Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1992-08-24
1995-05-23
Shoop, Jr., William M.
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318646, G06F 1546
Patent
active
054184410
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a deflection correcting method for a robot, in which the deviation between commanded and actual endpoint positions caused by deflection of the robot is determined, and command values for individual axes are corrected on the basis of thus determined deviation, whereby the robot endpoint position is controlled to a desired position.
2. Description of the Related Art
Recently, robots have been utilized in various industrial fields, and there is an increasing demand for higher accuracy of the robot.
However, the robot endpoint position or robot hand position tends to be displaced due to the presence of deflection caused by robot's own weight and load on the endpoint, backlash in a reduction gear, or the like. In the case of a teaching/playback method, however, no such problem will be encountered because the robot can be played back to a taught position and configuration. More particularly, when teaching a position and orientation to the robot, the teaching is made including the displacement of the endpoint position caused by the above deflection, backlash, or the like, so that the robot can be exactly controlled to the thus taught position and configuration during the playback operation of the robot. However, in case that a robot is operated in accordance with an operation program prepared off-line without using the robot, to which the program is to be applied actually, the deviation occurs between the robot endpoint position commanded by the operation program and the actual robot endpoint position due to the aforementioned deflection, backlash or the like, thereby causing the endpoint position displacement. When the endpoint position is displaced, the robot cannot recognize its own accurate endpoint position, and therefore, positional accuracy of the robot will be affected adversely. Thus, the displacement of the robot endpoint position caused by such deflection, etc. must be corrected in a suitable manner compared with a command value.
Conventionally known as a correcting method is a method for correcting the displacement in accordance with load acting on the endpoint, for instance. However, according to this correcting method in which the configuration of a robot is not considered, merely a fixed amount of correction is provided irrespective of the configuration of the robot. Therefore, depending on the robot configuration, an appropriate correction value cannot be provided, thereby resulting in a failure in achieving accurate correction.
Also known is a method in which the displacement of a link is determined using an analytical technique based on strength of materials or a finite-element method to correct the displacement of the endpoint. However, this method is not only time-consuming but also costly in calculating the displacement.
The conventional correcting methods have such problems, and thus it is difficult to have a robot recognize the accurate position of its endpoint which actually in a deflected state.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a deflection correction method for a robot, which is capable of easily determining displacement, caused by deflection, etc., of a robot endpoint from deflection angles of individual axes, as well as capable of simply and accurately correcting the displacement in accordance with the configuration of the robot, in a case where a robot operation program is prepared off-line, and the robot is operated according to this program.
Another object of the present invention is to provide a deflection recognizing method for a robot, which is capable of making a robot easily recognize an accurate position of a deflected robot endpoint or hand of the robot.
To achieve the above objects, in a deflection correcting method for correcting deflection of a robot, the present invention provides a deflection correcting method for a robot which comprises the steps of: determining joint torques acting on individual axes of the robot; determining deflection an
REFERENCES:
patent: 4143923 (1981-01-01), Whitney et al.
patent: 4530062 (1985-07-01), Inaba et al.
patent: 4874997 (1989-10-01), Daggett et al.
patent: 4894788 (1990-01-01), Stelzer
patent: 5047700 (1991-09-01), Szakaly
patent: 5049797 (1991-09-01), Phillips
patent: 5053973 (1991-10-01), Fujii et al.
patent: 5189351 (1993-02-01), Torii et al.
patent: 5206930 (1993-04-01), Ishikawa et al.
patent: 5263113 (1993-11-01), Naitoh et al.
Proceedings of the 1988 IEEE International Conference on Robotics and Automation, "Deflection Prediction for Serial Manipulators", vol. 1, pp. 482-487, 1988.
Fanuc Ltd.
Shoop Jr. William M.
Sircus Brian
LandOfFree
Deflection correcting method for a robot does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Deflection correcting method for a robot, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Deflection correcting method for a robot will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2142215