Data processing: generic control systems or specific application – Generic control system – apparatus or process – Plural processors
Reexamination Certificate
1999-03-02
2002-06-25
Picard, Leo (Department: 2125)
Data processing: generic control systems or specific application
Generic control system, apparatus or process
Plural processors
C700S002000, C709S209000
Reexamination Certificate
active
06411856
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a control method and a control unit therefor, and more particularly, it relates to a general operation control method in which a group of operating units performing a certain operation are managed to perform regular operation control following a prescribed rule, and to a control unit therefor.
BACKGROUND ART
Referring to drawings, a conventional general operation control method and a control unit therefor are now described with reference to a multi-optical axis photoelectric switch.
A multi-optical axis photoelectric switch has generally been employed as a safety for a press machine or as an intrusion warning unit in a dangerous zone. Such a multi-optical axis photoelectric switch is structured as follows: A projector having a plurality of projective elements and a photoreceiver having a plurality of photodetectors corresponding to the respective ones of the plurality of projective elements are arranged to oppose each other. Optical axes are formed between the respective ones of these plurality of projective elements and plurality of photodetectors, whereby a number of optical axes (optical paths) are formed between the projector and the photoreceiver. A detection area is set between the projector and the photoreceiver, the plurality of projective elements are successively rendered to emit light, and photoreceiving operations are performed by the photodetectors corresponding to the respective projective elements in a state synchronized with the projection timings. In the multi-optical axis photoelectric switch, photoreceiving signals by the photodetectors disappear when a light intercepting object is present in the detection area, and hence an object detection signal can be outputted by determining light intercepted states of the optical axes on the basis thereof. In a place where the multi-optical axis photoelectric switch is used, a press unit is stopped, or an intruder into a dangerous zone in a factory is detected and a warning is issued on the basis of such an object detection signal, for preventing an accident.
In such a multi-optical axis photoelectric switch, a synchronous signal transmitted from the projector to the photoreceiver is employed for synchronizing the timings of projecting operations and the timings of the photoreceiving operations. Such a synchronous signal may be transmitted from the photoreceiver to the projector. As transmission means for the synchronous signal, an electric one employing a wire, or an optical one employing light may be employed.
A specific example of the structure of the multi-optical axis photoelectric switch is now described.
FIG. 20
is a block diagram showing the structure of a multi-optical axis photoelectric switch. Referring to
FIG. 20
, this multi-optical axis photoelectric switch is structured by a pair of projector
1
and photoreceiver
2
. The projector
1
includes a sequential projection circuit
3
, a timing circuit
4
, and a plurality of projective elements
101
to
106
. The photoreceiver
2
includes a photoreceiving selection circuit
6
, a timing circuit
5
, a plurality of photodetectors
201
to
206
, an amplifier circuit
7
, a microcomputer
8
and an output circuit
9
.
The projective elements
101
to
106
, each formed by a light emitting diode or a laser diode, successively perform projection one by one. The photodetectors
201
to
206
are arranged opposing to corresponding ones of the respective projective elements
101
to
106
, and receive light projected from the corresponding projective elements. Each of the photodetectors
201
to
206
, formed by a photodiode or a phototransistor, converts the received light to an electric signal and outputs the same. The projective elements
101
to
106
and the photodetectors
201
to
206
are provided in a one-to-one basis, and the corresponding projective elements and photodetectors are arranged opposed to each other at a prescribed distance in a detection area. Adjacent projective elements and the adjacent photodetectors are each arranged at prescribed intervals. A plurality of optical axes (optical paths) are formed by such a plurality of projective elements
101
to
106
and plurality of photodetectors
201
to
206
.
The timing circuit
4
supplies a timing signal defining a projection timing to the sequential projection circuit
3
, while supplying a synchronous signal for synchronizing a projecting operation and a photoreceiving operation to the timing circuit
5
. The sequential projection circuit
3
is a circuit for successively driving the projective elements
101
to
106
one by one, and drives the projective elements
101
to
106
by successively feeding a driving current to the projective elements
101
to
106
in response to the timing signal received from the timing circuit
4
.
The timing circuit
5
supplies a timing signal defining a photoreceiving timing to the photoreceiving selection circuit
6
in synchronization with the synchronous signal received from the timing circuit
4
, while supplying a signal indicating the photoreceiving timing to the microcomputer
8
. The photoreceiving selection circuit
6
is a circuit for performing selective control of photoreceiving by the photodetectors
201
to
206
, and performs the following operation: The photoreceiving selection circuit
6
selects, in synchronization with a projective element performing a projecting operation, the corresponding photodetector on the basis of the timing signal supplied from the timing circuit
5
, and operates the photodetector to a photodetectable state. Thus, the corresponding projective elements and photodetectors successively perform projection and photoreceiving pair by pair. Further, the photoreceiving selection circuit
6
receive a photoreceiving signal supplied in response to photoreception by the photodetectors
201
to
206
, and supplies the photoreceiving signal to the amplifier circuit
7
.
The amplifier circuit
7
amplifies the photoreceiving signal supplied from the photoreceiving selection circuit
6
, converts the amplified signal from an analog signal to a digital signal and supplies the same to the microcomputer
8
. The microcomputer
8
compares the level of the supplied photoreceiving signal with a prescribed reference level, and determines whether or not an object has been detected, on the basis of the comparison result. In other words, the microcomputer
8
makes a determination that presence of an object is not detected when the level of the photoreceiving signal is in excess of the reference level, while making a determination that presence of an object has been detected when the level of the photoreceiving signal is lower than the reference level. The microcomputer
8
supplies a signal indicating such a determination result to the output circuit
9
. The output circuit
9
outputs an object detection signal capable of indicating presence/absence of existence of an object in response to the signal supplied from the microcomputer
8
. This object detection signal is employed for operations of various types of units in the aforementioned object detection.
When a plurality of such multi-optical axis photoelectric switches where projectors and photoreceivers are paired are used, there is a possibility of mutual interference, resulting in an erroneous detection, if the multi-optical axis photoelectric switches are arranged in such a manner that the photoreceiver of a certain multi-optical axis photoelectric switch possibly receives light emitted from the projector of another multi-optical axis photoelectric switch. The mutual interference in this case stands for the following phenomenon: When the projectors simultaneously perform projecting operations in the respective ones of two multi-optical axis photoelectric switches, for example, the photoreceiver in one multi-optical axis photoelectric switch may receive light emitted by the projector in the other multi-optical axis photoelectric switch. In such a case, it is possible that an object actually present is not detected, since lig
Sakai Yasunobu
Takahara Takayoshi
Takeuchi Hisashi
Foley & Lardner
Frank Elliott
Omron Corporation
Picard Leo
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