Patent
1993-03-18
1994-11-08
MacDonald, Allen R.
395 95, G06F 1500
Patent
active
053634748
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION:
The present invention relates to a direct teaching type industrial robot.
DESCRIPTION OF RELATED ART
A typical industrial robot is a teaching regenerative type robot to which a series of operations is taught by guiding the main body (manipulator) of the robot to a target position to cause it to memorize such position, and as methods for guiding the main body of such robot, there are a method of guiding indirectly by control buttons and a joystick and a direct teaching method of guiding directly by an operator by directly leading the forward end of a hand of the main body of the robot manually.
By the way, in the prior art examples of the direct teaching type robot, the robot is guided by an external force by restricting a current for a drive motor as described in Japanese Patent Laid-open Nos. 63-57185 and 63-57186.
Further, as a method for correctly measuring a force applied to the forward end of the hand of the robot, a method of eliminating a drift (offset) of a force sensor is known as described in Japanese Patent Laid-open Nos. 62-114891 and 62-114892.
In the prior art examples described above, however, no consideration is given as to how to deal with an erroneous operation of the operator and accordingly, there exists a problem that when a large robot is erroneously guided in the direction of gravity and the like, the motion of the robot exceeds and reaches to an unexpected position, causing a very dangerous situation.
Furthermore, when a force applied to the forward end of the hand is to be directly detected by a force sensor, an offset of the force sensor has to be adequately removed. In the prior art examples however, no consideration is given to such timing, causing a problem that a large burden is imposed on the operator.
Accordingly, it is an object of the present invention to provide a system for controlling a robot, which allows direct teaching safely all the time.
SUMMARY OF THE INVENTION
In order to achieve the aforementioned object, the system is provided with means for monitoring a magnitude of an external force applied to the forward end of a hand during direct teaching, so that the motion of the robot can be forcibly restricted when the external force reaches a predetermined value of thereabove.
Furthermore, when the system is operated to be set in a direct teach mode, a process for correcting the offset of the force sensor is performed automatically.
The force sensor is mounted at the forward end of the hand of the robot to detect an external force all the time. By monitoring a force detected by the force sensor, the discrimination is made as to whether an external force to operate the robot at an abnormal speed is applied to the robot or not, and when the external force becomes greater than a reference value, a mode of prohibiting the operation of the robot by the external force (position control mode) is set, or current supplied to a servo motor is cut off to prevent the robot from going into the erroneous operation due to an erroneous control.
The direct teach may be realized by simple operations by adapting a key for specifying the direct teach mode to perform each individual processing at a moment when its switch is pressed, during being pressed down and at a moment when it is released.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a flowchart illustrating a direct teach processing according to one embodiment of the present invention;
FIG. 2 is a flowchart illustrating a processing of direct teach state;
FIG. 3 is a schematic drawing illustrating a structure of the whole system of one embodiment of the present invention;
FIG. 4 is a block diagram illustrating an internal hardware of the unit (1) in FIG. 3;
FIG. 5 is a block diagram illustrating an internal hardware of the unit (8) in FIG. 3;
FIG. 6 is a flowchart of a communication interrupt processing; and
FIG. 7 is a flowchart of a timer interrupt processing.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, preferred embodiments of the system for controlling an i
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Andoh Takeshi
Kawasaki Kyoichi
Kurenuma Toru
Otomo Masami
Sarugaku Shinichi
Hitachi Construction Machinery Co. Ltd.
MacDonald Allen R.
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