Electricity: motive power systems – Positional servo systems – With protective or reliability increasing features
Reexamination Certificate
2001-04-02
2003-05-27
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Positional servo systems
With protective or reliability increasing features
C318S568160
Reexamination Certificate
active
06570355
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control apparatus for a robot, and in particular in an industrial robot, to a method of outputting a stop signal for the periphery of the robot and to the configuration of a safety circuit for generating the stop signal when the robot is stopped in case of abnormality in the periphery of the robot.
2. Description of the Related Art
An industrial robot is provided with emergency stop switches in order to secure the safety of both the operator of the robot and the workers in the periphery of the robot. Since these emergency stop switches are electrically connected to a safety circuit in series, the operation of any emergency stop switch causes the switching OFF of a servo power supply for driving a motor in the robot body.
These emergency stop switches indicate those switches for detecting the occurrence of a factor harmful to the safety, and include: an emergency stop switch provided in the body of the control apparatus; a door open-close switch provided in a safety fence for insuring a safety region in the periphery of the robot; an external emergency stop switch in a peripheral system; and an over travel switch for the robot body. Each switch is configured in linkage with the driving circuit of the servo power supply so as to control the switching ON permission and the switching OFF of the servo power supply. A prior art safety apparatus for an industrial robot is described below with reference to FIG.
8
.
In a safety circuit of a robot body
1
shown in
FIG. 8
, disposed in series are switches
21
to
2
n
each corresponding to a factor inhibiting the switching ON of a servo power supply
4
to the robot body
1
. One end of the switch
21
is supplied with a 24 V voltage, while the last end of the switch
2
n
is provided with a relay
3
for controlling the switching ON and switching OFF of the servo power supply, whereby a first signal line is formed. Further, a signal of servo switching ON permission is provided from a control apparatus
5
to the servo power supply
4
. Without a factor inhibiting the switching ON of the servo power supply to the robot body
1
, each switch
21
to
2
n
is closed thereby to provide the 24 V voltage on the first signal line. A relay coil
31
is then excited thereby to close a relay contact
32
. Then, finally, a servo power supply switching ON circuit in the servo power supply
4
is driven. When switched ON, the servo power supply starts to energize (control) a motor
11
included in the robot body
1
, while a lock (brake
12
) circuit of a shaft of the motor
11
is switched OFF.
In this state, when at least one of the switches
21
to
2
n
is operated (to become open) due to occurrence of a factor inhibiting the switching ON of the servo power supply, the first signal line is switched OFF, and the 24 V voltage is not supplied. At that time, by monitoring the potential in the end point on the relay
3
side of each switch with a control apparatus
5
, it is known which switch is open. Further, the relay coil
31
becomes unexcited thereby to open the relay contact
32
. The servo power supply is then switched OFF thereby to stop to energize (control) the motor
11
in the robot body
1
, while the brake
12
of the shaft of the motor
11
is switched ON.
As such, as is described in Japanese Laid-Open Patent Publication No. Hei 10-217180, when any of the switches
21
to
2
n
becomes open, the first signal line which is the servo power supply switching ON permission line is switched OFF, whereby the servo power supply is switched OFF thereby to cause immediate stop of the robot.
In the prior art safety apparatus for an industrial robot as described above, a signal for sending the emergency stop to external devices is output by the open-close of the relay contact
32
. Further, in a production line in which each of a plurality of robots is disposed in each work area, the emergency stop of each work area is monitored using the above-mentioned signal. Accordingly, even when a trouble occurs only in some of the work areas, the robots in all of the areas are immediately stopped. Therefore, even when a work area is to be stopped to ensure the safety in the work area in case of a trouble (such as a change of expendable parts) which concerns the work area alone and does not affect the other work areas, the whole line is stopped in accordance with the prior art configuration. This causes the problem of reducing the work efficiency.
Further, since the switching OFF of the servo power supply for the industrial robot is carried out by breaking the switch contact of a limit switch and the like of each switch
21
to
2
n
, in case of occurrence of a contact fusion in any switch, the servo power supply is not properly switched OFF even in case of occurrence of the emergency stop factor corresponding to the switch. Furthermore, the control apparatus
5
can not detect the occurrence position of the fusion, and hence the reliability of the safety circuit of the control apparatus
5
is not secured.
An object of the present invention is to provide a control apparatus for a robot in which the work efficiency is improved in the whole robot peripheral system including the robot, and in which considering the increase in the consciousness of safety such as the standardization of safety apparatuses, both the reliability of the safety circuit of the control apparatus for a robot and the ensuring of the safety are improved.
SUMMARY OF THE INVENTION
A control apparatus for a robot in accordance with the present invention comprises a switch circuit consisting of a plurality of emergency stop switches interconnected in series, wherein a servo power supply is switched ON or OFF by the switch circuit, and wherein each of the plurality of switches is provided with an intermediate output signal line for extracting the operation signal, or the emergency stop signal thereof.
In accordance with the control apparatus for a robot in accordance with the present invention, by connecting the intermediate output signal lines to peripheral devices outside the robot, a factor to cause the stop of the robot body alone can be distinguished from a factor to cause the stop of both the robot body and the peripheral devices. This permits the safety circuit of the whole robot system to be configured with flexibility, and accordingly the work efficiency can be improved without degrading the safety.
A control apparatus for a robot in accordance with the present invention comprises a switch circuit consisting of a plurality of emergency stop switches interconnected in series, wherein a servo power supply is switched ON or OFF by the switch circuit, wherein each of the plurality of switches comprises a first open-close contact and a second open-close contact both operating simultaneously, wherein every first open-close contact of each of the plurality of the switches is interconnected in series by a first signal line, while every second open-close contact of each of the plurality of the switches is interconnected in series by a second signal line, and wherein an intermediate output signal line for extracting the operation signal or the emergency stop signal of each of the plurality of switches is connected to at least one of the first signal line and the second signal line.
In accordance with the control apparatus for a robot in accordance with the present invention, a case to stop the whole system including the robot body, a case to cause the stop of the robot body and a part of peripheral devices, and a case to cause the stop of the robot body alone can be distinguished with each other. This permits the safety circuit of the whole robot system to be configured with flexibility, and accordingly the work efficiency can be improved without degrading the safety.
A control apparatus for a robot in accordance with the present invention comprises a switch circuit consisting of a plurality of emergency stop switches interconnected in series, wherein a servo power supply is switched ON or OFF by the
Aimi Kei
Matsumoto Kazunori
Morita Kunitoshi
Nakatsuka Takashi
Ohto Masahiro
Matsushita Electric - Industrial Co., Ltd.
Ro Bentsu
Stevens Davis Miller & Mosher LLP
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