Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1988-11-15
1990-02-27
Shoop, Jr., William M.
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318434, 318567, 318569, 318571, 364513, 901 9, B25J 1906
Patent
active
049049119
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a system for controlling a robot in which a control is carried out based on a detection of a force along the Z-axis of the robot. The device according to the present invention may be used in an industrial robot for carrying out, for example, an assembling job.
BACKGROUND ART
In general, when an industrial robot having a linked structure composed of a rotatable arm portion, a vertically movable shaft portion, and related devices is used to fix a worked article (workpiece) to an object article, it is possible that a related motion of a workpiece will deviate from a normal condition, for some reason, and an abnormal situation such as a collision of the workpiece with the object article occurs. Such an abnormality causes a failure of the robot and hinders the progress of the robot operation, and accordingly, effective measures are sought to minimize such problems and thus facilitate a smooth progress of the robot operation, although such appropriate measures have not yet been obtained.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide an improved system for controlling a robot in which a control is carried out based on a detection of a force along the Z-axis of the robot.
According to the present invention, there is provided a system for controlling a robot, characterized in that the system includes an electric motor for driving a shaft executing a Z-axis linear motion of the robot, a servo unit for carrying out a signal supply and a signal feedback to the electric motor, a control portion for supplying a control signal to and receiving a control signal from the stated servo unit, and threshold value supply portion for supplying a threshold value to the above control portion, a comparison between a motor torque instruction value and a threshold value supplied from the threshold value supply portion being carried out in the control portion, and an alarm being delivered and the process subsequently proceeding to a step of dealing with an abnormal condition, when the motor torque instruction value becomes greater than a predetermined threshold value, whereby a control is carried out based on a detection of a force along the Z-axis of the robot.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a schematic diagram of overall structure of a system for controlling a robot as an embodiment of the present invention;
FIG. 2 shows a structure of a robot to which the device of FIG. 1 is applied;
FIG. 3 illustrates a summarized structure of an assembly including a pulley, a ball-and screw nut and a ball-and spline nut, in the device shown in FIG. 1;
FIG. 4 summarizes a structure of a ball-and spline nut included in the structure shown in FIG. 3;
FIG. 5 shows an example of a movement of the top end of robot;
FIG. 6 is a flow chart showing an example of the operation of device shown in FIG. 1; and
FIG. 7 is a characteristic diagram showing an operation characteristics of the device of FIG. 1.
BEST MODE FOR CARRYING OUT THE INVENTION
A schematic diagram of a system for controlling a robot according to an embodiment of the present invention is shown in FIG. 1, and an industrial robot for an assembling job to which the system of FIG. 1 is applied is shown in FIG. 2.
The third axis mechanism i.e., the Z-axis of the robot 1 is shown in the left portion of FIG. 1. At the tip of a shaft 14, as the third or Z-axis, a band head 15 consisting of a band base portion 151 and grip fingers 152 and 153 is mounted. The grip fingers grip a workpiece 2 and insert the workpiece into a hole 31 in an object article.
The shaft 14 is driven by a motor 5 through a transmission system including a pulley 41, a pulley belt, and a ball-and-screw nut 17, providing a vertical movement in linear motion.
A rotary motion is transmitted from the pulley transmission system to the ball-and-screw nut 17, and consequently, a rotary driving force is applied to the shaft 14, but due to an action of a ball-and-spline nut located beneath the ball-and-screw nut 17, the motion of
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Nihei Ryo
Terada Akihiro
Torii Nobutoshi
Toyoda Kenichi
Fanuc Ltd.
Ip Paul
Shoop Jr. William M.
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