Boots – shoes – and leggings
Patent
1989-03-27
1990-12-18
Smith, Jerry
Boots, shoes, and leggings
36416701, 901 18, G05B 19415
Patent
active
049791273
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for automatically setting the point of operation of an end effector, i.e., a tool tip point (TCP), in an industrial robot.
2. Description of the Related Art
In mounting a tool on a tool mounting surface of a wrist portion, i.e., a faceplate, of a robot, the coordinate position of a tool tip point, in a faceplate coordinate system having its origin on the center point of the faceplate, must be set. When using a tool whose tip point position is unknown, therefore, such setting is conventionally effected by determining the coordinate position of the tool tip point on the basis of design drawings of the tool, and manually inputting numerical values indicative of the position into a control device of the robot.
However, the design drawings of the tool are often unavailable. In such a case, the coordinate position of the tool is conventionally set in the aforesaid manner after determining the position from actual measurements of various parts of the tool obtained by means of a measuring instrument. Actually measuring the tool, however, is troublesome and subject to substantial errors.
SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide a method for automatically setting a tool tip point, in which the position of the tool tip point in a faceplate coordinate system of a robot can be set easily and accurately, without requiring design drawings or a tool measurement by means of a measuring instrument.
In order to achieve the above object, a method according to the present invention comprises steps of: (a) causing a robot to assume at least four postures in a state such that the tip point of a tool is located on one point within a space in which the robot is installed, and instructing the robot of coordinate positions of the center point of a faceplate of the robot, in a base coordinate system set in the space, when the robot assumes the individual postures; (b) calculating the position of the center of curvature of a spherical surface passing through or near the individual coordinate positions thus given for instruction, on the basis of the coordinate positions; and (c) determining and setting the coordinate position of the tool tip point, in a faceplate coordinate system set for the faceplate, on the basis of posture vectors of the tool, the position of the center of curvature of the spherical surface thus calculated, and at least one coordinate position of the faceplate center point given for instruction in the step (a).
According to the present invention, as described above, the tool tip point is automatically set by only giving four or more points for instruction while changing the posture of the robot, in a state such that the tool tip point is located on the certain point within the robot installation space, so that the tool tip point can be set easily and with high accuracy, without requiring a manual input operation based on design drawings of the tool or actual measurements of the tool obtained by means of a measuring instrument.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of a tool on a robot arm for illustrating the principle of the present invention;
FIG. 2 is a diagram of a robot arm for illustrating the relationship between a base coordinate system and a faceplate coordinate system;
FIG. 3 is a block diagram of a robot to which is applied a method for automatically setting a tool tip point according to one embodiment of the present invention, and the principal part of a control circuit for controlling the robot;
FIG. 4 is an operational flow chart of an embodiment of the invention;
FIG. 5 is a diagram illustrating a method for approximating a sphere in accordance with various instruction points; and
FIG. 6 is a diagram illustrating a method for obtaining the vector of the center point of the sphere in the faceplate coordinate system at each instruction point.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring first to FIGS. 1 and 2, the principle of the
REFERENCES:
patent: 4698777 (1987-10-01), Toyoda et al.
patent: 4815006 (1989-03-01), Andersson et al.
patent: 4835710 (1989-05-01), Schnelle et al.
patent: 4853603 (1989-08-01), Onoue et al.
Hara Ryuichi
Mizuno Toru
Nishi Hiroji
Fanuc Ltd
Gordon Paul
Smith Jerry
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