Robots – Counterbalance
Patent
1991-04-15
1993-06-22
MacDonald, Allen R.
Robots
Counterbalance
395 89, 901 3, G05B 1918
Patent
active
052221997
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a motion control method for the teaching operation of a six-axis articulated robot.
BACKGROUND OF THE INVENTION
A conventional teaching operation is shown in FIG. 1. As shown, a teaching operation of a six-axis articulated robot, one of the following motion controls is carried out when the orientation of a workpiece 4 clamped is a tool (not shown) at each wrist flange of the robot as shown in FIG. 1(a) is changed to a desired relative orientation as shown in FIG. 1(c) with respect to an arbitrary working point A of a teaching operation tool 3:
(1) Each axis of the robot is controlled independently of the others, whereby a desired workpiece orientation is determined.
(2) A desired workpiece orientation is determined by the rotation around a reference coordinate axis on the main body of a robot and parallel displacement to the reference coordinate axis. (FIG. 1(b) and 1(c)).
(3) A desired workpiece orientation is determined by the rotation around the tool coordinate axis on the main body of the robot and parallel displacement to the tool coordinate axis. (FIGS. 1(b) and 1(c)).
The rotations described in (2) and (3) accomplish motion control by rotating around a control point R of a robot.
In method (2), the reference coordinate axes are defined by the reference coordinate axes (X.sub.R, Y.sub.R and Z.sub.R) which, in turn, define the coordinate system of the robot. In method (3), the tool coordinate axes refer to coordinates of a tool attached to the wrist flange of the robot.
However, according to the above-described methods, the workpiece 4 clamped by the robot assumes the desired orientation with respect to an arbitrary working point A by a method involving the control of each axis of the robot independently and the rotation of the workpiece around a coordinate axis with the control point R of the robot as the center of rotation with this method. The orientation of the workpiece 4 along cannot be changed without changing the position of the point P on the workpiece 4, meaning that the rotation and the parallel displacement must be repeatedly carried out, as shown in FIG. 1, resulting in a longer reaching operation time.
SUMMARY OF THE INVENTION
In view of the above, the primary object of the present invention is to attain a relative orientation between the workpiece 4 clamped by the robot and an arbitrary working point A without displacing the position of the point P as shown in FIG. 2.
For this purpose, the robot control method in accordance with the present invention is characterized by defining, through the reference coordinate system of the robot, an arbitrary working point A, and subsequently accomplishing the teaching operation of the workpiece 4 clamped or otherwise held by the robot with respect to the arbitrary working point, by controlling said arbitrary point A as viewed temporarily an end effector from a robot control point, and rotating the workpiece 4 about the working point, whereby the orientation of the workpiece relative to the working point A can be arbitrarily changed.
According to the present invention, the orientation of the workpiece clamped by the robot with respect to an arbitrary working point can be quickly changed to a desired orientation, thereby greatly shortening the teaching operation time.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a view used to explain some conventional teaching operations;
FIG. 2 is a view used to explain a teaching operation in accordance with the present invention;
FIG. 3 and 4 are views used to explain the definition of an arbitrary working point;
FIG. 5 is a vector diagram illustrating the relationship between a robot control point and an arbitrary working point;
FIG. 6 is a view illustrating the outside appearance of a six-axis articulated robot;
FIG. 7 is a view illustrating the projection over the Xo-Yo plane of the fixed coordinate system of a robot;
FIG. 8 is a view illustrating the projection over the Mo-Zo plane of a robot;
FIG. 9 is a block view illustrating the construction of a
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Minami Yoshikatsu
Tanaka Masato
Kabushiki Kaisha Yaskawa Denki Seisakusho
MacDonald Allen R.
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