Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1991-09-23
1993-02-16
Ip, Paul
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318567, 901 3, 901 15, 395 86, G05B 1918, G05B 19415, B25J 910
Patent
active
051874180
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of controlling an articulated robot having redundancy.
BACKGROUND ART
Recently, industrial robots are required to make more flexible movement to copy with more complex jobs, and tend to have an increased number of control axes that can be controlled simultaneously. Generally, the necessary and sufficient conditions that a robot has to meet in order to reach a desired wrist position and a desired wrist posture are that the robot have six axes. However, recent applications demand for industrial robots having redundancy which have in excess of six axes.
In order for a robot wrist to make interpolated motion, the position and posture of the robot wrist on a certain path have to be controlled by the rotational angles of the respective articulations of the robot. However, since the robots having redundancy which have in excess of six axes require an enormous amount of calculations, it is difficult to process data on a real-time basis during robot operation, and such robots have not been put to practical use.
As one solution to the above problems, there has heretofore been proposed a control method for determining the rotational angle of a fourth axis so that the sum of or the difference between the cosine of the rotational angle of a second axis and the cosine of the rotational angle of a sixth axis will take an extreme value in a seven-axis robot, as disclosed in Japanese Patent Laid-Open No. 64-42704 (or No. 42704/89). Japanese Patent Laid-Open No. 64-16389 (or No. 16389/89) discloses a method of controlling the position and posture of a robot wrist through the reconstruction of a virtual six-axis robot with redundancy axes fixed.
The conventional control methods are, however, limited to a seven-axis robot or require a robot to be controlled as a virtual six-axis robot. As the redundancy axes are temporarily stopped, not all axes are controlled simultaneously, and the robot is not controlled for flexible movement.
DISCLOSURE OF THE INVENTION
In view of the aforesaid drawbacks, it is an object of the present invention to provide a method of controlling an articulated robot so that all axes of the robot can be controlled simultaneously.
According to the present invention, a method of controlling an articulated robot having in excess of six axes and up to twelve axes, comprises the steps of dividing the axes into two groups each composed of six axes or less, those axes which are positioned on one side of a dividing point closely to a reference point serving as redundancy axes, those axes which are positioned on the other side of the dividing point closely to a robot wrist as basic axes and controlling the dividing point, as a first control point, by way of interpolation, and controlling the robot wrist, as a second control point, by way of interpolation with the controlled first control point regarded as a new reference point.
The axes ranging from the reference point to the first control point comprise six axes or less, and the axes ranging from the first control point to the second control point also comprise six axes or less. The first control point is controlled by way of interpolation, and the second control point is controlled by way of interpolation with reference to the first control point that has been controlled by way of interpolation, each interpolation is controlled according to the conventional control method.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing an apparatus to carry out a method of controlling an articulated robot according to the present invention;
FIG. 2 is a diagram showing first and second control points;
FIG. 3 is a diagram showing FIG. 2 in detail; and FIG. 4 is a diagram showing the control method according to the invention.
BEST MODE FOR CARRYING OUT THE INVENTION
According to the present invention, it is assumed that, as shown in FIGS. 2 and 3, a total of twelve axes are divided into two groups each composed of six axes, and a control point P as a first control point for redundancy axes 1
REFERENCES:
patent: 4408286 (1983-10-01), Kikuchi et al.
patent: 4488242 (1984-12-01), Tabata et al.
patent: 4529921 (1985-07-01), Moribe
patent: 4550383 (1985-10-01), Sugimoto
patent: 4594670 (1986-06-01), Itoh
patent: 4604716 (1986-08-01), Kato et al.
patent: 4665352 (1987-05-01), Bartelt et al.
patent: 4680519 (1987-07-01), Chand et al.
patent: 4705451 (1987-11-01), Mori et al.
patent: 4710884 (1987-12-01), Tokairin et al.
patent: 4712183 (1987-12-01), Shiroshita et al.
patent: 4823279 (1989-04-01), Perzley et al.
patent: 4894788 (1990-01-01), Stelzer
patent: 4967126 (1990-10-01), Gretz et al.
patent: 4970370 (1990-11-01), Hara
patent: 5065337 (1991-11-01), Hara
Minami Yoshikatsu
Tanaka Masato
Ip Paul
Kabushiki Kaisha Yaskawa Denki Seisakusho
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