G05B 1941, G05B 1925, B25J 922
Patent
active
058728945
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a control method for an industrial robot, and more particularly to a method of controlling a robot so that an approaching path to a designated taught point is coincident with a path designated in an operation program. The method of the present invention is applicable to a robot for use in handling and assembling a workpiece.
BACKGROUND ART
In moving a robot by a playback operation, an acceleration/deceleration control is performed for individual taught points in accordance with a positioning ratio designated in a motion statement in an operation program. Generally, it is advantageous to designate a lower positioning ratio for saving time for acceleration/deceleration to reduce a cycle time. Consequently, it has been a common practice to designate a lower positioning ratio for a taught point which does not require a high degree of positioning accuracy.
However, in a robot for performing an assembling operation by handling a workpiece, for example, if the lower positioning ratio is designated even for the taught point which does not require a high degree of positioning accuracy, there is a problem in operation reliability. FIGS. 1 and 2 show a typical case having such problem.
FIG. 1 shows a moving path in assembling a workpiece 3 by fitting it to another workpiece 4 by gripping the workpiece 3 by a hand 2 attached to a robot arm end 1. FIG. 2 is a chart showing the content of a path motion plan in which a smooth motion of 100% (a positioning ratio of 0%) is time t and an axis of ordinate representing speed V. whose position is predetermined with respect to the hand 2 of the robot, and a straight motion is designated for each of the path sections completed, a positioning of 100% is necessarily designated in the motion the direction of the movement is changed from horizontal to vertical, it is advantageous to designate "100% smooth", i.e. a positioning ratio of 0% time. forms a corner. Namely, as indicated by reference numeral 5, the robot is created so that a motion EFGH (instruction speed V23) for the path (a point C of time) of a deceleration control movement contained in a X-axis direction, as shown in FIG. 2. This means that a part (from the point C to the point D) of the motion for the preceding path section operation is not performed smoothly. In general, this tendency would be more remarkable when the command speed V12 for the path section
In order to avoid the foregoing problems, it has been a common practice to make a try-and-error adjustment operation including (1) lowering the
SUMMARY OF THE INVENTION
It is an object of the present invention to eliminate any influence of motion for the preceding path section from an intermediate point to an end point on a designated path section, so that an actual moving path of the robot is coincident with an intended path. Another object of the invention is to reduce the operator's labor involved in adjusting the teaching contents on a try-and-error basis and to eliminate any loss of the cycle time.
In the following description, "path-assurance" is referred to as assuring that an approaching path to an end point of a path section is not deflected from the taught path, and "path-assurance section" is referred to as a section where the path-assurance is performed (from the intermediate point to the end point on the path section).
According to the present invention, a path-assurance section is designated in a motion statement for a desired path section and a path motion plan is created based on the motion statement in a robot control system so that a motion for a preceding path section is completed when the robot reaches a start point of the path-assurance section (an intermediate point set between a start point and an end point of the path section).
The path-assurance section in the motion statement can be designated by (1) expressing the position of the intermediate point by a spacial length of the path-assurance section; (2) expressing the position of the intermediate point by a ratio of the path-assurance
REFERENCES:
patent: 4675502 (1987-06-01), Haefner et al.
patent: 4685067 (1987-08-01), French et al.
patent: 5144211 (1992-09-01), Daggett et al.
patent: 5467003 (1995-11-01), Kosaka et al.
Sakamoto Shinsuke
Terada Tomoyuki
Watanabe Atsushi
Elmore Reba I.
Fanuc Ltd.
Natnithithadha Navin
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